NG Condensing Boilers for closed loop radiant floor

[jonjon1]

And by the way , my company did millions of dollars in commercial boiler systems.
I can not remember the last job where a CI boiler was specified ? We did how ever install more than a couple Aerco mod con million btu units . No wall hung unit !
factory training and start up was required for them.
One job in perticular I remember , we removed a million btu oil boiler and installed 10 Glow core L.P gas units . They were designed with lead lag , outdoor boiler reset and some other specialty controls . The first yrs fuel saving paid for the new system. This was in 1991 when both fuels were cheap.

Many of us old men have forgotten more about boiler systems than we care to think about.

If you read my posts, you will see me say multiple times that COMMERCIAL systems are different than RESIDENTIAL, I am not going to go over why again lol, I already typed it out a ton of times, lol...

No argument from me there, commercial systems should be the high eff. stuff, the commercial high eff. stuff is great for what it does...

As far as mod cons being the future, I agree, 100% ci boilers will be gone someday, no doubt about it, but someday we may all be driving hybrids and electric cars too, so does that mean that 25 years ago when they started making them you should have bought one? NO, they were junk, no one knew how to fix them, parts were expensive, they didn't save you any money unless you drove a million miles {very similar to commercial and resi situation}, and they broke all the time...

Sadly like steam, cast iron will be gone someday, I will argue about that, I will hate to see them go and I have a feeling it won't be for a long time, because there are still a bunch of people out there that can do the math and see its not a smart move financially.

I am a cast iron guy I will not make excuses for it, and when mod cons change I will be a mod con guy, BUT ci isnt going anywhere until that happens. Mark my words this is what will change..
1- controls, gas valves, fan, and other components will be third party supplied and not unit specific {to an extent of course}, When honeywell is making the controls, and you just install a jumper for this boiler or replace a module for that one...

2- HX will be perfect, they are close, the TT is a great design, plastic collector got it a step closer, next they are going to have to change the sensors a bit, you will have clip in well sensors instead of thread in on other units, also they are going to be even easier to change, and they are going to have universal ones..

3- infinite modulation, there will be 2 hx's in a single unit, 1 for 1500btu to 10K and then another for 10K to XXXXX , so we will be seeing 2 stage modulation soon with very low miniums

4-PRICE, units will reflect what they should cost, because honeywelll will be doing the controls, and companies will be competing for the customer, prices will drop, they are easier to ship, cost less to make, etc Mod cons will be in the $1500 range before ci goes awaym we will see ci boilers costing more than mod cons before they are gone for ever...


I know I have not been in the business for 60 years, but I made my mark, I have met some of the best in the biz, I have traded ideas with some of the best minds in hydronics, and I will give anyone in need of it my advice, being honest here, I would LOVE for someone to convince me mod cons cost less than a ci boiler properly installed in the long run. I had a tech that worked for me swore by mod cons, didnt matter the brand he used to tell people they can save up to 40% and get me in all kinds of trouble, because after we install the unit they didn't save anything, lol... I put a weil mclain gold in my brother in laws house and his bill went up, lol.... Did it myself, 10% correct, heat load, high eff loop, everything, and it cost more to run lol, he has a radiant system with an indirect water heater, plus a couple zones of baseboard, he wanted the ci boiler {I put in, nothing special just a slant fin direct vent} replaced for the extra room, well the bill went up, and its not uncommon for that to happen.
I seen on of the largest companies around here get a ton of bad press because he was installing navians and with issues and everything else he almost went out of business, made the news papers all the compaints he was getting, advertising "savings up to 35%" thats hard to deliver, and most of the time when people say they save that, they are either lying to themselves or more to the story.

I had a customer who was a science teacher at my sons middle school, very smart guy, he bought an old house with oil fired steam heat, he heated it for 2 years and kept impeccable records of degree days gone by and fuel he used for indoor temperature...

Well he saved up some money and wanted to renovate the house, he spent 100K at least, new doors, windows, siding, insulation, etc. I ripped out the steam system and installed a mod con {you were not talking this guy out of a high eff, boiler} with low temp panel wall hung radiators... ODR, zoned to match minimum fire, done perfect...

He saved almost 30%, he went over all his records with me and showed me he saved 30%, so I asked him to figure out how much of that was from the cost of oil, in other words, figure out how much oil costs per btu and gas and then do the math.. He did it, 2 days later he called me and said he is much much less BTUs, I said of course because you tightened the envelope.

After all that he figured it to the penny, the payback for that boiler was something like 14 years, which isnt bad and I installed a gb142 in there which is a decent boiler and will last the 14 years pretty easily... BUT he didn't just do a boiler and he replaced a decent boiler {had a burnham mega steam}...

That is honestly about the biggest savings I ever seen, but he changed, fuels, emitters, type of heat, insulaltion, etc...

 

[Radix2]

Can you explain how you are using ODR with CI boilers ?

 

[jonjon1]

Can you explain how you are using ODR with CI boilers ?

Sure, so an ODR is just thermal targeting, {I'll expllain this quick incase anyone doesn't completely understand the concept}.
Most of the energy savings in heating systems is achieved from not heating the water as high, for instance to make steam you have to boil water, that takes a lot of energy, for a baseboard system you normally want 170-190* for it to have decent output per ln ft, 150 for hydro air units, for radiant panels say 135, for radiant floors 100 or so... It takes a lot more energy to heat water to 180 than 100, even if you triple the amount of water you are heating...

So now say you have baseboard you run at 180 {VERY COMMON}, at 180 degrees your baseboard puts out 650 BTU's per foot {all example numbers, flow rates, type of board, and install play a roll in output}. So if you have 10 feet of board in a 10x10 room you are putting out 6500 btus when circulating. Now if its only 50 degrees outside that room may only need 1800 BTU's, so you can't shrink your base board BUT you can lower the temperature, so that what we do is we use an outdoor sensor and a program with a preset curve. So as the temperature outside drops it raises the temperature of the heating fluid.

NOW what most people don't understand is mod cons do this BUT unlike a ci boiler, you can;t just start a mod con and run it for 4 minutes at a time, because whats going to happen is, its going to soot up, BECAUSE mod cons arent efficient until they run for a long cycle, the longer the cycle the better, SO that is why we want a modcon to NEVER shut off once it starts heating.

So a mod con holds very little water and because of that has to heat it fast {instantly} and continuously the burner can never shut off, because they use venturi gas valves this is not an issue and actually better for some parts of the unit, while the boards, pumps, and fan blowers take a beating from never getting a break, the ignition system {ones with intermittent ignition} and gas valves can last a very long time in this type of system {but of course since the manufacturers know this they will build them weaker, lol}...

Now a ci boiler has STORAGE, this in my professional opinion that I like storage. A negative of storage is {and pretty much the only negative} "stand by losses", so you heat 5 gallons of water up to 180 degrees and sit it in a cold room the temp is going to drop. BUT how much is trivial, the new boilers are well designed, insulated, sealed, etc, they don't lose much, PLUS if this is in your living space {even in your basement, heat rises} you are getting this energy one way or the other.

Now I agree old natural draft systems would lose lots of energy BECAUSE you couldn't turn off your chimney, it would just constantly draft, but that was fixed with draft dampers, direct vent, and outdoor intakes, a long time ago.

So back to storage, now your ci boiler will not modulate the burner, BUT why cant we modulate the temperature? We can, we used a Hydro level 3250 plus with the outdoor sensor kit {honeywell makes one too} and it works just like a wall hung, the outdoor sensor tells the control what temp it is out there, the control goes off its curve and tells the burner to run until that temp is made, NOW pair that with a delta T driven circulator and you can be just as system efficient as a mod con, if not more for high volume systems...

BECAUSE think of this, when your mod con is running it is constantly taking outside air into the combustion chamber and heating that up to heat the exchanger that can be 24 hours a day {actually in a properly designed system it will be 24 hours a day}. With a storage boiler, it fires X amount of btu's and then stops when the water battery is satisfied.

So lets talk about delta T circulators, they are very affordable now and its a simple premise, adjust your flow rate so that you don't pump water blindly without taking all the energy you can from it, so set it at say 25 degrees and if your water is entering the baseboard at 180 it will adjust its pump speed so that it goes slow enough to not come back to the boiler until it is 155...

OK, so heres another thing I will touch on, primary secondary piping, cast iron boilers dont like big temperature differences, you are pumping 140 degree water back into a piece of cast iron heated to 180, some cast irons take this better than others {buderus has a good mix for this}, another issue is if you come back super cold your ci boiler will condense and its not designed to condense so it will shorten its life, so to keep it from condensing you have to raise the flue temp which will lower efficiency...

So how do we get around that ? Primary piping, this is the practice of hydraulic seperation, awesome concept, you can do it with closely spaced tees or a hydraulic seperator, either way works perfect, if you google primary secondary piping you will find a ton of info, maybe even a couple of my articles..

The short explanation is we make a loop from the supply to the return of the boiler with its own system pump installed in it, then we take out the zones of heat with say closely spaced tees {what ever goes in a tee has to come out of it}, using properly sized pumps and paying attention to flow rates, loads, and pipe sizing you will get your system to its best efficiency and your boiler will last as long as it possibly can because the difference between its supply and return is 5 degrees, so there is no chance of thermal shock, no expansion and contraction differences from one end of the boiler to the other. uniform temps make for a happy boiler...


So to answer your question, use a hydrolevel control and odr kit {$200}, and it will change your boiler temp to match your load. A mod con CAN NOT do this with out burner modulation because 1- the short cycles would KILL it and 2- it has no storage so what good is heating up 1 gallon of water to your thermal target, lol it wouldnt work...

Some people will say storage is not a good thing, well than answer me this, why do the manufactures want us to use "buffer tanks", this is one of the things I called BS on when mod cons first came out, you need a 20 gallon electric water heater to store water, lol.. Water tanks last 5-6 years and you want to add it to a $10K boiler?

To this day you ask a boiler maker like burnham and they will say the systems work better with the "buffer tank", that is because boilers need storage!!! Now way around that. They have played with the modulation and flor rates to make them now work with out the buffer but they do work better with it than without it, so if you have a mod con with no buffer and it works awesome, it would work even better with the buffer!! Keep that in mind when your installer skips it... I hate buffer tanks, I will they would make a thick lifetime ss tank with super insulation then I would be a believer, but as of now they are making sub par stuff, so I am not a tank lover, especially in a heating system {I do like the hybrids for dhw though}...


SO thats it in a nutshell, lol.. There is a lot of info in this thread, that is pretty nice, hopefully it helps someone...
heres some info on the hl+ units..

http://www.nythermal.com/uploads/3200-3250 Plus Sheet.pdf

heres some info on delta t circ
bee is getting replaced by the veridian, I already installed a few v's they have been avaialble for a while but the website says 2015...
http://flopro.taco-hvac.com/product...et_rotor_variable_speed_circulator/index.html
http://flopro.taco-hvac.com/vt2218page.html

 

[Vermaraj]

To the OP:
I heat ~ 8000 sqft of radiant floors with a propane mod con. I had the system designed by a professional firm that specializes in radiant heat. System has 65 loops, 28 zones and is controlled by a Tekmar control system.

My experience has been great. The Buderus boiler has been in operation for 5 years and has failed twice. 1st time was for a clogged condensate trap which cost nothing to fix. 2nd time was a bad pressure sensor which I repaired myself for $100 or less.

Every two years I have it professionally cleaned and hear all sorts of tales of woe about mod cons and especially the aluminum heat exchanger in the Buderus. I throw them a bone and let them change the ionization rod and the ignitor for $300 and off they go.

In the end the house and basement is always at 70F, the garage at 60F. I will use 1200 gal of propane this year, my neighbors that have conventional boilers and do not heat their garages or basements are looking at 3000 gal of oil. Which, if I do the math right is approx 4800 gal of propane.

A lot of that savings has to do with the amount of insulation I put in this house. I am very pleased with the performance of the mod con. Professional design is key.

 

[Radix2]

So, you are saying that you are using the ODR to run the CI boiler at a low temperature like a mod con... How is this not going to cause condensation in the CI boiler ? ( which will destroy it from corrosion).

 

[BigGMC]

Verm -
Wow 28 zones! That layout must be impressive to look at

So are you saying that every two years you are spending $300 for an ion rod/ignitor in addition to the cleaning?
Do you have to neutralize the condensate?

 

[Vermaraj]

Every two years I pay $500 for a cleaning, combustion test and general check up. They always come up with a laundry list of things that "are likely" to break down.

Since there are two authorized dealers that provide service in the area I let them change the rod and ignitor for $300 every two years. Just to make sure if we have a breakdown in the dead of winter they will show up. Otherwise I could change them out in a few minutes for less than $100.

Condensate will eat through anything and kill any plants. I have a 10 gal sump that is full of marble chips that neutralizes the water before it discharges into a drywell in the back yard.

 

[BigNuge]

Sure, so an ODR is just thermal targeting, {I'll expllain this quick incase anyone doesn't completely understand the concept}.
Most of the energy savings in heating systems is achieved from not heating the water as high, for instance to make steam you have to boil water, that takes a lot of energy, for a baseboard system you normally want 170-190* for it to have decent output per ln ft, 150 for hydro air units, for radiant panels say 135, for radiant floors 100 or so... It takes a lot more energy to heat water to 180 than 100, even if you triple the amount of water you are heating...

So now say you have baseboard you run at 180 {VERY COMMON}, at 180 degrees your baseboard puts out 650 BTU's per foot {all example numbers, flow rates, type of board, and install play a roll in output}. So if you have 10 feet of board in a 10x10 room you are putting out 6500 btus when circulating. Now if its only 50 degrees outside that room may only need 1800 BTU's, so you can't shrink your base board BUT you can lower the temperature, so that what we do is we use an outdoor sensor and a program with a preset curve. So as the temperature outside drops it raises the temperature of the heating fluid.

NOW what most people don't understand is mod cons do this BUT unlike a ci boiler, you can;t just start a mod con and run it for 4 minutes at a time, because whats going to happen is, its going to soot up, BECAUSE mod cons arent efficient until they run for a long cycle, the longer the cycle the better, SO that is why we want a modcon to NEVER shut off once it starts heating.

So a mod con holds very little water and because of that has to heat it fast {instantly} and continuously the burner can never shut off, because they use venturi gas valves this is not an issue and actually better for some parts of the unit, while the boards, pumps, and fan blowers take a beating from never getting a break, the ignition system {ones with intermittent ignition} and gas valves can last a very long time in this type of system {but of course since the manufacturers know this they will build them weaker, lol}...

So back to storage, now your ci boiler will not modulate the burner, BUT why cant we modulate the temperature? We can, we used a Hydro level 3250 plus with the outdoor sensor kit {honeywell makes one too} and it works just like a wall hung, the outdoor sensor tells the control what temp it is out there, the control goes off its curve and tells the burner to run until that temp is made, NOW pair that with a delta T driven circulator and you can be just as system efficient as a mod con, if not more for high volume systems...

BECAUSE think of this, when your mod con is running it is constantly taking outside air into the combustion chamber and heating that up to heat the exchanger that can be 24 hours a day {actually in a properly designed system it will be 24 hours a day}. With a storage boiler, it fires X amount of btu's and then stops when the water battery is satisfied.

OK, so heres another thing I will touch on, primary secondary piping, cast iron boilers dont like big temperature differences, you are pumping 140 degree water back into a piece of cast iron heated to 180, some cast irons take this better than others {buderus has a good mix for this}, another issue is if you come back super cold your ci boiler will condense and its not designed to condense so it will shorten its life, so to keep it from condensing you have to raise the flue temp which will lower efficiency...

So how do we get around that?

The short explanation is we make a loop from the supply to the return of the boiler with its own system pump installed in it, then we take out the zones of heat with say closely spaced tees {what ever goes in a tee has to come out of it}, using properly sized pumps and paying attention to flow rates, loads, and pipe sizing you will get your system to its best efficiency and your boiler will last as long as it possibly can because the difference between its supply and return is 5 degrees, so there is no chance of thermal shock, no expansion and contraction differences from one end of the boiler to the other. uniform temps make for a happy boiler...


SO thats it in a nutshell, lol.. There is a lot of info in this thread, that is pretty nice, hopefully it helps someone...
heres some info on the hl+ units..

So, you are saying that you are using the ODR to run the CI boiler at a low temperature like a mod con... How is this not going to cause condensation in the CI boiler ? ( which will destroy it from corrosion).

Hey guys, I work in the Commercial/Industrial Burner/Boiler field. 18 years as a Field Tech/Project Manager, going on 3 in sales.

Just like in many instances, the best information lies within the middle of two sides of an argument. While I do not completely agree with jonjon1, he makes a lot of sense. See, as a self employed guy he has had to see the best and the worst of all types of systems, and likely learn it all the hard way...losing money & customers. If your livelihood depends on the reliability & performance of the equipment you sell & install it is easy to form a bad opinion of certain equipment.

In my field we wholeheartedly use & embrace Condensing Boiler Technology. I represent 2 different manufacturers of these boilers, and have started/serviced/sold them since 1996. The early years were painful, but emerging technology is ALWAYS painful. That doesn't mean we disregard it, it is coming wether we want it or not. And because I have embraced it I have found ways to avoid issues early in the system layout & design process. Proper selection & system layout are KEY to any high efficiency system. I have been part of hundreds of high efficiency system installs/startups/commissioning and have learned that old system layouts (the old way of doing things) is no longer applicable in terms of these systems. Not only do you need to select the right boiler and ensure proper system layout & design, you have to select (and properly apply) some key pieces of ancillary equipment to take advantage of the efficiency gains of a high efficiency boiler.

As I read this thread I noticed that jonjon1 made no reference to the system side changes needed to take full advantage of condensing boilers. Yes, I saw buffer tanks/loop changes/OAT reset in there....but what about the convection side? One cannot simply install a high efficiency condensing boiler and expect to save $$. If you run a condensing boiler above the condensing range you'll realize very little/no savings. This is likely the reason for the example projects not showing fuel savings. For example, if you are using baseboard to heat a house you need to run the system pretty hot (170-190 like mentioned above) otherwise natural convection will be very slow, and the house will not be heating properly...and just like that you're not taking advantage of the condensing/high efficiency portion of the unit. I suppose lots of customers get bent out of shape because they only read the glossy brochure that says "99%" efficient (and not the fine print that says you need 90 degree return water to get that efficiency) and want to save all that $$. They spend the extra money on a high efficiency unit, only to see their bill stay the same. Whats worse, is they likely have given to attention to the other heat robbing elements of their home (windows/doors etc.), those can easily offset any savings of a condensing unit. Whenever I talk to my customers about condensing boilers and the money they can save with them I immediately review their load side components. If those parts of the system aren't designed/capable of operating at lower temperature then a condensing unit is not a good fit. The only gains will be the higher heat exchanger efficiency, as well as reduced cycling due to the commonly higher turndown ratio (in the residential units modulation is still a rare thing, in commercial it is present in 90%+ of all units not matter the fuel).

It isn't magic, if the entire system & envelope is inefficient you're not going to improve your energy bills much (or at all) simply by changing the boiler alone.

Now on the other side, CI is a tried & true technology. I dare not even contemplate how many large commercial units I have started & worked on. If they are set up right they provide decades of service....no arguing that. I have CI at home, just installed 2 new Buderus 115's w/Riello burners in August of last year (2 family house). I do not have a tenant yet (putting the finishing touches on the first floor now) so i have had to heat the whole house myself again this year. I saved 20%+ already just changing the boilers from a WM Gold w/Beckett (one unit for the whole house). The reliability of CI is solid, but the lack of modulation (residential) and the inability to condense are sending it down the road to oblivion. Like jonjon1 said, it will take a while for it to go away altogether. When #2 oil gets crazy expensive, or the government finally kills it with regulations is when you'll see CI go away. I estimate this will happen inside of 20 years....but we will see.

To the OP: For a radiant system (inherently designed for condensing units) a high efficiency condensing unit is a no-brainer. Just be sure to size the unit properly to keep cycling down and you'll maximize your savings. CI has no place in the radiant world (unless you are stuck with oil).

To Radix2: He mentioned having to use a hydronic decoupler (primary/secondary loops). this device would prevent the boiler from seeing low return temps, while allowing the secondary loop (house loop) to drop as low as it needs to gain some efficiency. Not a lot of efficiency is gained using CI in this application because the boiler is till run too hot to gain much (a percent or two at most).

 

[jonjon1]

Every two years I pay $500 for a cleaning, combustion test and general check up. They always come up with a laundry list of things that "are likely" to break down.

Since there are two authorized dealers that provide service in the area I let them change the rod and ignitor for $300 every two years. Just to make sure if we have a breakdown in the dead of winter they will show up. Otherwise I could change them out in a few minutes for less than $100.

Condensate will eat through anything and kill any plants. I have a 10 gal sump that is full of marble chips that neutralizes the water before it discharges into a drywell in the back yard.

I used to love the gb142 and 162 boilers, aluminum hx or not, if you watch you water level {TDS, PH, ETC} and take care of it, its a 18-20 year boiler easy..

But my cost was around $4K when they came out and that was before they started coming with the low less header...

Here is the issue I seem you are spending $250 a year to maintain the units, have already had 2 service issues inside of 5 years!!! and are happy... Well I wish I had a million of you as customers, lol...

I would be confident in saying, with a house your size {I would love to see some pics, I am a fan of big houses, I was going to build 7500 sq, but my wife put the limit at 4K and we ended up with 4500 and honestly its still too much, we have 4 full baths, 5 bedrooms, and 4 parlors, lol} you would be better off with 3 ci boilers than the wall hungs, simple reason is storage, that energy will not go to waste, 86.5% efficient direct vented ci boilers, made to match your load using an ODR to control the fluid temp and your post would have been similar EXCEPT you would have said you spend $0 every 2 years and have not had a single service issue...

I would LOVE to see some pics of your system if you have a chance...

 

[jonjon1]

Hey guys, I work in the Commercial/Industrial Burner/Boiler field. 18 years as a Field Tech/Project Manager, going on 3 in sales.

Just like in many instances, the best information lies within the middle of two sides of an argument. While I do not completely agree with jonjon1, he makes a lot of sense. See, as a self employed guy he has had to see the best and the worst of all types of systems, and likely learn it all the hard way...losing money & customers. If your livelihood depends on the reliability & performance of the equipment you sell & install it is easy to form a bad opinion of certain equipment.

In my field we wholeheartedly use & embrace Condensing Boiler Technology. I represent 2 different manufacturers of these boilers, and have started/serviced/sold them since 1996. The early years were painful, but emerging technology is ALWAYS painful. That doesn't mean we disregard it, it is coming wether we want it or not. And because I have embraced it I have found ways to avoid issues early in the system layout & design process. Proper selection & system layout are KEY to any high efficiency system. I have been part of hundreds of high efficiency system installs/startups/commissioning and have learned that old system layouts (the old way of doing things) is no longer applicable in terms of these systems. Not only do you need to select the right boiler and ensure proper system layout & design, you have to select (and properly apply) some key pieces of ancillary equipment to take advantage of the efficiency gains of a high efficiency boiler.

As I read this thread I noticed that jonjon1 made no reference to the system side changes needed to take full advantage of condensing boilers. Yes, I saw buffer tanks/loop changes/OAT reset in there....but what about the convection side? One cannot simply install a high efficiency condensing boiler and expect to save $$. If you run a condensing boiler above the condensing range you'll realize very little/no savings. This is likely the reason for the example projects not showing fuel savings. For example, if you are using baseboard to heat a house you need to run the system pretty hot (170-190 like mentioned above) otherwise natural convection will be very slow, and the house will not be heating properly...and just like that you're not taking advantage of the condensing/high efficiency portion of the unit. I suppose lots of customers get bent out of shape because they only read the glossy brochure that says "99%" efficient (and not the fine print that says you need 90 degree return water to get that efficiency) and want to save all that $$. They spend the extra money on a high efficiency unit, only to see their bill stay the same. Whats worse, is they likely have given to attention to the other heat robbing elements of their home (windows/doors etc.), those can easily offset any savings of a condensing unit. Whenever I talk to my customers about condensing boilers and the money they can save with them I immediately review their load side components. If those parts of the system aren't designed/capable of operating at lower temperature then a condensing unit is not a good fit. The only gains will be the higher heat exchanger efficiency, as well as reduced cycling due to the commonly higher turndown ratio (in the residential units modulation is still a rare thing, in commercial it is present in 90%+ of all units not matter the fuel).

It isn't magic, if the entire system & envelope is inefficient you're not going to improve your energy bills much (or at all) simply by changing the boiler alone.

Now on the other side, CI is a tried & true technology. I dare not even contemplate how many large commercial units I have started & worked on. If they are set up right they provide decades of service....no arguing that. I have CI at home, just installed 2 new Buderus 115's w/Riello burners in August of last year (2 family house). I do not have a tenant yet (putting the finishing touches on the first floor now) so i have had to heat the whole house myself again this year. I saved 20%+ already just changing the boilers from a WM Gold w/Beckett (one unit for the whole house). The reliability of CI is solid, but the lack of modulation (residential) and the inability to condense are sending it down the road to oblivion. Like jonjon1 said, it will take a while for it to go away altogether. When #2 oil gets crazy expensive, or the government finally kills it with regulations is when you'll see CI go away. I estimate this will happen inside of 20 years....but we will see.

To the OP: For a radiant system (inherently designed for condensing units) a high efficiency condensing unit is a no-brainer. Just be sure to size the unit properly to keep cycling down and you'll maximize your savings. CI has no place in the radiant world (unless you are stuck with oil).

To Radix2: He mentioned having to use a hydronic decoupler (primary/secondary loops). this device would prevent the boiler from seeing low return temps, while allowing the secondary loop (house loop) to drop as low as it needs to gain some efficiency. Not a lot of efficiency is gained using CI in this application because the boiler is till run too hot to gain much (a percent or two at most).

Thank you so much for replying, you bring up valid points, I haven't mentioned getting a system ready for a mod con, and it is an issue, most customers don't want to pay for it, but I would go through the properties and look for trouble items, like bathrooms or hallways with thermostats {them lead to short cycling}, and 2000 sq foot homes will 11 zones {thats a mod con nightmare}, etc... I did have many customers that were fine with adding baseboard to help lower their curves high temp on a design day, hardest problem there was matching their old discontinued boards...

Next, I see you work in the commercial side, again, high efficiency is the way to go in that area...

I agree radiant is awesome with a mod con and when they are perfected I would understand your thinking, but as of right now, i can't see installing them just to save money, its not there, I looked, and can't see it...

I'll ask you this, besides the 10% combusiton efficiency difference where else would savings come from between say a...

50K btu, direct vented, out door reset thermal targeted boiler with a delta controlled pumping system

vs a $50K BTU mod con

I under stand the 10%, but where does more than that come into play?

stand by losses, I have measured them its a joke with the new boilers, and their losses are normally inside the heated property in one way or another.

turn down modulation- this is to keep the mod con running and one of its devices it needs to be efficient, no where have I seen a burner that turns down being more efficient then one that turns off?

in other words you need 10K BTUs, one burner makes 2K per minute for 5 minutes the other makes 10K for 1 minute, you end up with the same amount either way...


I have had this conversation with some of the smartest guys in the business, you show me where it comes into a residential building, explain to me where the extra savings comes from..

I am not arguing with the 10%, while I think that will be quicky eaten up by service, and the customer will lose in the end when the longevity is not there and parts are through the roof, but where is the extra????


Now I gave the 10% , but in truth, its not that much, I have a testo ca that is super accurate and super fast {newest bestist you can find and I watch mod cons start on the meter, vent-ignition-gas-fire 87% 88%, 89%, 89.6%, 89.9%, 90%...........................90%............................................90.1% 95 will come, but it better be perfect conditions or expect to see 93.8% 93.9% 94%........

I start a ci boiler, vent-ignition-gas-fire 84.8 85.0 85.5 and stays solid through the cycle gets there in 4 seconds and thats it...

So say your boiler cycles 2 times an hour for 20 minutes each time {warmer than design day} {would be considered a good running system}, that means the time it took lingering under 90% is lowering your average efficiency, no matter how you look at it...


BUT like I said and I asked Jeff from Buderus this way back when I was installing 60+ gb's a year, wheres the extra?


PS- I love the g115/215 series, and the rinnai is amazing on them, I even like them lt160 tanks, people say they are trouble, I have them out there 12 years old and looking brand new. When it comes to oil that is the guy to install, no doubt about it, good choice. I also pipe them primary secondary, that is the only oil boiler you can go 8 years with out cleaning if you have a good chimney {some chimneys 0 to neg draft, from cold or design, it makes for a sooty g series, if you have good uniform stable draft, just change the oil filter and clean the combustion fan blades every year, no need to vacuum, they always look brand new inside, and the riello is bullet proof when done correctly, such a better product than the carlin and beckett, which gt points for simplicity, BUT the are so cheap, you touch the parts on the riello and can tell they are well made.. Even the controls outlast any other I have seen, but when they go $$$$ be ready, lol...

 

[Mike007]

There are lower cost options available in condensing boilers. I recently installed a 40K BTU Lochinvar Cadet for a customer. Considering it's a no-frills boiler, I really liked it. Actual cost was less then a similarly sized direct vent CI boiler utilizing SS vent pipe. There is obviously more labor involved with the condensing boiler, but the customer received a $1000 rebate from the gubbment.

On the going green motive...... I'm all about going green. There's a ton of variables and scenarios. Lets say for arguments sake a modern condensing boiler will last 1/2 as long as a modern CI boiler.

It would be interesting to compare the fuel saved over the life of the boilers vs the natural resources burned in the manufacturing, installation and maintenance of 2 boiler vs 1. I don't know for sure, but the CI could end up being the more green option.

 

[BigGMC]

I've learned a lot here........except what "ci" stands for! Help!

 

[brewchief]

I've learned a lot here........except what "ci" stands for! Help!

Cast iron

Sent from my SM-G900V using Tapatalk

 

[BigGMC]

Cast iron

Sent from my SM-G900V using Tapatalk

Christ! All this time I'm thinking it was "combustion" something..............."incomplete"!? Lol

 

[koditten]

This thread is going back to physics 101.

IM loving it.

 

[jonjon1]

There are lower cost options available in condensing boilers. I recently installed a 40K BTU Lochinvar Cadet for a customer. Considering it's a no-frills boiler, I really liked it. Actual cost was less then a similarly sized direct vent CI boiler utilizing SS vent pipe. There is obviously more labor involved with the condensing boiler, but the customer received a $1000 rebate from the gubbment.

On the going green motive...... I'm all about going green. There's a ton of variables and scenarios. Lets say for arguments sake a modern condensing boiler will last 1/2 as long as a modern CI boiler.

It would be interesting to compare the fuel saved over the life of the boilers vs the natural resources burned in the manufacturing, installation and maintenance of 2 boiler vs 1. I don't know for sure, but the CI could end up being the more green option.

This is true they are getting affordable, BUT I have to say for the cost the Triangle tube is so far ahead of any other on the market in every aspect that is doesn't make sense to go with anything else.

For an inexpensive unit my choice would be the htp EFTC boilers, my cost is about $1980 for the unt and its about the best for the money, still the Triangle tube is only $1000 more and I prefer it.
BUT this is a nice boiler for the money, and if a mod con is the only way to go its the way to go and you need a combi unit the eft 55 is a nice place to start looking..

As far as them costing the same, I am not sold there. Even that inexpensive 55 is $2K, a 55k btu ci boiler can be had for $1280 {I just bought one}. granted the 55 is a combi, but I can add a fphx for $99 and make the ci boiler a combi too.

 

[jonjon1]

Christ! All this time I'm thinking it was "combustion" something..............."incomplete"!? Lol

thats funny...

 

[yeldogt]

I had a Buderus oil w/ indirect -- they can have low return temp water. I did have a bit of trouble with the burner until the flue was fixed.

With low NG prices -- I don't see a huge difference in costs between my two places and others with newer boilers.. For the typical consumer I wonder what the actually fuel savings are? Now ... propane is different .. thats what my new place will have and people are saying some mod cons don't like propane (dirty)?

 

[jonjon1]

I had a Buderus oil w/ indirect -- they can have low return temp water. I did have a bit of trouble with the burner until the flue was fixed.

With low NG prices -- I don't see a huge difference in costs between my two places and others with newer boilers.. For the typical consumer I wonder what the actually fuel savings are? Now ... propane is different .. thats what my new place will have and people are saying some mod cons don't like propane (dirty)?

NOTHING likes propane, lol... Severe cold can stop exposed tank in their tracks, that is never a good thing, but some people are stuck with it.

As far as mod cons, there are certain things you have to do when you install new tanks that no one does, in ground tanks are very few problems...

The trick to lp is Own your tanks...

 

[Vermaraj]

I used to love the gb142 and 162 boilers, aluminum hx or not, if you watch you water level {TDS, PH, ETC} and take care of it, its a 18-20 year boiler easy..

But my cost was around $4K when they came out and that was before they started coming with the low less header...

Here is the issue I seem you are spending $250 a year to maintain the units, have already had 2 service issues inside of 5 years!!! and are happy... Well I wish I had a million of you as customers, lol...

I would be confident in saying, with a house your size {I would love to see some pics, I am a fan of big houses, I was going to build 7500 sq, but my wife put the limit at 4K and we ended up with 4500 and honestly its still too much, we have 4 full baths, 5 bedrooms, and 4 parlors, lol} you would be better off with 3 ci boilers than the wall hungs, simple reason is storage, that energy will not go to waste, 86.5% efficient direct vented ci boilers, made to match your load using an ODR to control the fluid temp and your post would have been similar EXCEPT you would have said you spend $0 every 2 years and have not had a single service issue...

I would LOVE to see some pics of your system if you have a chance...

I have a little trouble following your train of thought.

First, the issues reported were trivial and did not require service visits.
Second, the pressure sensor issue was the subject of a Buderus service bulletin and should have been replaced by the installer.

With respect to the bi-annual cleaning. That is optional on a mod con or CI unit. Maybe the CI unit will last 10 years without cleaning, maybe it will breakdown in the dead of winter. Not a problem for you, your in the business. For me, replacement cost during winter is at least 2x summer installation cost. I live outside NYC and prices are already much higher than average on a good day.

Finally, installing 3 CI boilers hardly seems like a sensible way to save routine maintenance costs. The upfront cost of 2 additional: flues, low water cutoffs, pressure relief valves, circulators, gas lines, etc... Plus the additional pipe fitting and the cost of a control system to load balance and stage the boilers is substantial. Not to mention they are running at a lower efficiency to begin with.

 

[Mike007]

As far as them costing the same, I am not sold there. Even that inexpensive 55 is $2K, a 55k btu ci boiler can be had for $1280 {I just bought one}. granted the 55 is a combi, but I can add a fphx for $99 and make the ci boiler a combi too.

The Lochinvar Cadet was under $1800. A direct vent CI and the required stainless vent system was a little more. I'm sure if I priced a seal combustion direct vent CI (Apples to apples right?) it probably wouldn't even be close. The $1000 in rebates makes it a no brainer.

 

[jonjon1]

The Lochinvar Cadet was under $1800. A direct vent CI and the required stainless vent system was a little more. I'm sure if I priced a seal combustion direct vent CI (Apples to apples right?) it probably wouldn't even be close. The $1000 in rebates makes it a no brainer.

You should look into HTP, lochinvar is not much cheaper and htp is better {in my opinion. Lochinvar has control issues, fan issues, and hx issues, not all of them, but I serviced my share of knights which is a much higher line than the cadet...

It is all hit or miss I guess, but I agree the initial cost is helped by the $1000 rebate although the cost of the unit doesn't have as much to do with the initial install price as it should... Sadly I made less money installing ci biolers than mod cons.. for instance..

Basic 70K BTU ci install, natural, electronic ignition, built in lwco, 1 zone I would get $3150-$3600 depending on the specifics.
$1300 for the boiler, $250 for parts, 2 techs 6 hours profit $1500

Mod con like a solo 60, same thing with 1 zone would get $6900-7500
boiler would cost me $3200, rest of materials $800, labor 6 hours 2 techs be around $3000 in profit..

Them are real prices from my invoice software from last year...

now to be fair that is a basic ci install, a direct vent, with ODR, cold air intake, and primary secondary will add 3 man hours and around $800 to the job in materials, I would also make a bit more profit, a job like that would be about $1800 in profit, but the cost would still only be right around $4000 vs over $7000 for a mod con... So that rebate would be a moot point.

If you are installing it yourself most likely you wont be eligible for rebates or credit, as well as any technical support or warranties... {another trouble with mod cons, they are getting tough on checking who installed the units and voiding warranties, I blame Rinnai for starting that, lol I have seen at least 20 units people installed themselves that failed from nothing that has to do with the install get no support because of self install...

I didn't want to say this but I would be careful with the cadet, I put a lot of weight on the brands I have sold, if the company wont stand behind them I would and will, that takes a lot of faith in something, so when I did bid switches, I installed them in my own home, I ran them through their paces, I asked, I dissected, and tested until I was confident enough to put my name on them... This was learned the hard way, and thats how I got where I am today, I am honest, and stand behind my work no matter what, I had Bosch tell me they wouldn't cover tanklesses, I bit the bullet and bought the customer a different brand for free after 3 years!!! I had Budurus not warranty 3 of them cheap stand up indirects they used to peddle, I replaced them with smart tanks at my own cost one after 4 years, the other were much sooner...

I explained it to the customers, that the company won't stand behind the product but I installed it and I would, and that gets you a customer for life..

before I was bought out the company buying me sent out questioners in email to a random picking of my customers, out of 4900 they picked just under 500... I had no idea they were doing this actually niether did the company buying me it was the investing bank that organised and paid for it...
97% of them were returned with 5 stars in 15 fields, not one customer out of 400 and change gave me less than perfect in 15 fields!!!! I was told by the 3rd party investigating company that was the first time they ever seen that!!! And 97% return was also 12% higher return than any other company ever got, most of the time they get 40% of them back half filled out and more often its the person who was not happy with the work...

So I must have done something right, I give the credit to honesty in topics like this, I will sit down with a customer and tell them the ins and outs of something like this, until I know they understand...

 

[Mike007]

You should look into HTP, lochinvar is not much cheaper and htp is better {in my opinion. Lochinvar has control issues, fan issues, and hx issues, not all of them, but I serviced my share of knights which is a much higher line than the cadet...

It is all hit or miss I guess, but I agree the initial cost is helped by the $1000 rebate although the cost of the unit doesn't have as much to do with the initial install price as it should... Sadly I made less money installing ci biolers than mod cons.. for instance..

Basic 70K BTU ci install, natural, electronic ignition, built in lwco, 1 zone I would get $3150-$3600 depending on the specifics.
$1300 for the boiler, $250 for parts, 2 techs 6 hours profit $1500

Mod con like a solo 60, same thing with 1 zone would get $6900-7500
boiler would cost me $3200, rest of materials $800, labor 6 hours 2 techs be around $3000 in profit..

Them are real prices from my invoice software from last year...

now to be fair that is a basic ci install, a direct vent, with ODR, cold air intake, and primary secondary will add 3 man hours and around $800 to the job in materials, I would also make a bit more profit, a job like that would be about $1800 in profit, but the cost would still only be right around $4000 vs over $7000 for a mod con... So that rebate would be a moot point.

If you are installing it yourself most likely you wont be eligible for rebates or credit, as well as any technical support or warranties... {another trouble with mod cons, they are getting tough on checking who installed the units and voiding warranties, I blame Rinnai for starting that, lol I have seen at least 20 units people installed themselves that failed from nothing that has to do with the install get no support because of self install...

If you are not referencing a sealed combustion direct vent CI boiler, you are not comparing apples to apples.

 

[jonjon1]

If you are not referencing a sealed combustion direct vent CI boiler, you are not comparing apples to apples.

I did both...

me- a direct vent, with ODR, cold air intake, and primary secondary will add 3 man hours and around $800 to the job in materials, I would also make a bit more profit, a job like that would be about $1800 in profit, but the cost would still only be right around $4000 vs over $7000 for a mod con...

 

[Radix2]

Jon - how are you recommending using the ODR with a CI boiler - sounds like boiler set point? Also, what method to limit temps into pex/slab?

 

[Mike007]

I did both...

me- a direct vent, with ODR, cold air intake, and primary secondary will add 3 man hours and around $800 to the job in materials, I would also make a bit more profit, a job like that would be about $1800 in profit, but the cost would still only be right around $4000 vs over $7000 for a mod con...

The point I'm making, I cannot get a seal combustion CI boiler and SS vent for less then I paid for the Lochinvar Cadet. In fact, for the hell of it I just priced the CI seal combustion boiler from my supplier, just the boiler alone is slightly more expensive then the Cadet.

 

[jonjon1]

The point I'm making, I cannot get a seal combustion CI boiler and SS vent for less then I paid for the Lochinvar Cadet. In fact, for the hell of it I just priced the CI seal combustion boiler from my supplier, just the boiler alone is slightly more expensive then the Cadet.

I don't feel like calling my supplier but I believe the cadets are around $1850 {I don't have on in my system to see what I last paid}, but I did last pay $1480 for a sealed ci boiler, and I think it vented up over and out so maybe 3 90s, 2 5ft's, and 1 12", what ever it was the total venting cost was $211, thats ss double gasket with a concentric {they call them that but they exit separately} termination.

See I dont consider the venting to cost more because the mod cons don't vent for free, lol With all the things I hear {a lot of talk a few studies in the works} about PVC, CPVC, etc causing premature heat exchanger failure, I have been using polypro for a couple years now... Don't get me wrong I vented my share in PVC, but as soon as I heard the issues and suspicion of the pvc rotting out heat exchangers {chlorine washback} I switched, its cheap insurance, I mean I am charging the customer so I may as well give them something done right. There is no cheap way to vent, you can not go to home depot and use sewerage PVC to vent a boiler, you need to use pressure combustible venting approved pvc, not exactly free...

Plus the SS and poly pro is easier, cleaner, looks better, and will last longer {even though all of them will last a million years, lol...}...

I am not sure what brands you are using for ci, but williamson is the cheapest, slant fin and wm are close though... Plus if you are dealing with a company that doesnt stock them I am sure it will be more...

Not everyone has the same business and work style as me, actually I am almost alone, lol.. You see the math above, I make double installing a mod con and talk my customers out of it, I have yet to have someone call me and say they aren't happy with their ci boiler, but I have had a few not so happy with their mod cons, and you know what my insurance is? Everytime I sell one, I have a conversation similar to the one we are having right now, so they normally wont squawk too much because they don't want to hear the "I TOLD YOU SO", lol....

Anyway, I know what the scoop is, I have done this long enough and invested enough of my life into it to know the differences, I am not tlaking customers out of spending more money for less work for no reason, be serious, I am still in this to make money. I am being honest, I can sleep well knowing I do honest work and feel confident enough aobut how open minded I was when I made the decision and learned how I feel about mod cons...

Since I am here I will touch on another subject, the "correct" way I feel high efficiency should have been done....

I think it should have been done with ci, similar to wm gv90+ {not a perfect boiler but not bad}, you use a multi pass ci boiler as your primary and then a ss boiler as a secondary, pass the exhuast through it until there is no energy left in it and vent it with plastic... THey could make modular units that can be used either way, they can make retrofits for certain already in use and production boilers, etc... You know why they didn't? I do...

 

[jonjon1]

Jon - how are you recommending using the ODR with a CI boiler - sounds like boiler set point? Also, what method to limit temps into pex/slab?

OK, so heres how i do this, first the odr, is simple its all built in the control you choose. I like the hydro level so I will explain how that works when you install the os100 with it...

OK, so most resets work on a curve, which is fine BUT if you are a tech you will know that if you set that curve wrong, on a cold day the customer is not going to be happy when there house wont break 61, lol...

The hydrolevel will not let that happen because it is active control, you set you high and low limits, then you set a "reset ratio", so say you select 3.5, that means for every single degree the outdoor temperature rises the control will lower your boilers high limit by 3.5 degrees and the opposite for each degree drop it will raise the hl 3.5 degrees.
Now what I like about it {and I like this feature about how a lot of controls work like the bpa3 multi boiler control which I mentioned earlier}, it has a catch up feature, so say the call for heat isnt satisfied in x amount of time, it will raise the temp a bit, then more time goes by it will raise it again until it catches up. This is useful because sometimes things change, like you are bringing groceries in or open a window to clear some smoke from a burnt garlic bread, etc...


Now for controlling the temp to the floor...

You can use mixing valves, but I don't like this method myself, i have done plenty of floors with mixers and they work great, but there is a better way...

I use a Flat plate heat exchanger {fphx}, this works by mixing the energy between 2 fluids but never mixing the fluids. There are a few reasons I do this but the 2 main ones are..

1- I hate mixing valves, they mess with my flow rates, cost alot of money, need servicing, etc...

2- I don't like putting glycol in my boiler, it inhibits convection, lowers efficiency, and is corrosive.... Should be changed every 4-5 years, I am an animal when it comes to proper fluids in my water batteries, I want the right PH no matter what, i will fill it with poland springs if I can't get the right ph or tds on sight!!!!


So back to how the FPHX works, you have 4 taps, 2 of the taps go to your boiler like a zone of heat, the other 2 go to your manifolds to disperse the heated transfer fluids to your emitters...

So, one down sid eof a fphx is it can not transfer 100% of its energy, that is impossible to do, so if you put 140 degree water in, your slave side will only show 137 degrees out, I over size them and can easily show a 1.5% loss...

So, now how do you control this?

Simple, 4000 series aquastat, or get an a418 digital one if you want to be fancy, they are $58...

you install the aqustat on your slave side and when it is satisfied you boiler side will stop circulating hot fluid into the fphx... Then your emitters will take the energy out of that fluid and return it to the fphx which will cool down and call for more fluid on the boiler side, which will come from the ci's boiler storage....


Done right, this will rival how a mod con works with radiant!!!! May not be 100% as good as turning down the burner, but it is all over 99.5% and if your mod con needs a buffer tank, its is better than a mod con!!!!!

I am not making this stuff up, lol.. This is the BEST way to heat a floor, BUT people don't hear about it because 1- contractors don't know about it themselves and 2- the ones that do could care less and they do it the way they want....

Some of the problem with this industry is the words "Plumbing and Heating", we have a lot of plumbers out there installing heaitng systems, more than heating guys actually!!! We used to call Burnhams "the plumbers boiler" because it came almost all built, they even came with the service switch mounted, lol... Some plumbers have no business near a boiler, not all , but some. Think of it this way, a plumber that can do good boiler work, would not be fixing your toilet for $60 an hour when he can be making $160 an hour fixing your boiler. Most of them can get through an install {nothing fancy} but when faced with service are lost. not all, but a good amount, of the ones around here at least...
OK that rant is over, sorry...


back to the topic, Mod con -bad, cast iron - good

 

[jonjon1]

WOW, I just looked through this thread, I put more info in here than I would have given in one my classes!!!! This is free education time...

heres a system I just drew of how a system would look with a fphx and radiant manifold, now I obviously left of the 911s, prv, feed bridge, purge stations, etc.. But this is the basic design, your boiler water goes in and out of the fphx, as does the manifold, you have to do the math but you set your boiler controls high limit at say 115 degrees, then you set your radiant aquastat at what ever you want your floor temp to be - say 110. The room thermostat will call the ch circulator to circulate through the floor, when the fphx gets cold it will call in the boiler circulator which will have a full battery of 115 degree water in it...

you can see how this can be handy, you can use antifreeze with out having it in your boiler, you can use a higher boiler temp and power an indirect water heater, zone of baseboard, hydro coil, etc...

 

[Radix2]

I appreciate your efforts, but I am finding your design details a bit unbelievable...

What CI boiler allows operation at condensing (<130-140F) temperatures(..much less 115 or something) without causing catastrophic corrosion ? With a normal CI boiler running at 180, and a delta of 20, the return water is already down to 160...dropping from 180 to 160 (140 return) is not going to be worth anything efficiency wise. (your recommended W-M cgi has a "do not allow return temps below 130F" on about every page !)

Ok, so the idea on the HX is you will control the boiler pump with the HX temp ? The HX temp is going to be the same as the radiant loop if the CH pump alone is running (the HX has very little mass/volume so without the boiler running it is going straight to CH return temp in seconds)... so the boiler pump will always come on immediately if the CH pump is running ... so why not just do that. ...You seem to be copying the the idea of a buffer tank loop without the "buffer" - the boiler pump has to be running if the radiant loop is running as drawn - which also means that there is no real protection for the radiant floor against high boiler temperatures (or the boiler against low radiant temps)- you either need a buffer tank that can be controlled to a safe temperature via the boiler circulator or you need a tempering valve to limit HX temperature, or you need primary/secondary plumbing with bypass valves as it is normally recommended....?

Here is the relevant graph showing the efficiency gains possible with ODR targeting boiler temps- there is very little to be had above condensing temperatures from a boiler efficiency standpoint, the benefit is to go to very low (<100F) boiler temps when the outside temp allows it - something not possible with CI/non-condensing boilers.

To be honest, in evaluating what you are writing, it looks like you only understand/install mod-cons - since your "designs" would work for them, while being ill suited to CI boilers.

 

[jonjon1]

I appreciate your efforts, but I am finding your design details a bit unbelievable...

What CI boiler allows operation at condensing (<130-140F) temperatures(..much less 115 or something) without causing catastrophic corrosion ? With a normal CI boiler running at 180, and a delta of 20, the return water is already down to 160...dropping from 180 to 160 (140 return) is not going to be worth anything efficiency wise. (your recommended W-M cgi has a "do not allow return temps below 130F" on about every page !)

Ok, so the idea on the HX is you will control the boiler pump with the HX temp ? The HX temp is going to be the same as the radiant loop if the CH pump alone is running (the HX has very little mass/volume so without the boiler running it is going straight to CH return temp in seconds)... so the boiler pump will always come on immediately if the CH pump is running ... so why not just do that. ...You seem to be copying the the idea of a buffer tank loop without the "buffer" - the boiler pump has to be running if the radiant loop is running as drawn - which also means that there is no real protection for the radiant floor against high boiler temperatures (or the boiler against low radiant temps)- you either need a buffer tank that can be controlled to a safe temperature via the boiler circulator or you need a tempering valve to limit HX temperature, or you need primary/secondary plumbing with bypass valves as it is normally recommended....?

Here is the relevant graph showing the efficiency gains possible with ODR targeting boiler temps- there is very little to be had above condensing temperatures from a boiler efficiency standpoint, the benefit is to go to very low (<100F) boiler temps when the outside temp allows it - something not possible with CI/non-condensing boilers.

To be honest, in evaluating what you are writing, it looks like you only understand/install mod-cons - since your "designs" would work for them, while being ill suited to CI boilers.

OK, first the operating temp and corrosion..

I agree Oil cast iron boilers should be ran 130*, I have seen them run a bit less with out condensating, but 130-140 is ideal for them.

I have installed this many times, and have enough time to see it work for years and see now condensation or corrosion. I have talked to reps at wm and they agree, the boilers do not like cold returns with hot supplies, so 190 degree supply with a 125 degree return will shorten that boilers life. All installs differ a bit but the burner will burn off the condensation with most temps 115+ {natural gas flame}, I have had some condensate and raised the boiler temp until it stopped, never a problem after that, and never all the way to 130... That is their safe number...

Now the fphx has to be over sized and you are correct the boiler pump will run almost as much as the ch pump, but the pumps are controlled by delta so the ch pump slows to a crawl right after it starts running {they ramp on start up but slow right down}.

So what happens is the boiler having a tight hl to ll say 5 degrees {secondary aquastat controlled depending on your primary stat}, will always keep your temperature, it takes a LONG time for the radiant systems to take the energy out {once it is heated}, so say you set you boiler HL to 120, {the boiler will over shoot that a bit, because the ci keeps heating after the burner shuts off}, now your boiler pump will run {and slow} until the ch heat pump needs more heat, then it will start again for a short time and slow, your ch temps will be uniform but your boiler side will look like its hunting within 5 degrees...

Its hard to explain with out you seeing it all work, but it works very well, you need to watch piping size and have the flow rates correct, but its pretty simple.

This drawing doesn't show the primary secondary piping on the ch side , I just dumped it into a single manifold, you won't run an entire boiler into a single manifold, you will have ps piping on the ch side with another pump, each manifold will have its own pump and closely spaced tees.

What you have to understand is once the radiant loops are warm, you control the delta with the pumps, and the hx holds more energy than you think, I am not talking about using a 5 plate 3x10, you will use a fphx with some volume, for instance I have a small sidewalk melt system at a customers house that has a 20 plate 5x12, it works perfect, once the floor is heated on a 10 degree day I watched the ch pump run {doesnt shut off} and the boiler pump runs about 20 minutes an hour...

So if done properly you wont condensate, most ci boilers sitting on top of a heated floor or in a warm room, with direct vent and outdoor intake will not condense as fast as you think. I know its not the normal way to do this, but it works, I know a bunch of guys that have done it and I have done it a bunch of times. These systems are out there for years with no corrosion issues. I have seen some boilers condensate more than the burner can burn off around 110 degrees, but you raise the hl a bit and it goes away.


1 more thing to keep in mind is you are not rotting out a ci boiler in 10 years, I seen a budurus boiler used in a commercial building {heated a HUGE indirect for washing potatoes, worst smell I ever smelt in my life}, that had the hl set at 125 {who ever installed it never put an astat on the indirect just ran the pump non stop and hl at 125}, the boiler was leaking, but it was 20 years old, ran non stop for 20 years!!! It had a white soot all inside the chambers, was leaking between the rear section, but still lasted almost 20 years...

Plus if done correctly you wont condensate. I have had this conversation a bunch of times, the owner of the supply house I was buying from came out and looked over a job, he then started promoting the method once he seen it in action...

The best way I can explain this is the boiler acts like a large storage tank and the boiler circulator acts like a short cycling burner, the boiler stores the energy and the bc sends to as it is needed cycling on and off slowing down when there is a longer cycle...

 

[pseudorealityx]

To clarify...

You want 2 boilers so you can modulate
You need 3 pumps? (boiler circulator, primary loop, secondary loop)
2 expansion tanks
1 "oversized" flat plate heat exchanger
2 sets of stainless flues
controls so it's on the bleeding edge of condensing the flue gases

And you're saying that package is MORE cost effective than a condensing boiler setup?

 

[yeldogt]

My Buderus CI gas boiler runs with low return temp water. In the spring and fall I can tell you it is not running at 130 water. That's what they are designed to do.

I had thee WM boilers -- stone house in Chestnut Hill PA (big). Two were staged -- how do you keep the USA style CI boilers from getting too cold return water when staged. I bought and sold the house with the same boilers -- owned it about 10 years. never touched it.

 

[Radix2]

Why risk corrosion ? The efficiency benefit is almost nothing. Seems like a bad bet, and if the HX shows corrosion failure, no warranty. Please explain.


I have a boiler in my lake house that was installed in 1954 ( Kalamazoo). Never gets shut off, holds 180 in its belly, converted from oil to gas back in the early 70s... I am doing some renovation and thinking about a new boiler...this one is super inefficient, but spends much of the time holding the house at 55... Somehow I have a feeling that this one would still outlast something new...

Not feeling it though to run equipment outside of its design limits for little to no benefit.

 

[BigNuge]

This is why CI has no place with radiant. If you already have radiant tubing inside the cement floor, condensing is the way to go...no doubt.

Your Kalamazoo boiler was built when efficiency was of no matter. The same with a car of that age..big, heavy & sturdy. Today we need to utilize energy much more efficiently. Going green isn't just a fad anymore. Energy prices only go up, hardly ever go down. And when they go down it is for a short period of time.

 

[jvitez]

My in-laws were doing this exact financial exercise a few years ago. They're 1945 small 1.5 story house still has a 1960's conventional NG forced air furnace. They looked at electively replacing it with a new high efficiency model, but when they ran the numbers their savings were small because of the small heat load, even though they live in a cold prairie climate. They decided to keep using their old furnace until it becomes irreparable. They have it serviced every couple of years, and it keeps chugging along: old, big, strong, reliable, and inefficient. Not an unreasonable decision for their particular circumstance.

The differing opinions on this thread seem to come down to where the maximum benefit is being placed, whether on operating cost, capital cost, reliability, durability, or ROI. The right answer assesses all of these, and differs depending on the weight placed on each.

 

[BigGMC]

What would be the indication of condensing in a CI unit? Can you see it when looking into the firing chamber?

 

[Jackfre]

What would be the indication of condensing in a CI unit? Can you see it when looking into the firing chamber?

No you can't see it in the burner. Corrosion is an insidious process. The way you see it is you end up with a puddle on the floor at which time you go s***, oh dear!

JJ, if WM is saying 130 is the safe temp I would still be reluctant to run it at that temp. I think I'd install a mixing device (tempering valve?) on the return to increase the return at the boiler to 140. I think at 130 you have little margin for error. Given the inherent oversizing of CI boilers the shoulder seasons would worry me due to short cycles.

 

[jonjon1]

To clarify...

You want 2 boilers so you can modulate
You need 3 pumps? (boiler circulator, primary loop, secondary loop)
2 expansion tanks
1 "oversized" flat plate heat exchanger
2 sets of stainless flues
controls so it's on the bleeding edge of condensing the flue gases

And you're saying that package is MORE cost effective than a condensing boiler setup?

Yes, do the math, even a pair of 110K BTU slant fins at $2000 each is $4000, figure $380 to vent them {you can do it cheaper} if there are a couple of bends, 1 heat exchanger http://www.supplyhouse.com/FlatPlate-FG5X12-24-24-plate-1-Thread-40-GPM-Heat-Exchanger-5-x-12 I get them for $500 even, and that is a name brand FL 5 series, very nice unit, you can get ebay imports for about 1/2 of that and I have seen them last 10 years myself on an outdoor wood stove!!!
and the controls will run you another $600..

So do the math $4000+380+500 +600= $5500 an alpine 229 is $6000 JUST FOR THE BOILER!!!! You still need to pipe it and vent it, and as I said the venting for a mod con isn't free, maybe some have missed this in my posts, BUT you should at minimum use poly pro so you don't have any corrosion issues with your mod cons.
As far as the pumps go delta t pumps are only 160 each in under $500 for 3 of them {WHICH YOU WILL NEED FOR A MOD CON ALSO, THIS ISNT EXTRA}...


Heres the thing, if you are pro mod con for properties with loads under 400K BTU, you must have a reason, and must be happy with it, but there is no way you are going to convince me or defy the logic of these FACTS.

MOD CONS are going to be more expensive to install.
NOT last as long as a Cast Iron Boiler
Need an annual service
Have many more needed repairs and at a much higher cost
And only save you a maximum of 10% off of your heating bills before all of the above costs!!!

BUT they will...
Look pretty {although if you are looking for impressive a line of 3 small boilers piped correctly interests me a lot more}
take up very little room
and can hang on the wall...

If thats what you are looking for pay the cost, its that simple, I am not posting in here to convince myself, my hvac ideas have made it so I could sell my business in my mid 30's and retire before most people have bought their first home!!!!
I am not trying to convince someone who has already bought a mod con, I wouldn't want anyone trying to do that to me if I already spent money I can't get back, and I don't want you cursing me in 10 years when the unit needs a $1200 board that is no longer in production...
And I am not trying to convince the pro's in here, you need to sell what makes you money, I was fortunate enough to be able to see past the money that mod cons put in my mattress and want the customer to get the best "long term" investment in their basement, its why my business grew how it did...

It is as simple as that, think of it this way- I am a pro, licensed and insured, owned my own hvac business as well as over 35 investment properties that I carefully monitored every aspect of cost associated with them personally. I can PROMISE this is what will happen...

You install a Mod con in a property with energy costs of under $4-5K per year and you will lose money in the long run, as well as be without heat a few times and have more non sense in your life that you need...
The boiler will be changed twice to the single ci boiler.
And your annual savings will NOT pay for the service the unit needs over its life, never mind the fact that you will need 2 of them to 1 ci boiler...


IF you can not see the dis-value in that, than I can offer you NO help...

 

[jonjon1]

My Buderus CI gas boiler runs with low return temp water. In the spring and fall I can tell you it is not running at 130 water. That's what they are designed to do.

I had thee WM boilers -- stone house in Chestnut Hill PA (big). Two were staged -- how do you keep the USA style CI boilers from getting too cold return water when staged. I bought and sold the house with the same boilers -- owned it about 10 years. never touched it.

This is what you will see accross the board, stories like this "I had a ci boiler for 18 years, never touched it" I had that old boiler for 42 years, changed a circulator once, never had it even cleaned", etc... Then you look at the mod con posts, just in this thread "I have had it 5 years only paid $500 to clean it three times, changed a $100 part myself, and another $250 for a different service, and.... etc etc etc" Plus the countless problems I have personally seen, and a fast google search with the boiler you are choosing and the word "problem" will return more results than you will want to sift through...