NG Condensing Boilers for closed loop radiant floor

[jonjon1]

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.

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.

OK, first and again, as far as condensation goes, the 130 is nothing to be scared of, HOW MANY GAS WATER HEATERS HAVE YOU SEEN SET TO 120 AND NOT DRIPPING? I have seen HUNDREDS of them, they normally last longer, lol since they are not cooking out the sediment {not safe for legionella though, but never seen that first hand so can't comment on it either}...

It is easy enough to test for you will know when the boiler is condensing, believe me!!!!

As far as warranty goes, NO... I have NEVER had a company want a cast iron boiler back for a warranty claim NEVER, I have NEVER had them want to come out and look at it----- NEVER.... So if it fails do to condensation {care to guess how many times I have seen this happen? yup NEVER} you will still get the warranty...

I see A LOT of "reaching" here guys...

Truth is ci will last longer and be cheaper to run, just admit it, it will feel good, I promise...

I admit the mod con will give you 10% combustion efficiency {and it really won't even do that, but I have no problem giving it the benefit of the doubt}.....


One more time to touch on condensation and setup.

The glycol in your system not having the fphx will do MUCH more damage than any amount of condensation. I have brought boilers to condensation {NOT EASY TO DO WITH OUT SLOWING DOWN THE EXHAUST FAN AND TRICKING THE PRESSURE SENSOR EVEN WHEN FULL OF 120 DEGREE WATER} and its not going to happen with a uniform boiler temp, if you have 120 front to back and control your flow rates well, you will not condensate, your burners will have a nice dry flue way to heat up...

I have seen condensation in boilers running 180 HL and 130* returns, that is very possible and will happen fast, that is not what I am talking about here. I have experience with this exact setup, I have installed and setup more of them then some techs have done systems in total!!!

 

[jonjon1]

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.

I combustion analyzer will show condensation instantly, someone with experience will be able to feel it in the flue pipe of a natural boiler. I can hear it because I am a boiler whisperer, lol. If you have ever started up a cold boiler you hear that dripping sound, drip hiss, drip hiss for the first 20 minutes, thats condensation. This is common when starting a new boiler, you fill it with 50 degree water, and then start the burners she will condense, but it doesn't hurt anything.

We are not talking about cold returns {WHICH WILL MAKE A BOILER CONDENSE}, we are talking about a uniform boiler temp, with MAYBE a 2 degree difference from supply and return!!! The boiler WILL NOT CONDENSE, lol.. I feel like a broken record...

BUT as RADIX said, if you are scared about it, its just a matter of turning the dial and going up a few degrees... I like to run the coldest temp i can, and I do that on start up, I get the entire system to temperature, then do my combustion test, that tells me everything I need to know. I use a testo analyzer and a flir thermal imaging camera, that allows me to see everything that is going on.

Incoming combustion air temps, flue temps, boiler temps, boiler jacket losses, burner temps, etc etc etc... I can see condensation instantly, there is no sneaky condensation that you can not see, lol..

 

[Mike007]

Condensation doesn't only happen in the boiler. I have a customer who insists on being his own outdoor reset. He's constantly adjusting the boiler temp with the outdoor weather. Despite my warnings, he was commonly setting it as low as 135*. The chimney is literally falling off the house now in pieces. I took some pictures of it. I will post them later.

 

[jonjon1]

Condensation doesn't only happen in the boiler. I have a customer who insists on being his own outdoor reset. He's constantly adjusting the boiler temp with the outdoor weather. Despite my warnings, he was commonly setting it as low as 135*. The chimney is literally falling off the house now in pieces. I took some pictures of it. I will post them later.

Well that is a different issue, we are talking about direct vent units, in a natural draft atmosphere {which I don't advocate} yes you can run into premature chimney deterioration with a properly running gas boiler running at 190 degrees. I do not recommend running gas appliances in a chimney with out a SS liner, and that liner should be insulated and have a moisture trap of some sort in it to prevent 30ft of condensation from dripping into your boiler. We will leave that conversation for another thread, I am having enough trouble staying on track with just mod con vs ci, lol....


Since you brought up this customer, snap a picture of the inside of his flue chamber, even though that is a chimney vented system and doesn't apply to what we are talking about here, unless the chimney is pitched back to the HX, I will bet the chamber is CLEAN... Maybe just some white flakes here and there? Even in some of the worst accidental condensing boilers I have seen they are not rotting away Pit takes a long time}...

PS, I am not advocating making a ci boiler condense {unless its a gv90+}, and with the designs I am speaking of, you will NOT condense when set up properly, BUT I am curious as to what you see in there...

 

[pseudorealityx]

We are not talking about cold returns {WHICH WILL MAKE A BOILER CONDENSE}, we are talking about a uniform boiler temp, with MAYBE a 2 degree difference from supply and return!!! The boiler WILL NOT CONDENSE, lol.. I feel like a broken record...

Maybe you could stop telling us how awesome your early retirement is, and actually explain what you're talking about... For instance, what is this 2 degree delta T nonsense?

 

[Radix2]

OK, first and again, as far as condensation goes, the 130 is nothing to be scared of, HOW MANY GAS WATER HEATERS HAVE YOU SEEN SET TO 120 AND NOT DRIPPING? I have seen HUNDREDS of them, they normally last longer, lol since they are not cooking out the sediment {not safe for legionella though, but never seen that first hand so can't comment on it either}...

!

But that is not the question - I'm asking why?

Why try to run at these temperatures at all - are you doing it to get 1 or2% efficiency gain ? Or trying to avoid putting in hardware to protect the floor from high temps ?

You are recommending going against the manufacturers requirements - so what is the benefit?

And I can't imagine any way that a HX with a stratification of 180-130 could possibly condense more than a uniform 130 - after all, it is just a product of cold metal to flame contact..... And this whole uniform thing raises the question of how your boiler is supposed to work - after all, the delta t of the radiation has to equal the delta t of the boiler - if you drop 20 or 30 in the floor, your boiler has to put it back .... So 130 in is 150,160 out minimum.

 

[yeldogt]

I did radiant for the first time in the late 80's. I was just trying to warm a couple of floors and put in heated towel bars -- I had been in Europe for 6 months and wanted it here. It was almost impossible to get anyone to do it, had to ship most of the stuff from Germany. When I did it a few years later Buderus was new in the USA ... A guy named Lou .. basically faxed me designs ... most of the manuals were typed out translations from German. All the boilers were CI and all designed for low return water. Even running panel radiators in one house will result in low water part of the heating season. It's not an issue with CI -- it's an issue with the type of CI and the design of the combustion chamber -- both my CI boilers have SS liners.

I just spent yesterday afternoon speaking with an HVAC guy for my new build -- he likes WM wall hung boilers ... Who knows. I'm most likely going with two Carrier Infinity HP with furnaces or coils. I think this is an interesting thread ... If I had NG available what could be my savings trying to get an extra 10% from 1.5k a year bills going with a boiler that is 3x the price. Even if NG doubles to 6 from current 3 .. still not a lot. It's not going back to 12 of 2008.

 

[jonjon1]

But that is not the question - I'm asking why?

Why try to run at these temperatures at all - are you doing it to get 1 or2% efficiency gain ? Or trying to avoid putting in hardware to protect the floor from high temps ?

You are recommending going against the manufacturers requirements - so what is the benefit?

And I can't imagine any way that a HX with a stratification of 180-130 could possibly condense more than a uniform 130 - after all, it is just a product of cold metal to flame contact..... And this whole uniform thing raises the question of how your boiler is supposed to work - after all, the delta t of the radiation has to equal the delta t of the boiler - if you drop 20 or 30 in the floor, your boiler has to put it back .... So 130 in is 150,160 out minimum.

You don't have to run the cooler temps, I am just stating that it is not going to be the end of the world, if someone does, I have done it many times and have no condensation issues. Running the lower temps will give you better performance than running say 160HL, the FPHX's output will be more uniform since the circulator will run longer with 130 degree water for 160...

As far as setting the floors delta to 30, that will not translate directly to the other side of the heat exchanger, when you pipe both sides primary secondary {I didn't do this in the picture not to confuse people, not everyone can grasp the concept of 2 tees close together and I thought it would make more questions that the picture was worth} you will have really close supply and return temps.

Boilers like uniform temps front to back, burnham had a few issues with their boilers not being able to handle more than a 30 degree delta. Hot supply with cold returns is not good for any cast iron boiler, some will take it better than others {buderus does it well}...

I am throwing a lot of design ideas out here, and mixing them all together here and there, having a specific system to design would be much easier, and knowing what exactly we were trying to accomplish, I was trying to touch on everything a bit...

Knowing the exact heat loss and amount of element could get us a real world boiler part number, hx size, and some flow rates. Then we could figure what will work and what to use in a specific system. This thread is just a bunch of ideas thrown together to show how versatile a Ci boiler can be...


So to answer "why?" efficiency, easier on the system, longer bc run times, closer floor temps swings, etc...

 

[jonjon1]

I did radiant for the first time in the late 80's. I was just trying to warm a couple of floors and put in heated towel bars -- I had been in Europe for 6 months and wanted it here. It was almost impossible to get anyone to do it, had to ship most of the stuff from Germany. When I did it a few years later Buderus was new in the USA ... A guy named Lou .. basically faxed me designs ... most of the manuals were typed out translations from German. All the boilers were CI and all designed for low return water. Even running panel radiators in one house will result in low water part of the heating season. It's not an issue with CI -- it's an issue with the type of CI and the design of the combustion chamber -- both my CI boilers have SS liners.

I just spent yesterday afternoon speaking with an HVAC guy for my new build -- he likes WM wall hung boilers ... Who knows. I'm most likely going with two Carrier Infinity HP with furnaces or coils. I think this is an interesting thread ... If I had NG available what could be my savings trying to get an extra 10% from 1.5k a year bills going with a boiler that is 3x the price. Even if NG doubles to 6 from current 3 .. still not a lot. It's not going back to 12 of 2008.

You would get no savings from radiant/mod con to a well done hp/ 98% furnace/ac system. Just comfort and less expensive install.

radiant is a nice heat, comfortable uniform and warm in all the right places, can't argue with that...
But when people ask me about comfort and budget I always explain how a/c, filtration, humidity control, and heat for less than the cost of just heat can be more comfortable...

I installed a lot of Armstrong 97mv's and a few Lennox 98v's, both very nice units {I prefer them to trane and carrier for service and support reasons}...

You can buy an slp98v {98% efficient variable speed gas furnace}, with a case matched coil, and an xp25 heatpump, with all the goodies, electrostatic air filtering systems, steam humidification system, UV light system, matching lenox touch screen wifi thermostats, etc etc etc... For a lot less than just a basic radiant system would cost you, you would have a system that will last longer, be easier to use, easier to install, give you a/c and all the other bells and whistles and cost less to run than a radiant system...

I hat eto admit it but forced air is the way to go in all aspects, granted radiant has the comfort, BUT if I had to choose between radiant heat or heat and a/c I would take the heat and ac everytime...

 

[pseudorealityx]

For a lot less than just a basic radiant system would cost you, you would have a system that will last longer, be easier to use, easier to install, give you a/c and all the other bells and whistles and cost less to run than a radiant system...

The entire thread you've been shouting that ci boilers are going to last 40+ years with zero maintenance. Now a "variable flow" furnace with touch screen wifi thermostat is going to last longer? I thought all those electronics were the expensive failures on boilers????

I am so confused.

 

[mygarageone]

From what I have read about john Jon , he has put in more equipment in his short 15 yrs , than all of us combined. I thinkith there's some smoke there some where.
According to him he has installed 1000's and thousands of pc's of equipment and it seems like he knows everything there is to know. Sorry but this has been comming a while I just held my tongue.

I have been at this stuff for well into 40 yrs and have yet to install or learn anything compaired to him.

 

[jonjon1]

The entire thread you've been shouting that ci boilers are going to last 40+ years with zero maintenance. Now a "variable flow" furnace with touch screen wifi thermostat is going to last longer? I thought all those electronics were the expensive failures on boilers????

I am so confused.

Sorry you are confused, yes a furnace is about the longest lasting device you can buy, the new high efficiency series of furnaces coming out are pretty impressive, because they are running so cool and using the condensation to their benefit, their heat exchangers aren't a huge issue as older 80+ units that tended to have hot spots and material issues...

You can expect to see just as long if not longer life of a furnace than a boiler. And the electronics these furnaces have are pretty basic, I had to buy a board for a 97% furnace not too long ago {unit under water} it was $139-, now some brands are more expensive but they seem to have the 90+ furnaces pretty well engineered now...

Now, I am not talking about the $65 90+'s, while they are fine, you can expect 20-25 years out of them, some brands less... I am talking about the high end modulating variable speed furnaces. Even the new ecm vs motors they are using are seeming to be bullet proof, they don't get hot, they need no service, just awesome stuff..


ALSO keep in mind these furnaces do not need annual service like a lot of the mod con boilers do, its a different animal...

I have said a few times in here that I prefer a furnace and heatpump to any other type of heat, thats not a secret. And I am not condemning mod cons, they are getting there for sure, the tt prestige is a great unit, I am just trying to let people know what to expect for savings...

I watched the entire high efficiency wave come to a head, the country was looking to save fuel because it was getting expensive, when oil was 1.09 no one cared, "over size the boiler in the odd case it gets to -55 or I feel like opening all my windows, who cares, don't by energy rated windows, oils is cheap", when fuel went up we scurried trying to bring in equipment other countries had been using for a while, tankless water heaters, mod cons, etc found a place in the us market that was not there a few years earlier...

I feel like it has been taken advantage of, the customers are getting brainwashed into thinking they are going to save money when in the need it will cost you more, no matter what...

Now don't get me wrong I like making money, but I want to be able to sleep at night, I want to walk in your house and say "this unit will save you $260 a year, you should have it serviced every year, BUT every 2 will be OK if you don't use it for dhw, I expect it to last about 15 years, but you may get 20, its $10K, now for $5K I can install this unit, it will cost $260 more to run every year, but it should last 30-40 years, you wont have to do anything but service it if it breaks, expect 10 years with no service costs at all}..

There are safeties in place that stop premature failure of heating devices now, low water cut offs on FHW boilers, double high limits on furnaces, better heat exchanger design, better materials, better motors, etc...

Pseudo, What are you in the market to have installed, maybe I can point you in the right direction with less confusion...

 

[pseudorealityx]

From what I have read about john Jon , he has put in more equipment in his short 15 yrs , than all of us combined. I thinkith there's some smoke there some where.
According to him he has installed 1000's and thousands of pc's of equipment and it seems like he knows everything there is to know. Sorry but this has been comming a while I just held my tongue.

I have been at this stuff for well into 40 yrs and have yet to install or learn anything compaired to him.

If you (and me) had learned more, you (we) would already be retired.

You also get double points when you install 2 boilers instead of one to reduce maintenance costs.

 

[jonjon1]

From what I have read about john Jon , he has put in more equipment in his short 15 yrs , than all of us combined. I thinkith there's some smoke there some where.
According to him he has installed 1000's and thousands of pc's of equipment and it seems like he knows everything there is to know. Sorry but this has been comming a while I just held my tongue.

I have been at this stuff for well into 40 yrs and have yet to install or learn anything compaired to him.

WOW you are awesome, I am a millionaire inside of 20 years at it and you have 40 in and are what, still working? Maybe it has something to do with you not knowing how to spell compared and coming {in a system with spell check}, I had a bunch of techs with 30-40 years in the field working for me, I was giving them $21.50 an hour max because the first 20 years no longer apply, Good for you though...

If you (and me) had learned more, you (we) would already be retired.

You also get double points when you install 2 boilers instead of one to reduce maintenance costs.

Don't read my posts if you don't like them and don't hold your tongue for my sake, go ahead and speak your mind, its free...

I don't get anything out of posting this info, I was just trying to help shed some light, and offer a different take on the topic that the someone may have not seen or heard about, say no more gentleman, I won't offer another word. Good luck, guys...


PS, to the guys who Pm'd me for more info continue to do so, I don't mind helping, this is not uncommon for closed minds not to be able to open, I at least respect radix2 , we may not agree but he brought up good questions and valid arguments for information.

 

[pseudorealityx]

Don't read my posts if you don't like them and don't hold your tongue for my sake, go ahead and speak your mind, its free...

I don't get anything out of posting this info, I was just trying to help shed some light, and offer a different take on the topic that the someone may have not seen or heard about, say no more gentleman, I won't offer another word. Good luck, guys...

It's more that you keep ignoring the questions, and just telling everyone how awesome your system is because of your VAST experience. Lots of guys here have been in the industry as long as you've been alive. They MIGHT not be completely ignorant of these things.

Or you mention multiple times that the control boards and fans on HiEff boilers are huge problems and require constant replacement and they're so expensive. Then in the next post, you say that those same things, when on a furnace, are awesome and last forever.

Or ignoring the condensing issue with non-condensing boilers.

Or saying you're running the boiler at a 2 degree delta T.

Or ignoring the part load efficiency gains of a modular boiler.

 

[jonjon1]

It's more that you keep ignoring the questions, and just telling everyone how awesome your system is because of your VAST experience. Lots of guys here have been in the industry as long as you've been alive. They MIGHT not be completely ignorant of these things.

Or you mention multiple times that the control boards and fans on HiEff boilers are huge problems and require constant replacement and they're so expensive. Then in the next post, you say that those same things, when on a furnace, are awesome and last forever.

Or ignoring the condensing issue with non-condensing boilers.

Or saying you're running the boiler at a 2 degree delta T.

Or ignoring the part load efficiency gains of a modular boiler.

Did you read my posts I addressed all of them things,
I am not ignoring the condensing issue, I have watched boilers with sub 130 water in them running on high fire NOT condense, what more do you want?

2 degree delta is very possible and common when running primary secondary piping

And I agree that the mod cons are up to 10% more efficient, my issue is the longevity and replacement part issues with the fact that annual service will eat up energy savings...

As far as the boards and fans, I already addressed this, furnaces and boilers are different machines, its that simple.. The boards are cheaper can be swapped between some units and use universal models, fans are rebuildable in some of the higher end units and are NOT prone to the issues boiler inducers are....

So what did I not answer that you know better? NOTHING, you aren't reading the posts, because them have been answered multiple times, you are letting something else fuel your dislike of my approach.. What it is, is for you to figure out and care about because I couldn't care less of what you think, I already have you figured out, no matter what my age is, its not hard to get your number...

And I never said anyone here was not knowledgeable, show me where I said that...

its you doing the ignoring, isn't it?


My apologies to the OP...

 

[mygarageone]

John Jon
You may very well be the greatest boiler installer , tech person who ever lived.
But you have no humility what's so ever . We older men do not take to young ones who need to brag and strut there stuff. We've seen it all or most of it.
You remind me of men who would come into my shop looking for employment, bragging about how good they are , most never got past the interview. You see , I'll hire someone who tells me straight about there ability with out bragging about it.
People with no humility aren't well received.

And if you judge people based on there spelling ,boy are you in for a surprize. Intelligence can not be judged by one's spelling. I know men who never finished high school who are millionaires. They are smart as hell and you would never know it , if you didn't know them.
I will take a seasoned service tech with lots of wisdom ( experience ) than some one like you any day of the week
Why don't you tone down your know it all attitude and blend in .

 

[jonjon1]

John Jon
You may very well be the greatest boiler installer , tech person who ever lived.
But you have no humility what's so ever . We older men do not take to young ones who need to brag and strut there stuff. We've seen it all or most of it.
You remind me of men who would come into my shop looking for employment, bragging about how good they are , most never got past the interview. You see , I'll hire someone who tells me straight about there ability with out bragging about it.
People with no humility aren't well received.

And if you judge people based on there spelling ,boy are you in for a surprize. Intelligence can not be judged by one's spelling. I know men who never finished high school who are millionaires. They are smart as hell and you would never know it , if you didn't know them.
I will take a seasoned service tech with lots of wisdom ( experience ) than some one like you any day of the week
Why don't you tone down your know it all attitude and blend in .

Are you serious? You don't know me, I didn't just start doing this. What do you know about my "humility"? I never said I was the best. I never said there was no other way to accomplish something, you attacked me, I gave my qualifications and my ideas and practices, its that simple, you 60+ years old with 40 years experience so must know better? That is not how it works anymore and I am not saying you are a bad tech, but not being open to doin ci different is out of the question? Why because some sales rep told you mod cons are great lol get over it, there are people that couldn't tell you the difference between a spanner wrench and a cocker spaniel that can do the math between a mod con and properly installed ci boiler, ,when they have the correct information...

I read through your posts, for your 40 years experience I am not impressed,, sorry...

How dare you tell me about me from what you read on a forum where I am trying to give some information about something that I get paid to do. If I come off as a know it all that is your own insecurity. I am confident about my craft and I try to know the ins and outs of everything I can, I have taught seminars and classes, I have trained all the techs I have ever hired and I have done well. I am done responding to you and your non sense...

You are not in the market for a heating system and if you were you would do it the way you know, and that is fine, but I feel bad for you and your customers because that way is the only method you will ever have in your tool bag because you are closed to something different.

PS please go over my posts and find where I show no humility. Besides this one of course...lol

 

[Spire]

I for one appreciate the information Jonjon has been posting as well as the others that have been contributing (till the thread went to ****).

I never base any decision on a single thread in a single forum, but its great to read others professional opinions and learn from them.

 

[Can68]

I have just sent three hours catching up on this and have learned a lot. I too was sorry to see it head to the gutter, but so much information, it was great.

You see I have just recently build a detached 28x32 garage that I have been dreaming of for years (with some tips from this site, pictures to follow once I get around to posting an introduction in the forums) and wanted radiant floor heating. I went to my local supply store and was told they knew nothing about it and just sold the stuff. I should get professional help.

I then spent a lot of time learning what to do and designed and installed a 4 loop system which I was quite proud of. When I went to the same store just before pouring the floor to get a temp sensor the same guys at the counter wanted to know who did my design, what was the delta T, the 250 foot loops were to short, etc, etc. They did not know how to help but they had no problem picking it apart after the fact.

I have spent 28 years in the energy sector in Oil refineries and Nuclear power and the system JJ describes is in theory the same as a Feed-forward, 3 mode control, reflux driven system I once used in college to get a distillation column to produce Alcohol at >99%.

With this in mind I am leaning toward a CI ( I thought it meant Combustion at first too) but am not sure if I don't just need a single boiler? I will look up my heat calculations tomorrow. Loved the information about the heat plate vs tempering valve as well with the glycol separation.

Thanks everyone.

 

[yeldogt]

I have enjoyed the thread also ... not sure why people get so frustrated. I see this as similar to the "on demand" DHW discussions ... do you spend the money to install the more efficient/ complex unit or keep using a typical storage style. Having had and installed the "on demands" they require more maintenance .. and don't last as long. I never got any savings .. plus I don't like the operation

I don't think that Jonjon1 is disputing that the new technology is the future ... he is just pointing out some cost realities. I have noticed at least 3k more profit built into the modcon installs that i have priced out -- and in reality they look easier to install over a heavy CI boiler. My neighbor installed a Buderus mod con 4 years ago. Replaced an large old WM boiler, heating typical large radiators. Has required unscheduled services each of the past 4 winters since the install.

I installed Amana HTM's in my first two places back in the mid 80's -- google those. Way ahead of anything else -- I had reasonably good luck with mine.

 

[jonjon1]

I have just sent three hours catching up on this and have learned a lot. I too was sorry to see it head to the gutter, but so much information, it was great.

You see I have just recently build a detached 28x32 garage that I have been dreaming of for years (with some tips from this site, pictures to follow once I get around to posting an introduction in the forums) and wanted radiant floor heating. I went to my local supply store and was told they knew nothing about it and just sold the stuff. I should get professional help.

I then spent a lot of time learning what to do and designed and installed a 4 loop system which I was quite proud of. When I went to the same store just before pouring the floor to get a temp sensor the same guys at the counter wanted to know who did my design, what was the delta T, the 250 foot loops were to short, etc, etc. They did not know how to help but they had no problem picking it apart after the fact.

I have spent 28 years in the energy sector in Oil refineries and Nuclear power and the system JJ describes is in theory the same as a Feed-forward, 3 mode control, reflux driven system I once used in college to get a distillation column to produce Alcohol at >99%.

With this in mind I am leaning toward a CI ( I thought it meant Combustion at first too) but am not sure if I don't just need a single boiler? I will look up my heat calculations tomorrow. Loved the information about the heat plate vs tempering valve as well with the glycol separation.

Thanks everyone.

it sounds like a single ci will be fine for you, it sounds like you only have around 1000 lf of radiant tubing, What size is this tubing 1/2, 5/8, 3/4"? You need a heat loss done on the building to know what size boiler and what your flow rates and floor temps will be...

I try to run as much tubing as possible, depending on your outdoor temperature {design temp}, you may need supplimental heat, is your floor already poured?

Off the top of my head {I am not sure where you are located and what your coldest outside temp is or how insulated your building is but if I was designing a 900 sg ft floor I would have done 6- 300 foot loops of 5/8" tubing
. I would have staggered supply and returns, ran the perimeter and 6" on center over laps, so you put down 12" on center then ontop of that put another 12" on center but 6" off center. {depending on what pex you use, some are tough to get bends nice}.
This would give you a pretty low floor temp and be capable of some pretty good flow rates...

Either way a ci boiler with fphx will do you well, if you need more info on the install let us know, if the floor is poured let us know your heatloss and then we can figure what you will need for supplemental is any is needed...

 

[Can68]

I have all the calculations from the Uponor software I will send you sometime this weekend along with some pics of the tubing installation. Around 15000 btu/hr loss I think with R10 foam all around, R22 walls and R60 ceiling.

 

[Can68]

JJ: I looked at going with 3, 300 foot loops of 5/8 but don't remember now why I went with 1/2 instead? Likely availability of the tubing and headers, but it worked well with the interlocking R10 I found. I put some pictures on my profile page and sent you a PM.