Need Radiant Heat Input

[Grashopr]

Last year we built a new 60x60 shop to move our motorcycle paint and repair business into. After hearing about the benefits of Radiant Heat, we decided to go that route, and installed 3 zones; One zone for our display and office area. One for the paint booth, and the last one for the largest area of the building.

Each loop is as close to 300ft as we could make them, and if I remember right, we didn't cut off more than 15ft of any of the loops at the end. Zone 1 has 4 loops. Zone 2 has 3, and the large Zone has 7.

We hired a local plumber who was 'experienced' as a paid advisor and to build our manifolds and as a purchasing agent. He advised us that Bubble-Foil-Bubbble insulation under the slab (1.5" thick) was the industry standard for insulating the slab. This was last October. I have been reading since then that this setup has nearly no insulation properties at all. Argh... We have a 6" thick slab on top of the "insulation". 1/2" PEX throughout with the first perimeter loops spaced 6" apart, all interior loops 12" apart, minimal overlapping, mostly just where the surface exit is.

We do not have Gas or Propane service at the shop site, so we attempted (at our advisors dismay... should have actually listened on this point) to use two, 80gal 9kw (dual 4.5kw element) electric hot water heaters. 20.7GPH recovery rate at 90F.

Each of our Zones are built with a Taco Pump on the input from a main hot manifold feeding an input distributive manifold into the PEX where it goes into the floor. An output distributive manifold is connected to the PEX exits and feeds through a 1-way valve into a mixing valve in case we wanted to feed some of the cold return water back into the input of the Taco Pump.. these mixing valves were always closed.

From there, the return water feeds through another 1-way valve into the main return (cold) manifold and into the input of the first hot water heater at the bottom. The output of that hot water heater feeds into the top input of the 2nd hot water heater. Output of the 2nd goes into an air bleed then back into the main input manifold for each of the three zones.

The Shop is a 60x60 with 10ft ceilings. We had 6" of spray-in-foam insulation put in the walls (R30-ish), and blow-in insulation in Ceiling (R35/40-ish also). The shop has one 9'wide garage door (insulated) and one walk-in door. It has two 8' wide display windows that are in the South-Eastern corner in the Display Room zone.

After running the electric hot water heaters last winter 24/7 and having $500+/mo electric bills, we never (NEVER!!) changed the temperature of the floor any further than 2ft from where the PEX enters the floor. The Hot Water Heaters are one problem (too low GPM recovery rate), and possibly the Taco Pumps are either pumping too much or too little. I dont have the part numbers for the Taco Pumps to get you the size on them right now, but I am interested in getting advice on Zone Pumps that would be sized correctly anyways.

I have got the Propane company bringing us in a tank and am looking for advice on either boilers, water heaters, or tankless boilers. At this point, I am open to suggestions. I have been looking at the Takagi T-K Jr tankless boiler, but I'm afraid that it wont be able to keep up with all three zones. I am not opposed to running one Tankless Boiler for the large Zone and another for the two smaller Zones, but I have never heard of anyone doing this yet.

Any input on where to go would be greatly appreciated. Everything but the PEX in the flooring is changeable; but I need to get on it soon, as nightly temps are getting in the 40's currently and I would like to get the new system up and running before the slab cools too far down.

Thanks in Advance.

the 'Hopper

 

[HoosierBuddy]

I'd be afraid to try to jump in here too much other than to say you are correct that the FBF and the electric water heaters are likely much of the problem.

I'd recommend you contact someone that just does radiant heating and get a price from a boiler and advice on controls and pumps from them.

http://www.radiantec.com/index.php

You might talk to those guys.

Phil

 

[Bigrhamr]

Well the insulation may not be ideal and you would likely get quicker reaction time if the pex was up further in the slab. Even so if you are saying the temp doesn't come up at all then something just isn't right. Can you turn off individual zones or loops and see what happens if you try to heat a small area?

 

[tdkkart]

First, we need to look at a couple numbers:

1. Your building is 3600 sq/ft. Considering a very low heat loss number of 5 btu/square ft/hr you need approx. 18,000btu/hr to heat the building.

2. Assuming 100% efficiency, 1KW of electricity will produce 3413 btu's. You have 2 water heaters, or a max of 9KW of input, approx. 31,000btu/hr.

Considering the above are IDEAL numbers, even if you raise the heat load to 7.5btu/sqft/hr you're at 27,000 btu out, and then if you drop the water heaters to 85% efficiency you're at 26,350 input.

So, even with these 2 small decreases in efficiency you're in the hole already. It's no wonder it doesn't warm up.

These figures are just to maintain the temp, says nothing for actually raising the temp.

At $.10 per KW it's costing you $.90/hr to run the system, $21.60/day, or $648/month.

These are rough numbers, but I'm sure you can see where your problem is at.
You need more heat input to get the slab up to temp. Once it's up to temp it will throttle back a bit.

Which brings up another very important point. These systems are very efficient at maintaining a set temp, they are slow and expensive to raise the temp. Depending on your heat load, you will need at least 5* more floor temp than you want for ambient, so if you want 65* ambient you need to get started heating early in the season, before the core slab temp drops much below your desired ambient. Starting the system up after the floor is down to 40* is a bad idea.
If our weather keeps going as it is, I'll be starting my system in the next couple weeks.

 

[ixlr8]

Your manifold should have the ability to adjust flows through each loop. You should balance temps through each loop. Hopefully your system has a temp gauge for the hot water delivery, each loop should come back 10-15dF cooler than it went out. This should give you the proper flow through each loop. My neighbor is a plumber and he uses an optical IR temp monitor to check the temps of the return lines. If you have a Taco 007 pump, which is a heating system standard, it will be marginal for 300 ft loops of 1/2" tubing, you might want a larger pump. Have you had heat load calculations done to get an idea of what temp the water needs to be to get the BTU's necessary heat the shop?

 

[sneezer41]

First, where are you located? How cold does it get, how cold was the shop?

Second, with a booth fan running, you can easily use a billion dollars worth of heat.

Third, how are you running the system? you do not set back a radiant system

Yeah, the bubble was a mistake and the heaters are too small.

do a real heatloss calc, but that spraybooth will always blow it out of the water

My shop is 2/3 the size of yours, and I run 200 a month year round mostly due to the lights.

I would think that unless you are in Minn, that the 30k btu[I am taking the numbers above at face] it would have kept the place tolerable on most days 'Without the fan on'

 

[autoxbrian]

I still wouldn't abandon electric, depending on your area, I still believe for a few years electric costs per BTU will be better than a burnable. I have had this and been quite happy with it in my 1800 sq ft garage, they make some LARGE BTU units.. This one can put out almost 70k BTU, don't need that much, but it modulates in 500w increments, so it will remain efficient.

I too went the electric 80 gallon water heater route, failed, spent hundreds in the monthly bill(s) without enough heat to keep up. Did this and all was GREAT through last winter.

 

[Grashopr]

Can you turn off individual zones or loops and see what happens if you try to heat a small area?

I currently have the two smaller zones turned off and the 'big' zone turned on and the floor is running at a pretty consistent 60deg, but currently the nightly temps are still only in the low 40's, day temps are in the mid-70s, so it's not a big push to keep the slab at 60.

tdkkart: I agree, even by very 'sympathetic' numbers we have always been 'behind the curve' with the water heater setup. They recover less than 10gal/hour which is just rediculously slow. The Takagi T-K Jr shows the following for recovery rates:

That is in Gallons per MINUTE! Much much better recovery rate, and hopefully with a decent pump, the T-K Jr's 140,000 BTU (84% Efficient) will be able to heat the floor far better than our current setup. Thank you for the numbers.

ixlr8: We have ball valves on each loop coming out of the floor to be able to level the system a little bit. Although up til now, we haven't had the BTU input to even worry about leveling anything out.


sneezer41: I'm in Topeka, Ks. Temps routinely run in the teens for about 10 weeks a year, with dips as far down as negative 15 to negative 20 one or two nights. I know that the booth fan is going to **** heat out, but that was kind of one of the reasons for going with Radiant... if we can get the slab up to temp, having the booth fan on for 4 or 5 minutes at a time shouldn't be able to cool the pad down....

I have no idea what you mean by 'set back' a radiant system statement. I've described the system as well as I can. what part is confusing you?

Last winter we had just built the building, and the fan was not used at all (it wasn't even hooked up til April). The floor heat system never got the floor above 'frozen to the touch'... The current system just doesn't keep up.

 

[HoosierBuddy]

I still believe for a few years electric costs per BTU will be better than a burnable.

I object to that comment. Wait! No! I strenuously object to that comment!

Natural gas is roughly 1/3 to 1/4 the cost of power on a straight BTU to KW comparisson today and there is nothing but gloom and doom coming from the power companies as they moan about the costs of adding new generation, new transmission and new emissions controls in the near future.

There's no guarantee where natural gas prices and propane are going...but everyone in the energy industry will absolutely guarantee which way power prices are headed; through the roof.

Anyone that has gas available and is using power to heat water is paying too much. That has been true since at least 1970 and probably well before that.

Phil

 

[autoxbrian]

not to get off topic, but each person's cost per KWH makes a large difference once then calculated into a cent/BTU between burnable and electric.

Agreed that all costs are only heading up, makes me cry, but I agree.

 

[sneezer41]

I am not confused about anything.

I have been running radiant for years.

first, 'setback' means you do not ever ever shut the heat off or turn it down. Ever.

second, you keep talking about the floor temp and not the room temp. I could not care less what the floor temp is.

You have enough BTU's available that the room should be manageable in moderate weather. If the building is cold when it is in the 40's then I would first look to make sure that there is actually water moving through all of the tubes.

You made a bunch of mistakes on this system, don't spend too much more money before actually troubleshooting the system.

If you bleed the return side of any of the manifolds, do you ever get warm water?

You should.

If the water heaters are the issue, then they had better be running 24/7. If they are not, they are not the problem.

2 9kw heaters running 24 hours [2*9*24*30]=12960kWhrs, in Mass, that would be .17 per kW, 2200 bucks a month. Even if I read that you pay only .07 , that is still 900 bucks, and you have not run a light bulb yet. I have a well lit shop half the size of yours and if I don't run any machines, I pay 100 bucks to turn the lights on. Your water heaters are not running flat out.

I suggest you go to heatinghelp.com, 'the wall' and ask nicely, give lots of details, get some digital pics of your setup and take their advice. The people here are great, but you need a heating professional or you are just going to throw money at this and not solve your problem

 

[redsky49]

I respectfully disagree with all of the responses. At this point, enough amateurs have had their fingers in the pie and it is time to call in an expert. Find an experienced Engineer, Manufacturer's Representative or other qualified individual to sort out this mess.

First, perform a load calc to determine the actual heating/cooling requirements of your particular application. Some of the numbers being thrown around in this discussion are not based on reality.

Second, develop an "As-built" drawing of the existing system to establish exactly what you are working with. Note that flow rates are important, as are heat output of the water heaters.

Third, finalize the paint booth requirements as this may be the single largest heat loss source in the building.

Only after the above steps have been taken will you be able to start investigating a solution.

Be prepared to pay for this help, but remember that it was penny pinching that got you to this situation in the first place. And take internet advice with a grain of salt. It is well intentioned but frequently wrong.

The lack of proper slab insulation is regrettable but something you will have to live with. You still may be able to utilize (retrofitted) perimeter insulation, but this should be determined by a cost benefit analysis performed by an expert.

A close analysis may determine that the radiant floor system will lose too much heat to ever function adequately. Be prepared to accept that some other type of system may be required. This is another instance where the proper consultant may guide you to a zoned radiant system, a heat recovery system or some other alternative system. For a structure only occupied during normal business hours, a solar assisted system for instance, may be a viable alternative.

If you are going to go the propane route, I would recommend selecting an established US boiler manufacturer such as Burnham, Aerco, etc. I personally like cast-iron boilers for their longevity. I also don't like being the "beta tester" for some of the new vendors who are out there, so stick with something that is proven.

Taco pumps are fine, but for most radiant systems flow rates are pretty low. You can only determine the installed flow rates for your system by calculation or by testing by a Balancing Contractor. See items One and Two above.

Hang in there. This can be resolved, but please proceed in a well thought-out manner. Choose your advisor carefully. No more plumbers for HVAC design.

Good luck.

As always, offered only as opinion

 

[tdkkart]

I could not care less what the floor temp is.

2 9kw heaters running 24 hours [2*9*24*30]=12960kWhrs, in Mass, that would be .17 per kW, 2200 bucks a month.

You'd better care what the floor temp is, as it determines what your room temp will be. The floor temp HAS to be more than the desired room temp in order to heat the room.
You can also use the floor temp to do troubleshooting on an existing system.
Comparing the slab temp to the room temp will tell you very closely what your heat load is. If your floor temp has to be 80* to get a 60* room temp you have a problem.


Also, 2 80 gallon water heaters is not 2 9KW heaters. Each heater has 2 4500W elements, however unless they have been rewired only 1 element runs at a time in each heater, so therefore the total heat is only 9KW between the 2.

Radiant heat is not rocket science, and does not require a rocket scientist to design a successful system.

95% of the information can be found in this document from Zurn:
http://zurn.com/images/pdf/ZPM02101.pdf

The simple fact is that the OP does not have adequate heat input available to heat his building. How he deals with the problem will determine how successful the result is.

 

[Grashopr]

Redsky, I appreciate your position, and I completely agree that a knowledgeable professional would be a terrific step in the right direction. Problem is, radiant systems are still a sort of "Black Magic" here in Kansas and I have spoken with 4 'recommended experts' of which none gave me any warm fuzzies that they were doing anything more than guessing on what to do with my system. I have had two come out and see the system, with two very different (and not at all confidence inspiring) hypothesis on where to go next. It seems that the local guys have zero experience on troubleshooting a system, and just want to write down the square footage of the building and order a 'prepackaged' kit from their suppliers that is 'custom engineered' for my building. They dont take into account the fact that we're going to be sucking 20% of the air out of the building once a day, nor do they take into account that we have different numbers of loops in each of our Zones. So far it seems that me guessing (or trying to get information and make a 'slightly educated' guess) is going to be as productive as these so called 'experts' telling me I need to dig up half of my floor to find out exactly how thick the concrete is and where the PEX is overlapping at.

 

[Grashopr]

Sneezer: one of us is confused, and apparently it's me. I have been under the impression that my room temperature is controlled by floor temperature. If I can't get the floor above 35f, then how is the room going to warm up? Last winter, our average floor temperature was in the low 40's with the hot water heaters running 100% constantly 24/7 for 3 months straight. The return water temperature was AT BEST (after shutting down all but the smallest zone and dedicating all of our energy to trying to warm that area of the floor) 54f. "Water moving through the tubes"?? We purged each loop individually, then purged the zone manifolds. The problem isn't that we have air in the lines; we are moving enough cold water back into the hot water heaters to keep them 'on' long enough to run up the electric bill. If our pumps were not circulating SOMETHING, wouldn't the hot water heaters turn off eventually? Anyways, hot water heaters are a major part of the problem in my non-expert opinion. Their 7gph (gallon per HOUR) recovery rate is horrifically undersized to try to keep up with 3 taco pumps that are each rated above 15 gallons per MINUTE each. I would sure like to see your math showing the two hot water heaters being adequate, as you are the only one who's told me so far that they are anything but horrifically undersized for the system. If I can get them to work, I'm all ears.

 

[sneezer41]

I never said "anything" about your water heaters being at all the right size.

now, at this point, I would expect most people to "answer the damn question!"

it is really hard from 1500 miles away to see if there is air in your lines or not, or whether your pumps are working.

It is also hard to help when you do not answer questions

Next, when it is say, 50 degrees out, your building uses only a fraction of its design heat output. Of course you don't 'have' a design heat output.


Assuming what tdkart says about the total being 9kw being total, that is still 30k btu output, which a quick beer bag calc says ought to keep you 20 degrees over ambient. [seeing as your shop is 3x the size of my old house, it had a 40k btu heater that was good for an 80 degree delta, 3x40=120btu required, 30 available=20 degree delta.




"Do a REAL heat loss calculation!!!!"

Do not hire anyone who does not "Do a REAL heatloss calculation"

That includes anyone who quotes anything about btus per square foot.

Do not buy anything until you......."Do a real heatloss calculation!!!"

Or do whatever you want

 

[Grashopr]

There is no air in the lines... I dont know how much clearer I can be about that.

The pumps are working... also been said a few times.

I've gone over the Zurn heat loss calculator using 'high' and 'low' estimated nubmers for the unknowns, and it shows that we should be somehwere in the 82k BTU range on input. The only real question is what type of heat generator to go with (electric boiler, LP tankless boiler, LP standard boiler) and whether to run all of the zones as one large zone and skip trying to run them each individually or to continue running them seperately. I am hung up on how much volume I should be expecting to try to heat and pump and in an attempt to NOT be running the heater full time, should I be looking for something above 140kBTU max output (as in the Takagi T-K Jr)?

 

[redsky49]

Sigh....

Okay, let's get some facts on the table.

Electric water heaters produce hot water according to the following formula:

9kw x 3412 = 30708 btuh

30708 btuh
742.5 (factor for 90 deg. rise) =41.3 gph

However, a 90 deg. rise is typically for domestic hot water systems, not hydronic heating.

For heating purposes you will typically have a much smaller delta, along the lines of 20 degrees. In practice, the heating difference between 140/160 degrees and 100/120 degrees is nil. The available heat energy is the same. At a 20 degree rise the same 9kw heaters produce about four times the gph output as it does at 90 degree rise.

For energy savings you want to heat the water to the least highest temperature possible, commensurate with heat load and pumping requirements, boiler design, etc. Additionally, the PEX tubing has certain temperature limits that must be observed.

The number of heating loops requires a bit more design time (and installation cost), but has little to do with overall system performance. Or to put it another way, it offers more opportunities to make a mistake but is not inherently a problem. As long as you have the proper design, installation and commissioning, the system will operate as intended, whether one zone or twenty.

If I were to throw out a scientific wild *** guess (and I don't know where you are located) as to the heat requirements for your shop, I would think 40 btu per sq. ft. would probably be in the ball park, excluding the paint booth. That's roughly 144,000 btuh, plus the outside air for the booth, or about four and a half times the available heat capacity from the existing water heaters. This number is not intended to be anything other than a comparative estimate for discussion sake and should not be used for actual design. East and west Kansas have pretty different heating requirements. Perform a true load calculation.

I would also spend some time thinking about the spray booth and outside air makeup. You will have to preheat and filter this air, or try to incorporate into the central heating system (not recommended). Additionally, the air velocities and direction of flow may be critical to your booth (unless it is pre-engineered).

Unless the openings (doors and windows) to the outside are at least 4% of the floor area of your shop, you will have to provide some ventilation air for occupant comfort, and per code requirements. Since it also sounds like you have a show room, you will also want to avoid the transmission of odors from the shop area into the showroom. An experienced Engineer will be able to help you with this.

I know some firms in Colorado, but none in Kansas, so I cannot direct you to a knowledgeable Engineer in your area. I would suggest contacting Wirsbo or some other PEX supplier and asking them who is doing radiant systems in your area. You want a specialized designer, not merely a general HVAC guy, no matter how good he may be.

Best I can offer from a distance. Good luck.

As always, offered only as opinion

Just saw the Topeka reference. The historical data shows winter design temperature as 4 degrees F (99% number). This is pretty cold.

 

[Grashopr]

I appreciate both of you guys' input.. no matter how much I seem like I'm griping. I've gone over this so many times that I'm starting to get brain fade from it and fresh grey matter is always good


Here are my constants:
Shop Size: 60x60x10
Total Volume: 3600 Sq Ft
Ceiling: 10" of Loose-Fill Blow-in. R-factor of 32 (3.2R/in)
Walls: 6" of expanding foam. R-factor 39 (6.5/in)
Door: 105 sq ft of door area. R-factor 3
Window: 80 sq ft area: R-factor 3.2
Slab Insulation: R-factor 3
Target inside temp: 68

Surface Heat Loss Calculations:
Ceiling: 5400 BTUH
Windows: 1200 BTUH
Doors: 1600 BTUH
Wall: 2949 BTUH
Slab Back Loss*: 20686 BTUH

*Slab back loss figured with following: (6" slab)
Edge Heat Loss Estimate: 182.33
Perimeter Region Heat Loss: 5871
Under Slab Heat Loss: 14633

Air Exchange Heat Loss:
12648 @ 20F outside temp
7378 @ 40F outside temp

Total upward Load: (these seem REALLY low.... )
6.6 BTUH @ 20F
3.85 BTUH @ 40F

Total Useable Panel Upward Load (at 85% EFF.. estimate.. most likely higher than 85%; no real blocking objects other than motorcycles)
7.764 @ 20F
4.53 @ 40F

Floor Surface Temperature: 82F *(estimate... tough to rely on the low Upward Load numbers)*

Water Supply Temp: 120F

Pressure loss per loop (each almost exactly 300ft) at 120F with 100% pure water at 1GPM (max flow rate for 1/2" pex):
2.49PSI or approx 5ft of head per loop



Hopefully that helps a little...

 

[Grashopr]

Number of heating loops is not alterable at this point.. they are already in the floor. We are running 300ft loops of 1/2 Pex on 12" centers (except for the outer loop which is on 6" center for the outermost loop). 14 loops total.

 

[sneezer41]

You still never answered my question, what is the temperature in the building?

I don't care anymore anyway.

Your design case is for +20f, why? you said it gets to negative.


at any rate adding up your btu losses at 20 degrees, it is 44k btu.

By that measure, your building should stay warm, without any fans on, down to about 35 degrees. At 35 degrees, your heatloss should equal your heater output, and below that it should drift down with outside temp. It also takes more energy to raise the temp, so this is assuming the temp is warm to begin with

So, your heater is way way too small, you are doing a design case for the wrong temp, and you are not figuring in the fans[which might be really hard]

Figure a zero degree design temp, you will need over 60k btu,[it is just math] again without the fans.

Now if your building is acting as I describe, then get an appropriately sized boiler and you are good to go. If it does not act as I describe, you need to find out what else is wrong.

I think you should consider some reznor heaters in the area outside the booth, with lots of air intake outside the booth so you do not pull the heat out of the rest of the building.

 

[Grashopr]

Sneezer, area you always this negative, or is this a new thing for you? I dont see where you ever asked what the temperature in the building was... but if you had read my constants.. you will see that the target inside temp is 68 degrees.

I am crunching the numbers at +20F because that is about the coldest sustained temperature we get down to for more than a few hours at a time. If we dip into 15 or 20 below, it's for one night, but we haven't had more than a day of sub +10-degree weather in years. 84 was bad, but since then, it's been pretty mild up here in the winter. Go figure this year will probably be 40 below from Nov til Apr. If your 44kBTU number is correct, then I'm oversizing my system by 300% by going with a moderately sized LP boiler, with output of 140kBTU anyways.

The booth is going to pull a lot of air, but there isn't much we can do about that. It only runs for a minute or two at a time, as we aren't painting kenworths; we paint bike parts. I'm assuming I will need to run secondary heaters on days when I have a large booth load going through, but typically my airbrush and pinstripe work doesn't require the booth on at all, so I'm engineering without regard to the booth for now. If it is a MAJOR problem, next winter I will try to find an air makeup system or an alternative heated input system just for the booth.

that's the plan

 

[sneezer41]

I am usually much worse.


from my first post:

>>>>>>>How cold does it get, how cold was the shop?<<<<<<<

From my second post:

>>>>second, you keep talking about the floor temp and not the room temp. I could not care less what the floor temp is. <<<<<<

Now keep looking for a radiant heat guy, you need one. They are out there.

No one here can really help you. All I did was add your numbers together and come up with a total heatloss, a number apparently you had not come up with before, and it is the only number that is important.

There are charts that will tell you the design temp you should use for your area [30 second search says -10F] -10 is 30 degrees colder than your plan, which may be is not a good plan.

Seek...professional...help.....

BTW, when you have air in the lines, guess what happens, heat flows a few feet down the lines and nowhere else..........

And you still never answered the question.........what is the temperature in the room at this *very* moment.

 

[Grashopr]

right now, the thermostat on the wall says 67F

 

[jrhode]

I agree with others that the best thing you could do is get professional design help. radiantec is ok, but I recommend you get in touch with Rob at Northeast Radiant Technology, at http://www.nrtradiant.com/

They designed my system for my house and garage when I was building it; everything works flawlessly. They will do the heat calcs for your location, give you flow rates for your loops, recommend a heat source for you... everything you need to get your system up and running properly and as efficiently as possible, working with your tubing and setup.

The lack of good insulation under your slab is mainly going to effect your initial start up time/cost, as it will heat the earth as it heats the slab. After that, the earth acts as a heat sink, storing some heat.

I live in MN where we regularly get some -30's in the winter, and my 3600ft2 house is solely heated with radiant. We have a Triangle tube boiler that heats the radiant and DHW.

You could also check out Radnet, a radiant heat forum at
http://radnet.groupee.net/eve/forums

 

[sosplamou]

thanks so much for useful info

 

[Grashopr]

I agree with others that the best thing you could do is get professional design help. radiantec is ok, but I recommend you get in touch with Rob at Northeast Radiant Technology, at http://www.nrtradiant.com/

They designed my system for my house and garage when I was building it; everything works flawlessly. They will do the heat calcs for your location, give you flow rates for your loops, recommend a heat source for you... everything you need to get your system up and running properly and as efficiently as possible, working with your tubing and setup.

The lack of good insulation under your slab is mainly going to effect your initial start up time/cost, as it will heat the earth as it heats the slab. After that, the earth acts as a heat sink, storing some heat.

I live in MN where we regularly get some -30's in the winter, and my 3600ft2 house is solely heated with radiant. We have a Triangle tube boiler that heats the radiant and DHW.

You could also check out Radnet, a radiant heat forum at
http://radnet.groupee.net/eve/forums

Thank you!

 

[Possum]

Any updates Grashopr?

 

[sungrove]

Another thing to consider to reduce your energy costs would be to install hot water solar panels to your roof and then combine that with your other heat source. radiantec can help you with that.

 

[Grashopr]

We got the Takagi T-K jr in, with it on for a little over 20 mins running at 140F output (afraid to run 180F setting, as our system pressure at 180F is at 125psi, which is right at the pressure rating for that temp on the PEX), we raised our output temperature over 10F to just over 70F. First time I've got my output to anything above 55F. System is working well so far, will have to run it for a month and see about Propane usage.

 

[Holedgr]

Hey Grashopr.....how's the system workin??

 

[Grashopr]

the floor is working perfectly! Tonight they are talking about -20F (which is REALLLLLLLY cold for Kansas), it's +4F right now with a -6F windchill and I'm working in a long sleeved tee-shirt. Since installing the Takati TK-Jr, we've gone through about 280 gallons of Propane, which at our rate is costing me about $45/week, compared to over $350/mo when we were on electric, and it's actually warm.

We had our supply line to the 'hot' manifold built out of PEX, and when the system had been working for about 2 months, a brass tee let the PEX slip out. Unsure whether the peices were screwed together right to begin with or if the expansion and contraction caused the failure, but we moved the whole input line to copper and have had no more problems. I'm feeding 180F (the highest temp setting on the Takagi), and it seems to be working perfectly.

The only real 'downfall' is that my feet seem to sweat more at work, and it takes a while to get 'COLD' water out of the faucet. I'm a super happy guy. I'd recommend the TK-Jr to anyone building a shop of similar size.