radiant heat boiler size?

[stinkity stoink]

Hello all.
I am getting closer to finishing my detached garage and have some heat questions. The building is a 24'x26' garage the cieling is 16'. I am trying to find out what size boiler I need to heat the slab for radiant heat. I am not sure ,but I think a 50,000 btu might be too big. Plus that also bumps up the size of my gas line . Normally that wouldn't bother me ,but some one allready gave me 1/2" plastic gas line and all the fittings. I have my trench done and I want to finish this up.

By the way the garage is framed with 2x4 's. it will be insulated (walls and cieling). It has 5 windows 4'x3 each', 2 windows 5'x2' each, 1 door 36x80 and 2 garage doors 9'x7' each.

I am figuring that I have to run around 130 feet of gas pipe (natural gas). About 80' is buried . Ther will be about 20' in my house and about 30' in the garage.

Thanks

 

[Thump_rrr]

Please elaborate on your 1/2" plastic gas line. Is it standard schedule plastic pipe or is something similar to trac pipe ps-2 which is a Corrugated Stainless Steel Tubing (CSST)?
When sizing gas line you must always calculate all gas sizing from service regulator to the end of the longest run and not from the connection point in your system.

For example if you tie in your 130' conventional Schedule 40 plastic pipe into the existing manifold in your home which is 30' from your service regulator your supply calculation should be as if you were calculating a 160' run.

When using trac-pipe or any other type of CSST you must calculate the size using their proprietary formulas.

I do not know of any jurisdiction in Canada or the USA which permits unlicensed people from installing gas piping.

 

[stinkity stoink]

Its polyethylene pipe. It has the tracer wire in it. Same as the gas company.

I am licensed in trac pipe, but that doesnt mean I know a ton about it. They showed me a 15 minute video and gave me a test, bam I was licensed. It was quite a while ago. I do get code updates from them though.

as far as my gas line . I have 1" from the meter that branches off to serve my boiler, water heater, and dryer. So I was figuring my # of feet from the end of the 1".That is about 15 feet from the meter.

Thanks..

 

[HoosierBuddy]

OK...I'm surprised you haven't gotten more feedback here.

1. Where do you live? What it is the coldest temperature you expect to see? How much insulation are you planning on installing? Are the overhead doors insulated?

2. What temperature would you like to be able to hold in the garage? Is that constant or do you plan on turning it down when you aren't in there and cranking it up to work? If you are going to turn it down, are you going to turn it all the way off while you aren't out there?

If I knew all that I could advise you better...based on not knowing any of that though I'd say you should take all of that 1/2" PE back and get 3/4" instead.

Using GasCalc, at 1/2" Pressure drop 130 feet of SDR 9.3 1/2" (pipe size) PE will flow 42,289 BTU's/hour (assuming 1000 btu/cf natural gas). That's just on the straight pipe run and you also lose flow on elbows and other fittings...so while 1/2 MIGHT work it also MIGHT NOT...and burying pipe is a pain, so go with the larger pipe.

The last time I bought 3/4" PE it was roughly 34 cents a foot for High Density. Even if you pay $1/foot...you're only talking about 80-bucks worth of pipe. Remember...you can't use PE above ground or indoors. It ain't allowed.

Phil

 

[KenB]

There is a pretty good heat loss calculator here: http://www.warmmfloors.com/heat_loss_calculation.htm


Ken

 

[mobetta]

.......

I do not know of any jurisdiction in Canada or the USA which permits unlicensed people from installing gas piping.

around here(and most places I've been in the USA) any HOME-OWNER can run their own plumbing, electrical, etc- AS LONG AS it is all up to code and can pass an inspection. you can imagine what would happen if the state told peeps they couldn't do work on their own house. it would happen any ways, so they make a way for it to happen safely AND legally.

 

[Friartuck]

Did you insulate under the slab?? Using what size Insulation?? If good insulation (R-10 or better), consider using the Takagi-Jr. Tankless water heater. 105 degree water is its lowest setting which is ideal for radiant.

 

[stinkity stoink]

OK more info. I am in NJ. Coldest days are 3 or 4 deg. and not a ton of those (F). The garage Will be insulated R-13 for the walls & R-19 on the cieling. The garage doors are going to be insulated.

I am planning on keeping it a constant 50 deg. F. Maybe I will boost it to 60 on occasion. I wont' be sleeping in there yet (the wife might have other plans after I destroyed the yard).

The slab is not done yet ,but it will have a vapor barrier down. I was planning on putting the bubble wrap down (reflective) . I have read tons of different oppinions on this so I am not set in stone on that. The slab will be 6" to 7" thick (putting in a lift).

Around here we can run our own gas line with a home owners permit. Only on 1 family 2 family or more need a license. It will be inspected.

I will check that calculator thanks.

Thanks for the water heater suggestion. I was wondering if I could use a tankless water heater.

 

[sneezer41]

>>>>>>was planning on putting the bubble wrap down (reflective) . I have read tons of different opinions on this so I am not set in stone on that<<<<<

ton of different opinions, as in that stuff ***** and that stuff really *****?

Foam, 2 inch, under and around.

If you put piers in for the lift [IOW no foam there] you would never need more than 4 inches for the lift, and it would probably be just fine on the foam anyway

If you are not needing to keep it 70 at peak heat load, you can probably get away with less than 50k, but that is a pretty small boiler to begin with, so you have little to gain in going smaller, and may lose some ability to rebound. Probably a gas water heater is the answer

 

[HoosierBuddy]

Use high density polystyrene under your slab, not FBF.

The only good reviews I've ever seen on the bubble wrap is by the people who make or sell it.

Phil

 

[Friartuck]

Like Phil said, bubble material (I can't even muster up calling it insulation, R=1) is advocated by the people that sell it. There are at least three lawsuits by the Fed Trade Comm on it. Use 2 inch thick high density foam under the slab and on the inside of the foundation, down to frost level (for NJ is 30-36 inches). Given the two inch under the slab and R-13/R-19 combo you mentioned, the Tankless unit should work well.

Whereabouts in NJ are you?? I'm at exit 109 GSP.

 

[Sterff]

You need to do a heat loss calculation. We use the easy loop system.

 

[Friartuck]

What is the Easy Loop System??

 

[Sterff]

What is the Easy Loop System??

Its what you can use to size boilers for a home. Its not perfect but it will give you a general idea on how big of a boiler you need...
http://www.weil-mclain.com/en/multimedia-library/pdf/weil-mclain-pdf/other-downloads/easy_loop.pdf

 

[stinkity stoink]

Like Phil said, bubble material (I can't even muster up calling it insulation, R=1) is advocated by the people that sell it. There are at least three lawsuits by the Fed Trade Comm on it. Use 2 inch thick high density foam under the slab and on the inside of the foundation, down to frost level (for NJ is 30-36 inches). Given the two inch under the slab and R-13/R-19 combo you mentioned, the Tankless unit should work well.

Whereabouts in NJ are you?? I'm at exit 109 GSP.

Exit 135 . not too far from you.

Like I said not totally sold on the bubble wrap. People told me all I need is a thermal break, but I am no expert. That is why I am asking questions and reading.

I was worried about the boiler size because I have my trench dug to run the electric and gas. I wanted to finish that up over the weekend or by the beginning of next week.

I was figuring the most I needed was a 50,000 btu boiler. If I can get away with a tankless water heater that would be great.

Thanks.....

 

[Jeepskate]

OK more info. I am in NJ. Coldest days are 3 or 4 deg. and not a ton of those (F). The garage Will be insulated R-13 for the walls & R-19 on the cieling. The garage doors are going to be insulated.

As has been suggested, you should do a heat loss calc.

I am planning on keeping it a constant 50 deg. F. Maybe I will boost it to 60 on occasion. I wont' be sleeping in there yet (the wife might have other plans after I destroyed the yard).

Radiant is a set & forget...turn it on before you need it and leave the t-stat alone. It does not do quick recovery/temp changes like a forced air heater does...you'll be sucking down gas to make that 10 degree jump.

The slab is not done yet ,but it will have a vapor barrier down. I was planning on putting the bubble wrap down (reflective) . I have read tons of different oppinions on this so I am not set in stone on that. The slab will be 6" to 7" thick (putting in a lift).

In my observations, this is one of the main places that people screw up. As has already been stated, use 2" thick hi-density XPS under the slab and around the perimeter. What sneezer41 described is *exactly* how mine is done...2" foam and then I left open spots for where the lift posts will sit which gives me 6" of concrete there and 4" for the rest of the floor.

 

[stinkity stoink]

As has been suggested, you should do a heat
In my observations, this is one of the main places that people screw up. As has already been stated, use 2" thick hi-density XPS under the slab and around the perimeter. What sneezer41 described is *exactly* how mine is done...2" foam and then I left open spots for where the lift posts will sit which gives me 6" of concrete there and 4" for the rest of the floor.

I just started adding more fill for the slab. I will do it the way every one is reccomending. Thanks all

 

[urgti]

I have a similar sized garage going up and I was given a rough estimate of 60K BTU heat loss. Does that mean I can use a 118K tankless water heater just fine? I also want to use the tankless for a sink and washing the cars with warm water.

 

[Friartuck]

IMO, Yes. See the Takagi-Jr product sheet and manual. The unit has four temp settings for its range of 17K/20K to 140K BTU capability. I believe the lowest 113 degree setting is what most use for radiant applications.

http://www.tanklesswaterheaters.com/takagitkjr.html

Insulate well!!