Boiler for in-floor heat??

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Post by Hiezhaw » Thu. May. 16, 2019 5:33 am

I am looking at a boiler to run the in-floor heat in my garage, I have a 40 gal hot water heater and is not sufficient to heat my garage, the garage is 32X40 with 10' high walls with R-11 in the walls and R-40 in the ceiling, and 2" pink styro under the slab.Will this boiler run or do what I need to heat my shop.
Heres the info the seller sent to me about the boiler.
It is made by Weil-Mclain and is a manufacturer CG Boiler
Model # is CG-4-SPDN
The imput BTU/HR is 105000
Max heating capacity is 88000
It has a Grundfos 1 phase circulator pump attached to it in working order.
It is a natural draft boiler and needs to be vented out to the exterior with a metal chimney.
I do have the 5" exaust electric damper that will come with the unit.
Right now it's natual gas and I do not have natural gas going to the house or garage but he says it can be converted to LP, will a 100lb tank run it or will I need something bigger?

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Post by Rob R. » Thu. May. 16, 2019 6:09 am

That boiler should be plenty large to heat your building, but a 100 lb propane tank is not nearly enough.

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Post by franpipeman » Thu. May. 16, 2019 9:08 am

You just missed a 0 or on tank size right?.... a 500 might work. though . I try to get a entire seasons fuel deliver in one tank due to potential supply issues in the middle of the winter with propane.Im speaking gallons not pounds

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Post by LeoinRI » Thu. May. 16, 2019 4:40 pm

A pound of propane contains 21,548 BTUs

Your boiler will burn 105,000 btu/hour /21548 btu/lb = 4.87 lbs/hour.

A 100 lb propane tank will only last a little more than 20 hours.

I'm assuming here that the boiler runs full tilt at 105,000 BTU/hour.

Normally floor heating is done at much lower temperatures than domestic hot water or baseboard/radiant heat. Can your boiler temperature be set to those temperatures or does it have a controller for floor heating?
You may want to consult a floor heating expert.


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Post by lsayre » Thu. May. 16, 2019 5:48 pm

Average daily burn will be your maximum "required" daily burn divided by 2.5. And just because a boiler is rated for 105,000 BTUH there is no reason (initially at least) to assume that it will ever need to run that hard.

If it ever has to run full out for 24 hours you are looking at burning 206 lbs. of coal for that day. If that does turn out to be your single day max, your winter season average will be right close to 82 lbs. per day. That seems unlikely.

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