Info on new build

  • Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.

    We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.

    We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.
  • Hope everyone has a wonderful and warm Thanksgiving!
  • Super Cedar firestarters 30% discount Use code Hearth2024 Click here
Status
Not open for further replies.

Pat1991

New Member
Mar 20, 2015
2
Canada
Hey guys!
New to the forum, and I have been reading quite a bit on in floor heat and boiler setup. I'm building a 32 x 50 garage/house, eventually it will be strictly a garage after I build my house beside it but that could be a while. Now my plans are to go with a Benjamin CC500R Wood/Oil combo. I was looking on info for tubing lengths and size for the in floor heat, everywhere i go it seems they tell me I need 7/8 tubing with four 300 foot circuits at 16 inches apart. Now im not sure what you guys think about that?

On a side note me and my dad have put the same boiler in his garage but with no storage tank and was looking at info on how to do that and what size I should get.

Thanks in advance !
Pat
 
You should start with a load calculation and radiant design. It will give you the heat load for the building and radiant loops and lengths.

For best comfort and consistent floor temperature I would not exceed 12" on center. The tighter the spacing the more even the floor temperature. 18" will have some very wide, noticeable temperature gradients across the floor. It may be acceptable for a shop, not so nice for the residence.

Also the more tube, the lower you can run your supply temperature. once you have the load calculation in BTU/ sq. ft. you can look at different tube spacings and loop lengths.

1/2 loops 300' in length are common for many systems, I'd consider 9" on center also, it's worth the extra tube cost.

It cannot be changed once the concrete is poured.

Don't scrimp on underslab and edge insulation, that drives the operating cost for the life of the building. 2" minimum under and around the edges.
 
I'm seeing that 300' loops of 1/2" PEX (0.475" actual) with 12" spacing works pretty well, but shorter loops and closer spacing would be better if it works out for your layout and budget.

This morning I'm bringing a patio/three-season room up to temp. Floor is 1.5" concrete pavers with the PEX buried at the bottom of 1" of stone dust. Floor is 600 ft^2, with two 300 ft loops of 1/2" PEX with 12" spacing. Flow is calculated to be running at 1.75 feet-per-second/1.0 gpm. IR gun measures 125 degF supply and 104 degF return, so approximate rate of heat delivery is 20,000 btu per hour, or 33 btu per ft^2.

At the start of the loops I'm seeing 72 degF max / 63 degF min floor temperatures, and towards the end it's 67 degF max / 54 degF min. Shorter loops and closer spacing would bring all four numbers closer together.

This would be kind of a worst case situation for a concrete type of floor. I'm using a high supply temperature to bring the room up to temperature more quickly so the floor temperature hasn't had a chance to even out more. Plus the PEX is not a couple inches deep in concrete, it's just a 1/2" below the 1.5" pavers.

The differences in floor temperature are noticeable with stocking feet, but otherwise comfort is close to ideal.

And as Bob points out, need to pay close attention to insulation detail at the outside boundaries. It was recommended to me to use 4" thick horizontal for two feet in all along the outside perimeter. Search and study on http://www.greenbuildingadvisor.com/ for ideas on how to get this right.
 
Last edited:
I spent 17 years with one.

The wood side of that boiler is VERY inefficient, poor heat return from the amount of wood it burns. I don't think you could find a more inefficient design.

Plus word on the street in the town they are made in is they are closing operations - can't confirm, but it's what I heard.
 
  • Like
Reactions: flyingcow
Status
Not open for further replies.