Need help with my setup (OWB)

[Oxford]

I have been heating my house in VT for 11 years with a CB 5648, with an 80' run of 1" PEX and less than 2' elevation change. My circulator pumps are Taco 007's - off the shelf at any plumbing or big-box store. The house is a basement with radiant tubing in the slab, plus two currently unheated floors above. The entire house, with the exception of two second-floor bathrooms, is heated with the slab tubing. It's 4300 square feet total including the finished basement. That means that occasionally it's 72 degrees in the basement and only in the low 60's upstairs, but we like it that way. Not once in that time has there been a problem with the system "keeping up". I should add that ALL of my domestic hot water comes off this setup too, so I burn 365 days a year.

However, this year I am adding a 2-story, 24' x 36' garage/workshop to the heat load, also with radiant tubing in the slab. I also will be adding supplemental heat to my 18' round aboveground pool with a tube-style heat exchanger off the same loop. When the pool is being heated the garage loop is shut off, and vice-versa. I plan on adding several components to my system this year to ease up the wood demand. First will be a small electric or propane heater for DHW so that I can shut down the system in the summer for easier maintenance of the OWB. I am also going to finish hooking up all the under-floor staple-up tubing that I was supposed to be using for upstairs heat (and wasn't).

I average 10-12 cords of wood per year including DHW. It will go up a little bit when I start heating my garage, maybe another 2-3 cords.

I confess to a mind that says "Let's do the math" and I certainly don't want to pick on @Jon E, but the quote above is instructive when you actually Do the Math. Since you have two floors that are unheated because you haven't hooked up all of the under-floor tubing (boy, do I know that feeling) you are essentially heating one floor (approximately 1450 sf) and some DHW on 12 cords of wood a year. Figuring that a cord of mixed hardwood is about 20 million BTUs, you're using about 240 million BTUs per year. Figure OWB efficiency very generously at 50%, and you're putting about 120 million BTU/year to use. If you have a family of four, you can figure about 100 gal/day of hot water, or right around 60,000 BTU/day, or right around 22 million BTU of your boiler output. That leaves roundabout 98 million BTU over a 180 day heating season, about 23000 per hour on an hourly basis, or about 15 BTU/sf. Using BTU/hr=gpm*10000, where your temperature drop is 20 degrees F, you only need about 2.5 gpm to keep your floor warm, if your wood usage is really that low.

Again, I'm not picking on Jon, and I believe what he has posted. I think that his numbers illustrate just how important insulation is, and the benefits of earth sheltering, since he lives in the basement. If you live in a drafty old barn, better get used to what @Kevin in Ohio experienced his first winter. I also think that talking about using 2" Pex as your main line is probably overkill, unless you live in someplace that's about 10,000 square feet.

 

[Kevin in Ohio]

Kevin in ohio,
How many plate heat exchanger is that? Looks thin.

Dealer set me up with it and don't really know. Measures 12 x 5 x 2 1/2. Looks like 12? All I know it does the job.

 

[NSMaple1]

On the 2" thing, I just mentioned that to show how the numbers showed how small 1" is. A comparative thing, by the numbers. We all know the numbers don't always tell the whole story.

Don't nobody be putting in 2" on my account now.

 

[Timbercreek]

Think the biggest ive seen lurking around various sites is 1.5" plain pex sprayfoamed in the trench. 300' run or something crazy like that.

 

[lindnova]

1 1/4 would be the biggest I would go. 1/2" more on the diameter is nearly double the water carrying capacity.

1 1/2 is big and 2" is huge compared to 1" and hard to maneuver and install fittings. Ask me how I know.

 

[maplegrovetom]

Guys I've researched and researched, I'm still not finding the answer I'm looking for.

Here's the lowdown and layout.

I am building a house right now. It's a 1400sq ft ranch with radiant infloor heat in the basement. I have a CB 6048 ready to install. I will heat the infloor heat, DHW, a 24'x24' attached garage, and also run a heat exchanger in the furnace.

The problem I have is I'm not exactly sure what size thermopex line I need to run to my house. The run will be around 120ft. No elevation on the run. Can I just go with 1" thermopex or should I check on the 1.25"?? I have read that the smaller the line the more friction and less flow I will be able to get. Any help would be appreciated.

The stove will also be heat the polebarn I'm building with infloor heat. (32x56x12'walls)

Main question is how big of thermopex I should run to house.
2nd question is am I overloading this stove by heat in this much area? The polebarn will be zoned and more than likely partitioned off and only heating half of it.




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The most important thing you can do with this whole equation is to SPRAY FOAM THE HOUSE. I live in Michigan also. I heat 2500 sq. ft of 120 year old farm house with hydronic baseboard heat (to 74 degrees), domestic hot water year around, 800 sq. ft. of garage, and a 28' X 6' deep swimming pool to 90 degrees in summer with a home built OWB, 130' from the house running through 1" pex. Even on -25 degree, windy nights, the house still stays 70 degrees, and that's the first floor that hasn't been spray foamed.
When I installed the pex over 10 years ago, 1" was all that was available. If I had an option of 1 1/8" or 1 1/4" at that time, I would have used it. I run 1 taco 007 pump on this system, and through the years since it's been installed, average 12 - 15 full cord of wood per year.
It takes more wood to heat the pool in the summer than to heat the house, DHW, and garage in the winter.

SPRAY FOAM, SPRAY FOAM.

 

[Timbercreek]

^i second the notion. I gutted 3/4 of my.farmhouse and did sprayfoam and its so good i want to gut the rest.
But that dam plaster mess tho

 

[wise8706]

It's a brand new house and yes I am going with the spray foam.


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[Jon E]

I confess to a mind that says "Let's do the math" and I certainly don't want to pick on @Jon E, but the quote above is instructive when you actually Do the Math. Since you have two floors that are unheated because you haven't hooked up all of the under-floor tubing (boy, do I know that feeling) you are essentially heating one floor (approximately 1450 sf) and some DHW on 12 cords of wood a year. Figuring that a cord of mixed hardwood is about 20 million BTUs, you're using about 240 million BTUs per year. Figure OWB efficiency very generously at 50%, and you're putting about 120 million BTU/year to use. If you have a family of four, you can figure about 100 gal/day of hot water, or right around 60,000 BTU/day, or right around 22 million BTU of your boiler output. That leaves roundabout 98 million BTU over a 180 day heating season, about 23000 per hour on an hourly basis, or about 15 BTU/sf. Using BTU/hr=gpm*10000, where your temperature drop is 20 degrees F, you only need about 2.5 gpm to keep your floor warm, if your wood usage is really that low.

Again, I'm not picking on Jon, and I believe what he has posted. I think that his numbers illustrate just how important insulation is, and the benefits of earth sheltering, since he lives in the basement. If you live in a drafty old barn, better get used to what @Kevin in Ohio experienced his first winter. I also think that talking about using 2" Pex as your main line is probably overkill, unless you live in someplace that's about 10,000 square feet.

Thanks for doing the math, and for not picking on me... What I failed to mention is that the house is 10 years old, the basement is Reward ICF's with 2-1/2" of foam insulation on either side of the concrete wall, and the house is a timber frame with structural insulated panel walls and roof - 6" walls and 10" roof. My worst insulation is probably R-30+. It makes a huge difference if you're essentially living in a giant Igloo Cooler. I also had, up until last year, 8 people in the house. Some freeloaders (aka "children" or "offspring") decided to move out and go off to college.