HEAT SUPPLY for small addition.

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barkeatr

Member
Jan 22, 2011
212
Upstate NY
im building small office addition, the addition attaches to main building right where Outdoor Wood Gassifier thermopex line goes into the house. for numerous reasons i would love to tap into the line and use the return line to heat the addition. I would run it into a manifold and such. I would like to do this vs running a main line from the mechanical room to this addition. the main reason is that the pipe coming out of the hot water heater that heats my house is only 3/4" dia. i dont want to try to pull another zone from that single 3/4" line. Since its a hot water heater it doesnt have many "ports" to tap into.

anyway, my question is has anyone heated addition, outboulding...by tapping into thier main supply line? i heard something about avoiding low return temperatures to the boilers..but im not sure if that applies to a open atmosphere boiler. I have a profab 200 gasser.

barkeatr
 
How small is small, and what is the heat load you need? Low return waters returning to a boiler can shock the hot steel, causing issues there, and that is the purpose of the protection. Also, the boiler wants to burn above the condensation temperature, so you don't want it to be burning and condensing....unless it is a condensing boiler, which wood burners are not.

So if you were to cut into your return line, and take more heat out, you want to make sure you have return water protection....but you probably have that already, no? There should be a mixing valve of sorts that keeps the return water warm enough by mixing hot outgoing boiler water with the incoming return water, so the boiler return isn't too cold. So if you take some more heat out, and the water is cooler, presumably the return mix will compensate...but you need to know if you have the return protection already.

That said, how much heat do you need? Is your return water going to be warm enough to provide the heat? Are you looking for a little water to air exchanger? Baseboard? Radiant panel?

Is the hot water from the boiler always flowing in this return line, or only when there is a call for heat in the house? If not flowing, you might not get much flow in the office....though perhaps you could just run this loop with a small pump and suck water out of the return line....

Know your load, know your water temp minimum requirement, make sure your controls make sense, but it seems straight forward to me....
 
Lots of systems put OWB between house and barn, feed house first then the return to barn and back to boiler. If you did in floor with the lower water temp from return side all you would need to do is treat it as a secondary loop [couple Tee's,pump, Therm o-valve, t-sat, roll of pex,Misc fittings 500 bucks you got heat] It wouldn't change the operating characteristics of existing system, other then a even lower return temp when addition cycles on.
 
thanks for all the information.

I dont have the mixing valve protection you mention. If the water is too cold returning to a outdoor atmospheric type boiler, where does the condensation take place? on the outside of the water jacket? above the water level on the inside? I could see that being a problem..I will find out what the min return temperature is for this boiler. ( I know weather/humidity is a big factor)

I dont think i could reliably find out the heat load.

The water does flow continously regardless if heat load is on or not.

Thanks again, there is a lot to think about.

barkeater
 
Do you have the office space built yet? If not, and it is sitting on concrete, I'd certainly recommend putting in tubing in the floor...radiant is great....and you use low temp water (like no more than 120) so likely your system wouldn't really even notice the small load....

Completely agree with bigburner....seems like all you'd need would be a mixing sensor and small pump and you'd be all set.....especially since the water is always moving back to the boiler....
 
its not built yet, im placing the conrete for the slab next week believe it or not...putting tubes down this weekend. Its well insulated with 4" ridgid under slab. I like radiant a lot but would also like to mix in some quicker response heat...and for that i think i need higher water Temperatures. anyway...thanks for teh comments!
 
In another thread someone was talking about getting warm heat out of 130F water in a coil.....so you never know....it might be enough to get it up to temp. Maybe maintain a minimum with radiant and then the water to air to bring it up when you want to be in the space?

Sounds like you have a plan!
 
ok, that helps. another point, when we need that shot of hot air is usually the swing season so we (read momma) dont need like wicked amounts of hot water---- just a little. Middle of the heating season and the radiant floors are humping heat. Ya, i have a plan..building an addition in the middle of winter. I do like being outdoors however..today was sweet.

I see you have tekmar controllers i should look into that.
 
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