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bpirger Member Posts: 1
Hi All:

I've built a new addition and attached garage/shop to the house, radiant throughout.  I already have about 1400 sq ft of radiant in the house in concrete, about 1000 sqft below the floor upstairs, and have added 1000 sq ft in concrete for the addition, and 2200 sqft for the garage/shop.  I hope to heat the garage/shop to 45-50 or so...perhaps more on busy weekends.

In order to heat all of this, I have decided to purchase an outdoor gassifying wood boiler, namely a GARN with 1500 gallons of storage.  My current system uses a Buderus boiler (set to 0.6 gallon/hour), plumbed with a primary/secondary style, and using Tekmar 363 and 363 controllers.

I plan to add the GARN to the system plumbed on a secondary loop.  The GARN will be the primary heat source, using the oil only as backup.  I currently heat primarily with a woodstove, keeping the floors at about 66 or so with oil.  I don't use much oil for this...maybe 150 gallons a year.

I have attached a sketch showing my plumbing plans.  What I don't show on the plans is isolation valves for all the pumps and y-cleanouts on both sides of the HX.

The primary loop if 1 1/4" and I'm planning to run 1 1/4" microflex from the garn to the primary loop.

I'd appreciate any comments/critism/etc.  What am I missing?  Is there something else I should include?  Should I have any concerns of running the Buderus on the primary loop?  I have thought about plumbing it as a secondary loop as well...but it uses an Riello OC-3 with through the wall venting, so the loss due to chimney draft should be minimal.  The Buderus sits outside in its own "boiler shed" with a 500 gallon fuel tank...so a little heat in there would be a good thing to keep the fuel from jelling. 

Is there a controller that I can use to engergize G1 and GS when there is a call for heat and only fire the oil boiler if the primary loop doesn't get raised over say 125 in a couple of minutes (i.e. if the GARN water is cool)?

I have to get additional mixing controllers for the addition and two garage/shop zones...Hopefully not as expensive as the 362!  I do like the Tekmar controllers.

Thanks to all....I see this continues to be an outstanding site.  You helped me tremendously when I built the house and installed this system back in 2001.



  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    Spirovent location.

    Bear in mind that I am not a professional. But I think you want to locate the spirovent as close to the heat source as possible. Since you probably do not want two of these, I suggest putting it in the Boiler Shed right after the closely spaced Ts where the Plate HX connects to the primary loop. The reason I suggest this is that the hotter the water, the more effective the air extractor is at removing the microbubbles and dissolved air.

    I have the opposite in my house. I have the similar Taco air extractor, and it is located in the secondary loop, as specified in the boiler's installation manual. But the water in the secondary loop never exceeds 135F and is usually less than that. After my system was installed and filled, it took about two months to get the last little bit of air out of the system (most of it came out in a few minutes). If the water were at about 180F, it is my understanding that the last little bit of air would have been removed in about 2 weeks or less. It heated just fine, but the circulator to the upstairs zone made a slight air noise until the extractor got the last little bit of air out.
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