Tarm add on question

The way you describe it, it sounds like the Tarm is using the OB as a form of storage. Why does it heat the OB to only 140°F ? Why not 170 - 180. If your OB is like mine, the Tarm contains almost twice as much water as the OB. You probably get quite a bit of heat loss from the OB water storage, they are usually not well insulated. I would imagine the Tarm idles quite a bit, if the setup is exactly as you describe.

My Tarm is connected in parallel with the OB (as per Tarm's suggestion). In this way the house is heated by the Tarm or by the OB. When the Tarm is off the water flow automatically switches over to the OB. If you look on Bioheat's website, you can find the parallel plumbing diagram (with or without storage), compare it to yours, and see what you would need to do to change over.

Here's the pdf of the plumbing schematic:

http://www.woodboilers.com/userfiles/file/Solo Innova Plumbing(1).pdf

There are two aquastats involved here. One turns on the termovar circulator when the wood boiler gets up to 165 degrees after you first light a fire in the boiler. This same aquastat shuts OFF this circulator if the boiler temp drops below 165. The second aquastat also responds to wood boiler output temperatures and is normally set at 140 degrees. This is typically wired to the TT terminal on the oil burner such that if the wood boiler is putting out water above 140 then the oil burner is locked out (not allowed to fire). On the other hand, if the wood boiler output temperature drops below 140 - normally because it has run out of wood - then the TT terminal is allowed to close and the oil boiler takes over heating duty automatically.

Ideally you would use the drawing titled "Solo 2" at the following link, but if you are in a parallel system, you should be set up according to "Solo 4". Normally the parallel set up is used only if you have a tankless domestic hot water coil in the fossil fuel boiler. Please also note that Solo 4 is not recommended for systems with more than two zones. If you have more than two zones, you may want to reverse the supply and return lines to the oil boiler so that it is no longer in the figure eight schematic shown on Solo 4.

http://www.woodboilers.com/admin/uploads/public/Solo Plus Plumbing.pdf

please let me know if you have any questions at all,

Chris

I also have a Tarm and Buderus. I have the feed from the Tarm/tank tied right above the OB with a check valve so the OB does not heat up at all. There is 10 gallons of water in my Buderus and I figure if that heats up all the time it is just a waste.