Hi, I read all I can find, but I have no experience with oil or wood boilers. House has 10 yr old OHW boiler, 2 zones, and supplies DHW. about 1400 sq foot house, 2 zones. Shop is 103 feet away and will need 120 feet underground piping. A homemade transit, shows that the 2 boilers will be almost dead level to each other, the top of the wood boiler might be 2 feet higher than the top of the oil house boiler unit. The indoor wood boiler that will be in the shop, is a 1982 Jensen 24B. Pipes are not hooked up yet, but we test fired it with water jacket filled, about 20 gallon capacity. The combustion blower fan does kick out at the preset temp. This seems to be a closed system, as it says "30 PSI max" and has a pressure relief valve at top. The tag BTU only says: 100,000 MIN. I am lost with closed vs. open boilers? and I read that a closed system should have Oxygen barrier PEX? So, I can't order/or install underground PEX yet, until I know how to hook these two boilers together. Also, can I get by with the foil/bubble wrap piping, instead of the foamed Pex? I would like it to be very simple for this season, as it's a very late start. I am in the shop all day, so I can monitor it. I found this very simple diagram on this site, will this work? My questions are; is that a closed system? and should the indoor wood boiler circulator pump run 24/7? ...and the "air valve" shown, I would like to know about that. I assume I would have to add a second aquastat & circulator on the wood boiler tank to dump overheated water into a loop in the shop? I mainly want to heat the house zones, not the shop, as a priority. Thanks for any simple advice you can give.