12-23-2008, 03:13 PM
I recently did an oil to gas conversion boiler changeout. The existing piping is as follows. Boiler is heating first floor only (1200 ft/2). 2 zones because addition had been done a few years back. Why they didn't tie into existing system I'll never know. The original zone is a venturi type system, 1 1/4" main with branches coming of at each baseboard. The 2nd. newer zone is conventional 3/4" supply in one end of baseboard out the other back to the return. The homeowner just wanted the boiler changed, no piping work. After installation I bled all radiators upstairs on the old system and purged the other zone in the basement with P&B valves. The original venturi zone doesn't seem to heat up like it should. Now keep in mind that I didn't know how the system operated before the changeout so I have nothing to compare to. For all I know it was never a balanced system. Should there be venturi tees at each baseboard supply and return side? There doesn't seem to be any on the system but I could be wrong. Some of the baseboard piping is in a crawlspace and haven't had a chance to verify. I've heard that venturi tees should be on supply side only and some people say on supply and return.