I recently re-plumbed my oil furnace to incorporate my Froling. Previously, I had a taco pump that was connected directly to the boiler on the return side. So, if you were in my basement in front of the oil furnace, the lines from my heating zones came down through the ceiling, into a manifold up around the first floor joists and then ran about 5 feet or so down in 1" copper pipe, turned 90 degrees, through the circulator pump, and into the boiler. I now have an alpha pump that is on the supply side of the boiler. I removed the old pump on the return side and just replaced it with a straight piece of pipe with flanges. I've noticed that the long stretch of copper pipe on the return side of the boiler gets pretty hot (120-130f maybe or more) even when there is no call for heat. I've put my hand quite a ways up the pipe and it is very warm. Since the zone valves aren't open (and haven't been for days) when I noticed this, I figure hot water must be "backing up" out of the boiler and into the return pipe. I don't know if it has always been this way and I just noticed it - or if by relocating the pump I've caused this to happen (maybe it had a backlow preventer?). I'll be taking the oil furnace off line in a couple days to incorporate the dhw coil in my storage tank into the house supply, so that would be a good time to fix this issue (if it is an issue). I'd appreciate your thoughts about the right way to fix this if it needs fixing. If I missed a solution, please let me know. p.s. When I say heat trap, I'm thinking of doing something similar that I did on my storage tank - a u shaped design w\pipe. Thanks!