pressure gain

teddy

I have a old 2 pipe hot water system that i installed a new boiler into this fall. I have been back there a couple of times now, once for the relief valve leaking water through it and the second time for low water sensor safety not allowing boiler to come on. When I installed new boiler, I put on new b&g inline air seperator and left old expantion tank which is 4' long and 12" diam. I put the seperator in like normal, before pump so it dosent get added pressure from pump. Here's the issue. When the boiler is idle the water pressure is at 18lb and when the pump starts it goes down to 12 lb's and then starts to climb in pressure as water temp increases. when water temp. was up to 140 the pressure was already up to 22lb's. I stopped call for heat on system and when pump stopped running, the system pressure went to 34lb's and relief valve opened up and I lost pressure. I refilled system to 18lb's when it was off and when i turned on pump again, the pressur dropped again in system and started to climb again as temp went up. Do i have a improperly sized ex. tank in system. It sure seems to be problem to me, but then why did it work with old boiler.
Help me if you can

Thank's a bunch
d

Steve Paul_4

overpresure

It sounds like you are starting out with too high a pressure setting on your pressure regulating valve. They come factory set at 12PSI. Depending on how high your system is, the cold fill pressure should be regulated up or down to about 2 PSI higher than you need to fill the system. It also sounds like the expansion tank is waterlogged. It mst be drained or replaced. You should call in a Pro to remedey this situation.

brucewo1b

Drain all the water out of the expansion tank, recharge the system and try again. If the Expansion tank is getting water logged then it will act like to small of a tank and unless you have a three story building start at 12psi. Also if you have air vents close them with the old style tank or the air will keep mixing in with the tank water and keep venting out your vents.

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