relief valve relieving with boiler running and after shutdown

art bennett

I have installed a Teledyne Laars Propane fired boiler in my son's home. Since the installation, the relief valve continues to pop open with the boiler running and shortly after shutdown of the boiler. This situation becomes progressively worse as winter temperatures drop. On the recommendation of another heating specialist, I have changed the number 30 expansion tank to a number 60. This has not solved the problem. The diaphragm in the expansion is fine and static pressure also is fine. The water inlet valve is operating normally. I need help to resolve this problem.
Thank you in advance for any assistance which you could provide.

Rick Kelly_3

Relief Valve

What is the system pressure when bleedoff occurs? What is the pressure when bleedoff drops? Are these figures within the parameters of the relief valve being used (35psi typical). Most importantly what system pressure are you running at operating temperatures. If you are running at a typical 12-15psi @ operating temps, you're a long way off from a 35psi blowoff. What kind of limiting valve do you have controlling your make-up water?

[Deleted User]

relief valve

Are you sure the pressure reducing valve is not leaking by?
Sometimes when you refill a boiler and system, dirt in the water line will get under the seat of the PRV and cause it to leak, over-filling the system. I'd recommend starting there.

Glenn Harrison_2

Is this...

a copper fin tube boiler? If so, do you have a big enough pump to have the proper high flow required thru the heat exchanger?
Also, how many btu's is this boiler and what kind of emitters (baseboard, cast iron rads, etc.) is it connected to?

Plumdog

Check your piping-you must have a bypass on models 100K and up and should have one on the smaller models. You gotta keep flow moving in these fin tube boilers or they will overheat real quik. Follow the piping diagram in the installation manual! Good luck.