Hi all,

I recently had issues with relief valve leaking. I replaced with a new one however immediately after putting the new one in, a day latera I noticed the valve was leaking a bit.

Since my boiler runs from oil, and heats the water as well, I keep a timer on it during the summer months, just heating the house water during thre mornings to save oil. It turns on for 3hrs each morning. Until winter arrives, then obviously all day running.

I posted this below on Appliance Blog forum immediately after replacing the valve. Unfortunately, that HVAC forum is now read only. no tech.

I noticed the boiler (from a cold start, was shut off all day) reached my max set point of 190F, and the pressure read 25psi when the boiler shut off.

A minute later the boiler turned back on and ran for a while. It did not seem to increase in temp too much but the pressure went up to almost 40psi after about 5 minutes of running. It then shut down and at the same time, the pressure relief valve let about 1/2 cup of water out then stopped. It's ran a few times now since then and is holding just under 30psi and not leaking. Not confident I've fixed the real problem??

Whats the cause for it to shoot up to 40psi?

Above was back in March 2013. Update today 9/24/13 below.
The valve seemed to hold after it leaked a few times, then went away immediately after replacing. Until this morning.
Boiler turned on at 5am, at 5:15 I found the pressure relief valve wide open and water shooting from the pipe. Shut everything down, cleaned up and restarted. She cycled to temp 190Degrees, shut down and then cycled again 2x without the valve leaking.
What could cause the valve to periodically leak as such?

Any help greatly appreciated.