Relief valve keeps blowing off

allonsy1221

Hi all! I have a triangle tube wall hung gas boiler with an indirect DHW tank. Recently, every time I use my hot water, the relief valve blows off right after. I had a technician come by to replace the expansion tank, then another one came and replaced expansion again but also the water feed, air vent, and relief valve. Now it is happening again. One of them did notice that the water feed is using already heated domestic hot water, but did not redo it to be a cold water feed. Could the dhw for water feed be causing this problem?

pecmsg

sounds like a lot of guessing going on. I hope your not paying for each and every call.

pedmec

Which relief valve is blowing off. The one on the indirect hot water tank or the one on the boiler?

allonsy1221

the boiler relief valve is blowing off, but only when the hot water is used.

JUGHNE

Your indirect tank will have a boiler circuit of some fashion inside it.

If that boiler circuit has a small leak then the house pressure may be leaking into the boiler via the tank. House pressure might be 40 to 60 PSI and the boiler circuit would be only 15 PSI with a 30 PSI relief valve.

Or the pressure reducing valve which feeds water into the boiler might be passing water into the boiler raising that pressure.

Can you shut off the water supply to the reducing valve thus the boiler??

Easier and cheaper fix than the indirect tank replacement.

allonsy1221

Shutting off the valve feeding the supply was what the second technician just suggested… I'll give it a try. He said that would make sense since it only goes off after using the hot water. I had not noticed the timing until last night.

neilc

post some wide angle pictures,

maybe something is where it shouldn't be, or someone will see something,

HVACNUT

Is it also a T T indirect? No drain on the bottom of the tank?