help! Having problem with water coming out of relief valve on Mom's boiler. New expansion tank, checked pressure and reading 11PSI. Replaced pressure reducing valve and set pressure to 12 PSI. Put a remote gauge on the return line of the heating loop and its reading 20 PSI while the boiler is running and bleeds done to 12 PSI when system shuts down. The problem is that I have close to 30 PSI reading on the gauge on the boiler and it doesn't bleed down at all. The gauge is working as I've manually released the pressure. Its like the pressure is LOCKED in the boiler itself. Is there a check valve locking in this pressure?

Possible pin hole in the domestic coil ? Although that would cause increased pressure thru out the system.
There's not a closed valve at the expansion tank ? Automatic fill valve is not set to fast fill ?

Can you post some pictures of the boiler and the near boiler piping. Step back to try and get as much in as possible.

By any chance has a circulator been replaced recently?

Yes the circulator was replaced this past summer by plumbing company. I'm not at Mom's to tell the name but its an adjustable 3 speed set on medium , red and starts with G , (Gransum maybe). Pressure relief is also new as spring broke on old one. Pump flow arrow is going towards boiler on return loop.



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Here's the WAG on my part.....Zone valve system, circ on the return, gets replaced with something like a Grundfos 15-58FC. The FC means it has an internal flow check. If that is the case, call the plumber back and have him remove the flow check.It will pull right out with a pair of needle-nose.

Thanks Paul, I was suspecting something of that nature, everything has been fine for years but was hesitant to assume circulator would be problem. I'll do it myself to avoid a service call and an answer of we fixed the problem and that will be 250 dollars for the fix! Probably should change the O-rings while removed even though they were just replaced (standard O-rings ?). So I'm assuming that what is happening is, the furnace is firing up because the thermostat is calling for heat and then the heat call is satisfied while burner is running, then the burner stays running until the temperature shut down occurs and the circulator has shut off because no heat is called for, and all pressure within the furnace has no place to go because the check valve won't allow the excess pressure to go back to the return lines to cool as the expansion tank is at capacity and puking out some water?



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Is there zone valves on the supply side? is the boiler cold-start? In other words, if there is no call for heat does it go cold, or does it maintain temperature? I don't believe they are standard O-rings. Any plumbing supply should have them.



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3 zones, ranch house, 1 zone feeds bedroom, one zone feeds living,dining,and den, and one feeds basement. I believe its a cold start, however not 100% sure as heat is always in need. I've seen the temp. go down to 140#.

Have you been there yet, to check the circ?

No, Going over this morning 1-14-16
Okay went over to Moms and removed the check valve, filled system, and brought pressures down to start up the boiler, also turned recirc down to low speed. Boiler gauge staying around 21 PSI, return line is 12PSI. I'll give it 24 hours and see what happens as nothing seems to occur when I'm there.
Checked this morning everything is dry, temp. resting at 190 pressure steady at 21 on boiler



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I wonder why the difference in pressure at different areas? I wonder if the circ is adding pressure at the boiler? Does the pressure equalize the minute the boiler/circ shut off?

No, pressure stays at a constant 21 on boiler and return line returns to 12 as the pressure reducer valve is set at. Maybe there is another check valve within the boiler? Its a Utica.

Something strange going on. The pressure should equalize in the system while the boiler is running, even with check valves present. When you get a chance, post the model number of the boiler. Although it shouldn't make a difference. I'd like to see if there is anything odd about the boiler, anyway. I think the boiler gauge is sticking.



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