please re read this
“I have a boiler for home heat [hot water/baseboard) and the pressure relief valve is leaking because the pressure within the boiler is too high (the needle is pegged off the scale).”
Since it says HOT WATER wouldn’t you also look for a tankless coil that may have sprung a leak?
Then after you shut down the domestic C/W valve leading to this coil wouldn’t you then Drain down this system to within the proper operating pressure of this system by taking the height of this building and figuring . 434 times the height of the highest radiator above the boiler or let it just balance itself out like a normal cold water start up?
This is how I set my attitude gauge on “normal” reading PLUS an extra 4 PSI for a positive displacement (BUT why confuse the helpers trying to learn the very, very basics)
Watch the gauge and if no change then open the domestic valve again as this would show a defect right away correct?
Now if the gauge doesn’t move isolate the expansion tank drain same Or if a bladder type remove from system check the charge and then re install back into service correct so far?
Now drain that the obvious is taken care of check the automatic feeder.
of course you can check the “flow control valve” is indeed opening when the circulator comes on.
I was trying to give Dan a step by step way to trouble shoot this kind of system as Dan is a mechanic in his own right.
Harold between us didn’t you ever see a low pressure hot water boiler operating in excess of 75 PSI relief valve setting?
I have inspected and serviced low pressure hot water boilers operating just under 160 PSI @ 250 degrees F.
Checking the obvious I thought was the way to go. Step by step, and Never assuming