Pressure should be 12 PSI cold and increase to about 18-20 PSI when water is heated
up.
Do you have an expansion tank with a drain ? If so you might try draining it.
From what you say it sounds like you are trying to maintain 10 PSI when cold and
hot both which you can not do.
If you let out pressure when the water is hot, the automatic feed will just put it
back in when the water cools down.
Even though you indicated that the make up valve has been closed, I suspect it is
either not closed or is closed but defective and still allowing water through.


Rsrtgsprngs wrote:

Need help with a pressure problem. Two floor house with four heating loops. My
hot water heating system is 4 yrs. old and has been fine until a few weeks ago.
I checked the pressure gage and it read about 50 psi. Turned off the boiler
and jiggles the high pressure valve and wosh it dumped water on the floor.
Must have been stuck since it is supposed to go off at 30 psi.. Since then
service people put in a new fill regulator valve and closed the fill line valve
but pressure is still eratic. I drained out several pails of water just to try
to maintain about 10 psi when operating. Then a new vent valve was put in. But
the pressure still keeps climbing when the boiler gets hot and i'm still
draining about 1/2 pail every day. Repair guys don't seem to know what to do.
I'd appreciate any guidance.