Oil burner pressure goes up even if boiler is off

Izabela

Please help! We are so lost! There is water that keeps on coming from the pressure release valve. We had a handyman come in today to change it. The psi dropped he left and we are now back with that same problem 
psi went back up to 30 or over and the valve starts leaking again. The handyman has a surgery tomorrow and won’t be able to come in for few days. Any input is helpful 

HVACNUT

It could be a bad diaphragm expansion tank, a water logged (full) steel expansion tank, a feed valve over feeding, or a leak in a tankless coil or indirect heat exchanger. 
Where are you located? There's no reputable heating companies around?

Big Ed_4

Pressure builds when burner is off , you have a bypass . Either a bad pressure reducing valve or hole in heat exchanger . Shut off the pressure reducing valve as a test and if the pressure continues to rise it would be the hot water heat exchanger .

EdTheHeaterMan

If I may, I believe the post should read

Oil fired boiler pressure goes up even if boiler is off

Without more information I can only guess that this oil fired boiler also makes Domestic Hot Water (DHW). So if that is the case, there is the possibility that a heat exchanger coil from the DHW tank or DHW tankless coil is passing house water pressure to the lower boiler water pressure of the closed system.

In order to test the theory @Izabela would need to shut off the cold water feed to the DHW coil or tank. If the pressure stops increasing, then the problem is known. If the problem does not go away, then the automatic water feed PRV is defective. Close the valve to the automatic boiler feed to see if that results in pressure stabilization.

I hope this helps. If you need more help understanding this, we can help if you post some pictures of the boiler with all the pipe connections from different perspectives. High, low and angles.