I have a gas boiler with steam radiators. My boiler pressure keeps going up to 5 psi and the pressure relief valve opens. I adjusted the pressuretrol (0.5 psi with differential 2 psi) but cannot solve the problem. The burners seem to stay on even though the pressure in the boiler has passed the cut out setting. I am wondering whether this happens due to pressure relief valve, pressuretrol, or other sensing components.

Thanks.