PSI closed water system

[jtx]

I recently replaced my failed PRV and expansion tank on my 50 gallon ao smith. I matched the expansion tank psi to my incoming water pressure of 60. Once the water heater heats up, I seen the pressure hit up to 70. Is this an acceptable psi while the WH is heating up? I swapped a 2.1 gallon expansion tank with a 2 gallon. My w/h is set to 120 degrees, so I feel a 2 gallon tank is plenty. I could swap the tank with a 4 gallon, but I am not sure what is an acceptable range of psi increase. I don't believe an expansion tank eliminates the psi rising, just a place where it can push water into.

Thanks

 

[Reach4]

120 PSI max is quite acceptable rise with your thermal expansion tank, but some nervous folks would choose a smaller number.