Thermal expansion Tank size.

[Dean L]

Hi , What size thermal Expansion is recommended for a new boiler. I am have problems with the pressure relief Valve on the boiler opening. I was told that the expansion tank needs to be replaced. Right now the old one looks like a 3-4 gallon Thanks in advance.

 

[Sylvan]

Depends onhow many gallons of water are in the system.

How high is the highest rad, copper fin is etc.