HVAC Questions? Ask an HVAC Expert for Answers ASAP
You want it to be 12 PSI when installed cold. It will cause the pressure to rise to about 17 when hot, that is the standard for a hot water system in a residential system unless your home is much taller than a normal two story home, pressure = height in the system 17 PSI is good for a little over a 30 rise to the highest point of the piping system.
OK sorry that's a tank for domestic water its different from a boiler tank. You need to get one for a boiler system.