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Posted by HeatPro on January 22, 2007 at 17:35:28:
In Reply to: Re: Size expansion tank posted by Dave on January 22, 2007 at 15:27:07:
As most systems use a 30-lb relief valve - such 30-lb valves start lifting at 25 lbs, so as long as the system pressure doesn't exceed 24 lbs at most, it would work just fine.
Bladder (modern) type expansion tanks come from the factory set at 12-15 lbs, so as soon as a system that is completely filled with water starts expanding due to heating the water in the sealed system, the system pressure would jump up to 12-15 lbs right away. As yours doesn't do that there is something strange about your system.