i have a natural gas single zone forced hot water base board system, just replaced the cold water feed reducer, PRV, expansion tank, and temp pressure gauge. boiler ran fine for a few hours at 20psi with the cold water feed on, but after about 4 hours the pressure rose to 30psi and the PRV began to drip. I shut off the cold water and release pressure down to 20psi and the boiler is working normal.
any idea why this is happening only when the cold water feed is on?
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