We recently had a hot water solar system installed that heats both our domestic water and the water that flows through our baseboard heat. The solar system is working great, but we are having trouble with the furnace ( 20 yrs old) creating too much pressure. The plumber initialy thought it was the pressure realease tank that is directly ovr the furnace. It was replaced and we still have the pressure running at 20PSI, and sometimes it goes to 30 PSI and blows the PRV. The autofill vave is " factory set" at 12 PSI SUPPOSEDLY.

Anyone have any ideas?

Thank you in advance

You need a pressure regulator valve to reg the pressure going into the boiler from solar unit , Also check the Automatic fill valve from your water line to boiler for when it needs water. These two needs to be balanced to keep the boiler at approx 8 to 12 lbs on average boiler. If a problem persists the expansion tank is to small and can't balance the change in system.
Signed 21 Boat

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