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pump staring before low voltage valves open
My radiant floor heating system heats the first and second floor and my system is in the basement. When the zones of the second floor are heating a lot of air gets in the system. Not a problem for the first floor. A main feed and return, fed by a circulation pump, supply a manifold on the second floor that distibutes the hot water. There are low voltage valves on the return in the manifold to control the demand for heat. I recently noticed that the pump, which in my system pulls the water to the boiler not push the water fro the boiler, starts at the demand for heat will there is a delay before the valves open. My question is, could this pull on a closed system creat the air problem in my system. Please note that I have been told that the pump is also over sized (see my previous post).