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My 150,000 btu/hr (gross) boiler has two pressuretrols, one originally set at 3 psig cut-in and 4.5 psi cut-out, the second set at 9 psi cut-in and 10.5 psi cut-out.
Following advice in Dan's book I lowered the "lower" pressuretrol to 0.5 psi cut-int and 1.5 psi cut-out, and thte system seemed to work fine.
My question is: what is the second pressuretrol for? And how should I adjust this second pressuretrol?
They are both wired to a Honeywell VS820A regulator which is supplied by a millivolt generator. Thanks in advance