I am finally getting a grip on the controls that come with a SF260 harman. The Johnson Controls A350 (aquastat relay) is used to control the aux air blower for burn chamber when theres a heat loss(load demand) in water temp incoal boiler. The S350(stage) relay is the boiler Dump controller. The Y350 is the 24V transformer and bridge that interconnects the other 2 relays together and powers them.
Just trying to figure out how to stage the oil boiler, if possible off the A350, whithout interferring with blower operation. If possible, if not will need another aquastat for staging oil boiler off coal boilers temps for turning on circulator from oil boiler. Hmmmmmmm.