Combustion air damper for two furnaces and two replacement air dampers (One Power Close, One Power Open)
HMI Hoyme Manufacturing Inc. Special Note: Circuits are colored for clarification only and are not necessarily those found in actual installations. Combustion Air Damper Wires, however, are colored as shown.
Diagram #2B: Two Forced Air Furnaces having a common combustion air supply duct and two separate replacement fresh air supply ducts.
1. Combustion Air Damper for two appliances *(HOM-0x12-SF2)* but having only one combustion air supply duct. *(Damper has two separate operating circuits)*.
2. Power Close Replacement Air Damper (HAC-0x10- OPC) inter-connected to the HOM damper.
OPERATION: Combustion Air Damper is interlocked to both appliances so that the damper proves to be open to supply fresh air for combustion when either one or the other or both furnaces are firing. HAC Replacement Air Damper (PC) of the main furnace will open when either furnace fires but will draw in air whenever the main furnace circulation fan is running. HAC Replacement Air damper (PO) of the second furnace will open only when the second furnace fires and will close when the fire stops, regardless of furnace fan operation.
Optional switches, as shown, may be used on either HAC dampers to open upon demand.
1222-ld - Printed in Canada