120Vac vent switch, combustion air and replacement air(2 furnaces)
HMI Hoyme Manufacturing Inc. Special Note: Circuits are colored for clarification only and are not necessarily those found in actual installations. Wires of the Combustion Air Damper, however, are colored as shown.
Diagram #5A: Two Furnaces having a common combustion air and two replacement air supply ducts together with and exhaust fan controlled by a designated ventilation switch.
ADDED: 1. Combustion Air Damper (HOM-0x12-SF2) 2. HAC-0x10-OPC damper for primary furnace. 3. HAC-0x10-OPC damper for secondary furnace. 4. 120VAC Ventilation Switch. 5. ADP-1101-05A on primary furnace.
OPERATION: 1. Replacement Air Dampers are inter-connected to the Combustion Air Damper so that three dampers open during firing of either or both furnaces and close when firing stops. 2. Ventilation Switch turns on exhaust fan, primary furnace fan and opens both HAC dampers simultaneously without interference to AC. 3. Optional switch (i.e. toggle switch, timer, de-humidistat) to each HAC damper allows independent control of each damper.