Diagram #4: Forced Air Furnace having a replacement air supply duct.

 

ADDED: Replacement Air Control Damper, Power Close damper is recommended and c/w 1 Relay, (HAC-0x11-OPC).

 

OPERATION: 1. Replacement air damper is interconnected to the furnace so that the damper opens to provide fresh air during the heating cycle and closes to conserve energy when the fire stops. Damper remains closed irrespective of Furnace Fan operation. 2. Optional Switch, (i.e. toggle switch, timer, de-humidistat) allows Damper to open provided the HAC damper is the PC type.