Diagram #9: Forced Air Furnace having a combustion air supply duct and a replacement air supply duct together with an exhaust fan controlled by a designated ventilation switch and/or an interval timer.

 

ADDED: 1. Combustion Air Damper (HOM-0x11-SF1)  2. Replacement Air Damper (HAC-0x10-OPC) 3. Ventilation Switch to supply Controlled and Regular 120Vac, 3-Wire to furnace area. 4. Relay Adaptor with Interval Timer (TMADP-1102-TPX) to function as a control centre.

 

OPERATION: 1. Combustion Air Damper and Replacement air damper open during furnace firing. 2. Ventilation Switch turns on Ventilation Fan, opens Replacement Air Damper and turns on Furnace Fan simultaneously. 3. Interval Timer can be set for minimum or multiple consecutive settings of 15 minutes to turn on the Ventilation Fan, open the Replacement Air Damper and turn on the Furnace Fan simultaneously without interfering with the AC. 4. Optional switch (i.e. toggle switch, timer, de-humidistat) allows full control of Replacement Air Damper to open as required provided it is a PC type.