Manual

6
2. DAMPER MOTOR
The function of the damper motor is to power open or spring return close the dampers on the
discharge or intake of the unit. It will seal off or open the building to the make-up air supply.
Test: Remove damper motor linkage cover. Energize unit. Damper motor will open, pushing linkage to
open the damper blades. De-energize unit. Damper motor will close damper blades by spring
return.
3. AIR FLOW SWITCH
The function of this switch is to prove proper air flow across the burner before the burner circuit
can be energized.
Set: 0.3" W.C. for DFG-10/12 units.
0.4” W.C. for DFG-15/18/20 units.
Test: Restrict inlet or discharge to unit 50%. Air flow switch should open circuit to burner.
4. HIGH TEMPERATURE LIMIT SWITCH
The function of this control is a manual reset thermal cutout for primary over-temperature
protection of the unit.
Set: 155
°
F for DFG-10/12 units.
190
°
F for DFG-15/18/20 units.
Test: Adjust unit to high fire. Place thermometer in unit discharge. Close intake down until unit has
excessive cabinet temperature. This limit should trip at 200
°
F.
5. MILD WEATHER THERMOSTAT
The function of this control is to sense inlet temperature and act as an economizer. It will take
the burner out of the circuit if the inlet temperature is above the control setting.
Set: 5
°
F below room or discharge temperature controller.
Test: Adjust control setting below inlet temperature. Burner circuit will de-energize. Adjust above inlet
temperature. Burner circuit will energize.
6. HIGH GAS PRESSURE SWITCH
The function of this switch is to de-energize the burner circuit if the gas pressure to the burner is
above its setting.
Set: 8" W.C. - Manual reset to energize.
Test: Using test gauge in parallel with sensing tubing, adjust unit to high fire, increase regulator
pressure at gauge above 8" W.C.