Allied Air Enterprises 80G1UH2V Controls, Pressure Switch, Rollout Switch, Primary Limit Control

Controls

Following is a description of the operation of some of the controls used in this furnace. All models use one of each control, except as noted.

Pressure Switch

The pressure switch is a normally open switch that monitors combustion air flow. Inadequate air flow resulting from excessive venting system restriction or a failed combustion blower will cause the switch to remain open. A80UH2V and 80G2UHV models have two pressure switches.

Rollout Switch

The rollout switch is a normally closed switch that opens when abnormal temperatures exist in the burner area. This can be caused by a restricted heat exchanger causing burner flame to “roll out” into the vestibule area or burner box.

This switch must be manually reset by pushing the button on top to restore furnace operation. A80UH2V and 80G2UHV models have two rollout switches.

Primary Limit Control

This is a normally closed control that opens if abnormally high circulating air temperatures occur. It is an automatic reset control.

Auxiliary Limit Control

This is a normally closed control, located on the circulating air blower housing, that opens under abnormal “reverse air flow” conditions that could occur in a counterflow or horizontal installation if the circulating air blower fails. It is an automatic reset control.

Interlock (Blower Door) Switch

When the blower door is removed, the interlock switch breaks the power supply to the burner controls and blower motor. The switch operation must be checked to confirm it is operating correctly.

Checking and Adjusting Gas Input

The minimum permissible gas supply pressure for the purpose of input adjustment is 5"w.c. for natural gas or 11" w..c. for propane gas. This furnace requires conversion for use with propane (see Accessories section on page 26 for correct kit). The maximum inlet gas supply pressure is 10.5" w.c. for natural gas and 13" w.c. for propane. Gas input must never exceed the value shown on the furnace rating plate.

These units are equipped for rated input at manifold pressures of 1.7" w.c. (1st stage) and 3.5" w.c. (2nd stage) for natural gas. When these furnaces have been converted for use with

propane gas, the manifold pressures are 4.9" w.c. (1st stage) and 10.0" w.c. (2nd stage).

To measure inlet or outlet pressure, remove plug from desired pressure tap (inlet or outlet) as shown in Figure 38 and connect a water manometer or gauge to the proper pressure tap.

GAS VALVE SHOWN IN “ON” POSITION

Figure 38

These models have separate adjusting screws (3/32" hex) for 1st stage (marked “LO”) and 2nd stage (marked “HI”). The adjusting screws are positioned on either side of the barbed fitting (see Figure 38). Turn the adjusting screws clockwise to increase pressure and input; counterclockwise to decrease pressure and input. The pressure regulator adjustment is sensitive; one turn of the adjusting screw will result in a relatively large change in manifold pressure.

To adjust the regulator:

1.Set high-fire (2nd stage) setting by turning hex adjustment screw to desired rate.

2.Set low-fire (1st stage) setting by turning hex adjustment screw to desired rate.

Make sure the final high and low fire manifold pressures are within the allowable ranges specified above for the gas being used.

CAUTION

The furnace rate must be within +/- 2% of the appliance rating input.

Be sure to replace the inlet and outlet pressure tap plugs after testing and/or adjusting gas input.

506471-01 Issue 1034 Page 33 of 41