Nordyne G6RD 93+ Verifying Operation of the Supply Air Limit Switch, Description of Components

Verifying Operation of the Supply Air Limit Switch

To verify operation of the supply air limit switch, make sure that the blower door is in place and that there is power to the furnace. Completely block the return airflow to the fur- nace by installing a close-off plate in place of or upstream of the filter(s). Set the thermostat above room temperature and verify that the Sequence of Operation is as described in these instructions. The supply air limit switch should function to turn off the gas valve within approxi- mately five minutes. The circulating air and combustion blowers should continue to run when the supply air limit switch opens. Remove the close-off plate immediately after the supply air limit switch opens. If the furnace operates for more than five minutes with no return air, set the thermostat below room temperature, shut off the power to the furnace, and replace the supply air limit switch.

DESCRIPTION OF COMPONENTS

Figure 28 shows the location of each of the functional components described below. If any component of the furnace must be re- placed, use only factory authorized replace- ment parts. See the Replacement Parts List for each component.

Flame Sensor – The flame sensor acts to prove that flame has carried over from the ignitor to the opposite end burner. If no flame is sensed, the furnace will be shut down automatically.

Gas Valve – The gas valve controls the flow of gas to the burners. When the gas valve is energized it automatically opens and regulates the gas pressure in the manifold.

Pressure Switch – The pressure switch verifies that the inducer is drawing the combustion gases through the heat exchanger. It also senses a blocked condensate drain condition.

Vent Pressure Switch (G6RD Only) – The vent pressure switch reacts to blockage in the vent or combustion air piping. It is utilized in G6RD furnaces only.

Supply Air Limit Switch – The supply air limit switch prevents the air temperature leaving the furnace from exceeding the maximum outlet air temperature.

Vent Safety Switch – The vent safety switch shuts the furnace down if the outlet flue gas temperature increases above 160°F. This switch protects the plastic flue system and the inducer from over-temperature conditions.

Flame Roll-Out Switch – This switch provides flame roll-out protection to the furnace and combustion air inlet pipe.

	R
	C
	Y
	G
	W
Common
Leads	EAC
Connect
	HUM
Neutral
Lead of
Electronic
Air Cleaner
and/or Humidifier
Here.

3 Amp Fuse

COM

24 V

9	6	3
8	5	2
7	4	1

Neutrals

			Unused Motor
			Leads
6	3	HUM	M1	M2	M3
5	2
4	1

60 90	120	180
Blower Off
Timing

TWIN

Flame Signal

Light (Yellow)

Status

Light (Red)

COOL HEAT EAC XFMR L1

Humidifier Tap	Cooling
(.5A@ 120 VAC)	Speed Tap

Electronic Air Tap (.5A@ 120 VAC)

Heating Speed Tap

Figure 25. Blower Speed Tap Location

29