Allied Air Enterprises 4PGE Heating System, Heating Sequence of Operation, Circulating Air Blower

Insure unit is installed per manufacturer’s instructions and that line voltage and air flows are correct. Refer to Table 3 for proper superheat or subcooling values. Check superheat settings by measuring pressure at the suction line service port. For TXV systems, measure pressure at the liquid service port. Take line temperature within 2 inches of service port connection to its main tube. If unit superheat/subcooling varies by more than table allowance, check internal seals, service panels and duct work for air leaks, as well as restrictions and blower speed settings. If unit performance remains questionable, remove charge, evacuate to 500 Microns, and weigh in refrigerant to name plate charge. It is critical that the exact charge is re-installed. Failure to comply will compromise system performance. If unit performance is still questionable, check for refrigerant related problems such as, blocked coil or circuits, malfunctioning metering devices or other system components.

Heating System

With the proper thermostat and sub-base, continuous blower operation is possible by closing the R to G circuit. Cooling blower delay is also functional in this mode.

Heating Sequence of Operation

1.When the thermostat calls for heat, the combustion blower is energized by the ignition control.

2.When the speed of the combustion blower reaches proper RPM, the pressure switch closes, initiating the pre-purge timing (30 seconds nominal).

3.When pre-purge has expired, the ignition control energizes the gas valve, the spark electrode, and the flame sensor. The igniter sparks for 10 seconds, and the flame sensor senses that flame has been established. If the flame sensor does not sense that flame has been established

in the 10-second interval, then the ignition control will de-energize the gas valve.

4.The ignition control is designed to repeat this “trial for ignition” a total of three times. If, at the end of the third trial, a flame still has not been established, the ignition control will repeat the trial for ignition sequence 1 hour later. The 1-hour retry is indefinite. The ignition control can be reset by interrupting the unit power or the thermostat circuit.

5.Thirty seconds (nominal) after the initial trial for ignition, the circulation air blower will start.

6.When the thermostat is satisfied, the combustion blower and gas valve are de-energized. The circulating air blower motor will continue to run for a short period after the thermostat is satisfied.

Circulating Air Blower

Depending on the package unit model, the blower motor will be either a multi-tap PSC motor or a variable speed motor.

PSC Motor

The circulating air blower is controlled by a timing circuit in the integrated blower/ignition control. Timings are not adjustable.

Cooling – Blower “on” delay is 5 seconds after call for cooling. Blower “off” delay is 90 seconds after the cooling system shuts down.

Heating – Blower “on” delay is 30 seconds nominal after burner ignition. Blower "off" delay is approximately 120 seconds after the thermostat is satisfied.

		Adjusting Airflow (Variable Speed Motor Equipped Units Only)
Model					Cooling CFM @.50 Static				ADJUST, HEAT,
Nominal	Heating	Motor	ADJUST	HEAT	COOL	COOL	COOL	COOL	and COOL Taps
		HP	Setting	Setting					and Dehumidify
Cooling	Input				Setting Setting Setting Setting				Resistor
kBTU	kBTU				A	B	C	D	on Interface
24, 30	68	1/3	NORM	A	1000	800	600	900	Board
36	68	1/2	NORM	B	1200	1000	800	1100	ADJUST	HEAT	COOL
36	90	1/2	NORM	A	1200	1000	800	1100	NORM	A	A
									(+)	B	B
									(–)	C	C
42, 48, 60	83	3/4	NORM	C	1800	1600	1400	1200	TEST	D	D
										D1
42, 48, 60	110	3/4	NORM	C	1800	1600	1400	1200
										DEHUMIDIFY
42, 48, 60	138	3/4	NORM	A	1800	1600	1400	1200		CUT TO ENABLE

Table 4

Page 12 Issue 1008 506488-01