Carrier 48TJE008-014, 48TJD008-014, 48TJF008-012 Operating Sequence, Ð Altitude Compensation

Table 15 Ð Altitude Compensation*

	125,000, 180,000, AND		250,000 BTUH
	224,000 BTUH
			NOMINAL INPUT
	NOMINAL INPUT
ELEVATION
(Ft)	Natural	Liquid	Natural	Liquid
	Gas	Propane	Gas	Propane
	Ori®ce	Ori®ce	Ori®ce	Ori®ce
	Size²	Size²	Size²	Size²
0-2,000	31	41	30	38
2,000	32	42	30	39
3,000	32	42	31	40
4,000	32	42	32	41
5,000	33	43	33	42
6,000	34	43	34	43
7,000	35	44	35	43
8,000	36	44	36	44
9,000	37	45	37	44
10,000	38	46	38	45
11,000	39	47	39	45
12,000	40	47	40	46
13,000	41	48	41	47
14,000	42	48	42	47

*As the height above sea level increases, there is less oxygen per cubic foot of air. Therefore, heat input rate should be reduced at higher altitudes.

²Ori®ce available through your local distributor.

Safety Relief Ð A soft-solder joint at the suction line Schrader port provides pressure relief under abnormal tem- perature and pressure conditions.

Ventilation (Continuous Fan) Ð Set fan and sys- tem selector switches at ON and OFF positions, respec- tively. Evaporator fan operates continuously to provide con- stant air circulation. When the evaporator-fan selector switch is turned to the OFF position, there is a 30-second delay be- fore the fan turns off.

Operating Sequence

COOLING, UNITS WITHOUT ECONOMIZER Ð When thermostat calls for cooling, terminals G and Y1 are ener- gized. The indoor (evaporator) fan contactor (IFC) and com- pressor contactor no. 1 (C1) are energized, and evaporator- fan motor, compressor no. 1, and condenser fan start. The condenser-fan motor runs continuously while unit is cooling. If the thermostat calls for a second stage of cooling by energizing Y2, compressor contactor no. 2 (C2) is ener- gized and compressor no. 2 starts.

When the thermostat is satis®ed, C1 and C2 are deener- gized and the compressors and outdoor (condenser) fan mo- tor (OFM) shut off. After a 30-second delay, the indoor (evaporator) fan motor (IFM) shuts off. If the thermostat fan selector switch is in the ON position, the evaporator motor will run continuously.

HEATING, UNITS WITHOUT ECONOMIZER Ð When the thermostat calls for heating, terminal W1 is energized. In order to prevent thermostat short-cycling, the unit is locked into the Heating mode for at least 1 minute when W1 is en- ergized. The induced-draft motor (IDM) is then energized and the burner ignition sequence begins. The indoor (evapo- rator) fan motor (IFM) is energized 45 seconds after a ¯ame is ignited. On units equipped for two stages of heat, when additional heat is needed, W2 is energized and the high-®re solenoid on the main gas valve (MGV) is energized. When the thermostat is satis®ed and W1 and W2 are deenergized, the IFM stops after a 45-second time-off delay.

COOLING, UNITS WITH DURABLADE ECONOMIZER

ÐWhen the outdoor-air temperature is above the OAT (outdoor-air thermostat) setting and the room thermostat calls for cooling, compressor contactor no. 1 is energized to start

compressor no. 1 and the outdoor (condenser) fan motor (OFM). The indoor (evaporator) fan motor (IFM) is energized and the economizer damper moves to the minimum position. Upon a further call for cooling, compressor contactor no. 2 will be energized, starting compressor no. 2. After the thermostat is satis®ed, the damper moves to the fully closed position when using an auto fan or to the minimum position when using a continuous fan.

When the outdoor-air temperature is below the OAT set- ting and the thermostat calls for cooling, the economizer damp- ers move to the minimum position. If the supply-air temperature is above 57 F, the damper continues to open until it reaches the fully open position or until the supply-air temperature drops below 52 F.

When the supply-air temperature falls to between 57 F and 52 F, the damper will remain at an intermediate open position. If the supply-air temperature falls below 52 F, the damper will modulate closed until it reaches the minimum position or until the supply-air temperature is above 52 F. When the thermostat is satis®ed, the damper will move to the fully closed position when using an auto fan or to the minimum position when using a continuous fan.

If the outdoor air alone cannot satisfy the cooling require- ments of the conditioned space, economizer cooling is in- tegrated with mechanical cooling, providing second-stage cooling. Compressor no. 1 and the condenser fan will be en- ergized and the position of the economizer damper will be determined by the supply-air temperature. Compressor no. 2 is locked out.

When the second stage of cooling is satis®ed, the com- pressor and OFM will be deenergized. The damper position will be determined by the supply-air temperature.

After a 30-second delay, the IFM shuts off. If the ther- mostat fan selector switch is in the ON position, the IFM will run continuously.

COOLING UNITS WITH PARABLADE ECONOMIZER

ÐWhen the outdoor air is above the enthalpy control set- ting, and the room thermostat calls for cooling, the compres- sor contactor no. 1 is energized to start compressor no. 1 and the outdoor (condenser) fan motor. The indoor (evaporator) fan motor is energized and the economizer damper moves to the minimum position. Upon further call for cooling, com- pressor contactor no. 2 is energized, starting compressor no. 2. After the room thermostat is satis®ed the damper will spring return to the fully closed position.

When the outdoor air is below the enthalpy control setting and the thermostat calls for cooling, the economizer outdoor air damper is opened proportionally to maintain between 50 and 56 F at the mixed air sensor. If outside air alone cannot satisfy the cooling requirements, economizer cooling is in- tegrated with mechanical cooling and the second compres- sor is locked out. When the room thermostat is satis®ed, the damper will spring return to the fully closed position.

HEATING, UNITS WITH ECONOMIZER Ð When the ther- mostat calls for heating, terminal W1 is energized. In order to prevent thermostat short-cycling, the unit is locked into the Heating mode for at least 1 minute when W1 is ener- gized. The induced-draft motor is then energized and the burner ignition sequence begins. The indoor (evaporator) fan motor (IFM) is energized 45 seconds after a ¯ame is ignited and the damper moves to the minimum position. On units equipped for two stages of heat, when additional heat is needed, W2 is energized and the high-®re solenoid on the main gas valve (MGV) is energized. When the thermostat is satis®ed and W1 and W2 are deenergized, the IFM stops after a 45 sec- ond time-off delay. The economizer damper then moves to the fully closed position. When using continuous fan, the damper will remain in the minimum position.

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