Carrier 48TC*D08 appendix Differential Dry Bulb Control, Outdoor Enthalpy Changeover

Differential Dry Bulb Control

For differential dry bulb control the standard outdoor dry bulb sensor is used in conjunction with an additional accessory dry bulb sensor (part number CRTEMPSN002A00). The accessory sensor must be mounted in the return airstream. (See Fig. 80.) Wiring is provided in the EconoMi$er IV wiring harness. (See Fig. 73.)

In this mode of operation, the outdoor-air temperature is compared to the return-air temperature and the lower temperature airstream is used for cooling. When using this mode of changeover control, turn the enthalpy setpoint potentiometer fully clockwise to the D setting. (See Fig. 77.)

Outdoor Enthalpy Changeover

For enthalpy control, accessory enthalpy sensor (part number HH57AC078) is required. Replace the standard

ECONOMI$ERIV

ECONOMI$ERIV

CONTROLLER

GROMMET

RETURN AIR

SENSOR

RETURN DUCT (FIELD-PROVIDED)

C07085

outdoor dry bulb temperature sensor with the accessory enthalpy sensor in the same mounting location. (See Fig. 80.) When the outdoor air enthalpy rises above the outdoor enthalpy changeover setpoint, the outdoor-air damper moves to its minimum position. The outdoor enthalpy changeover setpoint is set with the outdoor enthalpy setpoint potentiometer on the EconoMi$er IV controller. The setpoints are A, B, C, and D. (See Fig. 81.) The factory-installed 620-ohm jumper must be in place across terminals SR and SR+ on the EconoMi$er IV controller.

48TC

Fig. 80 - Return Air Temperature or Enthalpy Sensor

Mounting Location

																														85		90	95	100		105	110
																														(29)		(32)	(35)	(38)		(41)	(43)
																												46
CONTROL				CONTROL POINT																					4	4
CURVE APPROX. deg. F (deg. C)
																					42								80
					AT 50% RH
	A				73 (23)													AIR											(27)
																				40
	B				70 (21)												DRY																		(%)
	C				67 (19)									POUND				3	8														HUMIDITY
	D				63 (17)
																36												75
													PER														(24)
														3	4
										BTU																						RELATIVE
													32
																								70
											30
																						(21)
									28
																							0
							ENTHALPY														1	0			0
								26												65				9			80
						2	4													(18)								70
																													0
					2	2											60												6
																													50
				2	0												(16)
																			A											4	0
			8											55
		1
														(13)			B															30
	1	6
													50
	4														C
1												(10)																						20
12									45				D
								40	(7)
																																					0
								(4)
																																					1
						35
						(2)
																												D C	B	A
																																					HIGH LIMIT
																																					CURVE
						35		40	45				50		55		60			65				70				75	80	85		90	95	100		105	110
						(2)		(4)	(7)				(10)	(13)			(16)			(18)				(21)				(24)	(27)	(29)		(32)	(35)	(38)		(41)	(43)
						APPROXIMATE DRY BULB TEMPERATURE--degrees F (degrees C)

C06037

Fig. 81 - Enthalpy Changeover Setpoints

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