Carrier 48HE003---006 Differential Enthalphy Control, Indoor Air Quality IAQ Sensor Input

48HE,HJ

Differential Enthalphy Control

For differential enthalpy control, the EconoMi$er IV controller uses two enthalpy sensors (HH57AC078 and CRENTDIF004A00), one in the outside air and one in the return air duct. The EconoMi$er IV controller compares the outdoor air enthalpy to the return air enthalpy to determine EconoMi$er IV use. The controller selects the lower enthalpy air (return or outdoor) for cooling. For example, when the outdoor air has a lower enthalpy than the return air, the EconoMi$er IV opens to bring in outdoor air for free cooling.

(cfm)	2500
MINUTE	2000
PER	1500
FEET
	1000
CUBICIN
	500
FLOW	0
			0.05			0.15			0.25
				STATIC PRESSURE (in. wg)
		Fig. 38 ---Barometric Flow Capacity									C06030
(cfm)	30
MINUTE
	25
PER	20
	15
FEET
	10
CUBICIN
	0
	5
FLOW	0.13		0.20	0.22	0.25	0.30	0.35	0.40	0.45	0.50
				STATIC PRESSURE (in. wg)
											C06031
		Fig. 39 ---Outdoor-Air Damper Leakage
(cfm)	6000
MINUTE	5000
PER	4000
	3000
FEET
	2000
CUBIC
	1000
IN
FLOW	0
	0.05			0.10	0.15	0.20	0.25		0.30	0.35

STATIC PRESSURE (in. wg)

C06032

Fig. 40 ---Return-Air Pressure Drop

SUPPLY AIR

TEMPERATURE

SENSOR

MOUNTING

LOCATION

SUPPLY AIR

TEMPERATURE

SENSOR

C06033

Fig. 41 ---Supply Air Sensor Location

C06034

Fig. 42 ---EconoMi$er IV Controller Potentiometer

and LED Locations

Replace the standard outside air dry bulb temperature sensor with the accessory enthalpy sensor in the same mounting location. (See Fig. 29.) Mount the return air enthalpy sensor in the return air duct. (See Fig. 44.) Wiring is provided in the EconoMi$er IV wiring harness. (See Fig. 36.) The outdoor enthalpy changeover set point is set with the outdoor enthalpy set point potentiometer on the EconoMi$er IV controller. When using this mode of changeover control, turn the enthalpy setpoint potentiometer fully clockwise to the D setting.

Indoor Air Quality (IAQ) Sensor Input

The IAQ input can be used for demand control ventilation control based on the level of CO2 measured in the space or return air duct.

Mount the accessory IAQ sensor according to manufacturer specifications. The IAQ sensor should be wired to the AQ and AQ1 terminals of the controller. Adjust the DCV potentiometers to correspond to the DCV voltage output of the indoor air quality sensor at the user-determined set point. (See Fig. 47.)

If a separate field-supplied transformer is used to power the IAQ sensor, the sensor must not be grounded or the EconoMi$er IV control board will be damaged.

Exhaust Set Point Adjustment

The exhaust set point will determine when the exhaust fan runs based on damper position (if accessory power exhaust is installed). The set point is modified with the Exhaust Fan Set Point (EXH SET) potentiometer. (See Fig. 42.) The set point represents the damper position above which the exhaust fans will be turned on. When there is a call for exhaust, the EconoMi$er IV controller provides a 45 ± 15 second delay before exhaust fan

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