Carrier 48TCA04---A12

TR1

24 Vac

COM

Vac

HOT

EF EF1

EXH

2V 10V

EXH

Set

2V 10V

DCV

Free

Cool

SO+

SR+

AQ1

DCV

Min

Pos

Open

Max

C06038

Fig. 81 --EconoMi$er IV Control

Differential Enthalpy 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.

Replace the standard outside air dry bulb temperature

sensor with the accessory enthalpy sensor in the same

mounting location. (See Fig. 70.) Mount the return air

enthalpy sensor in the return air duct. (See Fig. 79.)

Wiring is provided in the EconoMi$er IV wiring harness.

(See Fig. 70.) The outdoor enthalpy changeover setpoint is

set with the outdoor enthalpy setpoint potentiometer on

the EconoMi$er IV controller. When using this mode of

changeover control, turn the enthalpy setpoint

potentiometerfully clockwise to the D setting.

Indoor Air Quality (IAQ) Sensor Input

The IAQ input can be used fordemand control ventilation

control based on the level of CO2measured 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 setpoint. (See Fig. 82.)

1000

2000

3000

4000

5000

6000

2345678

800ppm

900ppm

1000ppm

1100ppm

RANGECONFIGURATION (ppm)

DAMPERVOLTAGE FOR MAX VENTILATIONRATE

CO SENSORMAX RANGE SETTING

C06039

Fig. 82 --CO2Sensor Maximum Range Settings

If a separate field-supplied transformer isused to power

the IAQ sensor, the sensor must not be grounded or the

EconoMi$er IV control board will be damaged.

When using demand ventilation, the minimum damper

position represents the minimum ventilation positionfor

VOC (volatile organic compounds) ventilation

requirements. The maximum demand ventilation position

is usedfor fully occupied ventilation.

When demand ventilation control is not being used, the

minimum position potentiometer should be used to set the

occupied ventilation position. The maximum demand

ventilation position should be turned fully clockwise.

Exhaust Setpoint Adjustment

The exhaust setpoint will determine when the exhaust fan

runs based on damper position (if accessory power

exhaust is installed). The setpoint is modifi ed with the

Exhaust Fan Setpoint (EXH SET) potentiometer. (See Fig.

76.) The setpoint 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 activation to

allow the dampers to open. This delay allows the damper

to reach the appropriate position to avoid unnecessary fan

overload.

Minimum Position Control

There is a minimum damper position potentiometer on the

EconoMi$er IV controller. (See Fig. 76.) The minimum

damper position maintains the minimum airflow into the

building during the occupied period.

When using demand ventilation, the minimum damper

position represents the minimum ventilation positionfor

VOC (volatile organic compound) ventilation

requirements. The maximum demand ventilation position

is usedfor fully occupied ventilation.

When demand ventilation control is not being used, the

minimum position potentiometer should be used to set the

occupied ventilation position. The maximum demand

ventilation position should be turned fully clockwise.

Adjust the minimum position potentiometer to allowthe

minimum amount of outdoor air, as required by local

codes, to enter the building. Make minimum position

adjustments with at least 10_F temperature difference

between the outdoor and return-air temperatures.

48TC