Bryant DURAPAC PLUS 581A User Manual download pdf (Page 32)

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Differential Dry Bulb Control

For differential dry bulb control the standard outdoor dry

bulb sensor is used in conjunction with an additional acces-

sory dry bulb sensor (part number CRTEMPSN002A00). The

accessory sensor must be mounted in the return airstream.

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

Fig. 26.

In this mode of operation, the outdoor-air temperature is

compared to the return-air temperature and the lower tem-

perature airstream is used for cooling. When using this mode

of changeover control, turn the enthalpy set point potentiom-

eter fully clockwise to the D setting.

Outdoor Enthalpy Changeover

For enthalpy control, accessory enthalpy sensor (part num-

ber HH57AC078) is required. Replace the standard outdoor

dry bulb temperature sensor with the accessory enthalpy

sensor in the same mounting location. When the outdoor air

enthalpy rises above the outdoor enthalpy changeover set

point, the outdoor-air damper moves to its minimum posi-

tion. The outdoor enthalpy changeover set point is set with

the outdoor enthalpy set point potentiometer on the

EconoMi$er IV controller. The set points are A, B, C, and D.

See Fig. 27. The factory-installed 620-ohm jumper must be in

place across terminals S

and + on the EconoMi$er IV con-

troller. See Fig. 26.

Differential Enthalpy Control

For differential enthalpy control, the EconoMi$er IV control-

ler 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. Mount the return-air enthalpy sensor in

the return-air duct. Wiring is provided in the EconoMi$er IV

wiring harness. See Fig. 26. 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 set

point potentiometer fully clockwise to the D setting. See

Fig. 28.

Indoor Air Quality (IAQ) Sensor Input

The IAQ input can be used for demand control ventilation

control based on the level of CO

measured in the space or

return-air duct.

Mount the optional IAQ sensor according to manufacturer

specifications. The IAQ sensor should be wired to the AQ and

AQ1 terminals of the controller. Adjust the DCV (demand

controlled ventilation) potentiometers to correspond to the

DCV voltage output of the indoor air quality sensor at the

user-determined set point. See Fig. 29.

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. 28. 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 activation to allow

the dampers to open. This delay allows the damper to reach

the appropriate position to avoid unnecessary fan overload.

Fig. 26 — EconoMi$er IV Wiring

LEGEND

IA — Indoor Air

IAQ — Indoor Air Quality

OA — Outdoor Air

OAS— Outdoor-Air Temperature Sensor

PL — Plug

RAS— Return-Air Temperature Sensor

SAT — Supply-Air Temperature Sensor

1 2 ... 27 28 29 30 31 32 33 34 35 36 37 ... 55 56

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Bryant DURAPAC PLUS 581A User Manual Page 32

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