Bryant 581C024--060 - Manual (Page 20)

20
Economi$er IV Control Modes
Determine the EconoMi$er IV control mode before set up of the
control. Some modes of operation may require different
sensors. (See Table 6.) The EconoMi$er IV is supplied from the
factory with a supply--air temperature sensor and an outdoor-- air
temperature sensor. This allows for operation of the EconoMi$er
IV with outdoor air dry bulb changeover control. Additional
accessories can be added to allow for different types of
changeover control and operation of the EconoMi$er IV and unit.
Outdoor Dry Bulb Changeover
The standard controller is shipped from the factory configured for
outdoor dry bulb changeover control. The outdoor--air and
supply--air temperature sensors are included as standard. For this
control mode, the outdoor temperature is compared to an
adjustable set point selected on the control. If the outdoor-air
temperature is above the set point, the EconoMi$er IV will adjust
the outdoor-air dampers to minimum position. If the outdoor air
temperature is below the set point, the position of the outdoor air
dampers will be controlled to provide free cooling using outdoor
air. When in this mode, the LED next to the free cooling set point
potentiometer will be on. The changeover temperature set point is
controlled by the free cooling set point potentiometer located on
the control. (See Fig. 35.) The scale on the potentiometer is A, B,
C, and D. See Fig. 36 for the corresponding temperature
changeover values.
Table 6—Economi$er IV Sensor Usage
APPLICATION
ECONOMI$ER IV WITH OUTDOOR AIR
DRY BULB SENSOR APPLICATION
Accessories Required
Outdoor Air
Dry Bulb
None. The outdoor air dry bulb sensor
is factory installed.
Differential
Dry Bulb
CRTEMPSN002A00*
Single Enthalpy HH57AC078
Differential
Enthalpy
HH57AC078
and
CRENTDIF004A00*
CO
2
for DCV
Control using a
Wall-Mounted
CO
2
Sensor
33ZCSENCO2
CO
2
for DCV
Control using a
Duct-Mounted
CO
2
Sensor
33ZCSENCO2†
and
33ZCASPCO2**
O
R
CRCBDIOX005A00††
*CRENTDIF004A00 and CRTEMPSN002A00 accessories are used on many
different base units. As such, these kits may contain parts that will not be
needed for installation.
† 33ZCSENCO2 is an accessory CO
2
sensor.
** 33ZCASPCO2 is an accessory aspirator box required for duct-mounted
applications.
†† CRCBDIOX005A00 is an accessory that contains both 33ZCSENCO2
and 33ZCASPCO2 accessories.
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. 37.)
Wiring is provided in the EconoMi$er IV wiring harness. (See
Fig. 29.)
In this mode of operation, the outdoor-air temperature is
compared to the return-air temperature and the lower temperature
airstream is used for cooling. When using this mode of
changeover control, turn the enthalpy setpoint potentiometer fully
clockwise to the D setting. (See Fig. 35.)
Outdoor Enthalpy Changeover
For enthalpy control, accessory enthalpy sensor (part number
HH57AC078) is required. Replace the standard outdoor dry bulb
temperature sensor with the accessory enthalpy sensor in the same
mounting location. (See Fig. 23 and 33.) When the outdoor air
enthalpy rises above the outdoor enthalpy changeover set point,
the outdoor-air damper moves to its minimum position. The
outdoor enthalpy changeover set point is set with the outdoor
enthalpy set point potentiometer on the EconoMi$er IV
controller. The set points are A, B, C, and D. (See Fig. 38.) The
factory-installed 620-ohm jumper must be in place across
terminals SR and SR+ on the EconoMi$er IV controller. (See Fig.
23 and 39.)
Differential Enthalphy Control
For differential enthalpy control, the EconoMi$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$er IV opens to
bring in outdoor air for free cooling.
Replace the standard outside air dry bulb temperature sensor with
the accessory enthalpy sensor in the same mounting location.
(See Fig. 23.) Mount the return air enthalpy sensor in the return
air duct. (See Fig. 37.) Wiring is provided in the EconoMi$er IV
wiring harness. (See Fig. 29.) 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.
581B
,C