Bryant 549B Series, Installation, Start-Up And Service Instructions Manual

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E. 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.
Refer to Table 6. The EconoMi$er IV is supplied from the fac-
tory with a supply air temperature sensor and an outdoor air
temperature sensor. This allows for operation of the
EconoMi$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$er
IV and unit.
Table 6 — EconoMi$er IV Sensor Usage
*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.
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$er IV will
adjust the outdoor-air dampers to minimum position. If the
outdoor-air temperature is below the set point, the position of
the outdoor-air dampers will be controlled to provide free cool-
ing using outdoor air. When in this mode, the LED next to the
free cooling set point potentiometer will be on. The changeover
temperature set point is controlled by the free cooling set point
potentiometer located on the control. See Fig. 25. The scale on
the potentiometer is A, B, C, and D. See Fig. 26 for the corre-
sponding temperature changeover values.
Differential Dry Bulb Control
For differential dry bulb control the standard outdoor dry
bulb sensor is used in conjunction with an additional acces-
sory dry bulb sensor (part number CRTEMPSN002A00). The
accessory sensor must be mounted in the return airstream.
See Fig. 27. Wiring is provided in the EconoMi$er IV wiring
harness. See Fig. 20.
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. See Fig. 25.
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. See Fig. 14. 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 potentiome-
ter on the EconoMi$er IV controller. The set points are A, B,
C, and D. See Fig. 28. The factory-installed 620-ohm jumper
must be in place across terminals SR and SR+ on the
EconoMi$er IV controller. See Fig. 14 and 29.
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 sen-
sor with the accessory enthalpy sensor in the same mounting
location. See Fig. 14. Mount the return air enthalpy sensor
in the return air duct. See Fig. 27. Wiring is provided in the
EconoMi$er IV wiring harness. See Fig. 20. The outdoor
enthalpy changeover set point is set with the outdoor
enthalpy set point potentiometer on the EconoMi$er IV
controller. When using this mode of changeover control, turn
the enthalpy set point potentiometer fully clockwise to the D
setting.
APPLICATION
ECONOMI$ER IV WITH OUTDOOR AIR
DRY BULB SENSOR
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**
OR
CRCBDIOX005A00††
0
1000
2000
3000
4000
5000
6000
0.05 0.10 0.15 0.20 0.25 0.30 0.35
STATIC PRESSURE (in. wg)
FLOW IN CUBIC FEET
PER MINUTE (cfm)
Fig. 23 — Return Air Pressure Drop
SUPPLY AIR
TEMPERATURE
SENSOR
MOUNTING
LOCATION
SUPPLY AIR
TEMPERATURE
SENSOR
Fig. 24 — Supply Air Sensor Location