3
*  CRENTDIF004A00 accessory is 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.
††
CRBDIOX005A00  is  an  accessory  that  contains  both  33ZCSENCO2
and 33ZCASPCO2 accessories.
GENERAL
See Table 1 for Package Usage and Contents.
The EconoMi$er IV system utilizes the latest technology available
for integrating the use of free cooling with mechanical cooling for
packaged rooftop units. The solid-state control system optimizes
energy  consumption,  zone  comfort,  and  equipment  cycling  by
operating the compressors when the outdoor-air temperature is too
warm,  integrating  the  compressor  with  outdoor  air  when  free
cooling  is  available,  and  locking  out  the  compressor  when
outdoor-air temperature is too cold. Demand controlled ventilation
is supported.
The EconoMi$er IV system utilizes gear-drive technology with a
direct-mount  spring  return  actuator  that  will  close  upon  loss  of
power.  The  EconoMi$er  IV  system  comes  standard  with  an
outdoor air temperature sensor, supply air temperature sensor, and
low temperature compressor lockout switch. (See Fig. 1.) Return
air temperature, indoor enthalpy and outdoor enthalpy sensors are
available  for  field  installation.  Field-installed  CO
2
  sensors  are
available. (See Table 2.)
Barometric relief dampers provide natural building pressurization
control. Barometric relief dampers are built into the design and are
standard.  An  optional  power  exhaust  system  is  available  for
applications  requiring  even  greater  exhaust  capabilities.  The
power  exhaust  set  point  is  adjustable  at  the  EconoMi$er  IV
controller. See Table 2 for sensor usage.
Fig. 1 — EconoMi$er IV Component Locations
Table 2 — EconoMi$er IV Sensor Usage
APPLICATION
ECONOMI$ER IV WITH
OUTDOOR AIR DRY BULB SENSOR
Accessories Required
Carrier and Bryant 
units
ICP units
Outdoor Air Dry 
Bulb 
None. The outdoor air dry bulb sensor is factory 
installed.
Single Enthalpy   HH57AC078  AXB078ENT
Differential 
Enthalpy 
HH57AC078 and 
CRENTDIF004A00*
AXB078ENT and 
CRENTDIF004A00*
CO
2
 for DCV 
Control using
a Wall-Mounted 
CO
2
 Sensor 
33ZCSENCO2
†
CO
2
 for DCV 
Control using
a Duct-Mounted 
CO
2
 Sensor 
33ZCSENCO2 and 33ZCASPCO2**
or
CRCBDIOX005A00
††
Outside Air
Damper
Economizer
Actuator
Low Temp.
Lockout
Wiring
Harness
EconoMi$er IV
Controller
Outside Air
Temp (OAT)
Sensor
Return Air Damper