Carrier /50HC 04-28, Controls, Start-Up, Operation And Troubleshooting, Page: 88 / 144

88
ENTHALPY SENSORS
The enthalpy accessories (part no. CRENTSNG002A00 and
CRENTDIF002A00) are field-installed accessories. The first
accessory (outdoor air only) determines when the enthalpy is
low relative to a fixed reference. Adding the second accessory
(return air) compares the enthalpy between the outdoor and re-
turn airstreams. In each case, the enthalpy 4 to 20 mA signals
are converted to a switch output which is read by the ECB.
When installing this accessory, the unit must be configured for
enthalpy-based control by setting Configuration

ECON

EN.SW to normally open (1). See Fig. 28 and Fig. 29
for wiring details. Normal status is an active switch which tells
the control that enthalpy is LOW. The actual switch terminal
LOW is normally closed. Refer to the Enthalpy Kit installation
instructions for more information on the installation.
RETURN/SUPPLY AIR TEMPERATURE SENSOR
The temperature sensor (part no. 33ZCSENSAT) is a field-in-
stalled accessory which may be installed on the common return
air duct and/or the common supply air duct near the unit. The
duct return air temperature (RAT) may be selected for display.
When installing the sensor, the unit must be configured by set-
ting Configuration

UNIT

RAT.S to YES. Using a RAT
will allow differential dry bulb control of the economizer. The
duct supply air temperature (SAT) may be used to replace the
SAT sensor that is internal to the unit. A supply duct SAT mea-
surement is valid for heating mode display while the factory-
standard internal SAT is not valid for heating due to its location
upstream of the heating section. When installing the supply
duct SAT, the unit must be configured by setting Configura-
tion

UNIT

SAT.H to ENBL . A SAT sensor in the supply
duct is the preferred configuration for systems with Carrier
variable volume and temperature (VVT) accessory controls.
The field connection terminal board has SAT and RAT termi-
nals. When installing field sensors, use these terminals accord-
ingly to connect into the MBB.
SPACE HUMIDISTAT
The Space Humidistat (part no. -HL-38MG-029) is a wall
mounted device with an adjustable setpoint to control humidity
levels. The humidistat input is provided on the field connection
terminal board. The Space Humidity Switch configuration,
Configuration

UNIT

RH.SW , identifies the normally open
or normally closed status of this input at HIGH humidity.
TB or TB B-HUM . . . . . . . Discrete Input to Board
TB or TB B-R-2 . . . . . . . . 24 VAC Dry Contact Source
NOTE: The humidistat terminals are only in use when the unit
is equipped with the Humidi-MiZer factory option.
SPACE HUMIDITY SENSOR
The space relative humidity sensor (part no. 33ZCSENDRH-
01 duct mount or 33ZCSENSRH-01 wall mount) is a field-in-
stalled accessory. The space relative humidity (RHS) may be
selected for use if the outdoor air quality sensor (OAQ) is not
used and an economizer board is installed. When installing the
relative humidity sensor, the unit must be configured by setting
Configuration

UNIT

RH.S to YES.
TB or TB B-LPWR . . . . . . . . . . . . . 24 VDC Loop Power
TB or TB B-SPRH . . . . . . . 4-20mA Input Signal
Units with EnergyX
®
System
EnergyX units consist of a factory-installed energy recovery
ventilator (ERV) device on a 48/50HC rooftop unit. The Ener-
gyX ERV unit is integrated into the base rooftop unit construc-
tion and is factory-wired. The ERV unit contains a control box,
supply fan(s), exhaust fan(s), and an enthalpy wheel assembly.
All control operations of the ERV are based on the rooftop
unit’s operation through communication with the Comfort Link
controller. See Fig. 42 and 43 for ERV wiring schematic and
component arrangement.
IMPORTANT: When wiring a field SAT sensor, the factory
installed on must be disconnected from the back of the ter-
minal board.