29
The enthalpy control receives t he outdoor air enthalpy
from the outdoor air enthalpy sensor and provides a dry
contact switch input to the PremierLink controller. A
closed contact indicates that outside air is preferred to the
return air. An open contact indicates that the economizer
should remain at minimum position.
Differential Ent halpy Control — Differential enthalpy
control is provided by sensing a nd compa ring the outside
air and return air enthalpy c onditions. Install the outdoor
air enthal py control as described above. Add and install a
return air enthalpy sensor.
Return Air Enthalpy Sensor — Mount the return--air
entha lpy sensor (HH57AC078) in the return--air duct. The
return air sensor is wired to the enthalpy controller
(HH57AC077). See Fig. 42.
LED
A
B
C
D
TR TR1
SO
SR
2
3
1
+
+
BRN
RED
GRAY/ORN
GRAY/RED
WIRE HARNESS
IN UNIT
BLK
RED
S
+
(RETURNAIR
ENTHALPY
SENSOR)
S
+
(OUTDOOR
AIR
ENTHALPY
SENSOR)
ENTHALPY CONTROLLER
NOTES:
1. Remove factory-installed jumper across SR and + before connecting
wires from return air sensor.
2. Switches shown in high outdoor air enthalpy state. Terminals 2 and 3
close on low outdoor air enthalpy relative to indoor air enthalpy.
3. Remove sensor mounted on back of control and locate in outside air-
stream.
C06019
Fig. 42 -- Outside and Return Air Enthalpy Sensor
Wiring
To wire the return air enthalpy sensor, perform the
following:
1. Use a 2--conductor, 18 or 20 AWG, twisted pair cable
to connect the return air enthalpy sensor to the enthal-
py controller.
2. At the enthalpy control remove the fa ctory--install ed
resistor from the (SR) and (+) terminals.
3. Connect the field--supplied RED wire to (+) spade
connec tor on the return air enthalpy sensor and the
(SR+) te rminal on the enthalpy controller. Connect
the BLK wire to (S) spade connector on the return air
entha lpy sensor and the (SR) terminal on the enthalpy
controller.
NOTE: The enthalpy control must be set to the “D”
setting for differential enthalpy control to work properly.
The enthalpy control receives the indoor and return
enthalpy from the outdoor and return air enthalpy sensors
and provides a dry contact switch input to the
PremierLink controller. A closed contact indicates that
outside air is preferred to the return air. An open contact
indicates that the economizer should remain at minimum
position.
Indoor Air Quality (CO2 sensor) — The indoor air quality
sensor accessory monitors space carbon dioxide (CO2)
levels. This information is used to monitor IAQ levels.
Several types of sensors are available, for wall mounting
in the space or in return duct, with and without LCD
display, and in combination with space temperature
sensors. Sensors use infrared technology to measure the
levels of CO2 present in the space air.
The CO2 sensors are all factory set for a range of 0 to
2000 ppm and a linear mA output of 4 to 20. Refer to the
instructions supplied with the CO2 sensor for electrical
requirements and terminal locations. See Fig. 43 for
typical CO2 sensor wiring schematic.
8
7
6
5
4
32
1
2
1
HG
24 VAC
OR
24 VDC
NC
ALARM
RELAY
CONTACTS
COM
NO
}
0-10VDC
SIG COM (J4-6)
4-20mA (J4-5)
+
+
-
+
-
C07134
Fig. 43 -- Indoor/Outdoor Air Quality (CO2) Sensor
(33ZCSENCO2) -- Typical Wiring Diagram
To accurately monitor the quality of the air in the
conditioned air space, locate the sensor near a return--air
grille (if present) so it senses the concentration of CO2
leaving the space. The sensor should be mounted in a
location to avoid direct breath contact.
Do not mount the IAQ sensor in drafty areas such as near
supply ducts, open windows, fans, or over heat sources.
Allow at least 3 ft (0.9 m) between the sensor and any
corner. Avoid mounting the sensor where it is influenced
by the supply air; the sensor gives inaccurate readings if
the supply air is blown directly onto the sensor or if the
supply a ir does not have a chance to mix with the room air
before it is drawn into the return airstream.
Wiring the Indoor Air Quality Sensor —
For each sensor, use two 2--conductor 18 AWG (American
Wire Gage) twisted--pair cables (unshielded) to connec t
the separate isolated 24 vac power source to the sensor
and to connect the sensor to the control board terminals.
To connect the sensor to the control, identify the positive
(4 to 20 mA) and ground (SIG COM) terminals on the
sensor. See Fig. 43. Connect the 4--20 mA terminal to
terminal TB1--9 and connect the SIG COM terminal to
terminal TB1 --7. See Fig. 44.
50TC
