10
Installing Differential Return Air Sensor
The CRDIFRASN01A00 differential return sensor kit must be
field mounted in the system’s return duct work. The kit includes a
wiring harness that connects the EconoMi$er X harness in the
return chamber of the unit to the provided HH57AC081 sensor.
Wire according to Fig. 23.
In addition to using the HH57AC081 (Honeywell C7400S) sensor
(see Fig. 21) for a single enthalpy sensor, it can also be used as a
differential return enthalpy or dry bulb sensor. Figure 22 shows
the dual enthalpy boundaries in the W7220 controller. With dual
enthalpy, the HIGH LIMIT boundary is ES1 when there are no
stages of mechanical cooling energized and HL (high limit) when
a compressor stage is energized. Table 6 shows the High Limit
Curves for each setting.
NOTE: To use the HH57AC081 sensor for differential return air,
the dipswitches on the sensor must be set to ON-OFF-OFF. (See
Table 5.)
When using the CRDIFRASN01A00 differential return enthalpy
or dry bulb temperature option, see Table 7 for California Title 24
setting requirements by region.
Fig. 23 — Wiring Differential Return-Air Sensor
California’s Title 24 High Temperature Limit
Settings
California’s Title 24 code requires a high temperature limit setting
for all dry bulb outside air economizer change over. The
temperatures vary by the region within California. See Table 7 for
high limit settings.
*Only the high limit control devices listed are allowed to be used and at
the set points listed. Others such as Dew Point, Fixed Enthalpy, Elec-
tronic Enthalpy, and Differential Enthalpy Controls, may not be used in
any climate zone for compliance with Section 140.4(e)1 unless approv-
al for use is provided by the Energy Commission Executive Director.
†At altitudes substantially different than sea level, the Fixed Enthalpy
limit value shall be set to the enthalpy value at 75°F and 50% relative
humidity. As an example, at approximately 6,000 foot elevation, the
fixed enthalpy limit is approximately 30.7 Btu/lb
LEGEND
Demand Controlled Ventilation
Refer to Fig. 17 for EconoMi$er X wiring. DCV instructions if
demand controlled ventilation (CO
2
sensor) is used. The CO
2
sensor will wire into the blue and black connections at the
controller as shown in Fig. 24. If a field-installed CO
2
sensor is
connected to the EconoMi$er X controller, a demand controlled
ventilation strategy will operate automatically. As the CO
2
level in
the space increases above the setpoint (on the EconoMi$er X con-
troller), the minimum position of the dampers will be increased
proportionally, until the Maximum Ventilation setting is reached.
As the space CO
2
level decreases because of the increase in fresh
air, the outdoor damper will follow the higher demand condition
from the DCV mode or from the free cooling mode.
Fig. 24 — CO
2
Wiring Connections to Controller
12-PIN FEMALE
PLUG FROM ECONOMIZER
BLU
BLK
GRA
GRA
GRA
GRA
GRA
GRA
GRA
PNK
VIO
6
7
2
3
10
11
5
1
12
9
4
8
RED
ORG
PL6
PLUG
12-PIN MALE
PLUG IN UNIT
BRN
YEL
*HH57AC081
DIFFERENTIAL RETURN
SENSOR. FIELD MOUNTED
IN RETURN DUCT
WIRING
HARNESS*
*PROVIDED IN
CRDIFRAS001A00 Kit
Table 7 — California Title 24 Regional High Limit Dry
Bulb Temperature Settings/
Air Economizer High Limit Shut Off Control
Requirements
DEVICE TYPE
*
CLIMATE
ZONES
REQUIRED HIGH LIMIT
(ECONOMIZER OFF WHEN):
DESCRIPTION
FIXED DRY
BULB
1, 3, 5, 11-16
OAT exceeds 75°F
2, 4, 10
OAT exceeds 73°F
6, 8, 9
OAT exceeds 71°F
7
OAT exceeds 69°F
DIFFERENTIAL
DRY BULB
1, 3, 5, 11-16
OAT exceeds
RA temperature
2, 4, 10
OAT exceeds return air temperature
–2°F
6, 8, 9
OAT exceeds return air temperature
–4°F
7
OAT exceeds return air temperature
–6°F
FIXED
ENTHALPY
†
+ FIXED DRY
BULB
All
OAT exceeds 28 Btu/lb of dry air
†
or
OAT exceeds 75°F
OAT
— Outdoor-air Thermostat
Black Wire
IAQ 2-10 VDC
Blue Wire
IAQ COM
