14
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$er X harness in the
return chamber of the unit, to the provided HH57AC081 sensor.
Wire according to Fig. 31.
In addition to using the HH57AC081 (Honeywell C7400S) sensor
(Fig. 30) for a single enthalpy sensor, it can also be used as a
differential return enthalpy or dry bulb sensor. Figure 29 shows the
dual enthalpy boundaries in the W7220 controller. With dual en
-
thalpy the high limit boundary is ES1 when there are no stages of
mechanical cooling energized and HL (high limit) when a
compressor stage is energized. Table 7 shows the High Limit
Curves for each setting.
When using the CRDIFRASN01A00 differential return enthalpy
or dry bulb temperature option, see Table 9 for California Title 24
setting requirements by region.
Fig. 31 —
Wiring Differential Return Air Sensor
California’s Title 24 High Temperature Limit
Settings
California’s Title 24 code requires a high temperature limit setting
for all dry bulb outside air economizer changeover. The
temperatures vary by the region within California. See Table 9 for
high limit settings.
*
Only the high limit control devices listed are allowed to be used and at
the setpoints listed. Others such as Dew Point, Fixed Enthalpy,
Electronic Enthalpy, and Differential Enthalpy Controls may not be used
in any climate zone for compliance with Section 140.4(e)1 unless
approval for use is provided by the Energy Commission Executive
Director.
†
At altitudes substantially different than sea level, the Fixed Enthalpy
limit value shall be set to the enthalpy value at 75°F and 50% relative
humidity. As an example, at approximately 6,000 foot elevation, the fixed
enthalpy limit is approximately 30.7 Btu/lb.
Demand Controlled Ventilation (DCV)
Refer to EconoMi$er X wiring diagrams Fig. 23 and 28 and
DCV instructions if demand control ventilation (CO
2
sensor) is
used. CO
2
sensor will wire into the blue and black connections at
the controller as shown in Fig. 23, 28, and 32. 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 controller), 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. 32 —
CO
2
Wiring Connections to Controller
IMPORTANT: to use the HH57AC081 sensor for differential
return air, the dipswitches on the sensor must be set to
ON-OFF-OFF. (See Table 8.)
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 9 —
California Title 24 Regional High Limit Dry
Bulb Temperature Settings
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 Temp.
2, 4, 10
OAT exceeds -2°F
6, 8, 9
OAT exceeds -4°F
7
OAT exceeds -4°F
FIXED ENTHALPY† +
FIXED DRY BULB
ALL
OAT exceeds 28 Btu/lb of dry
air or OAT exceeds 75°F
Black Wire
IAQ 2-10 VDC
Blue Wire
IAQ COM
