Hardware; Actuators; Supply Air Temperature Sensor; Outside Air Temperature Sensor - Carrier WeatherExpert 48LC Installation Instructions Manual

Hardware

Actuators —
The EconoMi$er R X damper actuators are direct- - coupled
types with spring- - return. Power is 24- - v from the W7220
outputs. Range of rotation is 95- - degrees; timing for
full- - range movement is 90 seconds to drive open in
normal operation, 30 seconds in Test Mode and 25
seconds for spring return.
These actuators are S- - bus enabled. The S- - bus is a
proprietary local equipment network that connects the
W7220 controller, one S- - enabled actuator and up to three
S- - type enthalpy sensors on a two- - wire communication
network. The S- - bus is polarity- - insensitive. Devices
attached to the S- - bus are automatically recognized by the
controller.
Actuator command position is defined in a 2- - 10 vdc
value. 2.0- - v is outside air damper position fully- - closed
(0% open); 10.0- - v is damper position fully- - open (100%
open). See Table 12 to correlate control voltage values to
outside air damper opening percentage.
Table 12 – Actuator Voltage vs. Damper Position
Vdc % Open Vdc
2.0 0 4.8
2.4 5 5.2
2.8 10 5.6
3.2 15 6.0
3.6 20 6.4
4.0 25 6.8
4.4 30 7.2
These units use a 3- - Nm (27 lb- - in.) torque model,
Honeywell Series MS3103K actuator.
Supply Air Temperature Sensor —
The W7220 controller uses a 20- - k ohm analog sensor for
Supply Air Temperature (SAT). The thermistor is attached
to a ring terminal. The ring terminal is attached to the
unit's supply fan housing, downstream of the unit's indoor
coil. The SAT sensor is connected to the W7220 input
terminals marked MAT. See Table 13 for sensor resistance
to temperature correlations.
The W7220 controller requires a valid signal from its SAT
channel in order to function. If the SAT connection to the
W7220 is lost, the W7220 will initiate an alarm condition
immediately. No economizing operation will be permitted
until this alarm is cleared.
% Open Vdc % Open
35 7.6 70
40 8.0 75
45 8.4 80
50 8.8 85
55 9.2 90
60 9.6 95
65 10.0 100
Table 13 – SAT/OAT Sensor Characteristics
Deg C Ohms
--- 30 415156
--- 25 301540
--- 20 221210
--- 15 163834
--- 10 122453
--- 5 92382
0 70200
5 53806
10 41561
15 32341
20 25346
25 20000
30 15886
35 12698
40 10212
45 8261
50 6720
Outside Air Temperature Sensor —
EconoMi$er X systems equipped with outdoor dry bulb
temperature changeover control include a 20- - k ohm
analog sensor to measure Outdoor Air Temperature
(OAT). This is the same sensor used for the SAT function;
see Table 13 for resistance vs temperature characteristics.
The OAT sensor is attached to the outside air damper frame.
It is connected to the W7220's OAT input terminals.
If an accessory enthalpy sensor is added to an EconoMi$er
X system with factory dry bulb changeover, disconnect this
OAT sensor wiring at the W7220's OAT input terminals.

Enthalpy Control Sensor Configuration—

The W7220 economizer control system can accommodate
up to three S- - bus enthalpy sensors. On EconoMi$er X
models with factory- - installed Enthalpy Changeover
control, one S- - bus sensor is provided in the economizer
outdoor section. Additional sensors may be added to
measure Return Air and Discharge Air conditions.
The Enthalpy Control sensor (Part Number: HH57AC081)
communicates with the W7220 Economizer controller on the
two- - wire local equipment network bus (S- - bus) and can
either be wired using a two- - pin header or using a side
connector. This sensor is used for all OAT (Outdoor Air
Temperature), RAT (Return Air Temperature) and DAT
(Discharge Air Temperature), depending on how its three
position DIP switch is set.
Use Fig. 56 and Table 14 to locate the wiring terminals for
each Enthalpy Control sensor.
Use Fig. 56 and Table 15 to set the DIP switches for the
desired use (location) of the sensor.
44
Deg F Ohms
--- 20 386130
0 193070
20 101820
32 70200
40 55420
45 47771
50 41258
55 35725
60 31035
65 27069
70 23719
77 20000
80 18473
100 11544
120 6768