14
HARDWARE
Actuators
The Economizer 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 6 to correlate control voltage values to
outside air damper opening percentage.
Table 6 – Actuator Voltage vs. Damper Position
Vdc %Open Vdc %Open Vdc %Open
2.0 0 4.8 35 7.6 70
2.4 5 5.2 40 8.0 75
2.8 10 5.6 45 8.4 80
3.2 15 6.0 50 8.8 85
3.6 20 6.4 55 9.2 90
4.0 25 6.8 60 9.6 95
4.4 30 7.2 65 10.0 100
Two different actuators are used, based on unit size. Unit
sizes 08 through 16 use a 3--Nm (27 lb--in) torque model,
Honeywell Series MS3103K. Unit sizes 17 through 30 use
a 5-- Nm (44 lb--in) torque model, Series MS3105K.
MS3105 Mode Select Dial — The MS3105 actuator has a
six--position Mode Select dial on its face. Positions 1
through 5 are component addresses. When used with
W7220 controller, the dial must be set at position 1 –
Address 11.
MS3105 TEST Mode — Position 6 on the Mode Select
dial is a TEST Mode selector. In this TEST mode, the
actuator will drive from closed to full--open and then
return to closed position. Be sure to reset the Mode
Selector dial to position 1, Address 11 after performing
this TEST mode.
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
units supply fan housing, downstream of the units
indoor coil. The SAT sensor is connected to the W7220
input terminals marked MAT. See Table 7 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.
Table 7 – SAT/OAT Sensor Characteristics
Deg C Ohms Deg F Ohms
--- 3 0 415156 --- 2 0 386130
--- 2 5 301540 0 193070
--- 2 0 221210 20 101820
--- 1 5 163834 32 70200
--- 1 0 122453 40 55420
--- 5 92382 45 47771
0 70200 50 41258
5 53806 55 35725
10 41561 60 31035
15 32341 65 27069
20 25346 70 23719
25 20000 77 20000
30 15886 80 18473
35 12698 100 11544
40 10212 120 6768
45 8261
50 6720
Outside Air Temperature Sensor
Economizer 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 7 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 Economizer
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 Economizer 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
LLECON--02SI
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