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VAV Supply Static Sensor
The supply duct differential static pressure sensor (A30) is an analog sensor with a 0-10VDC output over a range of 0-5"w.c
as shown in the following table. The sensor is powered with 24VAC.
Table 4
Static Pressure
Pressure "w.c. DC Voltage Pressure "w.c. DC Voltage Pressure "w.c. DC Voltage Pressure "w.c. DC Voltage
0 0 1.5 3 3 6 4.5 9
0.5 1 2 4 3.5 7 5 10
1 2 2.5 5 4 8
Relative Humidity Sensor - Optional
The indoor relative humidity sensor (A91) is an analog sen
sor with a 0-10VDC output over a relative humidity range of
0-100% relative humidity. The sensor is powered with
24VAC.
Enthalpy Sensor - Optional
The optional enthalpy sensors (A7 and A63) used with the
economizer have an output of 4-20mA. The sensor is pow
ered with 18VAC provided by M3 unit control.
Economizer Differential Pressure Sensor - Optional
Rooftop units installed with Smart Airflow™ will have a
Pressure Transducer (PT5) present in the economizer. PT5
requires 5VDC power supply (P266-5 and {P266-6) and
gives 0.25 VDC to 4 VDC output (P266-4) corresponding to
0” water column and 2” water column respectively. For all
practical purposes the output should be less than 1.2” wa
ter column if not an error code is stored and service alarm
output is turned on.
15-Second-Stage Power Exhaust Relay
K231 (Staged-Blower units equipped
with power exhaust)
The second power exhaust fan is controlled by K231.
A133 will enable K231 only when the blower reaches 70%
of full speed (adjustable ECTO). This prevents a negative
building pressure when the blower is operating in low
speed. Refer to the Unit Controller manual and ECTO la
bels on the unit.
16-Outdoor Fan Transformers T5, T59 (460V
units)
All 460 (G) voltage units use transformer T5 and T59. The
auto voltage to 230VAC transformers are mounted in the
control box. The transformers have an output rating of
0.5A. T5 transformer supplies 230 VAC power to outdoor
fans B4, B5 and B21. T59 transformer supplies 230V to out
door fans B22, B23 and B24.
17-Fuse F61 (Higher SCCR units only)
Fuse F61 is used on units with higher SCCR rating. F61
provides overcurrent protection to compressor and other
cooling components. F61 and S48 are located inside a
sheet metal enclosure in the unit left front corner mullion.
18-Blower Motor Overload Relay S42
The relay (S42) is connected in line with the blower motor
to monitor the current flow to the motor. When the relay
senses an overload condition, a set of normally closed
contacts open to de-energize pin #1 in plug P299 of the
A55 Unit Controller. A55 de-energizes all outputs. Units
will be equipped with a relay manufactured by Teleme
canique figure 4 or Siemens figure 5.
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