18
IM 738-2
Introduction:
Controls, Settings, and Functions
Controls, Settings, and Functions
Table 3 below lists all of the unit control devices. Included in
the table are the device symbol, a description of the device, its
function, and any reset information, its location, any device
setting, any setting ranges, differentials, and the device part
number.
Table 3: Controls, settings, and functions
Symbol
Description
Function
Reset
Location
Setting
Range
Differential
Part no.
CS1 & 2 Switch (toggle),
refrigerant circuit
Shuts off compressor control
circuits manually
N/A
Main control
panel
N/A
N/A
N/A
01355000
DAT
Discharge air
temperature
sensor
Senses discharge air
temperature
N/A
Discharge air
section
N/A
N/A
060004705
DHL
Duct high limit
switch
Prevents excessive VAV duct
pressures; shuts off fan
Auto
Main control
panel
3.5" w.c
(871.8 Pa)
0.05–5.0" w.c.
(12.5–1245.4 Pa)
.05" w.c.
(12.5 Pa), fixed
065493801
EFT
Entering fan air
temperature
sensor
Senses entering fan air
temperature
N/A
Inlet of supply
fan
N/A
N/A
060004705
FP1, 2 Evaporator frost
protection
Senses low refrigerant
temperature
N/A
Return bends
of
evaporative
coil
Opens at 30°F
Closes at 45°F
N/A
N/A
072501901
FS1
Freezestat
Shuts off fans, opens heating
valve, and closes outdoor
damper if low air temperature
at coil is detected
Auto
Heating
section
38°F (3°C)
or as required
35°F–45°F
(2°C–7°C)
12°F (7°C),
fixed
065830001
HP1, 2,
3 & 4
High pressure
control
Stops compressor when
refrigerant discharge pressure
is too high
Manual
(relay
latched)
Compressor
N/A
100 psi
(689 kPa)
047356120
LP1, 2 Low pressure
control
Stops compressor when
suction pressure is too low
(used for pumpdown)
Auto
Compressor
N/A
25 psi
(172 kPa)
047356111
MCB
Main control board Processes input information
N/A
Main control
box
N/A
N/A
N/A
060006101
MP1–6 Compressor
motor protector
Senses motor winding
temperature, shuts off
compressor on high
temperature.
Notes:
1.Unit size 018C compressors
include internal motor
protector.
2.Unit sizes 020C–036C,
circuit #1 compressors include
internal motor protector (refer
to unit wiring diagram).
Auto at
3400
ohms
Compressor
junction box
9 K–18 K ohms
700 ohms cold
N/A
044691509
OAE
Enthalpy control
(electro-
mechanical)
Returns outside air dampers to
minimum position when
enthalpy is too high
Auto
Economizer
section
“B” or as required
A–D
Temperature:
3.5°F (2°C)
Humidity:
5% fixed
030706702
Enthalpy control
(electronic)
Returns outside air dampers to
minimum position when
outside air enthalpy is higher
than return air empalthy
(use RAE)
Auto
Economizer
section
Fully CW past “D”
(when used
with RAE)
A–D
N/A
049262201
OAT
Outside air
temperature
sensor
Senses outside air
temperature
N/A
N/A
N/A
060004705
PC5
Dirty filter switch
Senses filter pressure drop
Auto
First filter
section
As required
.05-5" w.c.
(12.5–1245.4 Pa)
.05" w.c.
(12.5 Pa)
065493801
PC6
Dirty filter switch
Senses filter pressure drop
Auto
Final filter
section
As required
.05-5" w.c.
(12.5–1245.4 Pa)
.05" w.c.
(12.5 Pa)
065493801
Summary of Contents for RDT-135c
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