Page 8 / IM 178
Contr
ols, Settings, and Functions
Table 2 presents a listing of all the unit control devices. Included in the table are the device symbol, a description of the d
evice, its function, and any reset information, its location,
any device setting, any setting ranges, differentials, and the device part number.
Table 2. Controls, settings and functions
SYMBOL
DESCRIPTION
FUNCTION
RESET
LOCATION
SETTING
RANGE
DIFFERENTIAL
PART NO.
ADI
ADI Board
Collects and conditions analog and digital inputs.
N/A
Main control box
N/A
N/A
N/A
658160B-05
DHL
Duct high limit
Prevents excessive VAV duct pressures; shuts off fan.
Auto
Main control box
3.5" w.c. (871.8 Pa)
0.05–5.0" w.c.
0.
05" w.c.
654938B-01
(12.5–1245.4 Pa)
(12.5 Pa), fixed
FS1
Freezestat
Shuts off fans, opens heating valve and closes out-
Auto
Heating section
38
°
F (3
°
C) or
35
°
F–45
°
F1
2
°
F (7
°
C), fixed
658300B-01
door damper if low air temperature at coil is detected.
as required
(2
°
C–7
°
C)
MAT
Mixed air temperature
Senses mixed air temperature; sends signal to
N/A
Inlet of supply fan
N/A
3K ohms at
N/A
658295B-03
sensor
MicroTech controller.
77
°
F (25
°
C)
MCB1
Microprocessor Control
Processes input information and controls output re-
N/A
Main control box
N/A
N/A
N/A
654873B-08
Board
lays as appropriate.
OAE
Enthalpy control
Returns outside air dampers to minimum position
Auto
Economizer section
“B” or as required
A – D
Temperature:
3070
67D-02
(electromechanical)
when enthalpy is too high.
3.5
°
F (2
°
C)
Humidity:
5% fixed
Enthalpy control
Returns outside air dampers to minimum position
Auto
Economizer section
Fully CW past “D”
A – D
N/A
492622B-01
(electronic)
when outside air enthalpy is higher than return air
(when used with
enthalpy (used with RAE).
RAE)
OAT
Outside air temperature
Senses outside air temperature; sends signal to
N/A
Under condenser
N/A
3K ohms at
N/A
658295B-02
sensor
MicroTech controller.
section
77
°
F (25
°
C)
OBA, B, C
Output Boards
Holds MicroTech solid-state output relays.
N/A
Main control box
N/A
N/A
N/A
665422B-01:
A, B, or C
(16-position)
665422B-02:
(8-position)
665422B-03:
(4-position)
PC5, 6
Filter switch
Turns on clogged filter light on status panel.
Auto
Filter sections
As required
.05–5" w.c.
.05" w.c.
654938B-01
(12.5–1245.4 Pa)
(12.5 Pa)
PC7
Differential pressure
Senses supply fan pressure to prove airflow.
Auto
Supply fan section
.10" w.c. (25 Pa)
.05–5" w.c.
.05" w.c.
654938B-01
switch
(12.5–1245.4 Pa)
(12.5 Pa), fixed
RAE
Return air enthalpy sensor
Used to compare return air enthalpy to outside air
N/A
Economizer section
N/A
N/A
N/A
492622B-02
enthalpy (used with OAE).
RAT
Return air temperature
Senses return air temperature; sends signal to Micro-
N/A
Return air section
N/A
3K ohms at
N/A
658295B-05
sensor
Tech controller.
77
°
F (25
°
C)
SAT
Supply air temperature
Senses discharge air temperature; sends signal to
N/A
Discharge air section
N/A
3K ohms at
N/A
658295B-01
sensor.
MicroTech controller.
77
°
F (25
°
C)
SB1, 2
Staging Board 1 or 2
Provides stepped cooling or heating control.
N/A
Main control box
N/A
N/A
N/A
See IM 483
SD1
Smoke detector, supply air
Initiates unit shutdown if smoke is detected.
Manual
Discharge air section
N/A
N/A
N/A
490250B-01
SD2
Smoke detector, return air
Initiates unit shutdown if smoke is detected.
Manual
Return air section
N/A
N/A
N/A
490250B-01
SPS1
Duct static pressure
Converts static pressure signals to voltage signals
N/A
Main control box
N/A
0–5" w.c.
N/A
495450B-05
sensor #1
and sends them to MicroTech controller.
(0–1245.4 Pa)
1–6 VDC out
SPS2
Duct static pressure
Converts static pressure signals to voltage signals
N/A
Main control box
N/A
0–5" w.c.
N/A
495450B-05
sensor #2
and sends them to MicroTech controller.
(0–1245.4 Pa)
1–6 VDC out
Building static pressure
Converts static pressure signals to voltage signals
N/A
Main control box
N/A
-0.25–0.25" w.c.
N/A
495450B-06
sensor
and sends them to MicroTech controller.
(-62.3–62.3 Pa)
1–5 VDC out
SPS5
Dirty filter pressure
Sensors pressure drop across first filter bank and
N/A
First filter section
N/A
0–5" w.c.
N/A
495450B-05
sensor
sends signal to MicroTech controller.
(0–1245.4 Pa)
1–6 VDC out
Continued on next page
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