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SM Series Heat Pump
ECM INTERFACE BOARD
Refer to Figure #46, item [9] for ECM interface board
location. In addition to providing a connecting point for
thermostat wiring, the interface board also translates
thermostat inputs into control commands for the
Electronic Commutated Motor (ECM) fan motor and
provides thermostat signals to the unit's UPM board.
The thermostat connections and their functions are as
follows:
10
9
8
7
6
Figure # 51
[1] Motor harness plug
[2] Blower CFM adjustment
[3] Motor settings
[4] Dehumidification indication
[5] Thermostat contact inputs
[6] CFM count indicator
[7] Thermostat input status indication
[8] Reheat digital outputs
[9] Thermostat outputs
[10] 24 VAC
[11] Dehumidification method selector
CFM LED indication is an approximation. Utilize
conventional Test and Balance equipment for
accurate airflow measurement.
•
CFM count indicator (Figure #51 item [6]) blinks to
indicate approximate airflow in CFM and may flicker
when the unit is off.
•
Each blink of the LED represent approximately 100
CFM of air delivery so if the LED blinks 12 times,
pauses, blinks 12 times, etc. the blower is delivering
approximately 1200 CFM.
Revised 07-17
3
1
11
5
2
4
Thermostat Outputs
Y1
First Stage Compressor Operation
Y2
Second Stage Compressor Operation
G
Fan
O
Reversing Valve (energized in cooling)
W1
Auxiliary Electric Heat (runs in conjunction with
compressor)
EM/W2
Emergency Heat (electric heat only)
C
Transformer 24 VAC Common
R
Transformer 24 VAC Hot
H
Dehumidification Mode
Constant Airflow Motor
The Constant Airflow Motor is an Electronic
Commutated Motor (ECM) that provides a constant air
flow over a wide range of external static pressures, while
optimizing the power consumption of the motor.
This option allows the unit to have different air flow
settings depending on the mode that the unit is
operating; i.e heating, cooling, fan only, electric heat,
etc.
Airflow Selector
The airflow selector (Figure #50, items [2] & [3]) allows
airflow adjustment to meet application requirements
and to ease troubleshooting.
Only one dip switch can be enabled at a time. Refer
to Figure #52 for each airflow setting.
•
CFM Selector (Figure #52) must remain with only
"A" being enabled.
•
ADJUST Selector can be adjusted to NOM, (+), (-), or
TEST. NOM, (+) and (-) can be adjusted as needed
by application. TEST is used for troubleshooting to
override unit airflow to 100%
Figure # 52
ECM Interface Board | 21
8733942411 (2017/06)
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