Specifications

10 | Electrical SM AH Series Heat Pump
SM AH Series Heat Pump873392084 (2013/11) Subject to change without prior notice
ECM Interface Board
Figure # 12
THERMOSTAT CONNECTIONS
Thermostat wiring is connected to the 10 pin
screw type terminal block on the lower center
portion of the ECM Interface Board. In addition to
providing a connecting point for thermostat wiring,
the interface board also translates thermostat
inputs into control commands for the variable
speed programmable ECM DC fan motor and
displays an LED indication of operating status.
The thermostat connections and their functions
are as follows:
If the unit is being connected to a thermostat with
a malfunction light, this connection is made at the
unit alarm output.
To the left of the thermostat connection block are
a row of 2 red and 4 green LED’s. These LED’s
indicate the operating status of the unit. They are
labeled as follows:
Just above the connector block is a single red LED
labeled CFM that will blink intermittently when the
unit is running and may flicker when the unit is off.
This LED indicates the air delivery of the blower at
any given time. Each blink of the LED represent
100 CFM of air delivery so if the LED blinks 12
times, pauses, blinks 12 times, etc. the blower is
delivering 1200 CFM. Refer to Figure #10 for
factory programmed air delivery settings for the
SM Series.
1. For the condensate overflow sensor, connect ‘CS’ at the
condensing section to ‘CS’ at the air handler. Be sure to ground
power supply.
2. If service LED is utilized connect ‘ALR’ terminal on the UPM board
to ‘L’ on the thermostat sub base. The wiring may be spliced in the
air handling unit. The ALR output is always dry contact between
the OUT and COM Terminals. See Thermostat connections section
of this manual for additional information.
3. ‘O’ – reversing valve is energized in the cooling mode. Fail safe is
to heating.
4. Utilized when electric strip heater package present.
Y2 Second Stage Compressor Operation
Y1 First Stage Compressor Operation
GFan
O Reversing Valve (energized in cooling)
W1
Auxiliary Electric Heat
(runs in conjunction with compressor)
EM/W2 Emergency Heat (electric heat only)
NC
Transformer 24 VAC Common
(extra connection)
C1
Transformer 24 VAC Common
(primary connection)
R Transformer 24 VAC Hot
HUM Dehumidification Mode
If the thermostat is provided with a
malfunction light powered off of the
common (C) side of the transformer, a
jumper between “R” and “COM” terminal of
“ALR” contacts must be made.
If the thermostat is provided with a
malfunction light powered off of the hot (R)
side of the transformer, then the thermostat
malfunction light connection should be
connected directly to the (ALR) contact on
the unit’s UPM board.
EM
RED
Emergency Heat On
W1
RED
Auxiliary Heat On
O GREEN
Reversing Valve Energized, unit
is in cooling mode
Y2
GREEN
Second Stage Compressor On
Y1
GREEN
First Stage Compressor On
G
GREEN
Fan On