Ecm Interface Board; Thermostat Connections - Bosch Greensource SM024 Installation, Operation And Maintenance Manual

10 | Electrical

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:
Y2 Second Stage Compressor Operation
Y1 First Stage Compressor Operation
G Fan
O Reversing Valve (energized in cooling)
Auxiliary Electric Heat
W1
(runs in conjunction with compressor)
EM/W2 Emergency Heat (electric heat only)
Transformer 24 VAC Common
NC
(extra connection)
Transformer 24 VAC Common
C1
(primary connection)
R Transformer 24 VAC Hot
HUM Dehumidification Mode
If the unit is being connected to a thermostat with
a malfunction light, this connection is made at the
unit alarm output.
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.
8733920846 (2014/01)
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.
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:
EM
RED
W1
RED
O GREEN
Y2
GREEN
Y1
GREEN
G
GREEN
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.
Subject to change without prior notice
SM AH Series Heat Pump
Emergency Heat On
Auxiliary Heat On
Reversing Valve Energized, unit
is in cooling mode
Second Stage Compressor On
First Stage Compressor On
Fan On
SM AH Series Heat Pump