Sequence Of Operation; Cooling Mode - Bosch SM024 Installation, Operation And Maintenance Manual

SM AH Series Heat Pump
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.
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 Emergency Heat On
RED
W1 Auxiliary Heat On
RED
Reversing Valve Energized, unit
O GREEN
is in cooling mode
Y2 Second Stage Compressor On
GREEN
Y1 First Stage Compressor On
GREEN
G Fan On
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.
Just above and to the right of the thermostat
connection block are four sets of jumper pins
labeled ADJ, DELAY, HEAT and COOL. The ADJ set
of pins are labeled NORM, (+), (-) and TEST. AP
units will all be set on the NORM position from the
factory, however, airflow can be increased (+) or
decreased (-) by 15% from the pre-programmed
setting by relocating the jumper in this section.
The TEST position is used to verify proper motor
operation. If a motor problem is suspected, move
the ADJ jumper to the TEST position and energize
G on the thermostat connection block. If the motor
ramps up to 100% power, then the motor itself is
functioning normally. Always remember to replace
the jumper to NORM, (+) or (-) after testing and
reset the unit thermostat to restore normal
operation.
Do not set the ADJ jumper to the (-) setting when
electric heaters are installed. Doing so may cause
the heaters to cycle on their thermal overload
switches, potentially shortening the life of the
switches.
The other three sets of jumper pins are used to
select the proper program in the ECM motor for
the unit. Refer to Figure #7 for the proper jumper
placement.
To the left of the red and green status LED's is a
row of 1/4" male quick connects. These are used
to pass thermostat inputs on to the rest of the
control circuit. Remember to always turn off unit
power at the circuit breaker before attaching or
disconnecting any wiring from these connections
to avoid accidental short circuits that can damage
unit control components.

SEQUENCE OF OPERATION

Cooling Mode

See Typical Wiring Diagram at the end of the
manual. Energizing the "O" terminal energizes the
unit reversing valve in the cooling mode. The fan
motor starts when the "G" terminal is energized.
When the thermostat calls for cooling (Y), the loop
pump or solenoid valve if present is energized and
compressor will start.
Sequence of operation | 11
8733920846 (2015/01)