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Post-Installation System Checkout; System Operation; Unit Start-Up; Sequence Of Operation - Bosch SM Split CS Series Installation, Operation And Maintenance Manual

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SM Split CS Series Heat Pump
After completing the installation and before
energizing the unit, the following system checks
MUST be made:
1. Verify that the supply voltage to the heat pump
is in accordance with the nameplate ratings.
2. Make sure that all electrical connections are
tight and secure.
3. Check the electrical fusing and wiring for the
correct size.
Ensure the cabinet and electrical box are
properly grounded.
4. Verify that the low-voltage wiring between the
thermostat and the unit is correct.
5. Verify that the water piping is complete and
6. Check that the water flow is correct and adjust
if necessary.
7. Check the blower for free rotation, and that it
is secured to the shaft.
8. Verify that vibration isolation has been
9. Ensure the unit is serviceable.
10. Confirm that all access panels are secured in
Always check incoming line-voltage power
supply and secondary control voltage for
adequacy. Transformer primaries are dual
tapped for 208 and 230 volts. Connect the
appropriate tap to ensure a minimum
secondary control voltage of 18 volts. 24
volts is ideal for best operation.
Long-length thermostat and control wiring
leads may create voltage drop. Increase
wire gauge or up-size transformers may be
required to ensure minimum secondary
voltage supply.
Bosch recommends the following
guidelines for wiring between a thermostat
and the unit: 18 GA up to 60 foot, 16 GA up
to 100 ft and 14 GA up to 140 ft.
Do not apply additional controlled devices
to the control circuit power supply without
consulting the factory. Doing so may void
equipment warranties.
Check with all code authorities on
installation criteria including condensate
disposal/overflow protection criteria.
SM Split CS Series Heat Pump



1. Place the UPM board in "Test" mode.
2. Set the thermostat to the highest setting.
3. Set the thermostat system switch to "COOL"
and the fan switch to the "AUTO" position. The
reversing valve solenoid should energize. The
compressor should not run.
4. Reduce the thermostat setting approximately
five degrees below the room temperature.
5. Verify the heat pump is operating in the cooling
6. Turn the thermostat system switch to the
"OFF" position. The unit should stop running
and the reversing valve should de-energize.
7. Leave the unit off for approximately five
minutes to allow for system equalization.
8. Turn the thermostat to the lowest setting.
9. Set the thermostat switch to "HEAT."
10. Increase the thermostat setting approximately
five degrees above the room temperature.
11. Verify the heat pump is operating in the heating
12. Set the thermostat to maintain the desired
space temperature.
13. Check for vibrations, leaks, etc.


Cooling Mode
Energizing the "O" terminal energizes the unit
reversing valve thus placing the unit into cooling
mode. The fan motor starts when the "G" terminal
is energized.
The fan motor takes 30 seconds to ramp up
to operating speed and will run at the
fan-only rated airflow, as long as there is no
call for compressor or heater operation.
When the thermostat calls for first-stage cooling
(Y1) the loop pump or solenoid valve, if present, is
energized and the first stage of the compressor
capacity starts.
Subject to change without prior notice

Post-Installation System Checkout | 21

8733825873 (2020/05)


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