Bosch LM Split CS Series - User Manual

Bosch LM Split CS Series

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Installation, Operation, and Maintenance Manual

LM Split CS Series Heat Pump

8733827906 (2021/11)

LM024 | LM036 | LM048 | LM060

Table of Contents

Questions and Answers:

K
Kristina RussellAug 22, 2025
What to do if my Bosch LM Split CS shuts off due to high pressure?
- L
  lucasdouglasAug 22, 2025
  Your Bosch Heat Pump might be turning off due to a high-pressure control if the discharge pressure is too high. In 'COOLING' mode, this could be due to lack of water flow, entering water that's too warm, or a scaled/plugged condenser. In 'HEATING' mode, it could be due to a lack of load-side fluid flow, an inoperative blower, or clogged filter/ductwork restrictions. Another cause could be the unit being overcharged with refrigerant, in this case reclaim refrigerant, evacuate and recharge with the factory recommended charge. Also, check for a defective or improperly calibrated high-pressure switch.
J
Jennifer DavisAug 29, 2025
Why does my Bosch LM Split CS Heat Pump turn off because of low pressure?
- M
  Mr. Donald PhillipsAug 29, 2025
  Your Bosch Heat Pump may be turning off due to a low-pressure control if the suction pressure is too low. If in 'COOLING' mode, this can happen due to lack of airflow, entering air that's too cold, an inoperative blower, or a clogged filter/restrictions in the ductwork. If in 'HEATING' mode, it can be due to lack of water flow, entering water that's too cold, or a scaled/plugged condenser. It can also happen if the unit is low on refrigerant. Check for refrigerant leaks, repair them, evacuate the system, and recharge with the factory-recommended charge. Finally, check for a defective or improperly calibrated low-pressure switch.
A
Adam HowardSep 3, 2025
How to stop my Bosch LM Split CS from short cycling?
- P
  perrygilbertSep 3, 2025
  If your Bosch Heat Pump is short cycling, it could be due to several reasons. The unit might be oversized, requiring a recalculation of heating and cooling loads. The thermostat's location could be the problem. If it's near a supply air grill, relocate it. You might also need to adjust the heat anticipator. Also check for a defective or improperly calibrated low-pressure switch.
J
Joshua MillerNov 9, 2025
Why is my Bosch Heat Pump not cooling or heating enough?
- L
  Laurie RichardsonNov 9, 2025
  If your Bosch Heat Pump isn't providing enough cooling or heating, several factors could be at play. It might be undersized for the space, in which case you should recalculate heating and cooling loads, and consider adding insulation or shading. Check for leaks in ductwork or around doors and windows that could be letting conditioned air escape. Ensure adequate airflow by replacing any dirty filters. A low refrigerant charge can also cause inefficient operation. Other potential issues include a defective compressor (check if discharge is too low and suction pressure is too high), a defective reversing valve, or a restricted or defective TXV. Compare unit operating pressures to the pressure/temperature chart. Finally, the system may be contaminated with moisture or non-condensables, requiri...
U
uvelazquezNov 16, 2025
How to troubleshoot a Bosch LM Split CS Heat Pump that won't turn on?
- C
  Christina DavidsonNov 16, 2025
  If your Bosch Heat Pump isn't running, start by checking the power supply. Ensure the disconnect is closed and power is applied. Next, inspect the fuse or circuit breaker; replace the fuse or reset the breaker, making sure fuses are the correct size. If the voltage supply is low (below the minimum specified on the unit's data plate), contact your local power company. Finally, examine the thermostat. Setting the fan to 'ON' should make the fan run. Setting the thermostat to 'COOL' with the lowest temperature should start cooling (reversing valve energized), and setting it to 'HEAT' with the highest temperature should initiate heating. If nothing happens, the thermostat might be miswired or faulty. Verify 24 volts between 'R' and 'C,' 'Y' and 'C,' and 'O' and 'C' on the condensing section's ...

Bosch LM Split CS Series Specifications

General

Brand	Bosch
Model	LM Split CS Series
Category	Heat Pump
Language	English

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