Bosch LM Split CS Series Operating Instructions

Troubleshooting | 21LM CS Series Heat
8 733 920 847 (2014/01)Revised 01-14
TROUBLESHOOTING
Troubleshooting Information Solution
column may reflect a possible fault that
may be one of, or a combination of
causes and solutions. Check each cause
and adopt "process of elimination" and
or verification of each before making
any conclusion.
Unit Troubleshooting
Problem Possible Cause Checks and Correction
ENTIRE UNIT
DOES NOT RUN
Power Supply Off Apply power, close disconnect
Blown Fuse
Replace fuse or reset circuit breaker. Check for correct fuses
Voltage Supply
Low
If voltage is below minimum voltage specified on unit data plate,
contact local power company.
Thermostat
Set the fan to “ON”, the fan should run. Set thermostat to “COOL” and
lowest temperature setting, the unit should run in the cooling mode
(reversing valve energized). Set unit to “HEAT” and the highest
temperature setting, the unit should run in the heating mode. If neither
the blower or compressor run in all three cases, the thermostat could
be miswired or faulty. To ensure miswired or faulty thermostat verify 24
volts is available on the condensing section low voltage terminal strip
between “R” and “C”, “Y” and “C”, and “O” and “C”. If the blower does
not operate, verify 24 volts between terminals “G” and “C” in the air
handler. Replace the thermostat if defective.
UNIT OFF ON
HIGH PRESSURE
CONTROL
Discharge
pressure too high
In “COOLING” mode: Lack of or inadequate water flow. Entering water
temperature is too warm. Scaled or plugged condenser. In “HEATING”
mode: Lack of or inadequate air flow. Blower inoperative, clogged filter
or restrictions in duct work
Refrigerant
charge
The unit is overcharged with refrigerant. Reclaim refrigerant, evacuate
and recharge with factor recommended charge.
High pressure
Check for defective or improperly calibrated high pressure switch.
UNIT OFF ON LOW
PRESSURE
CONTROL
Suction pressure
too low
In “COOLING” mode: Lack of or inadequate air flow. Entering air
temperature is too cold. Blower inoperative, clogged filter or
restrictions in duct work. In “HEATING” mode: Lack of or inadequate
water flow. Entering water temperature is too cold. Scaled or plugged
condenser.
Refrigerant
charge
The unit is low on refrigerant. Check for refrigerant leak, repair,
evacuate and recharge with factory recommended charge.
Low pressure
switch
Check for defective or improperly calibrated low pressure switch.
UNIT SHORT
CYCLES
Unit oversized Recalculate heating and or cooling loads.
Thermostat
Thermostat installed near a supply air grill; relocate thermostat.
Readjust heat anticipator.
Wiring and
controls
Check for defective or improperly calibrated low pressure switch.

Bosch LM Split CS Series Specifications

General

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