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Bosch Greensource SM024 Installation, Operation And Maintenance Manual page 47

Greensource cdi series sm model water-to-air heat pumps
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Greensource CDi Series SM Model
Problem
FAN OPERATES
BUT THE MOTOR
DOES NOT
CHANGE SPEED—
ECM CONSTANT
AIRFLOW MOTOR
UNIT NOT SHIFTING
INTO COOLING
AND HEATING
EXCESSIVELY
COLD SUPPLY AIR
TEMPERATURE IN
COOLING OR
EXCESSIVELY HOT
SUPPLY AIR
TEMPERATURE IN
HEATING
Greensource CDi Series SM Model
Unit Troubleshooting
Check
Possible Cause
Is the motor
behavior only
Ramp-up programming
observed during
delays are still in effect
startup?
Is the motor not
stopping when
there is no call
Thermostat is in continuous
for cooling or
fan mode
heating from
thermostat?
High-external
Dirty air filter, closed
static
dampers, grills, dirty air coil
Reversing valve
solenoid
Faulty solenoid
energized
Miswired/faulty thermostat
Reversing valve
solenoid NOT
energized
Loose wire on "O" terminal
Dirty Filter
Fan speed too low
Reduced air flow
Excessive duct pressure
drop
Subject to change without prior notice
Unit Troubleshooting | 47
Action
Wait at least 5 minutes after the start-
up and then change the fan operation
based on thermostat call.
Change the thermostat setting to ON/
OFF (auto) fan operation instead of
continuous fan operation.
Remove the air filter and check that all
of the dampers, register, and grills are
open and free flowing. If removing the
filter corrects the problem, clean or
replace it with a less restrictive filter.
Also check and clean as needed the
blower wheel and secondary heat
exchanger (if applicable).
Check that the reversing valve
solenoid is receiving 12 VAC.
Check the resistance of the solenoid—
an open circuit may indicate a burned
out solenoid.
Check that the reversing valve
thermostat wire is connected to the
"O" terminal of the thermostat.
Check for a contact closure between
"O" and "R."
Check that the wires from the
thermostat to the unit are securely
connected and that the wires from the
electrical box to the reversing valve
are connected.
Replace filter.
Consult blower performance table and
increase fan speed if possible.
Consult blower performance table and
increase fan speed if possible.
8733819578 (2019/02)

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