Maintenance Diagnostic - Lennox BAC020SNM Installation, Operating And Maintenance

MAINTENANCE DIAGNOSTIC

REFRIGERATION
FAULT POSSIBLE CAUSE AND SYMPTOMS
Refrigerant charge too low
In Heat Pump Mode the temperature difference
between T outdoor and Tevap. (Dew) is too high
5°C < Delta T < 10°C excellent
10°C < Delta T < 15°C acceptable
LP PROBLEMS and
15°C < Delta T < 25°C too high
LP CUT OUTS
Refrigeration circuit blocked in distribution
Liquid line drier blocked. High temperature
difference between inlet and outlet of the drier
Contaminant in the expansion valve
Expansion valve not adjusted properly
Ice plug in the expansion valve.
Incorrect insulation of the thermostatic bulb of
the expansion valve
Low Pressure Switch cut out point too high
LP cut out due to not enough defrost on heat
pumps
Incorrect Airflow rates
HP PROBLEMS AND
HP CUT OUTS
Moisture or contaminants in the system
BALTIC R410A-IOM-0708-E
SOLUTION
Measure the superheat and sub-cooling:
Good if 5°C<SC<10°C and 5°C<SH<10°C
Bad if SC>10°C and SH too Low
Check superheat adjustment and charge unit (a
leak check must be carried out)
If too high check the coils are clean or check coil
internal pressure drop between the liquid line and
the suction line
Good if < 3bar
Too high if > 3bar (coil blocked)
Stop the fan and create icing of the coil.
Check all circuits freeze evenly across the whole
surface of the coil
If some parts of the coil do not freeze this could
indicate a problem with the distribution
Change filter drier
Attempt to free the valve adjusting element by
freezing the valve and then heating the
thermostatic element. Replace the valve if
necessary
Adjust the expansion Valve
Heat the main body of the valve. If the LP
increases and then decreases gradually, empty
the circuit and replace the drier.
Superheat too low: adjust superheat
Move the thermostatic element along the pipe
Insulate the Thermostatic element of the valve
Check the cut out pressure of the Low Pressure
switch: It must be 0.7+/- 0.2bar and must closes
at 2.24 +/- 0.2 bar
Adjust the CLIMATIC settings to extend the
defrost cycles or shorten the time between
defrosts
Heat pump mode:
Check the filter before the indoor coil
measure and estimate the airflow rate
increase the speed of the fan
Cooling mode:
Check the condenser fan (Amps)
Summer operation
Several hours after the unit has stopped, check
the correspondence between the measured
pressure and the outdoor temperature
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