11
MQH 11/08
Check that the condensing and evaporation temperatu-
res, during operation at high and low pressure detected
by the pressure gauges of the refrigerant, are within the
following range:
(on the units not provided with HP/LP pressure gauges for
the refrigerant, connect a pressure gauge to the
Schreader valves on the refrigeration circuit).
2.5
SYSTEM DIAGNOSTICS AND OPERATION AT FAULT CONDITIONS
FAULT
RESPONSE
LWT sensor failure
If in cooling then stop machine
EWT sensor failure
Use EWT = LWT + 5
EWT & LWT failure together
Stop machine
OAT sensor failure
Use OAT = 35 (cooling) – 8 (heating).
Variable speed in heating always in maximum speed
CP sensor failure
Fans to max speed when OAT > 20 °C
Fans to low speed when 15 °C < OAT < 20 °C
If OAT < 15 °C, stop the unit in cooling only Disable vs.
In heating, end defrost only with OCT > OCTe or Td > Tde
EP sensor failure
In cooling mode, correct CSPT to CSPT > FP + 7
In heating, if OAT < 10 °C start defrost routine every 40 mins and end
defrost routine after 90 sec.
OCT failure or CP & OCT failure
In heating, if OAT < 10 °C start defrost routine every 40 mins and end
defrost routine after 90 sec.
Variable speed in cooling: always in maximum speed.
EP & CP failure
Stop the unit
HP
Approx. 13 to 18 °C above the temperature of the air entering the condenser,
for R 410a units.
LP side
Approx. the difference between the temperature of the leaving water and saturated evaporating
temperature must be in the 2 - 4 °C for R 410a units.
