Hitachi RAS-(2-6)HVNP1(E), Service Manual

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8 Troubleshooting
221
SMGB0087 rev.0 - 12/2013
8
Phenomenon Cause Check item
Action
(Turn OFF the main switch)
Activation of the
high-pressure
switch due to the
excessively high
discharge pressure
(PSH)
Insufficient Air Flow to the Heat Exchanger (Outdoor Heat Ex-
changer during the Cooling Process or Indoor Heat Exchanger
during the Heating Process)
Check the heat exchanger
for dust or for clogging
Remove the dust or the clog-
ging
Check the air filter for dust Remove the dust
Check for any obstacles at
the inlet or the outlet of the
heat exchanger
Remove the obstacles
Check the service area Secure service area
Check the speed (Outdoor
Fan: Cooling / Indoor Fan:
Heating)
Replace the fan motor if
faulty
Excessively High Temp. Air to the Indoor Unit
Calculate the heat load
Reduce the heat load or use
a bigger unit
Check for hot air near the
ceiling (Heating)
Provide good circulation
Check for short-circuited air
(Heating)
Remove the short-circuited air
Check for other heat source Remove the heat source
Faulty High-Pressure
Switch
Faulty Pressure Switch
Measure the discharge
pressure. Check the conti-
nuity after the decrease of
the pressure
Replace the pressure switch
if faulty
Insufficient Contacting
Measure the resistance by
means of the tester
Fix the looseness. Replace
the connector
Incorrect Connection Check the connections Repair the connections
Overcharged refrigerant
Check the cycle operation
temp.
Charge the refrigerant cor-
rectly
Mixture of the non-condensate gas in the refrigerant cycle
Check the air temp. and the
pressure
Recharge the refrigerant after
the vacuum pumping
Clogging of the discharge piping Check for clogging Remove the clogging
Liquid line stop valve or gas line stop valve is not in operation Check the stop valves Fully Open the stop valves
Faulty magnetic
contactor switch
No power is supplied to the coil Check connections Set the connections properly.
No power at the A contact
Measure the resistance
using a tester
Replace the magnetic switch
if it is broken