Symptom Based Troubleshooting; Normal Operating Conditions; Symptom: The System Does Not Operate; Symptom: Cool/Heat Cannot Be Changed Over - Daikin VRV IV+ Service Manual

https://daikin-p.ru/catalog/vrv-daikn/naruzhnye-vrv-bloki-daikin
2.4

Symptom based troubleshooting

2.4.1

Normal operating conditions

Below items are a guideline on how to check normal operating
conditions of the unit. Still, values are for reference ONLY and
working conditions outside of this range do NOT necessarily address
abnormalities and errors. Operating conditions are a result of several
items to check together.
Item Description
Discharge superheat Discharge pipe
temperature –
condensation
temperature
Discharge superheat = discharge pipe temperature – condensation
temperature
▪ Discharge pipe temperature: Read out from discharge pipe
thermistor R21T/R22T depending on the compressor.
▪ Condensation temperature: Calculated by main PCB from
the pressure read‑out of the high pressure sensor.
Higher discharge superheat may result from refrigerant shortage or
compressor internal by‑pass.
Lower discharge superheat may result from low suction superheat
which is caused by wet operation.
Item Description
Suction superheat Suction temperature
– evaporation
temperature
Suction superheat = suction temperature – evaporation temperature
▪ Suction temperature: Read out from suction thermistor R3T
▪ Evaporation temperature: Calculated by main PCB from the
pressure read‑out of the low pressure sensor.
Suction superheat may be high if difference between [indoor set
temperature – indoor air temperature] is too high and will result in
high discharge superheat.
Suction superheat may be low if:
▪ Difference between [indoor set temperature – indoor air
temperature] is too low
▪ Discharge superheat is too low (<20 K)
▪ Outdoor unit judges wet operation
2.4.2

Symptom: The system does not operate

▪ The air conditioner does not start immediately after the ON/OFF
button on the user interface is pressed. If the operation lamp
lights, the system is in normal condition. To prevent overloading of
the compressor motor, the air conditioner starts 5 minutes after it
is turned ON again in case it was turned OFF just before. The
same starting delay occurs after the operation mode selector
button was used.
▪ If "Under Centralized Control" is displayed on the user interface,
pressing the operation button causes the display to blink for a few
seconds. The blinking display indicates that the user interface
cannot be used.
▪ The system does not start immediately after the power supply is
turned on. Wait one minute until the micro computer is prepared
for operation.
2.4.3 Symptom: Cool/Heat cannot be changed
over
▪ When the display shows
control), it shows that this is a slave user interface.
RYYQ+RYMQ+RXYQ8~20U7Y1B
VRV IV+ Heat Pump
ESIE18-14 – 2019.07
Normal value
25 K to 45 K
Normal value
5 K
(change-over under centralized
▪ When the cool/heat changeover remote control switch is installed
and the display shows
control), this is because cool/heat changeover is controlled by the
cool/ heat changeover remote control switch. Ask your dealer
where the remote control switch is installed.
2.4.4 Symptom: Fan operation is possible, but
cooling and heating do not work
Immediately after the power is turned on. The micro computer is
getting ready to operate and is performing a communication check
with all indoor units. Please wait 12 minutes maximally until this
process is finished.
2.4.5 Symptom: The fan speed does not
correspond to the setting
The fan speed does not change even if the fan speed adjustment
button is pressed. During heating operation, when the room
temperature reaches the set temperature, the outdoor unit goes off
and the indoor unit changes to whisper fan speed. This is to prevent
cold air blowing directly on occupants of the room. The fan speed
will not change even when another indoor unit is in heating
operation, if the button is pressed.
2.4.6 Symptom: The fan direction does not
correspond to the setting
The fan direction does not correspond with the user interface
display. The fan direction does not swing. This is because the unit is
being controlled by the micro computer.
2.4.7 Symptom: White mist comes out of a unit
(Indoor unit)
▪ When humidity is high during cooling operation. If the interior of an
indoor unit is extremely contaminated, the temperature distribution
inside a room becomes uneven. It is necessary to clean the
interior of the indoor unit. Ask your dealer for details on cleaning
the unit. This operation requires a qualified service person.
▪ Immediately after the cooling operation stops and if the room
temperature and humidity are low. This is because warm
refrigerant gas flows back into the indoor unit and generates
steam.
2.4.8 Symptom: White mist comes out of a unit
(Indoor unit, heat exchanger unit)
When the system is changed over to heating operation after defrost
operation. Moisture generated by defrost becomes steam and is
exhausted.
2.4.9 Symptom: The user interface display
reads "U4" or "U5" and stops, but then
restarts after a few minutes
This is because the user interface is intercepting noise from electric
appliances other than the air conditioner. The noise prevents
communication between the units, causing them to stop. Operation
automatically restarts when the noise ceases.
2.4.10 Symptom: Noise of air conditioners
(Indoor unit)
▪ A "zeen" sound is heard immediately after the power supply is
turned on. The electronic expansion valve inside an indoor unit
starts working and makes the noise. Its volume will reduce in
about one minute.
2 Troubleshooting
(change-over under centralized
Service manual
73