Serial Signals; Thermistor Open Or Short; Safety Time; Pump Down Switch - Sharp AE-XM24HR Service Manual

AEXM24HR
compressor is stopped, if the temperature is below 85°C,another
starting try will be made. Three retries are allowed. On the fourth
retry, a complete stop request signal is sent to the indoor unit,
and the outdoor unit will remain stopped until the indoor operation is
stopped.

1.5. SERIAL SIGNALS

Serial signals consist of all 96-bit signals.
If the condition as outdoor unit unable to receive a serial signal from
the indoor unit continues for 30 seconds, it closes the expansion
valve which corresponds to the room which can not be communicated.
If all indoor units can not communicate with the outdoor unit,
the compressor is stopped.

1.6. THERMISTOR OPEN OR SHORT

When compressor, heat exchanger, outdoor thermistor,
suction thermistor (CN8A) are in OPEN or SHORT condition,even if
they are in the condition which an operation signal is transmitted from
indoors, the compressor will not start. If any suction thermistors
(CN8C) become OPEN or SHORT resistance, the protective
procedure will work only for the cycle corresponding to the
malfunctioning suction thermistor.
1.7. MISWIRING CHECK
"Miswiring check" is conducted by detecting the indoor heat exchanger
indoor heat exchanger temp.
For example, when the expansion valve for only room A is open,
and the wiring is correct, the indoor heat exchanger temp for room
A will reduce.
If the wiring is incorrect, the indoor heat exchanger temp for a different
room will reduce.

1.8. SAFETY TIME

When the unit is operated by the remote control after the breaker is
turned on, the safety device of the compressor will work and the
compressor will not operate for 90 seconds.

1.9. PUMP DOWN SWITCH

When the PUMP DOWN SWITCH (SW1) is pressed for 5 seconds or
more, the total A/C system will start its TEST RUN automatically and
the compressor frequency will be 55 Hz.
When operating only the outdoor unit (cooling 55Hz fixed mode) to
make only the outdoor unit run in cooling mode,and apply a voltage
of 230 V AC to N and L on the terminal board and push the PUMP
DOWN SWITCH. (SW1) (Avoid operating the outdoor unit alone for
long periods of time.)
1.10. CONTROL OF COMPRESSOR OR AND EXPANSION
VALVE
For 90 seconds after turning on the AC power, the compressor will not
be activated even if indoor units request the compressor to do so.
If the compressor receives a request from one or more indoor units
indoor units after 90 seconds have passed, it will be turned on and the
expansion valve corresponding to the requesting indoor unit will be
opened.
When the indoor unit of a room requests for the cooling operation to
the outdoor unit and it runs responding to the request,
requests for the heating can't be accepted if the indoor units in other
rooms send individual requests.
If the indoor unit in another room sends a request for the heating
operation, the operation lamp and timer lamp of the indoor unit in that
room start flashing in turn to inform that the unit is in the standby
mode.
If the operation in one room is stopped while the indoor unit in another
room is in the stand-by mode,
the operation mode requested by the indoor unit
which is now in the stand-by mode will be accepted.
At this time, the compressor will be temporarily
stopped to switch the four-way valve and restart after 90 seconds.
During the cooling or dry operation, the expansion valve
corresponding to the indoor unit that is not running is closed.
Therefore, the refrigerant will not flow into those units.
However,if the heating operation is in progress, it is possible that it
flows into indoor units which are out of operation depending on the
cycle conditions.
As a result, the indoor exchanger may be heated up even if it is not
activated. This is not abnormal.
When the operations in all rooms are stopped, the compressor is
stopped,the expansion valves in all rooms are fully opened.
1.11. DEFROST OPERATION
(1) Overview
Defrosting begins during heating if the conditions for compressor
operation time and outdoor heat exchanger temperature are met.
When defrosting begins, the indoor and outdoor fans stop.
Defrosting stops when the temperature of the outdoor heat exchanger
goes above approximately 15°C.or defrosting time exceeds 10
minutes.
Defrost Defrost
mask time mask time
Heating Heating
begins begins
Defrosting Defrosting
Max. 10 min. Max. 10 min.
(2) Defrosting
If the compressor operation time is more than 20 minutes in the
heating mode and the outdoor air temperature and outdoor heat
exchange temperature satisfy the defrosting conditions,
the defrosting operation is started.
When the defrosting operation is started, the indoor fan starts to run
intermittently.
When the outdoor heat exchanger temperature reaches approx. 15°.C
or above or when the defrosting time exceeds 10minutes,
the defrosting operation is quit.
2 – 3
Defrost Defrost Defrost Defrost
mask time mask time mask time mask time
Defrosting Defrosting
Max. 10 min. Max. 10 min.