GS-XR217 - Sharp Air Conditioner Service Manual (repair manual). Page 3

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Split air conditioning systems comprise an indoor unit for horizontal
ceiling or vertical free-standing installation, connected to a
compact outdoor unit by means of refrigerant lines.
Conditioners are equipped with an adjustable speed rotary
compressor with inverter, and are controlled by a sophisticated
microprocessor board. 
The power-supply frequency adjustment function of the inverter
allows variation of the speed of the electric motor driving the
compressor. The implementation of this technological feature to
split system units permits automatic adjustment of compressor
speed, and therefore of the performance of conditioners during
heavy-duty operating conditions (daily or seasonal external
temperature peaks, temporary indoor loads) as well as during less
demanding periods (nocturnal or mid-season operation).
This feature also allows the unit to reach the set temperature
rapidly, then to maintain it while operating at lower power. Not only
are ambient temperature fluctuations reduced and comfort
conditions enhanced, but significant energy savings are made
thanks to the greater efficiency of the refrigerant system when
operating with partial loads, and the lower number of compressor
cut-ins and cut-outs.
Both the indoor and the outdoor unit are extremely silent and
characterised by their high standards of efficiency and reliability,
also thanks to the refined adjustment system which prevents
operating faults to ensure the safest of working conditions. 
The microprocessor control offers a range of operating programs,
and uses sophisticated “Fuzzy” and proportional-integral control
logic.
All conditioner functions are selected by means of an infrared-ray
remote control handset with liquid crystal display; in the event of
emergency, the system can be controlled by the push-button panel
on the indoor unit.
Operating programs:
– automatic;
– heating (heat pump models only);
– cooling;
– dehumidifying;
– ventilation only.
During the “automatic” function, the microprocessor adjusts the
rotary compressor and fan speeds according to information
received from internal and external sensors, independently
selecting the most appropriate operation parameters.
The “Full Power” function is designed for reaching the required
ambient temperature in the shortest possible time. Maximum output
is thereby achieved by the unit, and remains active for an hour after
settings have been made. 
During all operation programs (except for “automatic” and “Full
Power”), the user can select the internal fan speed. The remote
control handset can regulate the horizontal grille directing
conditioned air flow into the room. 
For a more detailed description of unit functions, see the user
manual.

The indoor unit is characterised by its compact size and attractive
design. 
The unit houses the following components:
– heat-exchange coil with aluminium fins;
– compact and silent 4-speed centrifugal fan section; 
– electrical enclosure housing the microprocessor board;
– temperature probes for complete control of unit operation;
– reusable air filter, easy to remove for cleaning;
– horizontal drive-type grille with manually adjustable vertical slats

for optimising air flow delivery; 

– auxiliary control panel;
– remote control signal receiver;
– operating (red) and timer (yellow) indicator LEDs.
The unit is supplied complete with mounting brackets for vertical or
horizontal installation, and remote control handset with batteries. 

The remote control handset can be used for setting all unit
operating parameters:
– function type:

automatic, heating, cooling, dehumidification, fan operation only,
“Full Power”;

– timer setting;
– internal fan speed control;
– ambient temperature control;
– conditioner ON/OFF control;
– drive-type air flow grille control.
The liquid crystal display shows all operation parameter settings,
thereby facilitating all programming operations.
The remote control handset is powered by two 1.5 V penlight
batteries, and can be used up to 7 m from the conditioner unit.

The outdoor unit is constructed partly in hot-galvanised sheet metal
with polyurethane powder paint finish, and partly in plastic for
durability and resistance to rust. 
The outdoor unit houses:
– soundproofed adjustable speed hermetic rotary compressor;
– heat-exchange coil with grooved copper tube and corrugated

aluminium fins;

– fan section with statically and dynamically balanced axial fan,

with protection grille; 

– refrigerant circuit, complete with expansion devices, valves,

silencer and cycle reversing valve (heat pump models only);

– temperature probes for complete control of unit operation;
– inverter electronic adjustment components;
– electrical enclosure with terminals for connection to power

supply.

The outdoor unit contains the entire refrigerant charge.

Units are packed in polystyrene and delivered in standard
cardboard boxes. 
The remote control handset is packed in the fan compartment of the
indoor unit.

Conditioning units equipped with inverter system select the rotary
compressor speed necessary to satisfy the requirements of the
room treated, while maintaining optimal comfort conditions and high
refrigerant cycle efficiency. Conditioner power output is therefore
determined by the required ambient conditions and falls within the
field of power output ratings available.
The automatic adjustment stages of the unit will now be described.
When the unit is switched on, the microprocessor uses proportional
logic criteria to select the most suitable frequency to be supplied to
the compressor, according to the difference between the room and
the set temperature. 
Fuzzy and integral logic functions then cut in on the basis of
parameters derived from the previous periods of operation (such as
the speed of ambient temperature variation in relation to exterior
conditions) to regulate the required operating power. In a certain
sense the unit “recalls” the previous operating modes, then uses the
information to program the time necessary to reach the ideal
conditions of ambient comfort.
When the ambient temperature approaches the set value (set point),
the conditioner unit reduces frequency so that the setting can be
reached accurately. Once the required ambient conditions are
reached, compressor speed is reduced to operate in the conditions
of maximum efficiency. In the event of heat load variation, frequency
is adjusted to maintain a constant ambient temperature. To prevent
icing of the indoor coil or the delivery of excessively cold air,
compressor speed is limited in accordance with the settings made
by the user. 
In the case of heat pump versions, the frequency adjustment
function allows the unit to maintain exactly the required power yield,
even in the event of a drop in the outdoor temperature. Defrosting is
also optimised to achieve an even greater heat yield over time. Icing
of the outdoor coil is controlled by checking the temperature of
outdoor air and of the heat exchanger; defrosting is thereby
performed only when necessary and in the shortest possible time. 
The operating frequency of the conditioner is further determined by
refrigerant cycle yield optimisation algorithms, as well as by criteria
of reliability and the fault prevention. During conditioner operation,
all operating parameters are constantly monitored, while automatic
adjustment functions guarantee operation even in conditions of
lower efficiency (i.e. outside min. and max. operating limits). 
Unit operating frequency is determined by the following parameters:
– Operating conditions of heat exchangers. During the cooling

cycle, the compressor speed is reduced when the temperature of