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Инструкция по эксплуатации Страница: 72

Airwell SLS 2702 [72/77] Maintenance

Page 71

English

Maintenance

9.6 Fans

The fans of the condenser, of axial type, are com-

plete with impeller with aerodynamic profile blades

and a cylindrical nozzle. The motor’s bearings are

lubricated forever.

Before starting the appliance, after any maintenance

operations involving the disconnection of 3-phase

connections, check that the direction of rotation of

the fans is the one indicated by the arrow (upward

air current). If the direction of rotation is wrong, in-

vert two of the three supply phases to the motor.

9.7 Dehydrating filter

The refrigeration circuits are provided with dehydrat-

ing filters.

The filter clogging is marked by the presence of air

bubbles in the sight glass, or by the difference be-

tween the temperatures measured downstream from

and upstream of the drying filter. If, once the car-

tridge has been cleaned, there are still some air bub-

bles, the appliance has lost a part of the refrigerant

charge in one or more points, that must be identified

and serviced.

9.8 Sight glass

The sight glass is used for inspecting the refrigerant

flow and the humidity % of the refrigerant. The pres-

ence of bubbles indicates that the dehydrating filter

is clogged or the charge insufficient.

A colour indicator is positioned inside the sight

glass. If you compare the colour of the indicator to

the scale on the ring of the sight glass, you can calcu-

late the percentage of humidity of the refrigerant. If it

is excessive, replace the filter’s cartridge, operate

the appliance for 1 day and then check the humidity

% again. When the humidity % is within the pre-de-

termined range, no other operations are required. If

the humidity % is still too high, replace the dehydrat-

ing filter again, start the unit and operate it for anoth-

er day.

9.9 Thermostatic expansion valve

The circuit of the unit is equipped with a thermostatic

expansion valve, with external equalizer. The valve

is shop-calibrated for an overheating of 5°C.

Procedure to check for overheating:

– Measure the suction pressure with the pressure

gauges on the board of the unit o using a pressure

gauge connected to the service valve on the suc-

tion side.

– From the pressure gauge’s temperature scale, mea-

sure the saturated suction temperature (Tsa) which

corresponds to the pressure value.

– Using a contact pressure gauge affixed to the out-

let fitting of the gas of the evaporator, measure the

actual temperature (Tse).

Overheating calculation (S):

S = Tse - Tsa

Overheating is regulated through the thermostatic

expansion valve.

Make the adjusting screw follow a complete turn,

and operate the appliance for five minutes.

Check again and, if necessary, repeat the regula-

tion.

If the expansion valve cannot be regulated, it is prob-

ably broken, and shall be replaced. The replace-

ment must be carried out by a Service Centre.

9.10 Evaporator

Check at regular intervals that the water side of the

heat exchanger is perfectly clean. To do this, mea-

sure the pressure drop, water side (see Section 8) or

measure the temperature of the liquid leaving and

entering the heat exchanger, and compare it to the

evaporation temperature.

To obtain an effective heat exchange, the difference

between the temperature of the leaving water and

the saturated evaporating temperature must be in the

5 - 7°C range. A greater difference would indicate a

low efficiency of the heat exchanger (i.e. the heat ex-

changer is dirty).

In this case, the heat exchanger must be subjected to

chemical cleaning, an operation that shall be carried

out by authorised engineers.

For other maintenance operations (extraordinary

overhauling, replacement of the heat exchanger

etc.), contact an authorised Service Centre.

9.11 Desuperheater and total heat

recovery condenser

Check at regular intervals that the water side of the

heat exchanger is perfectly clean. To do this, mea-

sure the pressure drop, water side (see Section 8) or

measure the temperature of the liquid leaving and

entering the exchanger.

To obtain an effective heat exchange chech the fol-

lowing:

- desuperheater: the difference between the tempera-

ture of the entering and the leaving water must be

about 5°

- total heat recovery condensers: the difference be-

tween the temperature of the leaving water and the

saturated condensing temperature must be about

10°

SLS2-en.qxp 29-06-2007 15:38 Pagina 71

Airwell SLS 2702 [72/77] Maintenance

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