Acson Air Conditioner Installation Manual download pdf (Page 17)

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SPECIAL PRECAUTIONS WHEN CHARGING UNIT WITH

COPELAND SCROLL COMPRESSORS

These precautions are intended for use with Copeland Scroll compressors only with R22, R407C, R134A, R404A, R507 and

R410A refrigerants but are not applied to Copeland reciprocating compressors or competitive Scroll compressors.

Scroll compressors have a very high volumetric efficiency and quickly pump a deep vacuum if there is insufficient refrigerant

in the system or if refrigerant is added too slowly. Operation with low suction pressure will quickly lead to very high discharge

temperatures. While this process is happening, the scrolls are not being well lubricated – scrolls depend on the oil mist in the

refrigerant for lubrication. A lack of lubrication leads to high friction between the scroll flanks and tips and generates additional

heat. The combination of heat of compression and heat from increased friction is concentrated in a small localized discharge

area where temperatures can quickly rise to more than 300˚C. These extreme temperatures damage the Scroll spirals and the

orbiting Scroll bearing. This damage can occur in less than one minute especially on larger compressors. Failure may occur in

the first few hours or the damage done during field charging may show up some time later.

Other typical field charging problems include undercharging, overcharging, moisture or air in the system etc. In time each one

of these problems can cause compressor failure.

Minimal equipment is required for field charging. The minimum equipment required to do a satisfactory job is:-

Set of service gauges Vacuum gauge

Hoses Scales

Vacuum pump Thermometer

The proper refrigerant charge should follow the volume as recommended by manufacturer and recommendation should be

followed by the installer.

1. Charging procedures – Single phase compressors

Evacuate the system to 500 microns Hg. (67Pa). To reduce evacuation time, use short, large diameter hoses and connect to

unrestricted service ports on the system. Quality of vacuum cannot be determined by time – a reliable vacuum gauge must

be used. (etc. electronic vacuum gauge)

Turn the refrigerant cylinder upside down, purge the charging hose and charge liquid through the liquid line charging port

until refrigerant no longer flows or until the correct charge has been weighed in. If additional charge is required start the

system and slowly bleed liquid into the suction side until the system is full.

Copeland recommends charging liquid in a CONTROLLED manner into the suction side until the system is full.

This recommendation does not hold true for reciprocating compressors where liquid charging into the suction side could

cause severe damage.

Carefully monitor the suction and discharge pressures – ensure that the suction pressure does not fall below 25 psig (1.7

bar) at any time during the charging process.

• Manifold Gauge will show cylinder pressure rather than suction pressure if the cylinder valve and Manifold

valve “A” are both open.

! Caution

There are many ways of charging liquid in a “controlled manner” into the suction

side:-

1. Use valve A on the manifold gauge set

2. Use the valve on the refrigerant cylinder

3. Charge through a Shredder valve

4. Use a hose with a Shredder valve depressor

5. Charge into the suction side at some distance from the compressor

6. All of the above

2. Charging procedures – Three phase compressors

The fundamental procedure is the same as for single phase models but the compressor can run in the wrong direction on

starting. If this happens reverse any two phases and start again. Short term reverse rotation will not damage the compressor.

All Specter compressors (Model: ZR90 to ZR19M) have internal discharge temperature protectors which are very effective

in preventing dangerously high discharge temperatures during charging. The protection module will trip and lock the

compressor out for 30 minutes. It is not normally necessary to wait 30 minutes for the module to reset. When the compressor

has cooled down the module can be reset by breaking the power supply to the control circuit. Very often the serviceman

does not understand why the module tripped and uses a jumper wire to bypass it. He continues to charge the system and

removes the jumper when charging is complete. The compressor may or may not run with the protector back in the circuit

but it is certain that the compressor has been damaged and premature failure is inevitable.

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Acson Air Conditioner Installation Manual Page 17

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