Vacuuming And Charging; Special Precautions When Charging Unit With Copeland Scroll Compressors - McQuay D Serie Manual De Instalación

Vacuuming is necessary to eliminate all moisture and air from the system. The series II Outdoor Unit is provided with flare valve fittings.
Vacuuming
Before vacuuming, perform leak check for refrigeration circuit. After the system
piping are properly connected, connect the flexible hoses to the correct charging
nipples as shown in the diagram. Ensure that flexible hose from charging nipples are
connected to the vacuum pump via standard servicing valves and pressure gauges
(gauge manifold). Vacuum the air conditioner system to at least 500 microns Hg. Do
not start the unit when the system is engaged in vacuuming.
Charging
Before charging, the vacuum must be held at 500 microns Hg for at least 15 minutes,
then break vacuum by charging R22 or R407C refrigerant. Operate the unit for 15
minutes and ensure the refrigerant charges is of correct by monitoring running cur-
rent, gas and liquid line pressures. Suction and discharge pipe pressure should be in
the region of 75 psig and 275 psig generally.
After ensuring the system is correctly charged, remove flexible hose from charging
• R407C must be charged as liquid. Usually R407C cylinder is equipped with a dip-pipe for liquid withdrawal. If there
is no dip-pipe, the cylinder should be inverted so as to withdraw liquid R407C from the valve.
• Do not top-up when servicing leak, as this will reduce the unit performance. Vacuum the unit thoroughly and then
charge the unit with fresh R407C according to the amount recommended in the specification.
SPECIAL PRECAUTIONS WHEN CHARGING UNIT WITH
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
Hoses
Vacuum pump
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 refrig-
erant 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 recom-
mendation 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.

VACUUMING AND CHARGING

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CAUTION
COPELAND SCROLL COMPRESSORS
Vacuum gauge
Scales
Thermometer
1-13
Vacuum Pump
Gas Pipe
Liquid Pipe
Gas Pipe
Liquid Pipe