Special Precautions When Dealing With R407C Unit; Vacuuming And Charging; Special Precautions When Charging Unit With Copeland Scroll Compressors - McQuay D series Installationsanleitung

SPECIAL PRECAUTIONS WHEN DEALING WITH R407C UNIT

• R407C is a zeotropic refrigerant mixture which has zero ozone depletion potential and thus conformed to the Montreal Protocol
regulation. It requires Polyol ester oil (POE) oil for its compressor's lubricant. Its refrigerant capacity and performance are about
the same as the refrigerant R22.
• POE oil is used as lubricant for R407C compressor, which is different from the mineral oil used for R22 compressor. During installation
or servicing, extra precaution must be taken not to expose the R407C system too long to moist air. Residual POE oil in the piping and
components can absorb moisture from the air.
• Refrigerant R407C is more easily affected by dust of moisture compared with R22, make sure to temporarily cover the ends of the
tubing prior to installation.
• No additional charge of compressor oil is permitted.
• No other refrigerant other than R407C.
• Tools specifically for R407C only (must not be used for R22 or other refrigerant)
i) Manifold gauge and charging hose
ii) Gas leak detector
iii) Refrigerant cylinder/charging cylinder
iv) Vacuum pump c/w adapter
v) Flare tools
vi) Refrigerant recovery machine
• Filter-dryer must be installed along the liquid line for all R407C air conditioners. This is to minimise the contamination of moisture and
dirt in the refrigerant system. Filter-dryer must be of molecular sieve type. For a heat-pump system, install a two-way flow filter dryer
along the liquid line.
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
current, 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 charg-
ing nipples and replace caps.
• 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.

VACUUMING AND CHARGING

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Caution
COPELAND SCROLL COMPRESSORS
Vacuum gauge
Scales
Thermometer
1-8
Vacuum Pump
Gas Pipe
Liquid Pipe
Gas Pipe
Liquid Pipe