Table of Contents
Advertisement
necessary to pump down into nearly a vacuum to remove all liquid refrigerant from the low side.
If the low-pressure switch opens, the pump down should stop immediately.
TM
Copeland Scroll
compressors trap a considerable volume of high-pressure gas between the
muffler plate and the top cap. When the compressor shuts down, the trapped gas will expand
back into the suction side of the system. This frequently causes a pulse of pressure to propagate
down the suction line and can cause the low-pressure switch to reset. The compressor must not
be allowed to short cycle which may result in oil pump out.
6
Maintenance & repair
6.1
Exchanging the refrigerant
Qualified Refrigerants and oils are given in section 2.4.1.
6.2
Replacing a compressor
CAUTION
Inadequate lubrication! Bearing destruction! Exchange the accumulator after
replacing a compressor with a burned out motor. The accumulator oil return
orifice or screen may be plugged with debris or may become plugged. This will
result in starvation of oil to the new compressor and a second failure.
6.2.1 Compressor replacement
When a compressor is exchanged in the field, a major portion of the oil may remain in the
system. While this may not affect the reliability of the replacement compressor, the extra oil will
add to rotor drag and increase power usage. The compressor should be run for 10 minutes, shut
down and the extra oil removed via the Schrader when fitted (only ZBH). This operation should
be repeated at least twice to make sure the proper oil level has been achieved. The oil level
should be maintained at midpoint of the sight glass.
In the case of a motor burn out, the majority of contaminated oil will be removed with the
compressor. The rest of the oil is cleaned through the use of suction and liquid line filter driers. A
100% activated alumna suction line filter drier is recommended but must be removed after 72
hours. It is highly recommended that the suction accumulator be replaced if the system
contains one. This is because the accumulator oil return orifice or screen may be plugged with
debris or may become plugged shortly after a compressor failure. This will result in starvation of
oil to the replacement compressor and a second failure.
6.2.2 Start-up of a new or replacement compressor
Do not start the compressor while the system is in a deep vacuum. Internal arcing may occur
when a scroll compressor is started in a vacuum.
Do not operate compressor without enough system charge to maintain at least 0.5 bar suction
pressure. A minimum suction pressure of 1.75 bar must be maintained during charging. Allowing
pressure to drop below 0.5 bar for more than a few seconds may overheat scrolls and cause
early drive bearing damage.
Do not operate with a restricted suction port.
Do not operate with the low-pressure cut out bridged.
Never install a system in the field and leave it unattended when it has no charge, a holding
charge, or with the service valves closed without securely locking out the system. This will
prevent unauthorized personnel from accidentally operating the system and potentially ruining
the compressor by operating with no refrigerant flow.
6.3
Lubrication
WARNING
Chemical reaction! Compressor destruction! Do not mix up ester oils with
mineral oil and/or alkyl benzene when used with chlorine-free (HFC) refrigerants.
The compressor is supplied with an initial oil charge. In the field the oil level could be topped up
with the recommended servicing oils (see section 2.4.1).
14
C6.2.7/0302-1007/E
Advertisement
Table of Contents
