Johnson Controls York YCRE 040, Manual

Page: 23 / 68

4.8 Electrical Connection
The following connection recommendations are
intended to ensure safe and satisfactory operation of the
unit. Failure to follow these recommendations could
cause harm to persons, or damage to the unit, and may
invalidate the warranty.
No additional controls (relays, etc.) should
be mounted in the control panel. Power
and control wiring not connected to the
control panel should not be run through
the control panel. If these precautions are
not followed it could lead to a risk of
electrocution. In addition, electrical noise
could cause malfunctions or damage the
unit and its controls.
Do not earth earth any portable electrical
or welding equipment via the chiller.
After connection do not switch on mains
power to the unit until it has been
c o m m i s s i o n e d b y J C I A u t h o r i s e d
personnel. Some internal components are
live when mains is switched on.
The unit ON/OFF switch on the front of the control panel
has been set in the “OFF” position at the factory.
This switch MUST remain in the “OFF” position until the
unit is commissioned by JCI Authorised personnel. If the
switch is set to the “ON” position before commissioning
then it must be reported to JCI, otherwise the warranty
may be invalidated.
4.9 Remote Refrigerant Condenser Systems
(YCRE models only)
General
For cooling of YCRE units, condensers are usually of
the remote air-cooled type either roof or ground level
mounted. Refrigerant systems should be designed and
installed by suitably qualified persons in compliance
with relevant national codes and standards. The
complete pipework system and condenser
MUST have
a Design Working Pressure of at least 27.6 barg.
Suitable controls (e.g. fan cycling) should be included to
keep discharge pressure within the unit operational
limits and at least 4.0 bar above suction pressure.
The condenser should be designed to provide sufficient
subcooling at its outlet to ensure that no 'flashing' will
occur in the liquid line to the unit, or in the filter/drier and
liquid valves on the unit itself. Liquid subcooling should
be 4°C to 10°C on arrival at the unit.
It is important to ensure that for each system the remote
condenser and liquid line volume is at least 1.65 times
the liquid volume of the operating refrigerant charge.
When the unit has been located in its final position, the
refrigerant system pipework can be connected.
Pipework and fittings
MUST be separately supported
and not cause any loading on the unit. Flexible
connections are recommended and will also minimise
transmission of vibrations to the building. Flexible
connections
MUST be used if the unit is mounted on
anti-vibration mounts as some movement of the unit can
be expected in operation.
Pipework Design
The following notes give guidance but should not be
considered exhaustive:
n
Discharge lines MUST be sized for guaranteed oil
transfer at minimum load step on the compressor.
P-traps and double risers may be required when
the condenser is sighted above the unit. Horizontal
runs should be inclined slightly towards the
condenser to aid oil transfer.
n
Where the condenser is above or level with the
unit, the discharge line should rise to at least the top
edge of the condenser at some point. This will
prevent liquid draining back to the compressor
during the off cycle.
n
Elbows, bends and valves should be minimised to
reduce pressure drop and prevent loss of
performance. The liquid line in particular should be
designed for minimum pressure drop to avoid
'flashing' in the liquid line which will cause loss of
performance and fault conditions to occur.
Particular care should be taken where the
condenser is below or level with the unit.
n
To avoid the risk of discharge gas pulsation's
causing undesired noise within the building, a
suitably sized discharge gas muffler may be fitted
in the discharge line near the unit. A slight loss of
performance may, however, result at full load.
Incorrectly or badly designed and/or installed
pipework systems may invalidate unit
warranty.
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035-21786-100 Rev. 1 (0909)