48
Centrifugal Chillers
IM 1044-2
Electrical System
Maintenance
of the electrical system involves the general requirement of keeping contacts clean and
connections tight and checking on specific items as follows:
1.
The compressor current draw should be checked and compared to nameplate RLA value. Normally, the
actual current will be lower, since the nameplate rating represents full load operation. Also check all
pump and fan motor amperages, and compare with nameplate ratings.
2.
Inspection must verify that the oil heaters are operative. The heaters are insert-cartridge type and can be
checked by ammeter reading. They should be energized whenever power is available to the control
circuit, when the oil temperature sensor calls for heat, and when the compressor is inoperative. When the
compressor runs, the heaters are de-energized. The Digital Output screen and second View screen on the
operator interface panel both indicate when the heaters are energized.
3.
At least once a quarter, all equipment protection controls except compressor overloads should be made to
operate and their operating points checked. A control can shift its operating point as it ages, and this must
be detected so the controls can be adjusted or replaced. Pump interlocks and flow switches should be
checked to be sure they interrupt the control circuit when tripped.
4.
The contactors in the motor starter should be inspected and cleaned quarterly. Tighten all terminal
connections.
5.
The compressor motor resistance to ground should be checked and logged semi-annually. This log will
track insulation deterioration. A reading of 50 megohms or less indicates a possible insulation defect or
moisture and must be further checked.
CAUTION
Never Megger a motor while in a vacuum. Severe motor damage can result.
6.
The centrifugal compressor must rotate in the direction indicated by the arrow on the rear motor cover
plate, near the rotation sight glass. If the operator has any reason to suspect that the power system
connections have been altered, (phases reversed) the compressor must be jogged to check rotation. For
assistance, call the local
Daikin
service location.
Cleaning and Preserving
A common cause of service calls and equipment malfunction is dirt. This can be prevented with normal
maintenance. The system components most subject to dirt are:
1.
Permanent or cleanable filters in the air handling equipment must be cleaned in accordance with the
manufacturer’s instructions; throwaway filters should be replaced. The frequency of this service will vary
with each installation.
2.
Remove and clean strainers in chilled water system, oil cooler line and condenser water system at every
inspection.
3.
Inspect the condenser tubes annually for fouling and clean if required. The dished water heads (aka end-
bells, water boxes) should be removed with care due to their weight. One method follows:
•
After draining water, remove all but four head bolts at roughly 10 and 2 o’clock and 4 and 8 o’clock.
•
Loosen the remaining four bolts to enable the head to be separated from the tube sheet sufficiently for a
clevis pin or hook to be inserted into an open bolt hole at the top of the head.
•
Attach a hoist to the pin or hook, lift the head to remove weight from the remaining bolts, remove the
bolts and carefully remove the head.
•
Do not try to install an eyebolt with machine threads into the head vent fitting, which has pipe threads.
•
Reverse this procedure to mount the head, using a new gasket.