OMM 1008-1
79
The MicroTech II operator interface touch-screen panel can display all superheat and subcooling
temperatures.
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:
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.
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.
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 the chilled water system 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 two head bolts at roughly 10 and 2 o’clock.
•
Loosen the remaining two 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 two remaining bolts,
remove the bolts and carefully remove the head.
•
Do not try to install a machine thread eyebolt into the head vent fitting, which has pipe threads.
•
Reverse this procedure to mount the head, using a new gasket.
Water Treatment
Make sure tower blowdown or bleed-off is operating. Set up and use a good maintenance program to
prevent “liming up” of both tower and condenser. It should be recognized that atmospheric air
contains many contaminants that increase the need for proper water treatment. The use of untreated
water can result in corrosion, erosion, sliming, scaling or algae formation. It is recommended that the
service of a reliable water treatment company be used. McQuay International assumes no
responsibility for the results of untreated or improperly treated water.
Repair of System
Pressure Relief Valve Replacement
Current condenser designs use two relief valves separated by a three-way shutoff valve (one set). This
three-way valve allows either relief valve to be shut off, but at no time can both be shut off. In the
event one of the relief valves are leaking in the two valve set, these procedures must be followed:
•
If the valve closest to the valve stem is leaking, back seat the three-way valve all the way, closing the
port to the leaking pressure relief valve. Remove and replace the faulty relief valve. The three-way
shutoff valve must remain either fully back seated or fully forward to normal operation. If the relief
