52
WGS 130A to 190A
OM WGS-5
system provided by others. At shut down, the reverse occurs where the condenser control
will be deactivated when the compressor stops as the Fan 1 fan contacts open.
Special considerations must be given to the condenser control including (but not limited to)
the following items.
1.
All WGS-A chillers have two refrigerant circuits and an evaporative condenser with two
refrigerant circuits is also required.
2.
A control system for each refrigerant circuit is required. It is best to have separate fans
and pumps for each refrigerant circuit to prevent "fighting" of control signals between
the two refrigerant circuits.
3.
The control system shall maintain a minimum condenser pressure at all times.
4.
The normal control philosophy is to maintain the lowest possible condensing pressure
above the minimum allowable to provide the best operating efficiency throughout the
chiller's entire operating range.
5.
For a normal starting sequence, it is best to start the fans first with minimum airflow.
As the condenser pressure rises, increase the airflow by increasing the fan RPM,
opening inlet vanes, opening outlet dampers, or other meaning of increasing airflow. If
condensing pressure continues to rise after maximum airflow is reached, start the
circulating pump (s). Reverse the sequence for the shut down procedure.
6.
Provide the maximum number of condenser staging steps as possible to provide as
stable operation as possible.
7.
Recognize that condenser pressure will change drastically and rapidly, when the water
pump starts and stops. This is the reason for starting the fan first in an increasing
capacity situation and stopping the fan operation last with a shutdown procedure.
8.
It is important for the control pressure settings for the fans and pumps to have a large
control band so that condenser component cycling does not occur. It is also good
practice for the fan and pump control to "overlap". Overlap means that the control
bands must be determined so that there is a pressure range between when a pump starts/
stops with fan operation. Use caution to be certain that fan & pump cycling does not
occur which causes rapid changes in condensing pressure which causes instability in the
refrigeration system.
9.
Refer to the installation, operation and maintenance manuals of the manufacturer of the
evaporative condenser for their guidelines and recommendations. Give special
consideration to preventing freezing conditions, make up water, and other functions
common to evaporative condensers that should be described in those brochures.
!
CAUTION
Use water treatment with evaporative condensers. Failure to prevent microbiology growth,
scaling and corrosion can damage the unit.
10.
Damage caused or contributed by improper water treatment may not be covered by
McQuay’s warranty.
Summary of Contents for WGS130AA: WGS140AW
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