Condenser Water, Head Pressure Control; Variable Inlet Vanes; Adjustable Frequency Drive; Disconnect Switch - McQuay SWP 018 Installation And Maintenance Manual

Condenser Water, Head Pressure
Control
An optional condenser head pressure control valve is avail-
able on units without water side economizer. This option
permits operation with entering water temperatures below
55°F. The valve is a two-way regulating valve controlled via
MicroTech II to maintain refrigerant head pressure .

Variable Inlet Vanes

An optional variable inlet vane assembly is available for
variable air volume applications. The assembly consists of
inlet funnels with integral sets of lever-actuated radial vanes,
one assembly for each side of the fan. The vanes, upon open-
ing, direct air in the direction of wheel rotation.
The vanes rotate 90 degrees from closed to full open in
response to the factory installed actuator motor. The actuator
is controlled by the unit's MicroTech II controller. The inlet
vanes operate in unison and are properly adjusted and tested
before the unit leaves the factory. The start-up contractor
must check the adjustments and retighten all bolts and ball
joints to insure that shipping and handling has not caused
misalignment.

Adjustable Frequency Drive

As an option an adjustable frequency drive (AFD), is avail-
able for airflow modulation. A manually activated bypass
contactor is provided to allow system operation in the event
of drive service.
Static pressure is controlled by the unit mounted MicroTech
II controller. Indication of current airflow is available at the
MicroTech II controller. Static pressure is sensed by one or
two factory mounted duct sensors. The installer provides and
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installs the sensor tubing from unit mounted sensor(s) to duct
location(s). The static pressure setpoint is keypad adjustable
through the MicroTech II DDC controller.
All variable air volume units include field adjustable duct
high limit safety control to protect ductwork from excessive
duct pressure.

Disconnect Switch

A factory mounted, nonfused main circuit interrupter for dis-
connecting the main electrical power is available. The switch
is located at the front of the unit on the control panel and is
accessible without unit penetration. The lug size information
is provided in Tables 11 and 12.

Dual Power Supply

The dual power block is an option for the power supply. This
allows the fan motor and control circuit to be isolated from
the compressor circuit. If the unit has the optional electric
heat it will be circuited with the compressors.

Electric Heat

Optional electric heat is available. Heat is controlled by the
unit's MicroTech II unit controller to maintain setpoint. The
heaters are factory installed and wired including branch fus-
ing and all safety controls.

Hot Water Control

A factory mounted, 1 or 2 row hot water coil is available,
with or without factory mounted control valve. The hot
water control valve is controlled by the unit's MicroTech II
controller to provide morning warm-up heat or heat for con-
stant volume application.
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