Condenser Water Flow Switch; Water Side Economizer; Condenser Water Head Pressure Control; Disconnect Switch - McQuay SWP Series Installation And Maintenance Manual

Condenser Water Flow Switch

The Water Flow sensor (WF1) is available to verify flow to the
unit condenser before compressor operation is allowed. The
flow sensor is factory wired, but the switch will have to be
field installed in the unit on the leaving water condenser pipe.
The shipping plug shall be removed from the water tube and
the water flow switch should be installed with thread sealer.
Installation of the switch should wait until all brazing
operations have been performed and before the system is
filled. If the unit senses a loss of condenser water, cooling is
locked out via the MicroTech III controller. When flow is
restored, the unit automatically resets. The water flow sensor
operates on the calorimetric principle using the cooling effect
of the flowing condenser water around its stainless steel tip to
provide flow detection.
The water flow switch is factory set at 39 ft./min. To make
adjustments, turn the potentiometer sensitivity shown in
Figure 35. The sensitivity adjustment screw is sealed under a
thin coating of glue. Use a small screwdriver to gently scrape
off the glue. Turn the screw counterclockwise to activate the
switch at a higher velocity. Turn the screw clockwise to
activate the switch at a lower velocity.
Figure 35: Adjusting Condenser Water Flow Switch

Water Side Economizer

A completely factory-installed, factory-piped, and
factory-controlled water side economizer system is available
on any constant or variable air volume system. Whenever the
entering water temperature is more than 5°F to 7°F below the
mixed air temperature to the unit, the control valves modulate
to provide cooling directly from the tower water (adjustable at
the MicroTech III keypad/display). The economizer system
can be used to provide 100% of the cooling demand or
supplement mechanical cooling by precooling the return air.
The economizer system consists of a water coil and two, two-
way, control valves. The unit's MicroTech III controller
modulates the control valves to satisfy the cooling demand
whenever the entering water is suitable. When the control
valves are in the 90% open position, the unit's compressors are
allowed to stage on to satisfy the cooling load. When the
entering water temperature is no longer suitable, the
economizer control valve closes and the unit is on 100%
McQuay IM 937
Potentiometer
sensitivity setting
Flow indication LEDs (switch
activated when green LEDs light)
mechanical cooling.
Two valve control arrangements are available from the factory.
The first maintains full flow through the unit condensers at all
times. This control arrangement is used for systems with
constant pumping systems. For installations with a variable
pumping system, the control valves are sequenced so flow is
removed from the unit whenever cooling is not required. A
mechanical clutch is provided on each valve to manually close
or open the valves.
The economizer system is factory piped and the coil takes
advantage of the same drain pan and condensate connection.
To vent air from the economizer coil, use the uppermost
cleanout plug. The torque requirement for the cleanout plugs is
10 inch-lb.

Condenser Water Head Pressure Control

An optional condenser head pressure control valve is available
on units without water side economizer. This option permits
operation with entering water temperatures as low as 40°F. The
valve is a two-way regulating valve controlled via MicroTech
III to maintain refrigerant head pressure.

Disconnect Switch

A factory-mounted, nonfused main circuit interrupter is
available for disconnecting the main electrical power. 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 Table 10 and Table 11 on page 16.

Dual Power Supply

A dual power block or disconnect is an option for the power
supply, which allows the fan motor and control circuit to be
isolated from the compressor circuit. If the unit has the
optional electric heat, it is circuited with the compressors.

Electric Heat

Optional electric heat is available. Heat is controlled by the
unit's MicroTech III unit controller to maintain the set point.
The heaters are factory installed and factory wired, including
branch fusing and all safety controls.

Hot Water Control

A factory-mounted, 1-row 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 III
controller to provide morning warm-up heat or heat for
constant volume application.

Battery Pack

An optional unit mounted battery pack is available. If the
electrical power fails, the battery pack provides power to drive
the actuator on the economizer valve closed and drive the
bypass valve closed when valves are independently controlled.
Unit Options
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