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Controls Interface
NOTICE
Proof of Flow Switch!
Failure to provide flow switches or jumping-out of
switches could result in severe equipment damage.
Evaporator and condenser water circuits require
proof of flow switches.
•
Failure to include the proof of flow devices and/or
jumping out these devices could cause the unit to
stop on a secondary level of protection.
•
Frequent cycling on these higher level diagnostic
devices could cause excessive thermal and pressure
cycling of unit components (O-rings, gaskets,
sensors, motors, controls, etc.) and/or freeze damage,
resulting in premature failure of the chiller.
Phase Monitor
A compressor can fail if operated in reverse for more than a
minute. A phase monitor is used on three phase power
systems to ensure that the electricity supplying the chiller/
heat pump is configured appropriately. A phase monitor
prevents a motor from operating in reverse—if any of the
three legs of power are landed incorrectly—and will shut
the system down upon detection of a reversed phase
condition.
Refrigeration Controls
Mechanical controls on the refrigeration system are
designed to provide safety for the major components and
for proper operation of the system.
Pressure transducers convert pressure into an electronic
signal that the microprocessor displays in pounds per
square inch (psi) or bar.
Temperature sensors transmit temperature data
electronically to the microprocessor for display in either
Fahrenheit (°F) or Celsius (°C).
Expansion Valve
An expansion valve is a metering device controlling the
flow of refrigerant to the evaporator based on the
evaporator superheat.
Superheat is factory-set for around 12 °F (6.7 °C). Close
the valve to increase superheat. To accurately read
superheat, install a temperature sensor at the evaporator
outlet. The sensor bulb should be located at the 4 o'clock
54
or 8 o'clock positions on the pipe for the most accurate
pressure measurement.
Ensure that the closed cell insulation covers the thermal
expansion valve sensing bulb. If insulation is missing, the
bulb will tend to feed more refrigerant to satisfy the
superheat setting.
Electronic and Manual Isolation Valves
(WXM)
Each brazed plate heat exchanger branch line includes a
manual inlet and an electronic discharge butterfly valve that
allows system flow to each active module to match the
cooling or heating requirements of the system. By isolating
individual modules that are not operating, the hydronic
system can have variable primary flow to water-to-water
heat pump modules.
The valves are the slow opening type - to minimize the
sudden change in flow to the previously active modules
and have a minimum opening cycle time of 30 seconds
between the fully closed and open position. The valves
have a minimum close off pressure of 75 psi , have a
maximum working pressure of 250 psi, and have roll
grooved connections. The actuators are rated for 24 VAC.
Reversing Valves (WXM)
The water-to-water heat pump reversing valve is an
electro-mechanical 4-way valve that reverses the
refrigerant flow direction. It moves heat from inside the
building to the outdoors (cooling mode) or removes the
heat from outside the building to the indoors (heating
mode).
Reversing valves are designed to lower the minimum
operating pressure difference between high and low side.
Sight Glass
When the sight glass shows a green indicator, no moisture
is present. When the sight glass shows a yellow indicator,
there is moisture in the refrigerant line. Bubbles can be
observed whenever chiller/heat pump cycling causes the
pressure to change up or down.
ARTC-SVX010A-EN
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