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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 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
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). Transducers vary in pressure ranges that
depend on the type of refrigerant used. Pressure
transducers are calibrated using the interface panel.
Temperature sensors transmit temperature data
electronically to the microprocessor for display in either
Fahrenheit (°F) or Celsius (°C). Temperature sensors are
calibrated using the interface panel.
Expansion Valve
An expansion valve is a metering device controlling the
flow of refrigerant to the load heat exchanger based on the
superheat.
ARTC-SVX006A-EN
Superheat is factory-set for around 12 °F (-11 °C). Close
the valve to increase superheat. To accurately read
superheat, install a temperature sensor at the load heat
exchanger outlet. The sensor bulb should be located at the
4 o'clock 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.
Solenoid Valve
The liquid-line solenoid valve is used in the refrigeration
cycle to provide a refrigerant pump-down cycle at the end
of a compressor's cycle. The liquid refrigerant is pumped
out of the load heat exchanger to eliminate liquid
refrigerant from migrating to the compressor in the off
cycle.
Reversing Valves
The 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. Pressure drop and
valve leakage are minimized.
Electronic and Isolation Valves
Each brazed plate heat exchanger branch line shall include
a manual inlet and an electronic discharge butterfly valves
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 the air source
heat pump modules. The valves shall be the slow opening
type to minimize the sudden change in flow to the
previously active modules. The valves shall have a
minimum opening cycle time of 30 seconds between the
fully closed and open position and shall have roll grooved
connections. The valves shall have a minimum close off
pressure of not less than 75 psi and shall be rated for a
maximum working pressure of 250 psi. The actuators shall
be rated for 24 Vac.
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 heat pump cycling causes the
pressure to change up or down.
Controls Interface
41
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