37
Components
7.0 COMPONENTS & CONTROLS
(-)P20 heat pumps are equipped with electronic
expansion valves (EXV). The advantage an EXV
is their ability to accurately control refrigerant
flow over a much wider capacity range than a
conventional mechanical TXV can. The Variable
Speed Outdoor Control (VSODC) uses inputs
from the suction line thermistor and suction
pressure transducer to precisely calculate suction
superheat and make necessary adjustments to
the refrigerant flow through the EXV to maintain
the optimum superheat level. The VSODC is
programmed to ignore short duration changes in
the pressure and temperature inputs which allows
more stable operation than conventional TXV’s.
The EXV utilizes an external 4-pole removable
stator for serviceability. An internal check valve
is provided that assures unrestricted flow in the
reverse direction when the system is operating in
the cooling mode.
For the (-)P20 model line there are 3 ferrite
rings and one filter applied on all models. The
ferrite rings are similar in purpose to the choke,
whereas they create an inductive field around the
assembled wires, but they do not filter the signals.
The ferrite rings are applied only for the purpose
of keeping the high voltage lines from cross
contaminating one another and thereby creating
unexpected operation and electromagnetic
interference. The single filter has been applied
to eliminate high frequency “noise” from the
incoming power line thereby making it more
efficient for the inverter to convert the incoming
line voltage single phase AC power into 3 phase
DC power.
7.6 Electronic Expansion Valve
7.7 Filter & Ferrite Rings
Filter
Ferrite
Ring
Ferrite
Ring
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