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Fujitsu FO20R Series Installation Instructions Manual page 37

Variable speed r-410a heat pump outdoor units
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7.7 Electronic Expansion Valve
20 SEER heat pumps are equipped with electronic
expansion valves (EXV). The advantage an EXV is
its ability to accurately control refrigerant flow over
a much wider capacity range than a conventional
mechanical TXV. 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
7.8 Filter & Ferrite Rings
There are 3 ferrite rings and one filter 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
serviceability. An internal check valve is provided
that assures unrestricted flow in the reverse
direction when the system is operating in the
cooling mode.
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.



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