Special Controls - Panasonic U-10MF1E8 Service Manual

4. Special Controls

In addition to ordinary heating and cooling operation, this system also includes the following 3 types of special
controls for control of the system as a whole.
1. Tube refrigerant recovery control
2. System refrigerant oil recovery control
3. Defrost control
4-1. Tube Refrigerant Recovery Control
This control recovers refrigerant from the tubing when the microcomputer is initialized immediately after power-ON,
after warning output occurs, and after a set amount of time has elapsed (standard = 60 minutes) when all outdoor
units are stopped.
This control is intended to recover refrigerant if refrigerant has accumulated somewhere in the tubing when the
units have been stopped for long periods, as well as to compensate for tubing thermal loss during heating start,
and is also used for oil recovery.
(1) Control when the outdoor unit heat exchanger is acting as a condenser (when all units are in Cooling mode or
at start of mixed operation when the cooling load is high)
Control time
Outdoor units
Electronic control valve Valves at all indoor units operate at a fi xed pulse according to the indoor unit capacity.
Indoor RAP valve kit
units
Fan
* When the above operation is fi nished, normal operation starts at the horsepower determined by the indoor units
where thermostats are ON.
(2) Control when outdoor unit heat exchanger is acting as a condenser (when all units are in Cooling mode or at
start of mixed operation when cooling load is high)
Control time
Outdoor units
Electronic control valve Valves at all indoor units operate at 480 pulses.
Indoor RAP valve kit
units
Fan
* When the above operation is fi nished, normal operation starts at the horsepower determined by the indoor units
where thermostats are ON.
4-2. System Refrigerant Oil Recovery Control
4-2-1. System refrigerant oil recovery cycle
This control is performed using the cooling cycle during cooling operation and using the heating cycle during
heating operation.
4-2-2. Start of system refrigerant oil recovery control
When the oil level in an operating compressor changes to 0, the compressor stops after 120 seconds. If this
compressor repeats this operation 3 times and the oil level does not reach 2, system refrigerant oil recovery control
is started.
* When the compressor has stopped because the oil level is 0, a count is added to the alarm counter. The counter
for this compressor is not cleared unless the oil level for that compressor reaches 2, or else alarm output occurs.
60 seconds
All outdoor units operate at maximum horsepower.
Valve kits at all indoor units operate in Cooling mode (ON status).
Fan operates at the set fan speed, stops, or operates at L speed, depending on the
indoor unit operation mode.
Minimum 1 min – Maximum 10 min [until max (pressure sensor temp., E1) ≥ 35°C]
All outdoor units operate at maximum horsepower.
Valve kits at all indoor units operate in heating mode (ON status).
Fan operates at the set fan speed, stops, or operates at L speed, depending on the
indoor unit operation mode.
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3-WAY SYSTEM
Control Functions
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