Toshiba MMU-AP0091H service manual Operation explanation and applied data, etc Remarks

No.	Item	Operation explanation and applied data, etc.		Remarks
5	Oil short	This control is provided to prevent oil shortage occurring in the
	protective	compressors of each outdoor unit.
	control	The control is achieved by ON/OFF operation of the solenoid
		valves SV3A, SV3B, SV3C and SV3D.
		(1) Oil-short protective control
		The oil shortage protection control function stops the outdoor	• Oil accumulated in the
		unit, if an oil shortage continues for 30 minutes, after 2		oil separator is returned
		minutes, 30 seconds the outdoor unit restarts.		to the compressor.
		If this function is activated on 3 successive occasions, an error
		check code (H07) is generated and the outdoor unit is
		stopped.
6	Refrigerant/Oil	(1) During cooling operation, this function is executed to regularly
	recovery control	to recover the refrigerant/oil from the indoor units and con-
		necting pipe-work back to the outdoor unit.
		This function is also performed to prevent stagnated refriger-
		ant accumulating in the outdoor heat exchanger during low
		ambient cooling.
		The control is managed by the header outdoor unit.
		1) Control conditions	•	Control for refrigerant/
		• Cooling oil recovery operation is executed approximately		oil recovery is per-
		every 2 hours.		formed approximately
		2) Contents of control		every 2 hours.
			•	Recovery lasts for
		• The recovery period lasts for approximately 2 or 3
				approximately 2 or 3
		minutes though this is dependant on the system capacity.
				minutes though this is
		(2) Refrigerant recovery control in heating room
				dependent upon the
		This function is executed regularly to recover the liquid
				system capacity.
		refrigerant from the indoor unit.
		It is also used to recover oil present in the outdoor heat
		exchanger during the heating overload operation (except
		during defrost operation).
		The control is managed by the header outdoor unit.
		1) Heating operation oil, recovery control is executed approxi-
		mately every hour.
		2) The period of recovery lasts for approximately 2 to 10
		minutes though this is dependent upon the load condition.
		(3) Control for refrigerating / whilst oil recovery in simultaneous
		operation.
		This function is executed to recover the refrigerating oil
		accumulated in the low-pressure gas inter-unit piping.	•	Heating operation, oil
		(regardless of all cooling operation/all heating operation).
				recovery is executed
		1) Control condition
				approximately every
		• When the combined time of the compressor-ON has		hour.
		reached 95 minutes in simultaneous operation.	• Recovery lasts for
		2) Control contents		approximately 2 to 10
		When the conditions have been satisfied, upon changing		minutes though this is
				dependent upon the
		the indoor unit mode from heating to cooling, (stop the
				load condition.
		indoor fan) the oil is recovered for a period between 2
		minutes 30 seconds to 10 minutes. The indoor unit in
		cooling operation continues operation.
7	Defrost control	(1) Defrost start condition	•	During the defrost
	(Reverse cycle	The defrost function is initiated when the measurement		operation, all solenoid
	defrost method)	temperature taken from the TE sensor is lower than -2°C for a		4-way valves are OFF
		period of 25 minutes after compressor initial start up and 55		and all compressors
		minutes after subsequent start ups.		are operating.
		(2) Contents of control
		• If the outdoor units are combined, the minimum duration for
		the defrost operation is 2 minutes.
		(3) Defrost stop condition
		• The outdoor fan speed and compressor inverter frequency
		are determined by the measurement of Pd pressure during
		defrost operation.

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