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

No.	Item		Operation explanation and applied data, etc.		Remarks
8	Release valve	(1) SV2 gas balance control
	control	In order to decrease the starting load on the compressor, SV2 valve
		is opened during the time the compressor is ‘OFF’, and the gas is
		balanced.
		(2) SV2 high pressure release control
		This function limits the pressure level during the low frequency
		operation of the inverter.
		(3) SV2 low pressure release control
		This function is used to prevent rapid pressure drop during transient
		operation of the unit. This is performed by the header unit only. The
		function is performed when required, except during ‘No demand’
		status or when the system is in ‘Standby’.
		(4) SV41, SV42 valves
		1) SV41, 42 low-pressure release control
		This function is used to prevent pressure dropping to low.
		The function is performed during defrost operation, heat start up,
		all cooling operation, or mainly cooling or part heating operation.
		•	Control contents (Defrost/heating start pattern)
			Turn on SV41 and SV42 when PS pressure ≤ 0.1MPa, and turn
			off SV41 and SV42 when PS pressure ≥ 0.15MPa.
		•	Control contents (All cooling operation, Mainly cooling, part
			heating operation)
			Turn on SV41 and SV42 when PS pressure ≤ 0.14MPa and Pd
			pressure ≤	1.8MPa, and turn off SV41 and SV42 when PS
			pressure ≥	0.24MPa and Pd pressure ≥ 2.2MPa
		2) High pressure release control
		This function is for gas bypass control which emergently prevents
		the high pressure cut.
		Turn on SV41 and SV42 when Pd pressure ≥ 3.5MPa, and turn off
		SV41 and SV42 when Pd pressure ≤ 3.45MPa.
		(5) SV6 valve
		1) Cooling bypass control
		This function is a liquid refrigerant bypass control to suppress the
		rise of the discharge temperature or the inside temperature of the
		compressor.
		Turn on SV6 valve when the discharge temperature (TD1 or TD2)
		becomes 96°C or higher and turns off when it drops below 84°C
		by bypassing liquid refrigerant.
		(6) PMV3
		1) High pressure release control (All heating operation)
		This function suppresses the rise of high pressure during the
		inverter low frequency operation when in all heating operation
		mode.
		Set up PMV3 opening to 45 pulses when Pd pressure = 3.45MPa.
		2) High pressure release control (All cooling operation)
		Set up PMV3 opening to 60 pulses when Pd pressure = 3.5MPa.
9	Frequency	(1) High pressure release control
	release	This function is to correct the operation command of the compressor
	control	and suppress the rise of high pressure.
		1) Control contents
		The operation frequency is decreased by 1 step when Pd pres-
		sure ≥ 3.4MPa. It is decreased by 1 step every 10 seconds until
		Pd pressure drops below 3.4MPa.
		2) Release condition
		• When Pd pressure ≤ 3.2MPa
		•	When refrigerant recovery control starts in all heating mode
		• During defrost operation, stop, thermo OFF

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