Mitsubishi Electronics MS-AWA Heat Defrosting Control, Discharge Temperature Protection Control

MXZ-3A30NA- 1

MXZ-4A

Number of operating	Capacity code	COOL (Hz)		DRY (Hz)		HEAT (Hz)
unit		Min.	Max.		Min.	Max.	Defrost
	4	25	58	25	20	70	58
1	7	25	58	25	20	70	58
	9,10	25	71	25	20	80	58
	12	25	80	35	20	80	58
	8 ~ 10	25	80	31	20	80	58
2	11 ~ 13	25	80	31	20	80	58
	14 ~ 16	25	80	42	20	80	58
	17 ~	25	80	42	20	80	58
3 (MXZ-3A)	12 ~	25	80	52	20	80	58
3 (MXZ-4A)	12 ~	25	90	52	20	103	58
4 (MXZ-4A)	16 ~	25	90	52	20	113	58

3-4. HEAT DEFROSTING CONTROL

(1) Starting conditions of defrosting

When the following conditions a) ~ c) are satisfied, the defrosting starts.

a)The defrost thermistor reads 26.6 °F or less.

b)The cumulative operation time of the compressor has reached any of the set values (31, 35, 45, 55, 65, 75, 85, 95, 105, 115, 150 minutes).

c)More than 5 minutes have passed since the start-up of the compressor.

Set value of compressor operation time (hereinafter referred to as defrost interval)

This is decided by the temperature of defrost thermistor and ambient temperature thermistor, the previous defrosting time. For example, the first defrost interval is 40 minutes long, and the second is 45 minutes long. The third and sub- sequent intervals are set to be longer, and less frequent, depending on defrosting time.

The third and subsequent defrost intervals follow any of the three patterns …5 or 10 to 20 minutes longer, the same, or 5 or 10 to 20 minutes shorter compared with the previous defrost interval … with the longest 125 minutes and the shortest 40 minutes.

(2) Releasing conditions of defrosting

Defrosting is released when any of the following conditions is satisfied:

a)The defrost thermistor continues to read 50.7 °F.

b)Defrosting time exceeds 10 minutes.

c)Any other mode than HEAT mode is set during defrosting.

3-5. DISCHARGE TEMPERATURE PROTECTION CONTROL

This protection controls the compressor ON/OFF and operation frequency according to temperature of the discharge tempera- ture thermistor.

(1) Compressor ON/OFF

When temperature of the discharge temperature thermistor exceeds 240.8 °F, the control stops the compressor.

When temperature of the discharge temperature thermistor is 176 °F (2A/3A30NA)/ 212 °F (3A30NA- 1

/4A) or less, the

controls starts the compressor.

(2) Compressor operation frequency

When temperature of the discharge temperature thermistor is expected to be higher than 240.8 °F, the control decreases 12 Hz from the current frequency.

When temperature of the discharge temperature thermistor is expected to be higher than 231.8 °F and less than 240.8 °F, the control decreases 6 Hz from the current frequency.

When temperature of the discharge temperature thermistor is expected to be higher than 219.2 °F and less than 231.8 °F, the control is set at the current frequency.

3-6. OUTDOOR FAN CONTROL

Fan speed is switched according to the number of operating indoor unit and the compressor frequency.

Fan speed			<Relation between compressor frequency and fan speed>
		Up		Compressor frequency (Hz)
High	Down
				Down	Up
			MXZ-2A	30	40
Low			MXZ-3A30NA
	Min. Compressor frequency Max.		MXZ-3A30NA- 1	40	50
			MXZ-4A

NOTE : When the indoor coil thermistor is 134.6 ˚F or more on HEAT operation, fan speed is fixed to Low speed. Or, the indoor coil thermistor is 113 ˚F or less on HEAT operation, fan speed is back to normal.

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