Electronic Function; Electric Control Working Environment; Main Protection; Compressor Current Limit Protection - Carrier 38MGR Series Service Manual

ELECTRONIC FUNCTION

Abbreviation
• T1: Indoor ambient temperature
• T2: Middle indoor heat exchanger coil temperature
• T2B: Indoor heat exchanger exhaust coil temperature (located on
the outdoor unit)
• T3: Outdoor heat exchanger pipe temperature
• T4: Outdoor ambient temperature
• T5: Compressor discharge temperature

Electric Control Working Environment

• Input voltage: 230V
• Input power frequency: 60Hz
• Indoor fan standard working amp.: <1A
• Outdoor fan standard working amp.: <1.5A
• Four-way valve standard amp.: <1A

Main Protection

Compressor Restart Delay
The compressor takes one minute to start up the first time. Further
restarts take three minutes.
Compressor Discharge Temperature Protection
When the compressor's discharge temperature rises, the running
frequency is limited according to the following rules:

• If 221°F (105°C) T5<230°F (110°C), maintain the current
frequency.
• If the temperature increases and T5
frequency to a lower level every two minutes until F1.

• If T5 239°F (115°C) for ten seconds, the compressor stops and
then restarts until T5<194°F (90°C).
Fan Speed Malfunction
If the outdoor fan speed is lower than 100RPM or higher than
2400RPM for 60 seconds or more, the unit stops and the LED displays
an E8 failure code.
Inverter Module Protection
The inverter protection module ensures that faults related to current,
voltage, or temperature do not damage the inverter.
Low Voltage Protection
VOLTAGE
Fig. 27 — Low Voltage Protection
If these protections are triggered, the A/C unit stops and the LED
displays the failure code. The unit restarts three minutes after the
protection mechanism turns off.
NOTE: If the low voltage protection triggers and the
voltage does not restore to normal within three
minutes, the protection remains active even after
the unit restarts.
26

230°F, decrease the
No limit
VOLT_LTM_FREQ1_ADD
VOLT_LTM_FREQ2_ADD
Specifications subject to change without notice.

Compressor Current Limit Protection

The temperature interval for the current limit is the same as the range
of the T4 frequency limit.
50
49
45
44
41
40
33
32
Fig. 28 — Cooling Mode
Table 23 — Cooling Mode
Difference between current limit and
CoolReturnI
CoolT4Zone5I Cooling T4≥50
CoolT4Zone4I Cooling 49＞T4≥45
CoolT4Zone3I
Cooling 44＞T4≥41
CoolT4Zone2I Cooling 40﹥T4≥33
CoolT4Zone1I
Cooling 32＞T4
CoolStopI Cooling stop protection current value
15
14
10
9
6
5
Fig. 29 — Heating Mode
Table 24 — Heating Mode
Difference between current limit
HeatReturnI
HeatT4Zone4I Heating T4≥15
HeatT4Zone3I Heating 14＞T4≥10
HeatT4Zone2I Heating 9＞T4≥6
HeatT4Zone1I Heating 5＞T4 current limit value
HeatStopI Heating stop protection current value
Indoor / Outdoor Units Communication Protection
If the indoor units do not receive the feedback signal from the outdoor
units for two consecutive minutes, the unit stops and displays a failure
code.
shutdown current
°
C current limit value
°
C current limit value
°
C current limit value
°
C current limit value
°
C current limit value
HeatT4Zone4I
HeatT4Zone3I
HeatT4Zone2I
HeatT4Zone1I
and shutdown current
°
C current limit value
°
C current limit value
°
C current limit value
38MGR-04SM