Electronic Functions; Main Protection; Operation Modes And Functions; Fan Mode/Cooling Mode - Carrier 38MARB Service Manual

38MARB: Service Manual

ELECTRONIC FUNCTIONS

Abbreviation:
•T1: Indoor room temperature
•T2: Coil temperature of indoor heat exchanger middle.
•T2B: Coil temperature of indoor heat exchanger outlet.
•T3: Coil temperature of condenser
•T4: Outdoor ambient temperature
•T5: Compressor discharge temperature
•Td: Target temperature
•Ts: Set Point Temperature

Main Protection

Three minute delay for compressor restart
Less than a 1 minute delay for the initial start-up and a 3 minute delay for
subsequent starts.
Compressor high temperature cutout
The unit stops working when the compressor high temperature cutout
opens, and restarts after the compressor high temperature cutout closes.
Compressor discharge temperature protection
Compressor discharge temp. T5>239°F(115°C) for 5s, compressor stops.
Fan speed is out of control
When the indoor fan speed is too low (300RPM) or too high (1500RPM)
for a certain time, the unit stops and the LED displays the failure.
Inverter module protection
The inverter module has a protection function for current, voltage and
temperature. If any of these protections engage, the corresponding code
displays on the indoor unit and the unit stops working.
Indoor fan delayed open function
When the unit starts up, the louver is active immediately and the indoor
fan opens 10s later. If the unit is running in the HEATING mode, the
indoor fan is also controlled by the anti-cold wind function.
Compressor preheating functions
Preheat parameters: When the T4 (outdoor ambient temperature) <37.4°F
(3°C), preheat function is activated.
Zero crossing detection error protection
If the AC detects the time interval is not correct for a continuous 240s, the
unit stops and the LED displays the failure. The correct zero crossing
signal time interval should be between 6-13ms.
Sensor protection at open circuit and breaking disconnection
If only one temperature sensor malfunctions, the air conditioner continues
to work however the error code displays on the LED, in the event of any
emergency use. If more than one temperature sensor malfunctions, the air
conditioner stops working.
Refrigerant leakage detection
This function is only active in the COOLING mode. The function helps
prevent the compressor from being damaged by a refrigerant leakage or a
compressor overload.
Open condition:
When the compressor is active, the evaporator T2 coil temperature value
has no or very little change.
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.

Operation Modes and Functions

FAN Mode
1. Outdoor fan and compressor stop
2. Temperature setting function is disabled and no setting temperature
appears.
3. Indoor fan can be set to high/med/low/auto
4. The louver operates same as in the COOLING mode.
5. Auto fan
T1
°F°C
10.8°F (6.0°C)
a
9°F (5.0°C)
b
7.2°F (4.0°C)
4.5°F (2.5°C)
1.8°F (1.0°C)
Fig. 19 —AUTO FAN Mode
COOLING Mode
Compressor Running Rules:
• When T1-Ts < -4°F (-2°C), the compressor stops.
• When T1-Ts > -1°F (-0.5°C), the compressor activates.
• When the AC runs in the mute mode, the compressor runs with low
frequency.
• When the current is more than setting value, the current protection
function activates, and the compressor stops.
Outdoor Fan Running Rules:
The outdoor unit runs at a different fan speed according to T4. For
different outdoor units, the fan speeds differ.
A A
82.4°F (28°C)
78.8°F (26°C)
B B
77°F (25°C)
73.4°F (23°C)
C C
71.6°F (22°C)
69°F (20°C)
D D
66.2°F (19°C)
62.6°F (17°C)
E E
Fig. 20 —Outdoor Fan Running Rules
18
H
(H-L)*0.75+L
(H-L)*0.5+L
c (H-L)*0.25+L
L
d
e
DC_FAN_HI_SPD_ADD ADD D DD D D D D D D D
DC_FAN_MID_SPD_ADD _A A A A
°
DC_FAN_MIN_SPD_ADD _ADD
DC_FAN_SLOW_SPD_ADD PD_A
DC_FAN_SSLOW_SPD_ADD SPD_A A
D D D D D D D D D D D D
DD DD DD DD D D D D
A A A D D D D D D D D D D D D
A A A A A A D DD DD DD DD DD DD DD D D DD