Electronic Functions - Carrier 38MBRC Series Service Manual

38MBRC: 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 (TP)
• Td: Target 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 Top Temperature Protection
The unit stops working when the compressor top temp. protector cuts off,
and restarts after the compressor top temp. protector resets.
Compressor Discharge Temperature Protection
When the compressor discharge temp. increases, the running frequency is
limited per the following rules:
• Compressor discharge temp. T5>239°F(115°C) for 5s, compressor
stops and restarts up until T5<194°F (90°C)
• 110<T5<239°F(115°C), decrease the frequency to the lower level
every 2 minutes.
• 221°F(105°C)<T5<230°F(110°C), keep running at the current
frequency.
• T5<221°F(105°C), no limit for frequency.
Fan Speed is Out of Control
When the indoor fan speed remains low (lower than 300RPM) for 50s,
the indoor fan shuts off and restarts 30s later. If the protection mode
engages 3 times when the fan motor restarts continuously, the unit stops
and the LED displays the failure.
When the outdoor fan speed remains low (lower than 100RPM) or too
high (higher than 1500RPM) for 60s, the unit stops and the LED displays
the failure. The malfunction clears 30s later.
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 controlled also by the anti-cold wind function.
Compressor Preheating Functions
Preheating Permitting Condition:
If T4<37.4°F(3°C) when the unit is first powered up within 5 seconds or
if T4<37.4°F(3°C) and the compressor has stopped for over 3 hours, the
compressor heating cable will work.
Preheating Mode:
A weak current flow through the compressor coil from the compressor
wiring terminal, then the compressor is heated without operation.
Preheating Release Condition:
If T4=41°F(5°C) or the compressor starts running, the preheating
function stops.
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
Condenser High Temperature T3 Protection:
• 131°F(55°C)<T3<140°F(60°C), the compressor frequency decreases
to the lower level until to F1 and then runs at F1. If
T3<129.2°F(54°C), the compressor keeps running at the current
frequency.
• T3<125.6°F(52°C), the compressor does not limit the frequency and
resumes the former frequency.
• T3>140°F(60°C) for 5 seconds, the compressor stops until
T3<125.6°F(52°C).
Evaporator Low Temperature T2 Protection:
• T2<32°F(0°C), the compressor stops and restarts when
T2=41°F(5°C).
• 32°F(0°C) ≦ T2<39.2°F(4°C), the compressor frequency is limited
and decreases to the lower level
• 39.2°F(4°C)=T2<44.6°F(7°C), the compressor retains the current
frequency
• T2>44.6°F(7°C), the compressor frequency is not limited.
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
°C
10.8°F (6.0°C)
a
9°F (5.0°C)
7.2°F (4.0°C)
6°F (3.0°C)
1.8°F (1.0°C)
Fig. 10 — FAN Mode
10
H
(H-L)*0.75+L
b
(H-L)*0.5+L
c
(H-L)*0.25+L
L
d
e