Specifications And Operations - Lennox MMA018SM4 Service Manual

18. Specifications and Operations

T1 Indoor ambient temperature
T2 Coil temperature of indoor heat exchanger
T2B Coil temperature of indoor heat exchanger outlet. (Located in outdoor unit)
T3 Pipe temperature of outdoor heat exchanger
T4 Outdoor ambient temperature
T5 Compressor discharge temperature
Input voltage: 230V
Input power frequency: 60Hz
Indoor fan normal working amp. is less than 1A
Outdoor fan normal working amp is less than 1.5A
Four-way valve normal working amp is less than 1A
Three minutes delay at restart for compressor
One minute delay for the first time start-up and three minutes delay for others
Temperature protection of compressor discharge
When the compressor discharge is getting higher, the running frequency will be limited as below rules:
If 215.6°F (102°C) < T5 < 244.4°F (115°C), decrease the frequency to the lower level every two minutes until to F1.
If T5 < 244.4°F (115°C) for ten seconds, the compressor will stop and restart till T5 < 194°F (90°C)
If the indoor units cannot receive the feedback signal from the outdoor units for two minutes, the unit will stop and display failure.
High Condenser Col
Temp Protection
Outdoor Unit Anti-
Freezing Protection
Running Rules
Preheating permitting
condition
Preheating Mode
Preheating Release
Condition
Preheating permitting
condition
Preheating Release
Condition
Table 2. Electronic Functions Abbreviations
Table 3. Electronic Control Working Environment
Table 4.
Table 5. Indoor/Outdoor Units Communication Protection
When T3>149°F (65°C) for three seconds, the compressor will stop while the indoor fan and outdoor fan
will continue.
When T3<125.6°F (52°C), the protection will release and the compressor will restart after three minutes.
When T2B< 32°F (0°C) for 250 seconds, the indoor unit capacity demand will be zero and resume to
normal when T2B> 50°F (10°C).
1. If the compressor frequency keeps lower than RET_OIL_FREQ1_ADD for RET_OIL_TIME1_ADD,the
AC will rise the frequency to RET_OIL_FREQ2_ADD for RET_OIL_TIME2_
2. During the oil return process, the EXV will keep 300p while the indoor units will keep the current
running mode.
Table 6. Compressor Preheating Functions
If T4 (outdoor ambient temperature)< 37.4°F (3°C) and newly powered on or if T4<37.4°F (3°C) and
compressor has stopped for over 3 hours, the compressor heating cable will work.
A weak current flow through the coil of compressor from the wiring terminal of compressor, then the
compressor is heated without operation.
If T4>41°F (5°C) or the capacity demand isn't zero, preheating function will stop.
Table 7. Compressor Crankcase Heater
When T4< 37.4°F (3°C) within 5 seconds of being plugged in, the crankcase heater will be active.
When T4< 37.4°F (3°C) and the compressor is not running for 3 hours, the crankcase heater will be
active.
If T4>41°F (5°C) or the indoor has capacity demand, the crankcase heater will stop work.
Main Protection
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