Why is it that I experience frequent burnouts of the air conditioner compressors in my house? I lose about 8 compressors within a year! Could it be because I used a 16mm aluminium cable as live and a smaller copper cable as neutral from the meter to our change over, a distance of about 10metres? I have checked every other thing but I still wonder about the frequent flashing/burning. Even the fan burns out sometimes.

What must i do to correct this.

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    What country are you in? – Grant Nov 23 '16 at 12:08
  • Hello, and welcome to Stack Exchange. What do you mean by "burning"? – Daniel Griscom Nov 23 '16 at 12:20
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    What size is the neutral wire? Also, what is the nameplate amperage on the compressor? – ThreePhaseEel Nov 24 '16 at 1:32

Any motor will burn out if there is insufficient voltage reaching it. Or it is overloaded.

Measure the voltage reaching the compressor, easily approximated by measuring at the electrical outlet. Do this while the a/c is running. Compare the voltage at the same place without the a/c running. If the voltage drops significantly (240 v to 210 v), that is a sign of inadequate or poorly installed wiring. Excellent wiring will barely have any drop (240 to 238 volts).

What is 16 mm aluminum cable?

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  • It's metric sized wire -- 16mm^2 is just shy of a 5AWG wire... – ThreePhaseEel Nov 24 '16 at 1:30

There are many other likely cause of compressor failure besides voltage problems. A replacement compressor on an existing system is statistically much more likely to fail than the compressor on newly installed system merely because the condition that killed the first compressor goes uncorrected when the compressor is replaced. The next compressor is killed the same way the first one died. Also, compressor burnouts can heavily contaminate a system and unless countermeasures are installed at the time the replacement is installed, contamination will doom an otherwise good replacement compressor to an early death.

Good ways to kill compressor:

  1. Liquid flood-back
  2. Inadequate oil return / lubrication
  3. Operating temp is too hot (compressor portion)
  4. Operating temp is too hot (motor portion)
  5. System contamination
  6. Incorrect electricity supplied (single phasing, voltage too high, frequency too low).

Of these possibilities, over-current problems caused by inadequate wiring is only one possibility for cause #4. I doubt this is your problem because virtually all residential units have a hermetic compressor with internal thermal protection for the motor winding. If this were the cause of your failures, the compressor would periodically stop for 15-30 minutes to cool down every time the winding overheated and it would do this many many times before the compressor motor burned out. You would probably notice this.

A compressor on a correctly functioning system should easily last more than a decade and likely more than 2 decades. Eight repeat failures on one system in one year is Keystone Cops level ridiculous. You need a more skilled technician to identify the underlying cause of the repeat failures.

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