Power trips every time my AC compressor starts — what's causing it?
The main breaker trips almost every time the AC compressor tries to start — I hear the click from the outdoor unit, then everything goes off. Resetting works for a while, then it happens again.
It is a small cafe in JLT, so downtime actually costs me. Is this the AC or the electrics?
3 answers
Please stop resetting it — a repeated trip on compressor start is the system protecting you from something. The compressor pulls a big inrush current for a split second when it starts; if the breaker is undersized or ageing, or the compressor capacitor is weak, that surge trips it. It can also be an earth or insulation fault inside the unit, which is the one you do not want to keep re-energising.
This is a licensed-electrician job, not DIY — they will clamp-meter the startup current and test the circuit. If it is tripping the MAIN and not just the AC's own breaker, treat it as urgent.
Agreed. Nine times out of ten I see this, it is a tired capacitor giving the compressor a weak, slow start, so it draws more current and trips. Cheap part. But get it diagnosed properly — a failing compressor can behave the same way, and you do not want to guess with a business on the line.
For a commercial-ish setup in JLT I would get the whole board checked while they are there. When trips are frequent, a proper electrical safety inspection is worth it because it rules out the genuinely dangerous causes rather than just clearing the symptom.
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