After a power cut our AC/chiller won't restart — is it broken, or a protection lockout, and what can I safely try?

Nine times out of ten this is protection working as designed, not a breakdown. Here's the order to think about it:

1. The anti-short-cycle delay (most common — just wait). Almost every compressor has a built-in 2-5 minute time delay before it will restart, so it never slams back on against high pressure right after power returns. So "won't restart immediately" is usually normal — give it five minutes before assuming anything's wrong. A hard-start kit helps older compressors here.

2. Phase-loss / phase-reversal lockout (the big one for chillers & 3-phase units). On three-phase equipment there's a phase-protection relay. If the power came back with a phase missing, low, or in reversed order (common after grid work or a generator changeover), the unit deliberately locks out to stop the compressor running on bad power and destroying itself. This is the classic "chiller won't come back after the cut" — and it's a supply problem to check, not a reason to force the machine on.

3. A tripped isolator/breaker or a control-board lockout that needs a reset.

What you can safely try: wait out the 5-minute delay; check the isolator switch and the breaker are on; on a split, one power-cycle at the isolator is fine. What needs a pro (don't DIY): anything showing an error/lockout code, a suspected phase fault, or repeated lockouts — those mean the supply or the protection circuit needs proper checking, which is core a water chiller service in Dubai territory. Do not keep resetting a unit that keeps locking out — it's protecting itself from something real (often a bad capacitor or a phase issue).