Connecting an air conditioner to a socket shared with other appliances is one of the mistakes that most often trips protections in a home, and it isn't always obvious why until you understand how the compressor starts.
Why it needs a dedicated circuit
The split unit needs its own electrical circuit from the consumer unit, never shared with other appliances: the compressor start-up draws several times its rated current for an instant, and can trip protections that are undersized or shared with other devices.
What cable size and circuit breaker apply
| Unit power | Cable size | Circuit breaker |
|---|---|---|
| Up to 3 kW | 2.5 mm² | 16 A |
| 3-5 kW | 4 mm² | 20 A |
The cable length from the consumer unit to the unit is calculated with a 10% margin for joints over the real measurement.
Example: for 12 metres from the consumer unit: 12 × 1.10 = 13.2 lm of cable to buy. This is the same calculation the PresupuestoYa calculator applies automatically for the AC Technician trade.
The thermostat: wired or WiFi
- Wired wall thermostat: the traditional option, with no need for WiFi in the home.
- WiFi / smart: lets you set schedules and switch the unit on before getting home, which in practice helps more efficient use than leaving it on all day. Always check the controller's compatibility with the unit's brand and protocol before quoting — not all WiFi controllers are universal.
Frequently asked questions
Can I connect the air conditioner to a normal shared socket? It isn't advisable: the compressor start-up draws several times its rated current for an instant, which can trip protections shared with other devices.
What cable size does a 4 kW split need? 4 mm², with a 20 A circuit breaker, since it falls in the 3-5 kW range.
Does a WiFi thermostat really save energy? Yes, indirectly: by allowing schedules to be set, it avoids leaving the unit on all day for convenience, which in practice reduces consumption.
Conclusion
Giving the air conditioner its own circuit, with the right cable size and circuit breaker for its power, avoids the most common problem in poorly quoted installations: protections that trip every time the compressor starts. Calculating by the unit's real power, not by eye, leaves a reliable installation from day one.
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