Electrics are the invisible part of a house, forgotten until something goes wrong. Homes built twenty or thirty years ago were designed for one or two air-conditioners, a fridge and lights. Today the same house may have air-con in every room, water heaters, an induction hob, a microwave, a washing machine and soon an EV charger. Overloading the original system causes not only voltage drops and frequent trips but is a major cause of house fires. For second-hand buyers and renovators, checking and upgrading electrics belongs near the top of the list.
Watch for breakers or fuses tripping when several appliances run, lights flickering or dimming when the air-con or pump starts, switches or sockets warm to the touch, scorch marks around sockets, an unexplained burning smell, and mild shocks from appliance casings or taps. That last sign indicates leakage without proper earthing — very dangerous; call an electrician immediately.
Many older homes use surface-clipped flat cable which, after decades, becomes hard, brittle and cracked, especially in hot roof spaces or where rodents gnaw. Original cable sizes may be too small for today's loads. Rewiring the whole house in conduit is worthwhile during a major renovation, allowing circuits to be redesigned for current use and earthing to be added. On a tight budget, start with high-load circuits: air-con, kitchen and water heaters.
| Component | Function | Note |
|---|---|---|
| Main breaker | Isolates the whole house | Sized to the meter and main cable |
| Circuit breakers per circuit | Overcurrent protection | Separate lighting, sockets, each air-con, water heaters |
| Residual-current device (RCD/RCBO) | Trips on leakage to earth or through a body | Critical for bathrooms, kitchens and outdoors |
| Earth terminal | Path for leakage current to ground | Connected to a properly installed earth rod |
| Surge protection (optional) | Reduces lightning and surge damage | Protects expensive appliances |
Old boards with cut-outs and wire fuses, no leakage protection and no circuit separation should be replaced. Labelling each breaker lets you isolate a specific point immediately when something goes wrong.
An earth gives leakage current a path to ground instead of through a person. Many older homes have no earthing, or three-pin sockets that aren't actually earthed. Proper earthing comprises an earth rod driven to standard depth, an earth conductor to the consumer unit, and earth wiring to sockets and appliances that need it — water heaters, washing machines, fridges. Earthing together with RCDs completes shock protection.
Typical Thai homes use single-phase meters in several sizes, and older homes often have small ones. If you plan more air-cons, an electric hob or an EV charger, have an electrician calculate total load first. If it exceeds the meter rating, apply to the Metropolitan or Provincial Electricity Authority for a larger meter, usually with matching upgrades to the service cable and main breaker. Very high-consumption homes may consider three-phase supply — discuss suitability and cost with the authority.
Electrical mistakes can be fatal. Choose an electrician with a competence certificate or a national skills standard qualification in building wiring, ask to see previous work, get quotes specifying cable, breaker and device brands and sizes, and request a circuit diagram on completion for future reference. For full rewires, having an electrical engineer design or inspect the work adds confidence.
It depends on the existing method. Surface wiring can be replaced with new surface conduit without chasing walls; concealed wiring requires chasing and re-plastering, best done during a major renovation.
Probably not; it is detecting real leakage on a circuit or appliance, such as a water heater with failing insulation. Have the electrician test circuit by circuit; never remove the RCD.
Look at the consumer unit, wiring age, meter size and whether earthing exists; press the RCD test button; have an inspector measure leakage and earth continuity — and use upgrade costs in price negotiation.
Modern electrics are the foundation of home safety and of modern living, from multiple air-cons to electric cars. Watch for warning signs, replace degraded wiring, upgrade the consumer unit, install earthing and RCDs, and use qualified electricians. More renovation guides on the MyProperty blog.
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