13A 掣位改專用充電線路13A outlet converted to a dedicated circuit
車位原本只有一個 13A 預留掣位。追查線徑後改為專用回路，加裝 RCBO 及刀掣，另掛獨立電錶。外觀分別不大，安全同帳單分別很大。The bay came with nothing but a 13A outlet. We traced the cable, converted it to a dedicated circuit with an RCBO and isolator, and hung a meter in the owner's name.
新界・新型屋苑New Territories · New estateWall Case 37kW獨立電錶Own meter
A recently built estate. The bay already had a 13A outlet on the wall with the meter cabinet beside it. The owner assumed an outlet meant charging was sorted, and had been using a portable 13A cable for months.
This is Type 3 of the four situations: half the infrastructure is there, and the missing half is the safety-related half.
The hard part
The outlet existing doesn't mean the cable behind it is rated for the job.
A 13A domestic socket is designed for short, intermittent loads. EV charging is a high current sustained for hours, and both the socket and the cable behind it heat up.
On-site measurement confirmed two things:
The cable feeding the outlet was sized for general domestic socket loads, not a sustained 7kW
The circuit had no dedicated residual current protection and shared a breaker with other bays
So even with a faultless charger, the heat and nuisance-tripping risk sat on the wiring side.
What we did
Traced it back to the board.
From the outlet back to the distribution board: cable size, breaker rating, and how many other bays sit on the same circuit.
Converted it to a dedicated circuit.
The 13A socket came out. In went a dedicated circuit with an RCBO (combined overcurrent and residual current) and an isolator, so this one bay can be isolated for maintenance without shutting down the run.
The charger itself carries 6mA DC leakage detection, which alongside the Type A RCBO covers both DC and AC leakage.
Fitted a dedicated meter.
Once the alteration was done we booked the utility. Previously the charging drew on the estate's supply with no way to check the usage; now it's billed to the owner, kWh by kWh.
Filed with management.
Altering the estate's existing wiring still needs written consent. But with the infrastructure already in place, submitting the installation proposal and the HK$20M third-party works insurance certificate made this far lighter than an older estate.
The outcome
A WR1 completion certificate on handover. Visually there's not much in it — same wall, one charger and one isolator added. The difference is that it trips on overcurrent, it can be isolated, and the bill is transparent.
Who this case is useful for
If your bay has a 13A outlet and you're charging off a portable cable, one thing is worth doing: touch the socket and plug after an hour of charging. If they're noticeably warm, convert it to a dedicated circuit sooner rather than later.
Send us photos of the outlet and the meter cabinet on WhatsApp and we can tell you upfront whether the cable needs replacing too.
你的物業與這個案例相似？Does your place look like this one?
傳送車位及電錶相片，我們會告知最接近哪一種情況、需時多久及費用多少。Send photos of your bay and meter. We'll tell you which case yours resembles, how long, and how much.
