Adding a new socket or AC point: load, wire size and what it takes

A new socket for a kettle and a new point for a 1.5-ton AC are not the same job. The first can often hang off the existing socket circuit. The second needs its own wire, its own MCB and, sometimes, a look at the capacity of the whole connection. Getting this right is what stops the new AC from tripping the board every evening in May.

Here is what goes into it, so you know what the technician is doing and what to ask for.

Light load, power load, dedicated load

Home circuits here fall into three types:

• Light circuits — lights, fans, small 6 A sockets. Thinner wire, 6 A sockets, a 6 or 10 A MCB.
• Power circuits — 16 A sockets for the fridge, washing machine, microwave, mixie, induction. Thicker wire, a 16 A MCB, and not too many sockets on one run.
• Dedicated circuits — one appliance, one line, one MCB. ACs, geysers, a borewell motor. Heavier wire again, sized for that appliance's current and the length of the run, with its own 16 or 20 A MCB.

A new phone-charger socket in the bedroom can go on the light circuit. A new 16 A socket for a second fridge should join a power circuit if one is nearby and not already loaded. An AC or geyser is always dedicated — no sharing, no tee-off from a neighbouring socket.

Why wire size matters

Wire is rated for how much current it can carry without heating. A 1.5-ton AC running in a Nellore afternoon, on a long run to a board at the other end of the house, on evening low voltage, is about the hardest thing you can ask of a domestic cable. Too thin, and the wire runs warm inside the conduit all summer; the insulation ages, the voltage at the AC drops, and the compressor works harder. The technician sizes the conductor for the current and the distance, then fits an MCB that protects that wire — not a larger one so it "doesn't trip".

The same applies to a geyser: 2 to 3 kW of heating element, its own heavy line, its own MCB, and a switch outside the bathroom's wet zone.

The sanctioned-load question

Your APSPDCL bill shows a contracted load. Homes that were connected as one-fan-one-light houses decades ago and now run two ACs, a geyser and a motor are often past it. The practical sign is a main MCB or meter-side cut-out that trips when everything runs in the evening. If you are adding a second or third AC, ask the technician to add up the connected load; if it is near the limit, a load enhancement application is the proper route, and it is better to know before the new point is wired than after.

Concealed or surface

Concealed is neater: a groove is chased in the wall, PVC conduit laid, wire pulled, and the wall plastered back. It is dusty, takes longer, and the patch needs painting. Surface casing-capping or PVC trunking runs along the wall; it is quicker, cheaper, makes no dust, and is the right choice in a rented home or on a finished marble or tiled wall. Neither is more or less safe if done properly — the wire and the MCB are what matter.

For an outdoor AC unit, the point for the outdoor unit and the cable between indoor and outdoor should be in conduit, and the isolator near the outdoor unit should be weatherproof — see the monsoon guide for why.

What to decide before the visit

• Where the appliance will sit, and roughly how far it is from the distribution board.
• Whether there are spare ways in the board. If not, the board may need extending — worth knowing up front.
• Concealed or surface.
• Whether the point should be on the inverter circuit (a fan or a light, yes; an AC or geyser, never).
• For an AC: whether a stabiliser will sit between the point and the AC, so the point is placed to suit it.

What not to do

Do not feed an AC or geyser from an existing socket, a multi-plug or an extension board. Do not fit a 16 A appliance to a 6 A socket with a converter plug. Do not add a socket by joining into a cable inside the wall with tape. And do not let anyone fit a bigger MCB to an existing thin circuit so the new load "works".

What it costs

On our rate card a new dedicated line — conduit and concealed, room or home — is New Wiring at ₹699, with wire, conduit, MCB and socket charged at MRP and shown before fitting. Replacing or upgrading a socket, switch or MCB on an existing board is MCB / Switchboard work at ₹350. If you are fitting a fan on the new point, Fan Install / Repair is ₹350. The technician confirms the material list before cutting anything; ask whether plastering the chased groove is included.

When to call

Any new AC, geyser, induction hob or motor. Any appliance that trips the MCB when it starts. Any home where the new point would be the third or fourth heavy load on a board that has not been looked at in years.