Power Out in Part of the House: Causes and What to Do, Step by Step

Why does power go out in only part of the house?

The electricity in a home is divided into circuits at the consumer unit. Each circuit is protected by a circuit breaker, and if the consumer unit has an RCD, the breakers sit behind it in groups. When only part of the house loses power, something has been cut at some point in that chain. The possible causes, from most to least common:

• A tripped circuit breaker: only the circuit that breaker feeds goes off, such as the kitchen sockets or one room’s lighting.
• A tripped RCD: every circuit behind that RCD goes off together, so the affected area is larger.
• A loose or burnt connection: a connection that fails in the consumer unit, a junction box or behind a socket cuts off every socket and light further along from that point.
• A lost phase: in homes or businesses with a three-phase supply, when one phase is missing, every circuit connected to it goes off.
• A broken neutral: rare, but dangerous. Its signs are covered separately below.

What should you check first when part of the house has no power?

A two-minute check before you go to the consumer unit tells you whether the problem is yours or outside:

• Do the neighbours or the building’s common areas have power? If they have the same problem, the fault is most likely in the distribution network; call the 186 electricity fault line.
• What exactly is not working? Only the sockets in one room, the whole kitchen, or a scattered-looking part of the house?
• Did the power go the moment you switched an appliance on? If so, that appliance is the prime suspect.
• Are lights abnormally bright, flickering or dimming? If so, go straight to the broken neutral section below.

A single room or a single function going off, such as only the kitchen sockets, usually points to one breaker. A scattered-looking part of the house going off together usually points to an RCD, or on a three-phase supply, to a lost phase.

How do you find and reset a tripped breaker or RCD?

Open the front door of the consumer unit; do not remove the inner cover or the panel in front of the breakers. The lever of a tripped breaker or RCD sits down or in a middle position, unlike the others.

• Push the lever fully down first, then lift it up in one movement. A lever stuck in the middle will not go up if you simply push it upwards.
• Unplug the appliances on the affected circuit before resetting the breaker. If the breaker stays on, plug the appliances back in one at a time; the one that trips it again is faulty.
• If the RCD trips again the moment you reset it, switch off all the breakers behind it, reset the RCD, then switch the breakers on one at a time. The breaker that trips the RCD again identifies the faulty circuit.
• If the breaker or RCD trips straight away with every appliance unplugged, the problem is in the cable, a socket or a junction box. Stop trying at that point.

Resetting a breaker over and over means putting the fault through the circuit again every time. A breaker that will not stay on after two attempts points to a fault that has to be found by measurement. For faults like this, our electrical fault finding and repair service usually reaches you the same day within Istanbul.

Why is there no power when everything in the consumer unit is on?

If every breaker and RCD is up but part of the house still has no power, the break is not in the protection but in the connection itself. Two possibilities stand out.

The first is a loose or burnt connection. Sockets and lights are usually fed one from the next in a chain; when one connection in that chain fails, everything further along goes dead while everything before it keeps working. If before the outage you noticed a socket running warm, scorching or crackling, or a light flickering on and off, the fault is most likely there. We cover the causes of hot sockets in detail in why sockets get hot.

The second, on three-phase supplies, is a lost phase. Some detached houses, villas and business premises receive electricity as three phases, and the circuits in the installation are spread across them. When one phase is missing, every circuit on it goes off together wherever it is in the building, which is why the outage looks scattered. A lost phase can be in the incoming supply, the meter or the main fuse. If the neighbours have something similar, call 186; if it is only you, the installation after the meter needs checking.

On three-phase systems, motor-driven equipment such as a three-phase booster pump can be damaged if it keeps running with a phase missing. If you suspect a lost phase, switch that equipment off.

What is a broken neutral, and why is it dangerous?

The neutral is the conductor current returns along to complete the circuit. When the shared neutral breaks on a three-phase system, the difference in load between the phases distributes the voltage unevenly: on some circuits the voltage rises far above 230 V, while on others it drops far below. A single failed connection at the building entrance or in the consumer unit can destroy electronics such as televisions, fridges, boiler control boards and chargers within seconds. In a single-phase home, a broken neutral leaves the affected circuits not working, but still dangerously live.

The signs are:

• Some lights glowing noticeably brighter than usual while others dim.
• Lights in other rooms changing brightness when you switch an appliance on or off.
• Appliances suddenly switching off, making unusual noises or smelling of burning.
• In a single-phase home, a voltage tester screwdriver lighting up on both holes of a socket that seems to have no power.

If you see any of these signs, do not wait: switch off the main switch immediately, unplug expensive appliances and call an electrician. If the problem affects the whole building or the building entrance, also report it to the 186 electricity fault line.

A broken neutral trips neither the circuit breakers nor the RCD, so do not expect them to protect you from it. The device that does protect against this risk is an over- and under-voltage protection relay fitted in the consumer unit: it cuts the supply automatically when the voltage leaves the safe range.

What should you not do before the electrician arrives?

Some things people do during an outage turn a simple fault into a dangerous one:

• Do not try to hold a breaker that keeps tripping on with tape or by wedging its lever.
• Do not replace a tripping breaker with a higher-rated one; that leaves the cable unprotected.
• Do not open the inner cover of the consumer unit or any junction box. The meter is sealed, and work on the meter and everything before it is a matter for the distribution company.
• Do not touch a socket or cable that seems dead without measuring it first; with a broken neutral, a circuit that is not working can still be live.
• Do not run high-power appliances from the dead room off an extension lead plugged into another room; you will overload the circuit that is still working.

What can be done to stop the fault happening again?

Most partial outages follow a warning given earlier: a warm socket, a breaker that trips now and then, a flickering light. Once the cause has been found and fixed, a few permanent measures keep it from happening again:

• Have every breaker in the consumer unit labelled with the circuit it feeds, so that next time you find the faulty circuit in seconds.
• If the whole house sits behind a single RCD, have the circuits split into groups, such as wet rooms and general use, so that one fault does not black out the entire house.
• Especially on three-phase systems, have an over- and under-voltage protection relay fitted in the consumer unit.
• Have the connections in the consumer unit and junction boxes checked for tightness once a year.

We cover consumer unit upgrades and protective devices on the consumer units and fuse boards page, and why breakers trip and how to test an RCD in our electrical installation guide.