Partial Power Loss · Kettering & Northamptonshire · NAPIT-Registered

Power Loss in Part of Your House?

Q: Why has part of my house lost power but not all of it?

In UK homes, electricity is distributed across multiple individual circuits — separate breakers for lighting, sockets, cooker, shower and so on. A partial power loss means one or more of those circuits has lost supply, while others continue to operate normally. The most common causes are a tripped MCB or RCBO at the consumer unit, a fault on the circuit wiring, a neutral connection failure, or, less commonly, a problem with the incoming supply before it reaches the board.

Q: All my sockets have stopped working but the lights are still on — why?

In a standard UK domestic installation, sockets and lighting are on separate circuits. If your sockets are dead but lights are on, the socket circuit's MCB or RCBO has tripped — or there is a fault on that specific circuit. Check the consumer unit. If an MCB or RCBO is in the tripped position, all appliances should be unplugged before you attempt to reset it. If it trips again immediately with nothing plugged in, there is a wiring fault on that circuit that needs investigation before re-energising.

Q: My upstairs has no power but downstairs is fine — what could cause that?

If power has dropped on an entire floor, it usually means either a dedicated upstairs circuit has tripped, or several circuits on the same RCD in an older split-load board have lost supply together. In an older installation with a single or split RCD, a fault anywhere on the RCD-protected section can remove power from several circuits at once. In a modern board with individual RCBOs, each circuit fails independently — so losing multiple circuits simultaneously on a modern board points to a more upstream problem: the main switch, the incoming tails, or the DNO supply.

Q: Is it safe to keep resetting the breaker?

Resetting an MCB or RCBO once — with all appliances unplugged — is reasonable to confirm whether the issue was a transient overload or a faulty appliance. If the breaker trips again immediately with nothing plugged in, or if it holds briefly and then trips again under light load, there is a fault on the circuit wiring. Continuing to reset it does not clear the fault — it just re-energises the fault repeatedly, which can accelerate damage and create a fire risk.

Half the house dark, one floor without sockets, lights on but nothing else working — partial power loss can mean several different things. Finding which one matters. We diagnose it properly, with test equipment, not guesswork.

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Understanding the Fault

What Partial Power Loss Usually Means in a UK Home

In a UK domestic property, the electrical installation is divided into individual circuits — sockets on one circuit, lighting on another, then separate dedicated circuits for the cooker, shower, EV charger and so on. Each circuit has its own protective device (MCB or RCBO) in the consumer unit. When one of those devices operates — either because the circuit has been overloaded, because a fault has caused earth leakage, or because there is a short circuit in the wiring — that circuit loses supply while everything else continues normally.

This is entirely by design. Circuit-by-circuit protection is a fundamental safety feature of modern installations. The problem is that the protective device operating is a symptom, not the diagnosis. The breaker tripping tells you something happened on that circuit — but not what, or why, or whether it's safe to restore power.

How UK Consumer Boards Work — and Why It Matters for Diagnosis

Modern Board (RCBOs)

Individual RCBO per circuit

Each circuit has its own combined MCB + RCD device. If one circuit develops a fault, only that circuit trips — no other circuits are affected. On a modern board, losing multiple circuits simultaneously usually points to the main switch, the incoming tails, or the DNO supply before the board.

Older Split-Load Board

Shared RCD for a bank of circuits

Older consumer units often use a single RCD protecting a group of circuits (the "protected" side). If any circuit on that protected side develops an earth fault, the shared RCD trips — removing power from every circuit in that group. This is why, on an older board, several circuits going down together often points to a single earth fault on one of them.

What Your Symptoms Suggest

What You're Seeing	Likely Starting Point
One circuit dead, others fine	Single MCB/RCBO trip — check the consumer unit
All sockets dead, lights on	Socket circuit(s) RCBO/MCB tripped
All lights on one floor dead, sockets fine	Lighting circuit RCBO/MCB tripped
Several circuits dead together (older board)	Earth fault on one of those circuits tripped the shared RCD
Breaker won't hold when reset	Persistent wiring fault — needs IR testing before re-energising
Breaker holds briefly, then trips again	Intermittent fault — appliance issue or thermal condition on wiring
No obvious trip, power just stopped	Neutral connection failure or loss of supply — needs urgent investigation
Flickering then power loss on whole house	Check if neighbours are affected — may be DNO supply issue

Call Us Without Delay If:

You can smell burning anywhere in the property
The breaker trips immediately every time you reset it
Several circuits have failed with no obvious cause
The power loss was preceded by a loud bang or flash
Power is flickering erratically across the whole property

What We Look For

Common Causes We Check For

Tripped MCB or RCBOThe most common cause of a single circuit going down. An MCB trips on overcurrent — the circuit was carrying more than the breaker's rated current, usually because too many appliances ran simultaneously, or an appliance developed a fault. An RCBO trips on earth fault current — current is leaking to earth somewhere on the circuit. The diagnostic approach for each is different.

Shared RCD trip (older boards)On older split-load boards, all circuits on the RCD-protected section share a single RCD. Any earth fault on any of those circuits will trip the RCD and remove power from the entire group. Identifying which circuit caused the trip requires systematic isolation — de-energising the affected section, then re-energising circuits one at a time with insulation resistance tests to locate the faulty circuit before restoring supply.

Neutral connection failureA broken or very high-resistance neutral connection — at the consumer unit, in a junction box, or within an accessory — is a less common but more serious cause of partial power loss. Because neutral carries the return current for all circuits, a neutral failure can cause unusual symptoms: lights that flicker and dim as current finds alternative return paths, or some circuits dead while others remain live. This condition can also create overvoltages on some circuits, which can damage sensitive equipment.

Damaged cableA cable that has been physically damaged — pierced by a nail or screw during building or decorating work, caught under a heavy item, or compressed by joists — can cause a short circuit between conductors. This creates a sudden high-current fault that trips the MCB immediately. In some cases the cable damage is in a location that makes finding it difficult without systematic testing from the consumer unit outward.

Water ingressWater tracking into a socket, light fitting, outdoor supply, or an area of conduit can create insulation leakage that trips an RCBO. Bathrooms, kitchens (below bathrooms upstairs), garages and outdoor circuits are the most common locations. The fault may be intermittent — only presenting when the fitting is wet — which can make it appear to clear and return without pattern.

Faulty appliance causing tripAn appliance with a developing fault — a failing motor winding in a washing machine, a damaged heating element in an oven, degraded insulation in a garden power tool — can cause an earth fault that trips the RCBO. The appliance itself may still appear to work intermittently. Systematic isolation — removing appliances one by one and retesting — usually identifies the culprit, but the wiring also needs testing to confirm the circuit itself is sound.

Our Process

How Entigen Diagnoses Partial Power Loss

Map the Affected Circuits

We establish exactly which circuits have lost supply and which haven't. We inspect the consumer unit, note the breaker positions, and confirm whether the board is a modern RCBO board or an older split-load arrangement. This changes the diagnostic path significantly.

Appliance Elimination

With the circuit de-energised, all appliances are unplugged from the affected circuit. We then attempt to re-energise with nothing connected. If the breaker holds, we re-connect appliances one at a time under controlled conditions to identify the causative device. If the breaker trips with nothing connected, the fault is in the fixed wiring.

Insulation Resistance Testing

With all accessories removed from the circuit and connections open at the consumer unit, we measure insulation resistance at 500V DC across L-N, L-E and N-E. Any reading below the 1MΩ minimum threshold confirms wiring insulation has been compromised. Very low readings — tens of kΩ or below — indicate a serious fault requiring location and repair before the circuit can be re-energised.

Fault Location

Using the insulation resistance readings and physical access points on the circuit, we locate the fault — whether it's a damaged cable, a failed accessory, or water ingress into a fitting. We section the circuit if necessary by disconnecting at intermediate points and retesting to narrow the location of the fault.

Repair and Verification

Once located and repaired, we retest the full circuit before re-energising. We also check the consumer unit connections — particularly the neutral bar and the incoming tails — to confirm the fault hasn't caused secondary damage at the board. A minor works certificate is issued.

Important Safety Note

Why You Shouldn't Keep Resetting the Breaker

A circuit breaker tripping is the installation telling you something is wrong on that circuit. Resetting it once — with all appliances unplugged — is a reasonable first step to establish whether the issue was a transient overload or a piece of faulty equipment.

But if the breaker trips again immediately with nothing connected, or trips repeatedly under normal use, continuing to reset it does not resolve the fault. It re-energises the fault each time. On a circuit with damaged cable insulation, or a connection that is arcing, this accelerates the damage — and can create a fire risk at the fault point before the protection trips again.

The same is true of the older practice of "uprating" a fuse or using a re-wireable fuse with heavier wire to stop it blowing. Increasing the protection threshold doesn't remove the fault — it just makes the protection less likely to operate before the fault causes damage or fire.

The right approach

One reset with appliances unplugged → if it holds, reconnect appliances one at a time → if it trips again with nothing connected, leave it isolated and call us. Don't keep resetting.

Related Services

We cover Kettering and the surrounding Northamptonshire area — Barton Seagrave, Burton Latimer, Corby, Wellingborough, Northampton, Earls Barton, Rushden, Desborough, Rothwell and surrounding areas.

Common Questions

Partial Power Loss FAQs

Why has part of my house lost power but not all of it?+

In UK homes, electricity is distributed across multiple individual circuits — separate breakers for lighting, sockets, cooker, shower and so on. A partial power loss means one or more of those circuits has lost supply while others continue normally. The most common causes are a tripped MCB or RCBO at the consumer unit, a fault on the circuit wiring, a faulty appliance, or a neutral connection failure. The diagnostic approach depends on how many circuits are affected and what type of consumer unit you have.

All my sockets have stopped working but the lights are still on — why?+

In a standard UK domestic installation, sockets and lighting are on separate circuits. If sockets are dead but lights are on, the socket circuit's MCB or RCBO has tripped. Check the consumer unit. If an MCB or RCBO is in the tripped position, unplug all appliances from that area first, then try resetting it. If it holds with nothing connected, an appliance was likely the cause — reconnect them one at a time to find which one triggers the trip. If it trips immediately with nothing connected, there is a wiring fault that needs testing before the circuit is re-energised.

My upstairs has no power but downstairs is fine — what could cause that?+

If power has dropped on an entire floor, it usually means either a dedicated upstairs circuit has tripped, or several circuits on the same shared RCD in an older split-load board have lost supply together. On a modern RCBO board, losing multiple circuits simultaneously — with no obvious individual trip — points to a problem upstream of the individual breakers: the main switch, the incoming tails, or the DNO supply. Check whether the problem is also affecting neighbours, which would suggest a DNO supply fault rather than an internal wiring issue.

Is it safe to keep resetting the breaker?+

Resetting an MCB or RCBO once with all appliances unplugged is reasonable, to confirm whether the issue was a transient overload or a faulty appliance. If it trips again immediately with nothing plugged in, or holds briefly and trips again under light load, there is a fault on the circuit wiring. Continuing to reset it re-energises the fault repeatedly — which can accelerate damage and, in the case of a wiring fault with compromised insulation, create a fire risk. The circuit should remain isolated until an electrician has tested and cleared it.

Fault Support

If your issue sounds similar, these pages may help you understand the fault before getting in touch.

Mains Power Loss RCD Keeps Tripping Fuse Keeps Blowing Electrical Faults & Fixes Emergency Electrician

Lost Power in Part of Your Kettering Home?

We'll find what actually caused it — using insulation resistance testing, circuit isolation and systematic diagnosis — and fix it properly before reconnecting anything.

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