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How to isolate electrics safely in a UK home

Updated: October 2026

You are about to change a switch, a fused spur or a length of cable, and the breaker is already off. That click is not the end of the job. Learning how to isolate electrics safely in the UK means finding the right device, keeping it off, and proving the conductors are dead before you touch them. If you cannot do those three things, you stop. This page is the sequence and the point where a householder hands the work to someone competent. It does not rank products. The device still has to match the job, which is what the [mains isolation switch comparison](/hub/electrical-equipment/mains-isolation-switch) and the [buying guide](/hub/electrical-equipment/mains-isolation-switch/sub/mains-isolation-switch-buying-guide) are for.

You are about to change a switch, a fused spur or a length of cable, and the breaker is already off. That click is not the end of the job.

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On this page
  1. 1.Switching off and isolating are different
  2. 2.The sequence before you touch a conductor
  3. 3.Other supplies, and the fuse you do not pull
  4. 4.Where a householder stops

Switching off and isolating are different

Regulation 12 of the Electricity at Work Regulations 1989 asks for a way to cut off the supply, and separately for isolation so that the separation stays secure. Cutting off stops the current. Isolation means the break cannot be closed again while you are working, except by you. Electrical Safety First also names a local fused connection unit as one possible means of isolation when it is under the control of the person doing the work. The spur has to be the one that feeds the cable, you have to be able to keep it off, and you still test. A rocker that anyone in the house can push back on is switching off, not isolation.

The sequence before you touch a conductor

Identify the point of isolation and confirm it is the only feed to the part you are about to touch. Secure it. On a padlockable handle that means a lock and a key that stays with you. A fuse carrier is not a lock on the neutral. Prove the voltage indicator on a known live source, or on a proving unit, before you trust it. Test the conductors you are about to work on. Prove the indicator again afterwards, so a dead reading is not a dead tester. A neon screwdriver is not that instrument. The WFIS100's lid, which comes off only when the lever is off, is not a substitute for the test.
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Other supplies, and the fuse you do not pull

Best Practice Guide 2 tells you to include every source, not only the consumer unit. A solar array, a generator or battery storage can keep conductors live after the main switch is open. If you cannot see how that second source is isolated, you cannot prove dead. UK Power Networks states that the cut-out and its fuse belong to the network, and that only the supplier removes that fuse. What that enclosure is for is on the meter isolator switch page. If the only way you can see to make the installation dead is that fuse, you stop and you ask the network or a competent electrician.

Where a householder stops

In England a new circuit, a consumer unit, or work in a bath, shower, pool or sauna room is on the notifiable list in Approved Document P. Like-for-like replacement of an existing accessory is not. You also stop when you cannot identify a single means of isolation, when the voltage indicator does not prove, or when a second source is present and you do not know its isolator. A 13 A spur does not isolate a house, and a switch whose listing says it has no arc extinguishing is not something you open on load and then call safe.

Common questions

Is switching the breaker off enough?
No. Switching off cuts the supply at that breaker. Isolation means the break stays secure while you work, and the conductors are then proved dead. Someone else can reset a breaker. A label is not a lock. Electrical Safety First and the Health and Safety Executive both separate those steps. You still prove the tester before and after the test on the conductors.
What does lock-off mean if the plate has no padlock?
You keep control of the point of isolation yourself. On a workplace isolator that is a unique-key padlock, and a hasp if more than one person is working. On a domestic spur with no hasp, people remove the fuse and keep it with them. That does not lock the neutral. If you cannot stop the switch being turned on, you do not have isolation, and you stop.
How do I prove the spur is dead?
Use a voltage indicator you have just proved on a known live source or a proving unit. Test the conductors at the point you will touch. Prove the indicator again. A neon screwdriver is not that test. The spur has to be the one that actually feeds the cable, and it has to stay under your control for the whole job. A dead reading from an unproved tester is not evidence.
What if there are solar panels?
Isolate the solar supply as well as the mains, and do the same for a generator or battery storage. Best Practice Guide 2 treats those as sources that can keep a circuit live after the main switch is open. If you cannot find that isolator, or you cannot prove the conductors dead with it open, you do not start. Panels on the roof do not switch themselves off because a downstairs breaker is down.
Can I pull the main fuse instead?
No. The cut-out fuse is the distributor's, and UK Power Networks says only the supplier removes it. It is not a spare isolator for DIY. Use the customer's isolator or the correct local switch, then prove dead. If neither exists, the work is not yours to force by pulling that fuse.
When do I stop and call someone?
Stop for a new circuit, a consumer unit, meter tails, three-phase, a bathroom or shower zone, or any job where you cannot prove dead. Stop if you are unsure which device feeds the cable. Like-for-like replacement is a narrower case, and it still needs a secure isolation and a proper test. Doubt about the feed is enough reason to call a competent person.
Does a fused spur count as a means of isolation?
Electrical Safety First names a local fused connection unit as one possible means of isolation when the person doing the work has control of it. You still secure it and prove dead. It isolates that spur, not the installation. A double-pole plate with no fuse carrier is not the same device. A spur does not replace the main switch for work on the whole supply.

Related pages

Best mains isolator switch

Mains isolation switch

Mains isolation switch: which kind you actually need

Meter isolator switch: what sits beside your meter

Rotary isolator vs fused spur for one UK appliance

Sources

Public UK sources are listed below. Shelf prices and star lines are the amazon.co.uk figures in the product files. Checked October 2026.

  1. HSE HSR25, Electricity at Work Regulations 1989, regulation 12 (retrieved October 2026)
  2. HSE, work near electricity (retrieved October 2026)
  3. Electrical Safety First, Best Practice Guide 2 issue 4.3 (retrieved October 2026)
  4. IET Wiring Matters, July 2026, Table 537.4 (retrieved October 2026)
  5. IET extractor-fan FAQ (retrieved October 2026)
  6. Approved Document P 2013 (retrieved October 2026)
  7. SI 2012/3119, regulation 12(6A) (retrieved October 2026)
  8. UK Power Networks, a typical domestic supply (retrieved October 2026)