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Mains isolation switch: which kind you actually need

Updated: October 2026

You are in a UK kitchen or a meter cupboard, about to buy a mains isolation switch for a boiler, a bathroom fan or the supply itself. Amazon.co.uk has mixed a £4 plate, a small outdoor box and a 100 A enclosure under one phrase. Those are different devices. A mains isolation switch disconnects 230 V, or only the circuit you mean to work on, and it has to stay off while that work happens. Start with current, then poles, then the standard printed on the listing, then whether you can keep it off where it will live. The ten listings, with prices and review counts, are on the [mains isolation switch comparison](/hub/electrical-equipment/mains-isolation-switch).

You are in a UK kitchen or a meter cupboard, about to buy a mains isolation switch for a boiler, a bathroom fan or the supply itself.

Our top picks

BG BG Nexus 852

Best overall

BG BG Nexus 852
9.2/10about £4.76
View offer
Knightsbridge Knightsbridge CU6300N

Best value

Knightsbridge Knightsbridge CU6300N
9.2/10about £3.74
View offer
WCED WCED WFIS100

Rank 3

WCED WCED WFIS100
8.6/10about £21.00
View offer
On this page
  1. 1.Four different switches share this name
  2. 2.Current, poles, then the standard
  3. 3.Lock-off, IP and what else is in the box
  4. 4.Where you stop and which page is next

Four different switches share this name

In this set the cheap white plates are 13 A. The BG Nexus 852 and 951 are switched fused connection units with an LED, and the listings cite BS 1363 Part 4. The Knightsbridge CU6300N is titled as a 13 A double-pole switch at £3.74, and its table does not list a fuse carrier, so it is not the same object as a fused spur even though some reviews mention a fuse. Beside those sits the BG NBS15-01, a 10 A three-pole fan isolator, which is not a boiler plate. The Tiardey and RiseNova boxes are titled 16 A with an IP65 claim. The three WCED enclosures, from £21 to £30, are the meter-side boxes. A 16 A title does not become a house switch by sitting in the same grid.

Current, poles, then the standard

A whole-house switch in this set is 80 A or 100 A. A fixed appliance on a final circuit is 13 A, or 10 A if you are buying the fan plate. A 16 A rotary is not a substitute for the enclosure beside the meter. Double pole opens live and neutral on a single-phase appliance, which is what a boiler spur usually needs. A timer fan with a permanent live needs three poles if you want local isolation of permanent live, switched live and neutral. The IET fan guidance puts that isolator outside bathroom zones 0, 1 and 2. Four poles are for three-phase. A disconnector to BS EN 60947-3 is for isolation off load. A switch-disconnector to the same standard can isolate on load.
BG BG Nexus 852

Testsieger

BG BG Nexus 852
9.2/10about £4.76
View offer

Lock-off, IP and what else is in the box

Regulation 12 of the Electricity at Work Regulations 1989 requires a way to cut off the supply and to isolate it so the break stays secure. The Health and Safety Executive's practical line is to lock off, keep the key and prove dead. A sealable lid or a padlockable handle matters at a meter or outdoors. A domestic rocker does not lock itself. The WFIS100 is the example in this set: the lid comes off only when the lever is off, and the listing includes an 80 A fuse and a 100 A fuse. IP65 is the outdoor claim on the two 16 A rotaries. IP20 on the Knightsbridge plate and the fan isolator, and IP00 on the LIDER, are indoor figures. RiseNova carries the IP65 claim and has no reviews in the file. The WEC440SP at £30 adds a Type 2 surge protective device to a 100 A isolator.

Where you stop and which page is next

In England, Approved Document P 2013 and regulation 12(6A) treat a new circuit, a consumer-unit change, or work in a special location as notifiable. A special location here means a bath or shower zone, or a room with a pool or sauna. Like-for-like replacement is not on that list. Connecting equipment to an existing isolator is the document's own non-notifiable example. You stop, and you call a competent person, for meter tails, three-phase, a bathroom zone, or any case where you cannot prove the conductors dead. You do not pull the distributor's cut-out fuse. UK Power Networks states that fuse is theirs. The meter isolator switch page stays with the 100 A enclosures. How to isolate electrics safely is the sequence once the device is the right one.

Common questions

What current do I need?
You match the switch to the job, not to the lowest price in the search. A whole-house device in this set is 80 A or 100 A. A fixed appliance on a final circuit is 13 A, and the fan plate is 10 A. A 16 A rotary title is a local box. It does not become a meter switch because a bullet also says 100 A. If the manual states a fuse, that fuse sits in the connection unit.
Is a fused spur an isolator?
A switched fused connection unit to BS 1363-4 can be the local means of isolation for a 13 A appliance when it is under your control and you then prove the conductors dead. It opens a spur. It does not isolate the whole installation. The Knightsbridge plate is titled as a double-pole switch, and the table does not list a fuse carrier, so do not treat every white plate as a fused spur.
Double pole or four pole?
Double pole opens live and neutral on a single-phase appliance. Three poles are for a fan that also has a permanent live. Four poles are for three-phase, which is why the WEC4400 is not the default for a normal house even though it is rated 100 A. Read the voltage lines as well. That listing prints 400 V in a bullet and 230 V in the table.
Which standard should the listing name?
For a 13 A fused unit, look for BS 1363-4 or BS 1363 Part 4. For a household isolating switch, the IET points at BS EN 60669-2-4. For a disconnector or switch-disconnector, look for BS EN 60947-3 and read whether it is off-load only. A page that cites CE, UKCA and RoHS, as the LIDER listing does, has not named the fused-unit standard.
Is swapping a plate notifiable in England?
Like-for-like replacement of an existing accessory is not on the notifiable list in Approved Document P. A new circuit, a new consumer unit, or work in a bath, shower, pool or sauna room is. Connecting kit to an isolator that is already there is the document's non-notifiable example. That English rule is not the rule in Scotland or Northern Ireland.

Related pages

Best mains isolator switch

Rotary isolator vs fused spur

Mains isolation switch

How to isolate electrics safely before any UK work

Meter isolator switch: what sits beside your meter

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)