Wylex 100A dp isolators in plastic enclosures.

I'd suggest that it is because they do not split one source to feed a multitude of smaller circuits, nor contain any MCB or RCD devices. In that sense they have more in common with a shower isolator, albeit better built than the average shower isolator.

Personally I'd always assumed the 'similar' clause was to stop someone putting a load of fuses and MCBs into a DIY box made of solid rocket fuel, and in effect saying ' that is OK, because it is not an official CU'.

Also, such switches are often installed ahead of a consumer unit that incorporates RCD protection and is connected to a TT supply. Requiring a metallic case would introduce new risks. If the phase conductor contacted the metallic case, then the whole installation would have virtually line voltage on all earthed or bonded parts.

Because one switch on its own isn't "switchgear", whether or not it's "similar" to a CU.  Put two of them together in the same box, and that's another matter.

Because one switch on its own isn't "switchgear", whether or not it's "similar" to a CU.

Agreed. To my mind the "similar switchgear" is meant to cover situations like large domestics with a 3-phase supply where something like a B type distribution board might be used in place of a consumer unit, as such DBs don't quite meet the part 2 definition of a consumer unit.

   - Andy.

If all else fails, read the definitions.


I agree that a single switch is not a "switchgear" assembly.


I have always thought of a consumer unit as supplying solely final circuits, but that is not what the definition says. It does, however, imply single phase: "incorporating manual means of double-pole isolation on the incoming circuit(s)".


I agree with AJJ that a main (three-phase) DB might be construed as a "similar switchgear assembly", but were they ever made with plastic enclosures?

Are  Metal clad two modular enclosures consumer units?


Andy Betteridge

Are  Metal clad two modular enclosures consumer units?

Depends on what you put in it! If you could squeeze a switch disconnector and an MCB in there then yes (single module switch disconnectors are available for smaller ratings - e.g. https://www.cef.co.uk/catalogue/products/4370332-20a-2-pole-1-module-switch-disconnector-isolator) (with suitable type approval of course).


Perhaps also an RCBO if that provides the functions of both an isolator for the incoming circuit and overcurrent protection for the outgoing. Perhaps.


But you just put a single switch or RCCB in there, then no.


  - Andy.

You may think it was similar to a consumer unit if you put a couple of MCBs in it.

Probably better counts as just an isolator if all you fit is a double pole switch. Empty, it is just a metal box.

I would not want to see one before or containing the incoming RCD on a TT installation in a damp cellar or a stables though.

It looks pretty now, after a few years I'd be far less sure after rust has burst the paint, and all gaps are filled by  a thick crust of slightly damp  straw dust  held by cobwebs.

I have seen  enough rusting 'Old Bill' and similar era cast-iron kit in old farms and churches, still live and hard to make safe, in various states of decomposition, to put me firmly in favour of non-corroding enclosures for the very sort of locations where the TT supply is most common.

Much as the DNOs are a law unto themselves, I think they are right in this, and  there are good reasons that service heads, meters, henley blocs and DP isolators are plastic bodied, we would do well to remember it. In a centrally heated semi-detached house with TNC-s earth, we do not need to worry so much.

I think that a double pole switch does meet the definition of switchgear as defined in Part 2. I suppose reading "similar" can be used to avoid  using metal cladding but think about what the regulation is intended to do.



I am thinking of fitting a Wylex REC2 isolator with the integrated surge protection to the tails of the supply in my home in Norfolk. I want to do this as I am intending to have the key meter changed to a credit meter and I am bound to get a smart meter.


That will allow me to be able to change my MK plastic consumer unit and my E& consumer unit. Why an SPD? I have a long overhead LV run to a distant pole transformer supplied from overhead HV lines an no sign of surge protection on the Tx. Very flat fenland country with a dark grey colour on the flash density map!


I have seen new Wylex consumer units with main switches with tunnel terminals and 2 screws. Does anyone know if the REC 2 version with the SPD comes with tunnel terminals?