Plywood backboard for BS EN61439-3 compliant consumer unit

If you are not routing the cables through the back of the CU, and the wall is masonry, you could fix it direct.

not a problem so long as integrity of the DB enclosure is not compromised.


Other contrary views are a sort of " race memory" due to the open back type DBs circa 1960s that required a bakelight back installed on non brick/ non plaster/ non masonary walls.

and the wall is masonry, you could fix it direct.


You could, but what if the wall is stone and you end up with just two fixings and the CU distorted due to the uneven wall? I know you could use resin fixings and packing washers etc but what aspect of using a ply backboard wouldn't comply?


Regards


BOD

The existing consumer unit in question is going to be re-located onto a new stud wall hence the plywood backboard.


Regards


George

For those who would object, what is the perceived concern ?

I presume that folk imagine that if there is a fire going on in the metal box, and we do not expect any fuse or circuit breaker to operate before the box ignites the wooden board ? I consider that to be most unlikely.  At the sort of temperatures that will ignite plywood (glowing red or orange perhaps) there are so many other problems that what the backing is doing the least of your worries.  A non- combustible backing, such as asbestos cement,  might make sense if that was the only risk, but there are other problems with that.

Also, how close to the edge of the non-combustible backing do you bring the rest of the installation - do you then mandate pyrotenax cables or steel conduit for the wiring and the use of solid metal light switches etc.  It makes very little sense to demonise consumer units without the rest of the installation.


Certainly the wiring regs have no objection, I think you would be compliant with '7671 even if the board was made from a sheet of solid rocket fuel, though it is not sensible for other reasons, not least as  screws tend to tear out ( the stuff being a rubbery consistency with oxidiser embedded).

Agree with your comments Mike although I will steer clear of a solid rocket fuel back board :)


Thanks


George

Looks like fire retardant hardwood faced plywood (18mm) is going to be the better (safer) option here and hopefully keep the DNO happy.  Security of the fixings should not be a problem here.


Regards


George

Looks like fire retardant hardwood faced plywood (18mm) is going to be the better (safer) option here and hopefully keep the DNO happy.

DNO supply and fit their own board for their equipment. If its in a cellar, the main worry is that it is rot proof.  Your consumer unit [DB] should not go on a "DNO board" , that is, share the same board as the cutout and meter are on [unless they give permission].


I doubt they would care what your DB was mounted on, so long as it was not on their board.


When I fit a wood contraption for ease of fitting a DB or CU, my main concern would be to ensure the wood is fairly rot proof. Marine ply does the job.

Thanks for your comments Alcomax. From the other comments received so far on this topic I'm reading that it is ok to use plywood to mount a consumer unit providing the integrity of its fitting does not compromise compliance to BS-EN6143-3 or BS 7671.


Regards


George