As per subject, do I need a metal enclosure for an isolation switch between the meter and consumer unit?
Given CUs ought to be metal cased, I would have though the principle would apply to a switch powering the board. Yet the normal suspects only stock ABS enclosures.
Some suspects are also selling CUs where the lid can stay down, which again I would have thought would be against the principle of a semi-sealed CU?
There is some debate as to whether this side of the consumer unit is governed by BS7671, or whether the supplier can do whatever they want on their side (subject to the own risk assessments). I don't see anything conclusive, but note plastic isolators are commonly installed (although possibly many predate 17th edition Amendment 3?).
Another argument is whether an isolator with through terminals is classed differently from a CU with many connections. Shower isolators carry a lot of current but aren't metal, for example.
The risk is loose connections in the wiring causing overheating. The front of the breakers would seem to provide some protection between that fire escaping from the CU (although I couldn't say if for 30 minutes or whatever the fire protection time is).
Theo
Given my meter is a plastic affair it does make a mockery of the standard.
I thought the requirement of a metal CU was to contain fire, and to stop sagging wires from collapsing.
MCBs, RCDs and main switches are in their own plastic housing. I don't see the difference between a lid that stays down, or having no lid, or even having a transparent acrylic lid.
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