The answer has to be that its not great, but it is clearly common and experience suggests it's  not usually a matter of life and death in an inaccessible location.

Why is a floor ceiling void not making something inaccessible ? I'd argue in many cases  it is.

It is a lot better than just twisting - and the old ceramic screwits were common floating about in ceilings and floor voids in 1950s and earlier work.

I think its never been strictly 'correct' but rather like leaving the CPC off, which used to be common, especially on lights, the tolerance for doing so has become less over time, and the relative cost of materials to labour makes it harder to justify.

Mike.

mapj1 said:

but it is clearly common and experience suggests it's  not usually a matter of life and death in an inaccessible location.

For protection against electric shock, I'd agree it's more than likely no great shakes.

For protection against fire, I'm not so sure. There are two considerations:

1. 'pollution degree' ... the terminal block is designed for the level of dust and detritus in a suitable enclosure, not whatever is floating around in the ceiling void. This of course varies, but older properties were not as well sealed etc. etc.
Contamination has two general effects. First, it might accelerate corrosion (and many screw terminal blocks these days, for example, use steel screws). This could lead to overheating in the terminal block itself. Second, pollution is important to considering the effectiveness of insulation, and if the detritus does become damp for any reason (e.g. humidity in winter) this could cause the insulation to fail, and ignite fluff etc.

2. Electrical enclosure or appliance casings usually have some degree of tests to demonstrate they help reduce the risk of fire (e.g. glow wire tests). So, if there is a 'bad connection' there is more chance of being contained in the enclosure, than causing a smouldering fire in the void.

mapj1 said:

but it is clearly common and experience suggests it's  not usually a matter of life and death in an inaccessible location.

For protection against electric shock, I'd agree it's more than likely no great shakes.

For protection against fire, I'm not so sure. There are two considerations:

1. 'pollution degree' ... the terminal block is designed for the level of dust and detritus in a suitable enclosure, not whatever is floating around in the ceiling void. This of course varies, but older properties were not as well sealed etc. etc.
Contamination has two general effects. First, it might accelerate corrosion (and many screw terminal blocks these days, for example, use steel screws). This could lead to overheating in the terminal block itself. Second, pollution is important to considering the effectiveness of insulation, and if the detritus does become damp for any reason (e.g. humidity in winter) this could cause the insulation to fail, and ignite fluff etc.

2. Electrical enclosure or appliance casings usually have some degree of tests to demonstrate they help reduce the risk of fire (e.g. glow wire tests). So, if there is a 'bad connection' there is more chance of being contained in the enclosure, than causing a smouldering fire in the void.