Metal Consumer Units Query .

[SBS Dave]

BYB 522.8.5, states "Every cable or conductor shall be supported in such a way, that it is not exposed to undue mechanical strain and so that there is no appreciable mechanical strain on the terminations of the conductors, account being taken of mechanical strain imposed by the supported weight of the cable or the conductor itself."



Try pulling these out, when correctly tightened!!

SBS Dave

 

[Essex1]

so

why are we now required to comment on the DNO side of things when completing an EICR now then?

I think it would be good practice to make a comment of you saw a damaged meter or head anyway, whether or not it was a requirement.

 

[Nicky Tesla]

https://www.youtube.com/embed/hg5eZkq2KgE?feature=oembed
http://www.edwardes.co.uk/en/products/wylex-eiu-cable-gland-kit-for-metal-consumer-units

 

[Andy™]

nice find

 

[Murdoch]

Because BS7671 requires that we comment.

Whether the DNO considers it an issue is down to them.

Hum.... I've noticed this - and we can issue a C1 for dodgy DNO equipment/cables - yet have no way to ensure its improved - makes our job of issuing a "satisfactory" EICR rather problematic IMHO

 

[SLIPSHOD & SLAPDASH]

https://www.youtube.com/embed/hg5eZkq2KgE?feature=oembed

Interesting   link. However i am trying to work out if you can test like that as its the same cable looped rather than L & N so is that actually inducing anything ?

Also what is he using for the supply, an Arc welder ?

 

[Andy™]

it would be no different to having L&N through different holes - imagine the loop is an appliance etc

looks like he is using an arc welder - hopefully its AC and not DC...

 

[ProDave]

So 120A and only a 2 degree temperature rise.

Pretty well dubunks separate holes as a significant problem then?

That was AC by the way, that meter only reads AC amps.

 

[Andy™]

So 120A and only a 2 degree temperature rise.

Pretty well dubunks separate holes as a significant problem then?

That was AC by the way, that meter only reads AC amps.

just what i was thinking - never really tried it or seen much evidence of anything getting too hot, but him running that at 125a, i did expect it to get a bit warmer

 

[ProDave]

just what i was thinking - never really tried it or seen much evidence of anything getting too hot, but him running that at 125a, i did expect it to get a bit warmer

the temperature rose by 2 degrees.

He commented "the cable feels a bit warm" as you would expect.

I'll bet the cable warmed up by more than the metal box.

 

[Tony S]

[SIZE=medium]One thing that stands out in that clip:[/SIZE]

[SIZE=medium]It’s an open enclosure therefore good heat dissipation. Fill it with run of the mill gubbins, add the cover and then burry it in a wall or under several layers of kids toys, coats etc. See what the temperature rise is after a few hours of sustained load.[/SIZE]

[SIZE=medium]I worked in R&D, “what do you want the figures to show?”[/SIZE]

[SIZE=medium]If you don’t believe eddy currents can do damage. I was duty engineer when one of our transformers decided to hold a firework party. The insulation around three of the seven singles had melted. The contractor had replaced the brass locknuts we had issued with steel.[/SIZE]

[SIZE=medium]One of the biggest problems is many “electricians” don’t know about our friend Eddy.[/SIZE]

 

[roys]

Hi Tony, what am I missing, how does the steel lock nuts make any difference, would the cables not be terminating into a brass on stainless steel gland plate and so eliminating the eddy currents.

I agree the steel locknuts are not a good idea but for different reasons, corrosion, dissimilar metals.

 

[Doc Hudson]

[SIZE=medium]One thing that stands out in that clip:[/SIZE]

[SIZE=medium]It’s an open enclosure therefore good heat dissipation. Fill it with run of the mill gubbins, add the cover and then burry it in a wall or under several layers of kids toys, coats etc. See what the temperature rise is after a few hours of sustained load.[/SIZE]

[SIZE=medium]I worked in R&D, “what do you want the figures to show?”[/SIZE]

[SIZE=medium]If you don’t believe eddy currents can do damage. I was duty engineer when one of our transformers decided to hold a firework party. The insulation around three of the seven singles had melted. The contractor had replaced the brass locknuts we had issued with steel.[/SIZE]

[SIZE=medium]One of the biggest problems is many “electricians” don’t know about our friend Eddy.[/SIZE]

And it is outside with a starting ambient temperature of 10 degrees. As you say I wonder what the results would be in an enclosed space starting off at 18 to 25 degrees, with and enclosure of slightly thinner metal?

Doc H.

 

[kerching]

Going out on a limb here, and bearing in mind I have given this NO THOUGHT WHATSOEVER..........what would be the effect if the metal enclosure was earthed?......as in the demo it is isolated on a piece of wood

I must admit that in over 40 years in the job I have seen numerous individual holes for cables and never witnessed any overheat

I have also seen An EEx box about 18" square, full,of water, ALL pyro ends blown off and the water boiling like a kettle....AND it was at a Petrol Station

Just wondering

 

[Tony S]

[SIZE=medium]It was a standard GEC gland plate like this[/SIZE]

[SIZE=medium]

[/SIZE]

[SIZE=medium]The slot stops eddy currents forming. If a steel locknut is used it creates a massive magnetic flux which will heat the locknut to glowing.[/SIZE]

[SIZE=medium]The transformer that failed was on a new plant, as more sections came on line the load increased to about 1000A per phase. Two conductors per phase so that’s 500A flowing through the 2½” locknut.[/SIZE]

[SIZE=medium]For a reason only known to the contractor he replaced the brass nuts on the front three phase conductors. They got very hot and the heat transferred to the brass gland melting the insulation and one went bang. REF protection picked it up and killed the 11KV.[/SIZE]

 

[roys]

Interesting, I always knew about the theory in putting slots in gland plates but never seen it done, any Gland plates I have dealt with have always been brass, stainless or some other exotic non ferrous material, Do you think steel lock rings would make any difference with a brass gland plate?

About 5 years ago I was doing client acceptance checks for HV transformers and the gland plates were coated so I questioned the material as it looked like steel (hence why I thought it was coated, stainless was usually left 'naked' so to speak) contractor proved it was stainless to me with a magnet.

 

[SBS Dave]

Hi Tony,

Thanks for the diagram, which shows the slots, exactly like mine.

Presumably, the manufactured plate would be finished in such a way, as not to necessarily show the slot filler.

SBS Dave

 

[Tony S]

[SIZE=medium]The advantage of the filler is keeping out creepy crawlies. One of our works found the LV box with an ants nest in it.[/SIZE]

 

[Tony S]

[SIZE=medium]The advantage of the filler is keeping out creepy crawlies. One of our works found the LV box with an ants nest in it.[/SIZE]

[SIZE=medium] [/SIZE]

[SIZE=medium] [/SIZE][SIZE=medium]Interesting, I always knew about the theory in putting slots in gland plates but never seen it done, any Gland plates I have dealt with have always been brass, stainless or some other exotic non ferrous material, Do you think steel lock rings would make any difference with a brass gland plate?

About 5 years ago I was doing client acceptance checks for HV transformers and the gland plates were coated so I questioned the material as it looked like steel (hence why I thought it was coated, stainless was usually left 'naked' so to speak) contractor proved it was stainless to me with a magnet.[/SIZE]

[SIZE=medium] [/SIZE]

[SIZE=medium]It would have the same effect, the brass may dissipate the heat a bit more but not to that extent. It’s still going to go bang eventually.[/SIZE]

[SIZE=medium]We had to use metal to comply with M&Q regs. Some use paxolin but in the event of a fault it’s liable to blow out.[/SIZE]

 

[NozSpark]

Wow.... thanks Roy's you've made me look something up...

I always assumed that stainless steel was magnetic,,, I didn't realise that you could get a non magnetic version