Advice on regulation 521.5.1

[davesparks]

It just came into my head Dave, bit strong saying you hate kids though, you were one once ? :smiley2:

Hate as in I have a phobia of them. I cannot stand to be in close proximity to small children and babies.

 

[Darkwood]

Hate as in I have a phobia of them. I cannot stand to be in close proximity to small children and babies.

Your life must have been hell at school then

 

[andyb]

Considering that fault currents can be in the thousands of amps it will probably take a fraction of a second for the eddy currents to become a problem. Don't forget current has more effects than just heating the conductor, the magnetic fields will cause mechanical stress at those levels.

Have to take your word for that Dave, it's a science that I know nothing.
I did a job a couple of weeks back where the lives to a three phase board were all taken into the board through their own neatly drilled 20mm hole. At the time each phase was drawing about 20a, there was no heat or sign of any damage. It had been like this for 20 years.

 

[Midwest]

Thought I would invest in the latest copy of Guidance note 1, Selection & Erection. Curious, I looked up 'Ferromagnetic enclosures, cable entering; (521.5.1) All the conductors of a circuit should generally follow the same route. Live cables of the same circuit may cause overheating if they enter a ferromagnetic enclosure through different openings (page 97, 7.4)

 

[shanky887614]

Thought I would invest in the latest copy of Guidance note 1, Selection & Erection. Curious, I looked up 'Ferromagnetic enclosures, cable entering; (521.5.1) All the conductors of a circuit should generally follow the same route. Live cables of the same circuit may cause overheating if they enter a ferromagnetic enclosure through different openings (page 97, 7.4)

exactly what i was getting at, the earth is only live during fault conditions

 

[Risteard]

exactly what i was getting at, the earth is only live during fault conditions

That isn't true. There will be a certain amount of legitimate earth leakage from appliances. Don't forget that there is functional earthing as well as protective earthing.

And as pointed out, under fault conditions there could be a significant current flowing.

 

[Deleted member 26818]

Also there will be some voltage and current on the earth conductor where PME conditions apply.

 

[R G]

So are the wylex tail glands with the 2 holes only not be used then?

Wiska make glands that have 3 holes in and made for this purpose ..

 

[Dave OCD]

Hate as in I have a phobia of them. I cannot stand to be in close proximity to small children and babies.

That's an unusual one, I have the same problem with snakes.:smile5:

 

[Lucien Nunes]

When the SWA is used as the CPC outside the box, and a length of 6491X lugged onto the banjo bolt serves on the inside, the low resistance path connecting them together is via the brass of the banjo and the bolt, rather than through the enamelled steel enclosure which might make relatively poor contact and is of lower conductivity compared to the brass. So in the event of a fault the banjo bolt carries most of the fault current through a separate hole.

What's the solution? Single hole banjo? Moebius bolt that goes through both holes and back to where it came from? Slot the banjo bolt hole across to the gland entry?

 

[R G]

That's an unusual one, I have the same problem with snakes.:smile5:

Funny that I have the same , must stay off this forum ...

 

[netblindpaul]

When the SWA is used as the CPC outside the box, and a length of 6491X lugged onto the banjo bolt serves on the inside, the low resistance path connecting them together is via the brass of the banjo and the bolt, rather than through the enamelled steel enclosure which might make relatively poor contact and is of lower conductivity compared to the brass. So in the event of a fault the banjo bolt carries most of the fault current through a separate hole.

What's the solution? Single hole banjo? Moebius bolt that goes through both holes and back to where it came from? Slot the banjo bolt hole across to the gland entry?

Do like I do and put the banjo inside?
Not an issue really outside or inside, the contact area is greater inside, than out.
Don't drill the enclosure, why would you?

 

[Dave OCD]

That isn't true. There will be a certain amount of legitimate earth leakage from appliances. Don't forget that there is functional earthing as well as protective earthing.

And as pointed out, under fault conditions there could be a significant current flowing.

There is no functional earthing in a domestic installation.

 

[Risteard]

There is no functional earthing in a domestic installation.

There mightn't be much, but I wouldn't say none (on appliances).

 

[Lucien Nunes]

Indeed, functional earthing is where most legitimate leakage current comes from. Not that it has anything much to do with eddy currents - they start being a problem with hundreds of amps, not a few mA.