Glanding 3 phase into metal distribution board.

[-Matt]

Quick question, have a small caravan site to wire up.

Have 3 phase supply and TT earthing, 30ma RCD in each individual pods.

Was planning on using a 100ma type S incomer in the main DB to protect the sub feeds. ( this should stop a dodgy caravan tripping the whole site being 100ma time delay).

However not overly familiar with TT and 3 phase in terms of protecting the tails.

Ive been told by my niceic assessor with single phase and metal consumer unit, it is fine to just use the special stuffing glands.

However i dont think they make them for 3 phase?

So how would you do this?

Or would it be best to just get a seperate insulated board to house the RCD and then main switch in the DB?

Anyone any advice on this?

 

[Ian1981]

The tails should be wired via the load side of the S type rcd within a separate insulated enclosure hence will have fault protection to them when they enter the 3 phase DB.
Take them through a suitable entry protecting against sharp edges like a bush and locknut combo or something similar.

 

[Pete999]

The tails should be wired via the load side of the S type rcd within a separate insulated enclosure hence will have fault protection to them when they enter the 3 phase DB.
Take them through a suitable entry protecting against sharp edges like a bush and locknut combo or something similar.

But not in seperate holes for each phase

 

[Ian1981]

But not in seperate holes for each phase

If an electrician is installing if,Who would do such a thing?

 

[Pete999]

If an electrician is installing if,Who would do such a thing?

Ian I have seen "Electricians" do exactly what I warned against, you often get poorly trained guys doing it, I was helping my Son do an alarm system in a barn, brought all 4 tails into the enclosure in seperate holes, he was there working, well you must know me by now I couldnt keep my gob shut, had to tell him, got told to Fox Trot Oscar. Don't know what the outcome was, the barn is still there though.

 

[-Matt]

Thanks guys, upfront plastic box it is then, was just hoping to simplify slightly by having it all in one box.

And yes all tails will enter through one brass bush.
( i have however come across a fair amount of new domestic boards where the tails come through separate glands! even with single phase I'm pretty sure this is a NONO!)

 

[Ian1981]

Thanks guys, upfront plastic box it is then, was just hoping to simplify slightly by having it all in one box.

And yes all tails will enter through one brass bush.
( i have however come across a fair amount of new domestic boards where the tails come through separate glands! even with single phase I'm pretty sure this is a NONO!)

Yeah it’s a no no and I bet there’s countless DBs where the tails enter the DB without protection against abrasion.

 

[camerabloke]

Ian I have seen "Electricians" do exactly what I warned against, you often get poorly trained guys doing it, I was helping my Son do an alarm system in a barn, brought all 4 tails into the enclosure in seperate holes, he was there working, well you must know me by now I couldnt keep my gob shut, had to tell him, got told to Fox Trot Oscar. Don't know what the outcome was, the barn is still there though.

I told the customer that the sparky had done it wrong and then he paid me to do it properly
By the way you can bring it in separate glands if you slot the metal dB

 

[davesparks]

You can use separate glands with slots between the holes or use a non-ferrous gland plate.

 

[Pete999]

I told the customer that the sparky had done it wrong and then he paid me to do it properly
By the way you can bring it in separate glands if you slot the metal dB

And the dipstick that ordered the Electrician runs his own business, going wrong somewhere Mate, you think????? Seems the less you know the more money you make, the dipstick.

 

[stevethesparks]

Ref posts 8 & 9, as long as the locknut used on the glands is also brass/non-ferrous as many glands come with a steel locknut.

 

[Pete999]

Ref posts 8 & 9, as long as the locknut used on the glands is also brass/non-ferrous as many glands come with a steel locknut.

Must disagree there Steve, wht's to stop the steel of the gland by passing the brass gland, scientifically correct but practical? no chance.

 

[Pete999]

Must disagree there Steve, wht's to stop the steel of the gland by passing the brass gland, scientifically correct but practical? no chance.

Proof

 

[stevethesparks]

If you are slotting a steel enclosure to enable phases to enter through separate routes, whether by bush gland or whatever, if you use a steel locknut then you have negated the point of slotting the steel plate in the first place, as you will be magnetically bridging the slot from either side. Where slots are made for this purpose then brass fittings - either side, would be favourite.

 

[Pete999]

If you are slotting a steel enclosure to enable phases to enter through separate routes, whether by bush gland or whatever, if you use a steel locknut then you have negated the point of slotting the steel plate in the first place, as you will be magnetically bridging the slot from either side. Where slots are made for this purpose then brass fittings - either side, would be favourite.

Steve, I respect your thoughts, but disagree, experience tells me, although theoretically it works, practically and experience tells me it's a No, sorry Mate.

 

[Pete999]

If you are slotting a steel enclosure to enable phases to enter through separate routes, whether by bush gland or whatever, if you use a steel locknut then you have negated the point of slotting the steel plate in the first place, as you will be magnetically bridging the slot from either side. Where slots are made for this purpose then brass fittings - either side, would be favourite.

Use a plastic stuffing gland then

 

[davesparks]

Steve, I respect your thoughts, but disagree, experience tells me, although theoretically it works, practically and experience tells me it's a No, sorry Mate.

He’s right, steel locknuts will magnetically join the two sides of a slot in a steel gland plate.
Tony who used to frequent this forum has a good story of contractors using steel locknuts for glands transformer tails and it causing eddy current problems.

 

[Pete999]

If you are slotting a steel enclosure to enable phases to enter through separate routes, whether by bush gland or whatever, if you use a steel locknut then you have negated the point of slotting the steel plate in the first place, as you will be magnetically bridging the slot from either side. Where slots are made for this purpose then brass fittings - either side, would be favourite.

Use a plastic stuffing gland then

Steve, I respect your thoughts, but disagree, experience tells me, although theoretically it works, practically and experience tells me it's a No, sorry Mate.

3 dislikes from 3 respected guys, made me rethink, I reread and reread the post and came to the conclusion that I was wrong, so I humbly retract my thoughts.

 

[Pete999]

If you are slotting a steel enclosure to enable phases to enter through separate routes, whether by bush gland or whatever, if you use a steel locknut then you have negated the point of slotting the steel plate in the first place, as you will be magnetically bridging the slot from either side. Where slots are made for this purpose then brass fittings - either side, would be favourite.

Use a plastic stuffing gland then

Steve, I respect your thoughts, but disagree, experience tells me, although theoretically it works, practically and experience tells me it's a No, sorry Mate.

3 dislikes from 3 respected guys, made me rethink, I reread and reread the post and came to the conclusion that I was wrong, so I humbly retract my thoughts. Still reckon a plastic stuffing gland would be the answer.

 

[RWJ]

Tony who used to frequent this forum has a good story of contractors using steel locknuts for glands transformer tails and it causing eddy current problems.

I miss Tony and his vast knowledge, I used to look after his GIF animations. Shame he decided to go the other route when Ben's forum closed.

Anyway back on topic!!!!