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Does anyone have any thoughts on the best way to terminate an SWA into the new style flush CUs such as Hager's, BG's etc.? I ask as all seem to either employ oval or square knockouts, which is great for the surface boards when using truncking etc. but no great if you are trying to comply with Reg 522.6.204 and 522.6.204 where your tails would effectively be inside a wall / burried less than 50mm from the surface.

So far the best but not really ideal solution I have come with for top or bottom entry (to overcome what seems like a design flaw to myself) is that you would need to terminate the armoured cable into something like a galvanised adaptable box that you mount hard up aginst the bottom of the CU oval / sqaure entry to get the SWAs cores safely into the CU (using gromet / gromet strip on all edges etc.). I know the Hager board has a round KO on the left and right hand side but this would causes an issue in most cases in terms of space to allow for the cable bend. You then have issues with your cables falling outside of prescribed zones as you are likely to want to route them verticle up or down in the wall once out of the CU.

So intrested to know what others think would be a good solution or thoughts from anyone who has had to fit any of these newer flush units.
 
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  • #3
I use a holesaw.
I also thought of that but due to the position of the KOs and the frame that then sits indside the CU to allow for different wall depths there doesn't seem like there is enough material left to not weaken the CUs integrity too much. I have uploaded the Hager flush PDF for refereance as just one example.

Also for anyone with too much time on their hands ;) here is the Hager video on their flush CUs


Looking at their video unless there is a 30ma RCD upstream then the example installation is no compliant with the regs. If there is a 30ma RCD upstream then there is no way of ensuring selectivity if the board is full of 30ma RCBOs
 

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Andy78

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Why not use metal protection for the tails so they comply with 522.6.204 ?
A buried gland is not accessible for inspection.
 
D

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A lot of copper showing there on the factory fitted links.
 

Andy78

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A lot of copper showing there on the factory fitted links.
There always are unfortunately. Comes from the insulation being a sleeving rather than being bonded to the conductor more tightly like in tails cables.
 
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  • #9
OP Where is the MET in this scenario?
So I am looking at this as being the MET is located else where such as a meter cab or under the stairs with the CU located some distance away (over 3m cable required) feed from a switch fuse (e.g. Wylex or Lewden).
 
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  • #11
There always are unfortunately. Comes from the insulation being a sleeving rather than being bonded to the conductor more tightly like in tails cables.
I take your point about the gland but was considering whether that was the lesser of the two evils in terms of providing suitable mechanical protection. With an SWA where the armour is not being relied on for the earthing arrangements (so 3 core SWA single phase) and the other end is earthed and inspectable. Is that worse that say using metal protection such as trunking (conduit would require adaptable box with no means of verifying that the consuit was earthed once all sealed up) where the earthing arrangments of the trunking could not be verified either once burried.
 

Andy78

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I take your point about the gland but was considering whether that was the lesser of the two evils in terms of providing suitable mechanical protection. With an SWA where the armour is not being relied on for the earthing arrangements (so 3 core SWA single phase) and the other end is earthed and inspectable. Is that worse that say using metal protection such as trunking (conduit would require adaptable box with no means of verifying that the consuit was earthed once all sealed up) where the earthing arrangments of the trunking could not be verified either once burried.
I was meaning the use of steel protection for the tails that would protect against nails and screws which does not require earthing.

You could just do what all the other new build lads do and just stuff the swa through the back of the board with no gland or anything. Seems to be the current standard.
 

Midwest

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Why not use metal protection for the tails so they comply with 522.6.204 ?
A buried gland is not accessible for inspection.
In this instance, would the gland not be identifiable (from inside the CU), therefore easily located and could be inspected with the removal of a piece of plasterboard? Its not as if the joint is being buried in the ground, aka reg 526.3.
 

Andy78

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In this instance, would the gland not be identifiable (from inside the CU), therefore easily located and could be inspected with the removal of a piece of plasterboard? Its not as if the joint is being buried in the ground, aka reg 526.3.
It's not usual to have to dismantle the fabric of the building during an inspection.
 
As long as one gland is readily accessible at the source end and the armour is not relied upon for the cpc it does not really matter if one is no longer accessible as it serves one purpose, connection of the cable. Verifying its integrity down the line is not an issue.
 
D

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Yes as long as the armour is earthed at the source end, it’s not really necessary to have access to the gland at the other end.
 
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  • #18
In this instance, would the gland not be identifiable (from inside the CU), therefore easily located and could be inspected with the removal of a piece of plasterboard? Its not as if the joint is being buried in the ground, aka reg 526.3.
The trouble with a lot of the flush boards is the gland would have to be made off inside a seperate enclosure outside of the CU as they do not have round KOs or enough remain space around the pre punched oval or sqaure KOs to make your own whole. As I say seems like a lot of a design own goal really...
 
If there is space behind the board in the cavity and it does not restrict the cable route get a steel adaptable box, chuck/recycle the lid and fix to the back of the board using the old lid fixing points. Gland cable to the side of the box.
 

Andy78

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As long as one gland is readily accessible at the source end and the armour is not relied upon for the cpc it does not really matter if one is no longer accessible as it serves one purpose, connection of the cable.
Yes as long as the armour is earthed at the source end, it’s not really necessary to have access to the gland at the other end.
With an SWA where the armour is not being relied on for the earthing arrangements (so 3 core SWA single phase) and the other end is earthed and inspectable.
I take this point, it's a very good one and full of sense. I'd still be reluctant to bury a gland behind plasterboard myself if I could avoid it though. Creature of habit maybe.
 
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  • #21
As long as one gland is readily accessible at the source end and the armour is not relied upon for the cpc it does not really matter if one is no longer accessible as it serves one purpose, connection of the cable. Verifying its integrity down the line is not an issue.
Would you still be happy with it if you had to make the gland off in an metal adaptable box so as to provide mechanical protection as you to pass the cores from the SWA through the irregular shaped KO on the flush CU? (see back off envelope sketch below - couldn’t find a fag packet :) )

Obviously the adaptable box wouldn’t be accessable once the plaster board had been put on.

FA7DE2F4-416F-4CE4-81FC-9D838928640E.jpeg
 
That would be okay but if there was space I would fit the box to the back, lid removed and use the four fixing to secure it.
 
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  • #24
That would be okay but if there was space I would fit the box to the back, lid removed and use the four fixingsvto secure it.
Thanks. I agree if there is space bolt on the back that would be great. I was thinking about bolting to the bottom or top back edge (couldn’t bolt towards the front due to the insert frame) if mounting like a service intake type arrangement in my pic.
 
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  • #25
I’d just somehow gland swa into side of CU, surely that’s achievable somehow?
They provide a KO either side seemingly for that but when you look at install instructions and vid they show their ideal mounting position with the CU sat firmly against the studs in either side. So potential you are removing a lot of material to allow the gland to pass through a stud which might well need aditional bracing if installed in a typical stud wall. I just can’t understand why they haven’t seemd to consider the regs more fully when designing this product - but I have probably missed something obvious.
 
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  • #27
I’d carefully drill through one of the Knock outs.
It certainly could be worth a try. Worst case it doesn’t work and you end up having to go back to using an adaptable box.
 

AJshep

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It certainly could be worth a try. Worst case it doesn’t work and you end up having to go back to using an adaptable box.
I understand the reason for the post. Alot of CUs need drilling out, and alot come with square Knockouts etc. But like spin says if your careful your usually find its not a problem.

If your that worried ( and this is going to be a flush CU) how about fixing circular galvanized conduit box lid (with a couple of m6 nuts and bolts) to the bottom of the hager CU and drilling through both this and the CU, it should help stop the weld breaking on the KO.
 
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davesparks

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I just can’t understand why they haven’t seemd to consider the regs more fully when designing this product - but I have probably missed something obvious.
They probably haven't considered SWA being glanded into a flush CU because it is an unusual method if installation. These boards are intended for domestic use so will be designed on the basis of T&E being used.
 
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  • #30
They probably haven't considered SWA being glanded into a flush CU because it is an unusual method if installation. These boards are intended for domestic use so will be designed on the basis of T&E being used.
I get what you are saying and that perhaps it is an unusual choice from the norm but with the likelihood that these boards are going to be insulated some distance from the supply point and therefore the tails are likely to be buried in the fabric of the building for some or most of that journey the options seem somewhat limited.


As I said in an earlier post it was this article that got me considering the issue in more depth How To Install Meter Tails To Consumer Units - https://professional-electrician.com/technical/tales-of-the-unexpected/ and then questioning the design of these types of CU.


And whilst
You could just do what all the other new build lads do and just stuff the swa through the back of the board with no gland or anything. Seems to be the current standard.
might be tongue in cheek to a certain extent it is also sadly true! I know from reading a lot of the post on this forum that pretty well everyone that posts here on a regular basis wants to do the right thing rather than shall we say the fashionable thing ;)


Thanks to everyone that has replied though it has been really interesting having everyone’s input in mulling this over :)
 
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