CU replacement with earthed conduit and singles

[i=p/u]

Maybe someone on here can do for you dartlec, and you can watch.. and take 2%

 

[timhoward]

This is certainly a good challenge! A few reckless random ideas...

Last resort - plug in MCB's and up front RCD?!

Or using the old board as a template for cutting holes in the new board for the the lower circuits, maybe clean up and re-use old bushes if imperial. Very Very carefully shorten the top two, use bonding nipples to earth them and copex to get them to the new CU with separate CPCs.

OR how about replacing the lower board with two pieces of larger metal trunking and solder/crimp heat shrink new longer wires on them. You at least get multiple goes at the hole spacing then.

Or how about getting a fabricator to make a new front for the Wylex and it can just be a joint box.

 

[Pretty Mouth]

If the conduit is metric, then presumably earthing nuts would fit the threads? Not sure that's of any help or not.

Is there a reason BS951 clamps couldn't be used to earth the conduit? This article from PE lists their intended uses, and kind of leads me to believe they would be okay for this:

Clamps, Earthing and Bonding: Correct Selection and Installation

BS 951 specifies the performance and important mechanical requirements for metal clamps that are used to provide mechanically and electrically sound earthing and bonding connections to metal tubes. The

tinyurl.com

 

[Vortigern]

I am not clear as to whether you have an earth/cpc on the circuit, yes or no? So what you can do is cut the conduit back and use flexible conduit to go to the new box. That would need a cpc already in the circuit. If not then can you pull one in? As to the conduit being earthed, at the junction boxes such as where the lights are and inspection T's and 90 degrees etc you can put a fly lead joined to your cpc if this is not already done, secured with a round crimp and brass pan head screw. If there is no cpc then you need special tester to ensure continuity of the conduit earth. It puts out a high current and where the joins are it sparks if they are loose (forget what it is called) If this is not an option then you will have to draw in a cpc if you can access the inspection boxes??? Getting out the bushes requires a tool for the brass bush that you can buy at denmans. I have never found a jammed or impossible bush when doing this sort of thing but it does require the right tool. CK do one, bush spanner I would think it is called but it is not like a spanner. Oh and the best way to draw in an extra cable is to pull out one of the existing (one single) and attach two singles taped on to the one you are pulling out.

 

[westward10]

If you have space to the left terminate the upper conduits to a steel adaptable box, fit 20mm serrated washers, assuming they are metric to maintain continuity and bolt a separate cpc to the box again with serrated washers and connect to board with flexible or solid conduit. Do the same with the opposite lower conduits then fit the new board left of these direct to the other remaining lower conduits again with serrated washers. If they are imperial you need imperial entries metric will be oversized. Yes accessories need cpcs to the back boxes.

 

[Dartlec]

If the conduit is metric, then presumably earthing nuts would fit the threads? Not sure that's of any help or not.

Is there a reason BS951 clamps couldn't be used to earth the conduit? This article from PE lists their intended uses, and kind of leads me to believe they would be okay for this:

Clamps, Earthing and Bonding: Correct Selection and Installation

BS 951 specifies the performance and important mechanical requirements for metal clamps that are used to provide mechanically and electrically sound earthing and bonding connections to metal tubes. The

tinyurl.com

I did wonder that.

That article only mentions 'bonding conductors' to metal tubes, and earthing conductors to rods, but can't see any reason why they wouldn't be functional - just not sure enough of the way they are normally done...

There are really only 4 circuits needed, so I may be able to fit an RCBO board to the top left in place of the off peak one - and then use the existing board merely as a junction box....

 

[Dartlec]

I am not clear as to whether you have an earth/cpc on the circuit, yes or no? So what you can do is cut the conduit back and use flexible conduit to go to the new box. That would need a cpc already in the circuit. If not then can you pull one in? As to the conduit being earthed, at the junction boxes such as where the lights are and inspection T's and 90 degrees etc you can put a fly lead joined to your cpc if this is not already done, secured with a round crimp and brass pan head screw. If there is no cpc then you need special tester to ensure continuity of the conduit earth. It puts out a high current and where the joins are it sparks if they are loose (forget what it is called) If this is not an option then you will have to draw in a cpc if you can access the inspection boxes??? Getting out the bushes requires a tool for the brass bush that you can buy at denmans. I have never found a jammed or impossible bush when doing this sort of thing but it does require the right tool. CK do one, bush spanner I would think it is called but it is not like a spanner. Oh and the best way to draw in an extra cable is to pull out the existing )one single and attach two singles taped on to the one you are pulling out.

No CPCs at any fitting - just live conductor singles pulled to each point - with the conduit acting as the earth...

From documents on site it looks like this was done by SEB in 1976, so it in theory should be metric - just never seen one still in place in a domestic property - usually its the even older (thinner) piping that wasn't earthed - and has had twin and earth pulled through after that...

As far as I can see there are no inspection boxes or access to any of the conduit - it appears to be in the concrete floor/ceiling or buried entirely in the walls...

Each back box does appear to be properly fitted with bushes though, and the standard Hi Zs test gave acceptable results at each point I tested....

 

[telectrix]

You need to test R2 at every point to ensure conduit is electrically connected throughout, then use conduit as cpc. flyleads may be required for any new accessories fitted.

 

[Dartlec]

Update on this:

I managed to just squeeze a Fusebox CU in the gap so left the Wylex board as a junction box. Still need to find a suitable permanent cover for it - I'm thinking maybe the lid of an adaptable box screwed into the existing cover with self tapping... Or possibly even just a suitable size bit of PVC sheet or similar?

Had to run some SWA externally to supply the cooker and hob that had been bodged by the same kitchen fitter who screwed the sockets up in my dodgy trade pics post...

Not ideal - but also not the job where there was time (or budget) for me to get into cutting and finishing conduit - which would have been a nightmare anyway with the space and access I think...

Since the photo I added a label stating the conduit was essential earthing so should not be removed.

Maybe if/when it's next empty I'll have a chance to sort it all out properly....

 

[westward10]

Should have done something like I suggested in #15 time and budget should not be relevant although my suggestion would not really have compromised either.