Reconnecting existing electrics

[NozSpark]

I've got a job to do which will entail reconnecting a consumer unit and final circuits back to the supply... about 3 months ago I disconnected it because the building had a roof leak in that area which wasn't found for a couple of months (if not more),,, the plaster board walls are also being ripped out where they have been affected by water... I have recommended that after the plasterboard has been removed that it allowed to dry throughly and anti fungicidal paint or whatever applied to the walls before anything else is done.

Now the existing supply to this CU (disconnected) is just DI 25mm tails... about 25m of them straight off henly blocks :redcard

So my question is how can I reconnect this..

DNO only allow 2 or 3 meters of exposed tails to CU's without additional protection

Burried cables <50mm require RCD protection (although this is a commercial building so it could come under instructed persons)

IMHO I would like to install this as a SWA submain with a switch fuse at the origin and a new DB (with RCBO protection) for the final circuits (if re-using the existing they will be throughly tested and inspected before replastering)

 

[springcrocus]

Now the existing supply to this CU (disconnected) is just DI 25mm tails... about 25m of them straight off henly blocks :redcard

Nothing to do with your question, Noz, I just find it funny that your "double insulated" has become "domestic installer" with the forums auto-underline feature.

 

[Sidewinder]

Noz,

Actually, they are not double insulated are they?

They are insulated & sheathed!...

RD&H

 

[NozSpark]

Yeh I know, but for some reason I always seem to call them DI.. really need to get away from that

so does it sound like a good plan, or am I over thinking things (again)???

 

[Sidewinder]

Noz,

Can't really think about your prob at the mo sorry!!!!!!!!

 

[NozSpark]

Noz,Can't really think about your prob at the mo sorry!!!!!!!!

No problem mate,,

hope you manage to recover your data (somehow)

 

[Manator]

You say that the DNO will not allow more than 3 meters of cable, are you getting this mixed up with requirements for isolation?

If the cables are surface mounted there is no requirement to RCD, and provided there is a double pole isolator between the henley and the CU ( henley side), then I see no problem. Personally I would like to do it as you say with a SWA submain, It has two advantages, if you use a core as well as the amour for earthing the Zdb is reduced and makes the cable calcs a lot easier to design and manage for final circuits, and is hardier to knocks and bangs, such as everyday usage and abuse.

 

[NozSpark]

I was considering the fact that the DNO want FUSED protection for tails over 3m and that they should be visible throughout

the existing tails were 25 meters (ish) long and buried behind plasterboard for most of that, they were also connected directly to henly blocks with no fused protection or isolation apart from the cutout

another problem is that my client doesn't use this part of his building and has no real intention of using it, but wants the electrics re-instating... IMHO he could do with renting it out to someone, but he's not too bothered about that either

 

[Manator]

I see your problem now, if the cables are buried there is no way you can reconnect without protection to the cables which will involve RCD protection. I am just debating if this is exsisting and therefore not subject to any change, or as a responsible person can we really allow ourselves the luxury of this rule?

I think I would be having a word with the client, the money he/she has spent so far could extend to having the electrics done right.

 

[NozSpark]

I see your problem now, if the cables are buried there is no way you can reconnect without protection to the cables which will involve RCD protection. I am just debating if this is exsisting and therefore not subject to any change, or as a responsible person can we really allow ourselves the luxury of this rule?I think I would be having a word with the client, the money he/she has spent so far could extend to having the electrics done right.

That is the exact internal debate that I'm having as it'll be quite a bit of additional cost.

I did tell him however that it was installed incorrectly in the first place when I was disconnecting it and that I'd need to install a switch fuse as a minimum.....

there are other sub mains to an upstaris DB or two wired in exactly the same way, I will recommend that these are rewired, but his company develops and maintains software so any outages have to be planned

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and prolonged outages could cost him megga

 

[Dunx]

Hi mate,

I think your plan is the better one! As soon as you reconnct then obviously you take responsiblity for it and what the CU is connected to. 25m of tails even in sight is a code 2 in my book. depends where they run but there is a big risk of future mechanical damage because you have no idea what may happen to the structure of the building. I suppose you could enclose them somehow but its not a great idea.....

SWA 3 core sub main with a 60/80A fused isolator at Henley end. No need for RCD.

Personally [and its tough to say without actually being there] I would give a price for the SWA but politely decline to reconnect if the owner won't pay for it. I nver believe anything that people tell me about the future of their property.... could be a take away in 2 months time!

Dunx

 

[Megaohm7]

If the Consumers unit is still in the existing position as before then I can't see why you have to do anything with the tails as if the DNO are that bothered then they would be fitting switch fuses everywhere where the tails exceed 3m in length.I've had this out with a few guys from the DNO in the past and none of them seemed concerned about it. It seems like it's pass the buck to the electrician all the time. Rant over !! lol

 

[Chr!s]

Whats the Ze ? and whats the protective device?

 

[SLIPSHOD & SLAPDASH]

How did you safely disconnect & how are you going to reconnect the existing cables ?

 

[NozSpark]

Whats the Ze ? and whats the protective device?

From what I remember it's a TNS supply and the current protective device for these tails is the cutout,, but with respect I'm not asking for advice on what size of cable to use, I'm asking if I can reconnect or if I'm duty bound to replace (with surface mounted cable or SWA)?

TBH I really need to pin him down on what he is planning to do with this part of the building.. i.e. does it really need it's own supply or can it run off a submain??

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How did you safely disconnect & how are you going to reconnect the existing cables ?

Let's just say it had to be a planned disconnection, out of henly blocks

and that reconnection will be the reverse process

Power was OFF for disconnection and will be OFF for reconnection

however as a minimum it'll be getting a switch fuse, but TBH I'm going to tell him it needs a switch fuse and SWA to a new MC (RCBO) board

 

[Chr!s]

From what I remember it's a TNS supply and the current protective device for these tails is the cutout,, but with respect I'm not asking for advice on what size of cable to use, I'm asking if I can reconnect or if I'm duty bound to replace (with surface mounted cable or SWA)?

The regs are not retrospective so i see no reason as to why you need to fit a new sub mains?

I think you need to decide as to what level of risk is exists.

And as you've pointed out theres exemptions for buried cables.

 

[Sidewinder]

Fuse switch & S type RCD?

Also control of instructed persons?

Not read all the posts, just thought I'd throw this in!

27% again!

 

[NozSpark]

Just been back to this job today to have a look now that the plasterboard has been removed from the wall that had suffered the most damp..

After talking to the customer he is happy that the sub-main is rewired in SWA (surface) with a switch fuse at the supply to a MC DB with RCBO protection for the final circuits.

Now in several places there are cables that are/will be running out of safe zones, my thought was to run what I can see/re route in minitrunking and note the rest as a comment on the EIC.

Oh, and he IS going to let the unit back out,,, maybe even move his upstairs offices out and split the building up a bit more.... Flat above, shop to front and this workshop to rear...

 

[SPECIAL LOCATION]

Sounds OK to me... and sound like he's a bloke that can understand a bit of common sense!

Always nice when you get a customer like that!

:Salute