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Discuss Use an old cable for lighting circuit? in the Electrical Forum area at ElectriciansForums.net

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DGClarke

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Hi
We are rewiring a house, and know that we'll need a Part P inspection after the work is complete.

I wonder if we can use the exisitng feed for the upstairs lights (it runs nicely in the walls to the loft space through a long conduit run, so won't be trivial to replace.

The cable is 1960s vintage, is good quality PVC cable in grey with 1.5mm2 standed condictors and a solid earth.

The core colours are Red/Black. Cable is in good condition.

It seems daft to have to replace one perfectly good cable with another, just to change conductor colours if the Part P regulations don't REQUIRE us to to this.

Any advice gratefully received

Dave
 
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W

WarrenG

  • Thread Starter Thread Starter
  • #2
Hi
We are rewiring a house, and know that we'll need a Part P inspection after the work is complete.

I wonder if we can use the exisitng feed for the upstairs lights (it runs nicely in the walls to the loft space through a long conduit run, so won't be trivial to replace.

The cable is 1960s vintage, is good quality PVC cable in grey with 1.5mm2 standed condictors and a solid earth.

The core colours are Red/Black. Cable is in good condition.

It seems daft to have to replace one perfectly good cable with another, just to change conductor colours if the Part P regulations don't REQUIRE us to to this.

Any advice gratefully received

Dave
Dave first things first.

Why are you rewiring in the first place?
Is somebody qualified (i.e. a Part P scheme member) rewiring the property?
Have the lighting cables had a Insulation test to check the condition of the cables?

Under Part P you will need an Inspection at first fix for sure.

I would suggest even without looking at the cable that it will need replacing.

You have to bear in mind you are talking about a 1960's, 48 years old cable that has been used and taking an electrical load on a day to day basis. Just because it may look good to you does not mean that it is good. It is very simliar to saying something that works and something that works safely.

I have personally taken out lighting circuits where the cables look ok in certain area's but in the loft they have been chewed away by squirrels and the like leaving a major fire hazard.

The insulation of all cables will break down over a period of time which is why the maximum recommended Periodic Inspection and Test Report on a domestic property is 10 years. If you have had this done then it will give an idea (at the date tested) of what condition the cable is in?

If you are looking to bring the property upto a safe standard then I would recommend that you replace all your properties cables if they are all in a 1960's condition.

It may seem like hassell, but worth it in the long run.

Hope this helps!

Warren
 
D

DGClarke

  • Thread Starter Thread Starter
  • #3
Warren

Thanks for the reply, and I take your (very valid) point about the age of the cable, and the quality of the insulation. For sure there have been rats in the loft in the past and they're certainly capable of knawing through cable. We will certainly replace it now that you have reminded me

We are rewiring because it needs it (bedrooms with only ONE single socket etc). There are a whole lot of new sockets/lights to install as well as changes to other parts of the system.

We will not be using a Part P electrician to do the work, as we can do this ourselves, even so far as doing the insulation check. We have the necessary equipment to do it.

We ARE going to apply to the local authority and pay to have the work inspected and certified as Part P compliant once it is complete. The building regs that we are submitting to the local authority will state that we are rewiring and that a Part P inspection is requested at first fix.

Thanks for your fast and informative response.

Dave
 
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WarrenG

  • Thread Starter Thread Starter
  • #4
Dave,

No problem, glad to help.

Just a quick reminder that we are now working to the 17th Edition Wiring Regulations. i.e lighting cables buried less than 50mm from the surface require RCD protection.

Warren
 
D

DGClarke

  • Thread Starter Thread Starter
  • #5
Yes, we're going to use a 17th edition consumer unit, and we are aware of the safe zones for cables run in the walls.

I would like to ask one supplementary question if I may.

We are installing small halogen spot lights either side of the bed. The live and neutral come down vertically from the ceiling in plastic conduit to the light and then drops a further 12" or so, again in conduit to a switch/dimmer.

It seems to me that the tidyiest way to wire this is to strip the outer sheath for the last 12" or so and then run only the live inner wire to the dimmer. The neutal breaks out at the lamp, and then we run a separate switched live (brown colour again maybe) back to the lamp from the dimmer.

My son-in-law is against this. He wants to put sheathed cable in both segments. This will need a join in the live behind the lamp.

It seems to me that you'll end up with a really tidy solution with NO unneccessary joins if you run the unsheathed inners in the conduit.

I was wondering what if anything the regs say about that.
 
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WarrenG

  • Thread Starter Thread Starter
  • #6
Sorry Dave I can't say that I would agree with that? :mad:

The sheath of the cable is there for protection and should be left in place.

Us sparkes get a right grilling for leaving bare earth wires any where (not that I do personally), so stripping and leaving a 'live' wire unprotected is a no-no.
 
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D

DGClarke

  • Thread Starter Thread Starter
  • #7
Sorry Warren, I certainly didn't mean BARE wires, live or earths.

But I guess you knew that and are telling me to leave the cable completely sheathed, even though we're running these conductors in conduit for protection.

OK. I'll shut up now, and take your good advice.

I think I might buy a Part P self training CD course and take the exam.

Thanks again.
 
M

montybaber

  • Thread Starter Thread Starter
  • #8
I cant see the problem as long as you run a single core (insulated) cpc to the switch along with the switch wire and common, the conduit is sufficient means of protection for the cable and running singles in pvc conduit is normal practice.

like you say one less join :)

Is somebody qualified (i.e. a Part P scheme member) rewiring the property?
2 completely different things my friend;)
 
J

johnnyb

  • Thread Starter Thread Starter
  • #9
Can,t see any problem as long as the lighting circuit is on rcd as you stated,which it would be using 17th ed con/unit, but make sure that when you strip the T&E at the fitting u make sure that the cpc is sleeved g/y and also make sure that the upstairs lighting circuit is on the same rcd side as the downstairs ring main.
 
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WarrenG

  • Thread Starter Thread Starter
  • #10
I cant see the problem as long as you run a single core (insulated) cpc to the switch along with the switch wire and common, the conduit is sufficient means of protection for the cable and running singles in pvc conduit is normal practice.

like you say one less join :)



2 completely different things my friend;)
Very, very true montybaber, lol.....it wasn't meant how it read.
 
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uksel

  • Thread Starter Thread Starter
  • #11
DGClarke: my apologies for sounding rude, but you don't come across as confident enough to be doing this job. if you are tripping up at these hurdles then perhaps you might be biting off a bit more than you can chew

i know it would be hard to not get offended, but a full rewire is serious stuff and should be done by a competent person as throughout you will be the duty holder, you don't come across as sure of yourself, or what you are doing

again apologies if you are offended
 
S

sparkyork

i personally think he sounds like he's gonna be ok. he's just got a few questions about his new installation, that he obviously wants doing properly first time round.

competance is a fine line in reality, have a go harry down the road wouldnt even come on a site llike this and ask questions, he would lash his cables in, keep the existing upstairs lighting feed and probably not use grommets and also not inform labc.
i would recommend if not allready purchased that he maybe gets a copy of 17th osg just so he's got a good reference point. electrics half the time is just common sense, and generally just 3 wires, and the odd sw/wire.

good luck with the job matey, sure you'll be fine
 
D

DGClarke

  • Thread Starter Thread Starter
  • #13
Guys

Thanks for all your replies, I do appreciate it. I now have to persuade my son-in-law to do it my way (not easy).

Can someone clarify a point for me? What is "cpc"? It is obviously a term for the unsheathed earth wire (hence the g/y sleeving), but what do the letters stand for?.

I was going to ask ONE more question, but I think JohnnyB has already answered it.

Obviously all lights are RCD protected as are the rings, but I take it that the correct arrangement is for the downstairs ring and upstaris lights to share an RCD and vice versa.

This makes sense to me, so If I have a ring trip out I still have lights

You are all stars - thanks

UKSEL

I am NOT offended, but anyway thanks for being so diplomatic.

I have no concerns at ALL about doing this work. I have a degree in electronics, so the "electrical" aspects of this are NOT a problem. What is a problem is the REGULATIONS. I want to be sure that when we apply for an inspection it's going to pass.

I don't want to trip up on some tiny regulation that I didn't know about. This is why I was asking about running singles in conduit, and what the position was regarding old, but apparently servicable cable.

I understand why you posted though, and you can be forgiven for thinking that perhaps I'm not up to the task.

Maybe I'll take Sparkyork's advice and get a copy of the 16th edition doc

Sorry meant to say 17th edition obviously
 
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1

12345aob

  • Thread Starter Thread Starter
  • #14
I hope you don’t live near me- building control won’t let anyone without 2391 do anything. I just had a chat over the phone to them today- there so helpful!
 
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WarrenG

  • Thread Starter Thread Starter
  • #15
Guys

Thanks for all your replies, I do appreciate it. I now have to persuade my son-in-law to do it my way (not easy).

Can someone clarify a point for me? What is "cpc"? It is obviously a term for the unsheathed earth wire (hence the g/y sleeving), but what do the letters stand for?.

I was going to ask ONE more question, but I think JohnnyB has already answered it.

Obviously all lights are RCD protected as are the rings, but I take it that the correct arrangement is for the downstairs ring and upstaris lights to share an RCD and vice versa.

This makes sense to me, so If I have a ring trip out I still have lights

You are all stars - thanks

UKSEL

I am NOT offended, but anyway thanks for being so diplomatic.

I have no concerns at ALL about doing this work. I have a degree in electronics, so the "electrical" aspects of this are NOT a problem. What is a problem is the REGULATIONS. I want to be sure that when we apply for an inspection it's going to pass.

I don't want to trip up on some tiny regulation that I didn't know about. This is why I was asking about running singles in conduit, and what the position was regarding old, but apparently servicable cable.

I understand why you posted though, and you can be forgiven for thinking that perhaps I'm not up to the task.

Maybe I'll take Sparkyork's advice and get a copy of the 16th edition doc

Sorry meant to say 17th edition obviously
Dave

CPC = Circuit Protective Conductor. And you are correct regarding the RCD situation.

Warren
 
M

montybaber

  • Thread Starter Thread Starter
  • #16
I hope you don’t live near me- building control won’t let anyone without 2391 do anything. I just had a chat over the phone to them today- there so helpful!
thats ridiculous!
 
S

sparkyork

thats ridiculous!

ill second that monty! who the swear word do labc think they are?! i aint got 2391 yet, gonna start the course soon mind. didnt bother the nic so why should it bother them! phhht beaurocrats
 

ian.settle1

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Mentor
Arms
ill second that monty! who the swear word do labc think they are?! i aint got 2391 yet, gonna start the course soon mind. didnt bother the nic so why should it bother them! phhht beaurocrats
I'll third it, none of the bugger's are electrically qualified either.
 
D

DGClarke

  • Thread Starter Thread Starter
  • #20
Hey guys, we've just performed the insulation test on the upstairs ring, and I'm certain we're just fine. The megger turned in a reading of about 2 Giga Ohms (2000 MOhms). The cable was separated from the consumer unit at the time of the test, and I was wondering if we ought to be performing the test with the wires connected and the MCB open.

Just for the record, what do the regs say? What is the lowest resistance that is acceptable?
 
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uksel

  • Thread Starter Thread Starter
  • #21
i think it's 0.5 MegaOhms

and anything less than 2 MegaOhms requires further investigation.

couldn't say for sure without the book infront of me
 
D

DGClarke

  • Thread Starter Thread Starter
  • #22
Hey Guys,

You've probably forgotten all about me.

I just thought I'd pop on to this forum to let you all know I have decoded to take the exams.

I have my 2382 exam on 1st April. The course I bought online has an exam simulator buillt in and I have been practicing.

I got 92% on my last practice (pass is 80%) so I'm hopeful.

Once that is out of the way it's on tot he 2391 (looks harder).

Cheers all
 
P

pushrod

  • Thread Starter Thread Starter
  • #23
GOOD LUCK, be interested to hear how you get on.
 

old dog

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Arms
i think it's 0.5 MegaOhms

and anything less than 2 MegaOhms requires further investigation.

couldn't say for sure without the book infront of me
hi it is now 1.0 megohm min and as you say < 2megohms further investigation
 
D

DGClarke

  • Thread Starter Thread Starter
  • #25
GOOD LUCK, be interested to hear how you get on.
Hey pushrod - thanks, and I will let you know how I get on this Wednesday.

I am hoping for a reasonable pass. In my practice exams I am routinely getting over 90%, and on ONE occasion I actually got 100%.

Of course these are not the real thing, and I have no idea how different the real exam is going to be.

On the face of it, the 2382 looks like an exam that ought to be reasonably easy to pass (famous last words).

If you are thinking about training, I'd say go for it. The 2382 looks a lot easier than the 2391, so make a start.

I used the ELECTA course. Buy online for about £70 (both 2382 and 2391). This gives you the simulator (for 2382 at least), so you can practice in exam conditions.

I'll post on Wednesday with the outcome. Because it's a computer based exam, you get ther results on the day.
 
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Spudnik

  • Thread Starter Thread Starter
  • #26
The 2391 is one of the hardest courses/exams you will experience in this industry.

It carries quite a high failure rate.

You would be better off going on a course at a training centre.
 
D

DGClarke

  • Thread Starter Thread Starter
  • #27
The 2391 is one of the hardest courses/exams you will experience in this industry.

It carries quite a high failure rate.

You would be better off going on a course at a training centre.
You're not wrong. I have started reading the online couse material. You know what?

The first thing they say is that the failure rate for the 2391 is greater than 50% of entrants.

Although your advice is good, I'll look at the online stuff before making a decision. I don't really want to have to pay a small fortune and take time off work to attend a course, but it might come to that.

Thanks for your advice, I may have to take it (but I hope not).
 
D

DGClarke

  • Thread Starter Thread Starter
  • #28
Well, I passed :) Quite well I think.

Section scores as follows:

Scope, object and fundamental principles - 100%
Definitions - 100%
Assessment of general charateristics - 100%
Protection for safety - 71.4%
Selection and erection of equipment - 93.3%
Inspection and testing - 83.3%
Speciall installations or locations - 100%
Appendices - 66.7%

Bit disappointed about the Appendices amd Protection results, but what the heck,

The test was much harder than I expected. The trouble with doing the practice exams is that the same questions keep turning up, and of course you know the answer. I was completing the 60 questions in 40 mins and getting 92% overall. In this exam I needed the FULL 2 hours, and I still had to guess about 4 answers.

Still that's out of the way now.

Pushrod, I say go for it!
 
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