testing/identifying unsuitable cable.

I'm looking at reinstating a 15A spur to a socket in our kitchen for an oven. The previous owner had an all gas cooker which (I guess) whould just have been plugged into the ring main for any leckie it needed.

There's an existing cable with plenty slack terminated under the kithen floor connected though to a 15A fuseway in the fusebox. The cable looks quite old, slightly heavier than 2.5mm2 (based on my vernier measurement) and the earth is twisted steel (?) strand rather than solid copper.

I'm pretty sure I'm going to rip it out and run a new cable just to be sure, but before I go to all the trouble (and it will be a lot of trouble) is there anyway to test the integrity of the existing cable?

How do I tell if it's got the old friable insulator on it?

Reply to
urchaidh
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Don't chance it either way. Renew it and be sure it's safe. Old tinned cable isn't going to be near the present requirements for the wiring, so it's cheaper, safer and lots less hassle to replace it all while the jobs opened up to see it all.

To test the integrity fully means expensive meters and megers. It's not worth the expensive on one cable mate, believe me. Just take a look on the web for "Electrical Insulation Tester" and you'll see what I mean.

Reply to
BigWallop

Are the circuit conductors stranded or solid? The old 7/029 or thicker cables often had tinned copper conductors. You may be mistaking tinned copper for steel if you are basing your idea on colour. Steel conductors would be very unusual and easily confirmed with a magnet.

The conductor continuity can be checked with a low resistance tester, the insulation value can be easily checked with a Megger. Unfortunately you should also inspect the condition and verify there are no branches or spurs off it and it is in good/satisfactory condition (no rodent or other damage) This may not be possible:-(

With your eyes and try bending it to see if bits crack and falls off. If its anything but PVC or MICC you should chuck it anyway. You can of course use it as a pull wire to draw in a new cable

Kitchens are special locations under the fat controllers new regs and require notification of ANY work to building control. Proper Testing and Certification is required.

Reply to
John

Don't bother. Put in a new cable and use 10mm while you're at it. That will be ample for anything anyone is likely to want to run off it in the future. Leave spare length at each end. (The fusebox can be upgraded later if needed, but putting in the bigger cable now will save the disruption later.)

Owain

Reply to
Owain

Probably 7/0.29 line and neutral and 3/0.29 earth. Tin plated copper.

If PVC insulated quite likely to still be in perfectly serviceable condition. If rubber - not.

Just about all cables deteriorate most where they are terminated. So if it looks in good condition at the ends it should be fit for further service - if PVC.

Rubber verses PVC?

However, you say you wish to run an oven off it. As a radial? Many ovens may be just plugged into the ring main. Those that can't usually require rather more than a 15 amp feed, for which this cable wouldn't be suitable.

Reply to
Dave Plowman (News)

Condition test: bend the exposed ends, after isolating them. If it doesnt crack, its ok mechanically.

A bit of basic electronics makes it easy to insulation test. dioe and capacitor from mains gives 330v. 2 of those gives +330 and -330, a total of 660v difference. Add a cheap meter set to current range and you get a reading of any leakage current at 660v. Or a fried =A35 meter.

To do that youd need to be competent enough to regard it as obvious how that would be connected up, that it is live working, and that it must be disconnected from CU and insulated from people cats etc. If not, leave well alone.

CPC resistance test: parallel N and L conductors at one end, and join all 3 at other end. Now youve got 3 strands of CPC and 14 strands of phase. Now:

Total R =3D Rphase + Rcpc. And we know that Rcpc =3D 3/14 x Rphase. thus total R =3D (1 + 3/14) x Rcpc.

Rcpc =3D 0.82 x Rtotal.

A much easier option is to get someone with a PAT tester to come test its Rtotal (to work out Rcpc) and insulation. If necessary.

I'm only saying this because the OP indicated it would be a grim job to replace, and theres no need to replace if it works fine. It might well be plastered in here there and everywhere, and require removing fitted stuff to get to it, replaster etc. Theres nowt wrong with using old wire iff its in good condition and upto the job, and sometimes it is.

NT

Reply to
bigcat

Yes - I recently found some dead 7/029 PVC in my house and removed it. It was in perfect condition.

Reply to
Dave Plowman (News)

Yeah, it'll have to be a 13A oven with a plug. I thought I might add an extra radial (on a spare 15A fuseway) for it rather than have it on the kitchen ring main.

Would that have to be 20A fuseway? In that case I guess I could make it a proper radial and have another socket on it for the fridge (

Reply to
urchaidh

Has the kitchen got its own ring? If not, would it be feasible to use this cable to do that? Then modify the rest of the ground one into a new ring?

It obviously depends on where your CU is and accessibility under floors, etc.

Reply to
Dave Plowman (News)

The kitchen has its own ring, just finished that sorting that out. I didn't do a diversity calcualtion for load, but my tendancy to over-engineer led me to the idea of a second dedicated spur for the oven, even though it will be a sub 13A device on a socket.

Am I being overcomplicated, should I just plug in the oven to the ring?

Access around the kitchen is fine and easy as I have the floors up at the moment and it's going to be replastered soon. From the kitchen to the CU is a real PITA. The CU is an old sytlee fuse box. Upgrading it is on the list. Cables from the last possible accessable point in the hall to the CU are well buried in the wall.

Reply to
urchaidh

Well, many houses are done like this, and it works ok in practice.

In that case I would seriously consider using the cable to run a dedicated feed to the fridge freezer, not the oven. Put this feed on a non RCDed line, if youre not TT. Now an RCD trip wont cost you your freezer contents. Kitchens contain the majority of the prime RCD tripping items.

NT

Reply to
bigcat

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