Duff cable ???

[Lyngarth]

Hi

I have two double sockets in my garage and wanted a third. So before I started work I did a quick Zs check, got 1.01 so all OK.

I didn

 

[paul b b]

have you meggerd it?

 

[sparkytim]

Measure the end to end resistence of each core

If 2.5 then both L and N should be equal and CPC should be about 1.66 times higher reading

 

[Lyngarth]

Hi

Right then, just done end to end and got this...

L-L = 0.38

N-N = 0.36

cpc-cpc = 0.41

Cable is 2.5 t&e

So it looks like the problem is with the cpc.

The thing I don't understand is I used this cable last week ( well some of it ) and it was fine.

Cheers

Lyngarth

 

[m4tty]

1) When was your meter calibrated and are the batteries good?

2) Have you tried IR testing the cable.

Them readings look suspect as cpc not 1.67 x the Line or Neutral.

Where did you get the cable from, is it old stuff?

Cheers

 

[sparkytim]

NO THAT LOOKS GOOD as expected

Slight differerence in values to calculation probably due to contact difference when measurements taken

I would investigate your original circuit and connections again.

Be carefull when measuring LOW RESISTENCE continuity's

If using croc clips squeeze connections tight it can make a difference

If using probe press HARD same reason

0.2 or 0.3 of an ohm is very small value

When Zeroing leads with croc clips put FIXED side to FIXED side if not you can be measuring thru the spring clip and that can add resistence in.

Its all a learning curve some of us are just abit further round the corner ahead of you, having learnt these things the hard way.

 

[Lyngarth]

Hi,

Not done ir test, but will give it a go later, my fluke is only 7 months old, plus i still have my mates here and get the same.

The cable is only 2 months old and got its from wilts.

 

[Evans Electric]

What make is the cable , we had a couple of warnings recently on dodgey makes, I cannot,of course ,remember the names now.

 

[SPECIAL LOCATION]

HiRight then, just done end to end and got this...

L-L = 0.38

N-N = 0.36

cpc-cpc = 0.41

Cable is 2.5 t&e

So it looks like the problem is with the cpc.

The thing I don't understand is I used this cable last week ( well some of it ) and it was fine.

Cheers

Lyngarth

using the resistance figures from table 9A pg 166 OSG...

L-L 0.38 ohms worth of 2.5mm conductor (0.38/7.41)x1000= 51.3metres

N-N 0.36 ohms worth of 2.5mm conductor (0.36/7.41)x1000= 48.5metres

E-E 0.41 ohms worth of 1.5mm conductor (0.41/12.10)x1000= 33.8metres

thats approx 17.5m worth of discrepancy!!?

I personally would have expected the readings to be a bit closer..

the L & N are within 2.8m of each other.. but the E is is bit off...

BUT for your original post problem its OFF in the wrong direction! lower not higher?

Have you got a calcard or check box to test your meter on?

May be a loose connection when doing your tests?

:|

 

[bengie]

where did you break into the ring? are the cables clipped? check the sockets at either side of this JB if the cables aren't clipped as it could be a loose connection at one of those that is affected by you moving the cables around. but from the fault finding you've done it does sound like a suspect bit of cable.

 

[Evans Electric]

Just a thought , its not old cable , R + B with a 1.00 mm earth is it ?

 

[batty]

My Fluke 1652 gives duff readings on continuity tests which is the fused leads. I am going to use unfused leads on continuity tests.

 

[Lyngarth]

Hi

Thanks to all who has replied.

As to my meter, no I don't have a calcard but have tested a known socket in my house (noted down reading to keep an eye on the meter until I get a card) and its reading the same as normal, plus my mates meter gives the same readings.

The make of cable is draka and new colours.

Will go back tomorrow and check all connections and retest.

Maybe not the best thing to do but having the spur in 4mm (for the time being until I get some more 2.5) won't do any harm will it ??

Cheers

Lyngarth

Will post back tomorrow with the test findings.

 

[Apache]

Hi Maybe not the best thing to do but having the spur in 4mm (for the time being until I get some more 2.5) won't do any harm will it ??

course not. Why not just leave it?

 

[bengie]

its not perfect to mix and match sizes but tbh going bigger is no issue at all in terms of electrical integrity as all your going to do is lower you resistance readings etc

 

[M107]

When I got spurious Zs readings using the fluke & plug lead I quized the fluke rep at the wholesalers when getting it caled, he said without looking it'd be the lead.

Sure enough a twist of the red plug while fitted to the unit & the Zs reading changed.

A gentle pull & the red plug detatched from the lead.

A well know (by fluke) problem, complained & the fluke rep sorted a brand new replacement lead there & then.