Failing insulation resistance

[apdevelopments]

I went to quote on a simple job today.
Some old by is buying a new cooker and wants the wiring ready.
I carefully pulled out the old cooker to see what was behind and all there is behind is a 10mm cable coming out of the wall.
I recommended to fit a proper cooker connection point, Sink the single box in the wall where the cable comes out. Nice and easy.
He was happy with that as it wouldn't affect his wall paper behind the cooker.
I was planning to issue a minor job certificate for this job as its such a simple job.

We are talking old boy here so not alot of money to spend.

I was able to fit him in today so after the go ahead I set about testing the circuit before I go in for the attack.

Out comes the meter and I fully test his cooker circuit.
I always test before I do anything to double check that everything's ok before I start.
So continuity 0.17 ohms Ok.
Insulation resistance. Line and cpc: Pass. Line to neutral FAIL!!!! CPC to neutral: Pass!

Everything was disconnected at each end. Consumer unit to cooker switch.

He is still using his old cooker right now as I didn't start the job and just put everything back.

He is still using a old 1960's fused Wylex consumer unit.

I did mention upgrading his consumer unit but like he can afford it. probably not.

Cable is burred in plaster so threes not much to see and its a 30 meter run from consumer unit to cooker.


What would you do in this situation?

 

[SirKit Breaker]

If you are just changing the appliance, with no alteration to his circuit, then as i see it, it is OK, as the IR is low, inform him that sooner rather than later the cable will need replacing. But the over riding thing here will be the manufacturers instructions for the new appliance. If it says must be installed in accordance with BS7671 then that is how it must be installed, so whilst i appreciate the old fellow may not have much money, his new cooker must be fitted properly, and if it isn't you can bet your bottom dollar that if it breaks, an engineer comes out and says it isnt installed properly so the warranty is invalid it WILL BE YOUR FAULT even though it isnt, and the old lad will expect you to pay cos it wasnt fitted properly. Tread carefully, or you will end up out of pocket, its too easy to try and be nice to the customer only to get it thrown back in your face at a later date.

Cheers..........Howard

Cheers..........Howard

 

[telectrix]

when you say L/N fail, what was the reading?

 

[Hawk81]

This might be a very obvious question but was there an isoation switch for the cooker and did it have a neon and if yes was it switched on?

 

[SirKit Breaker]

This might be a very obvious question but was there an isoation switch for the cooker and did it have a neon and if yes was it switched on?

Thats a good point:smartass2:

Cheers.........Howard

 

[telectrix]

This might be a very obvious question but was there an isoation switch for the cooker and did it have a neon and if yes was it switched on?

i thought that, but he said he'd dissed both ends. maybe he meant the end at the cooker, leaving the isolator in circuit.

 

[Hawk81]

i thought that, but he said he'd dissed both ends. maybe he meant the end at the cooker, leaving the isolator in circuit.

That's what I am thinking

 

[apdevelopments]

Hi.
Thankyou for your reply's.
I also thought about the neon in the cooker switch so I completely disconnected the switch all together.
I tried the tests from both the cable coming out of the wall and from the cooker switch point. Everything was ok from the cable coming out of the wall to the cooker switch. But somethings defiantly wrong between the switch end to the consumer unit.

What was the reading. I must admit I didn't write it down at the time. I was looking at the big X that came up.

I know what you mean about peoples bodge wiring. Only last week i wired up somebody boiler with a nice new fcu to replace the chaps 13 amp plug with twin and earth going to it with the earth cut off.

So back to the cooker point. So he will need a nice new 10mm 30 meter run. But then I cant do that because his old rubbish consumer unit wont have rcd protection so he will also need a secondary consumer unit with a RCD.
Much better to replace the whole thing with a nice new consumer unit.

Probably want the job done for fifty quid as well.

Looks like one to walk away from.

Many thanks

 

[Hawk81]

Once I came across a similar situation and it turned out that someone had joined into the feed to the cooker and fitted a FCU in the roofspace to supply the extractor fan.

 

[alanl]

Yes, it sounds like something else is connected to the circuit - it is rare to get a L - N insulation fault, as any screws/nails going through the cable would only touch L-E or N-E.
Also, any junctions boxes in the run that could have a build up of pigeon/mice poo etc, giving a low IR reading. Found one yesterday that was covered in pigeon muck in a loft, amazing how far it had got into the box.
Alan.*

 

[keniff]

If there's a load u cannot find try joining live and neutral together and insulation test between them together and earth see what reading you get

Sorry misread, that won't help on l-n fault lol

 

[i=p/u]

well thast what i was thinking , someones tapped off it. and for the rcd protection you could just extend cables or raise protection device (32A)to give you 5 seconds disconnection time.

maybe im wrong here but sure somone will say dont take this post on as its bull shat

 

[Goody]

A secondary CU, exclusively for the Cooker circuit with 30 metre 10mm cable run or simply walk (drive) away. :auto:

 

[Amp David]

Once I came across a similar situation and it turned out that someone had joined into the feed to the cooker and fitted a FCU in the roofspace to supply the extractor fan.

Seen this once too, JB in the loft with 1.5 T&E supplying a bathroom cabinet light!!!

 

[SPARTYKUS]

Once I came across a similar situation and it turned out that someone had joined into the feed to the cooker and fitted a FCU in the roofspace to supply the extractor fan.

I would put money on this esp. the reading is 0.2 Meg Ohms for example.

Assume nothing! is there an extractor bodged off the cooker circuit, or a hob ignitor? Or anything really.

 

[Goody]

I would put money on this esp. the reading is 0.2 Meg Ohms for example.

Assume nothing! is there an extractor bodged off the cooker circuit, or a hob ignitor? Or anything really.

I second that.

 

[telectrix]

or even next door's shower?

 

[SPARTYKUS]

or even next door's shower?

through the loft .... love it