Hob Tripping

[nrg]

Hi Guys

I have a customer that is having constant random tripping of their RCD. After quite a lot of investigation I have found two things.

1) There is a lighting track in the kitchen that has LED gu10 style fittings that glow slightly even when the light is switched off. It is a track system and having checked there is a voltage of 34v between earth and neutral.

2) If the hob is connected (not switched on or under load) and I run a loop test on the house main circuit the RCD trips. If I turn off the breaker for the hob the loop test comes back fine. 0.51. I know this is a little naughty but I turned the hob circuit back on and removed the earth for the circuit at the board. The loop test worked fine and showed @ 0.51. As soon as I connected the earth again and ran the loop test it tripped again. I carried out a IR on the circuit from the boards and got 138 ohms. I removed the hob completely and did an IR on the hob and got >299. So I ran another new cable from the board to the hob and did and IR with the hob connected and got 138ohms.

I have no idea what is going on now unless there is a problem with the hob. Do you think the randomness of number 1 could have anything to do with it ?

Any help or pointers would be appreciated

It's a 12way board protected with a RCD MainSwitch 30mA. TNS using suppliers outer sheath for earth. Ze 0.28

Adam

 

[rugbymacc]

have you checked the tripping current of the rcd ?

 

[Zeespark]

TNS + 30mA RCD main incomer? cant be correct surely???

AndyGuinness

 

[matt.leung]

You wil get funny IR results if testing the cable with the hob still connected. also does the cooker hob circuit have an isolation switch with a neon in it. If so this will also give you funny IR test results.

have u tried end to end continuity tests on the hob supply circuit cable (long lead)...?

 

[NozSpark]

Have you had a look at the wiring actually at the hob??

I replaced a Voltage operated ELCB for a RCD a few years ago and ended up finding....

This

and

this

 

[batty]

Have you had a look at the wiring actually at the hob??I replaced a Voltage operated ELCB for a RCD a few years ago and ended up finding....

This

and

this

Its a bu..er when manufaturers put the cables the wrong way round it confuses the diyers.

 

[Riggy]

TNS + 30mA RCD main incomer? cant be correct surely???AndyGuinness

Why can't it be correct?

 

[sparkytim]

BRB

Pg 39

314.1

 

[Riggy]

BRBPg 39

314.1

Apologies, didn't realise it was a new installation

 

[sparkytim]

Is this a new type Hob with electronic controls?

Had similar problems with high leakage current

If not then sounds like low insulation problem with elements.

 

[matt.leung]

have you tried connecting a different load on the end of the circuit, to see if the RCD still trips?

 

[SPECIAL LOCATION]

When I read the title of this thread I though it was some new drugs craze!

gotta try that Hob trippin.............

way out!

 

[nrg]

Hi Guys

Thanks or all the suggestions, can I clear a few things up.

* It's not a new installation it's about 8 year old. I queried that the whole system was covered by a 30mA RCD but having checked with my old man he said that's the way it was done by some sparks way back then !!!

* The RCD Trip current is 17mA

* I removed the Isolator and hard wired it ! Still the same issue

* Not tried another load, didn't have anything with similar characteristics

* The hob is about 4 years old and was installed at the time of putting the kitchen in.

It has electronic controls.

Since telling my customer to keep the hob isolator switched off, he has not had any more tripping issues. He is going to get an appliance engineer in to look at the hob.

I