Faulty cooker or supply?

[ImayKnow]

Could one of you electricians possibly please advice on this:

http://www.diynot.com/forums/appliances/faulty-cooker-or-supply.366142/

 

[Iggifer]

what kind of fuseboard do you have?

Fuses or an RCD/MCB combo?

And by the wall switch, do you mean something like this:

 

[RF Lighting]

It certainly sounds like a supply problem. My guess will be a failed isolator, or connection to it.

With the cooker circuit isolated at the consumer unit, carefully remove the isolator and if possible, upload a photo of what you find onto here for us to take a look at.

 

[ImayKnow]

It's the switch type rcds and the switch is more like this (not identical but similar):



http://www.screwfix.com/p/mk-2-gang-45a-cooker-switch-with-13a-switched-plug-socket-neon-white/25231

 

[Taylortwocities]

It sounds like a loose connection, somewhere. As soon as a load is applied, the connection fails.

Could be in the fuse board, in the switch or at some hidden and dodgy connection.

 

[securespark]

Yeah, or it could be a burnt-out neutral with enough of a connection to run a neon, but not anything with more grunt.

 

[ImayKnow]

Cheers guys, I talke it they are supply side problems, rather than the cooker? I am trying to prevent calling out a sparky only to find it was the cooker at fault!

 

[ImayKnow]

There is a forum entitled 'appliances' where I initially posted this topic, but nobody replied so I thought I would see if the electricians could offer any help, which they very kindly did when I posted a link back to the original post. Now the moderators are moaning that I have done this - WHY - it has enabled me to get some valued responses?

Moderators please apply a little bit of common sense.

Any way whinge over!

It has been mentioned that the fault could lay with the neutral, is there any way I can test this on the mains with a multi meter where the cooker cable connects to the wall?

Thanks

 

[securespark]

You could check with a multimeter where the connections come into the cooker.

Check between L&N, L&E and N&E and post the results here.

 

[ImayKnow]

Cheers SP. what settings do I want to be on?

 

[DetlefSchmitz]

You want volt a.c. at least 250V. The measurements may not help unless you have the cooker switched on at the time.

 

[Porque223]

You want volt a.c. at least 250V. The measurements may not help unless you have the cooker switched on at the time.

And using the calculated resistance of the cooker and your 230v supply voltage you can calculate the resistance of the connecting wires.
More than 1/2 ohm probably means a bad connection somewhere upstream.

I use a 1500W hair dryer to load suspect wiring but you need to know the wire diameter and distance back to the panel to know how much the voltage should normally drop at the appliance. For us it's supposed to be less than 5%.

What is the wattage rating of your cooker?

 

[Spark123]

A cold cooker element has a lower resistance than when it is hot so the maths might get a bit difficult!
Without going too far into it, as the neon indicator is going out when loaded then it will be a fault on the cooker circuit. Isolators don't last forever so is a good place to start looking. It could also be a damaged cable or a fault in the consumer unit.

Unless you know what you are doing as taking live voltage measurements is dangerous (can lead to shock or burns if you do it wrong) then it may be a good time to call in an electrician.

 

[ImayKnow]

Cheers guys. Point taken about getting in an electrician.

 

[Porque223]

A cold cooker element has a lower resistance than when it is hot so the maths might get a bit difficult!
Without going too far into it, as the neon indicator is going out when loaded then it will be a fault on the cooker circuit. Isolators don't last forever so is a good place to start looking. It could also be a damaged cable or a fault in the consumer unit.

Unless you know what you are doing as taking live voltage measurements is dangerous (can lead to shock or burns if you do it wrong) then it may be a good time to call in an electrician.

For Nichrome it's maybe 10% less when cold. Some of these elements level out the power for changes in voltage.

A go/no-go test for closed relay contacts is >0.1v = bad and <0.03v = good. Switch contacts probably close with greater force so the contact resistance may be lower than for relay.
I must have a half dozen switches in the basement so if I pass 10A through all of them in series I should get a good idea of the variation in closed contact voltage drop for good switches, average value and standard deviation.