Oven cable melted cable and casing - can't work out why

[SashaWu]

Good Morning,

Recently got a new oven - hooked it up the same as every other oven I've had. However the live wire seems to have melted, melted the plastic casing and blown the fuse.
https://i.Upload the image directly to the thread.com/bnOJTEW.jpg

Any thoughts?

 

[Wilko]

Hi - my thought is the L (red) has overheated, melted its insulation and likely the insulation on the green earth wire and created a short circuit which has blown the fuse. Or not, as it's hard to be accurate from just a pic, sorry. The question is why did it happen? A poor connection, an undersized cable for the load or a faulty oven are some reasons.

 

[SashaWu]

Thanks for your time and thoughts,

Sorry - I should have stated that the earth wire is unaffected, it's completely clean, I just moved it over a bit for the photo to get a better angle.

The thing is - this is the exact same setup as the previous oven, even down to the plastic cable box. The cable has been use for an oven for years.

 

[marconi]

Can you provide a picture of the rear side of the connector block?

 

[Pete999]

Loose connection?
What size in KWs is the cooker?
What size is the cable?
What size is the Fuse / Circuit breaker?

 

[Lucien Nunes]

The connection was insecure and of high resistance; the heat has melted the plastic housing and probably allowed the terminal to short-circuit to the metal casing. It's not clear whether your side of the connection was at fault or the internal one(s) hence Marconi's question. From the pattern of burning, I think it's your connection.

Common causes are crossed threads - the nut feels tight but isn't clamping the cable or cable not in position so that it creeps out from under the washer. Did you give it a good tug-test after fitting?

 

[Octopus]

Unless you tell us the rating of the oven and the cable size we are merely guessing

 

[Phil Thompson]

Id have gone with Lucien on my diagnosis.

 

[marconi]

I have enlarged the image you provided and can see what might be interpreted as a few strands of the red conductor which have been cut back to where the insulation ends. Thus there might have been a reduction in conductor cross sectional area. This would cause both an increase in current density and resistance - contributing to higher Ohmic heating (IsquaredR).

Is this the case?

The cable has a single CPC conductor and stranded live conductors so looks like 4 or 6 mm2 T/E.

Murdoch is spot on - we need to know the power of the oven, type of oven and size of cable.

 

[derek]

Was the appliance connected by a competent person as per the instructions on the oven?
It is easy for the unskilled to miss what would be obvious to a more experienced person and good termination of electrical equipment is a skill in itself.