Using pre installed cooker circuit for 13amp or 16amp oven. (2)

[winston1]

Once again the MODS have censored me from answering on the original thread WHY, WHY, WHY?

SUNRAY wrote: All I've stated is:
1) Under fault conditions with an element shorting to earth the fault current could be anywhere from the original rating of the element to the full potential earth fault current (could be thousands of amps)


Indeed, but not for long with a correct installation fitted with a RCD (any type) it would trip above 30mA.

 

[JohnW2]

Once again the MODS have censored me from answering on the original thread WHY, WHY, WHY?

One of life's mysteries, perhaps? I'm sure the clue will be in what you posted there (which I imagine will no longer be visible to us).

 

[SUNRAY]

Once again the MODS have censored me from answering on the original thread WHY, WHY, WHY?

All I've stated is:
1) Under fault conditions with an element shorting to earth the fault current could be anywhere from the original rating of the element to the full potential earth fault current (could be thousands of amps)

Indeed, but not for long with a correct installation fitted with a RCD (any type) it would trip above 30mA.

And all I did was put forward a scenario where there wouldn't be a RCD:

Are you saying this is not correctly installed?
I see no nasties, no signs of heat, no incorrect copper showing. In fact it's quite a tidy fuse box for its age.

Admittedly it's not to the latest regs...

Actually, urm, hang on a minute, as has been mentioned before; "complies with previous edition" is in the current regs. So it is actually correctly installed as far as I can see.

 

[JohnW2]

And all I did was put forward a scenario where there wouldn't be a RCD: ...

I think you will find (or would be able to find, had it not been removed!) that it was a very familiar looking message (including the usual image) about "MIs being wrong" which impaired winston's ability to continue posting to the other thread

Kind Regards, John

 

[winston1]

Once again the OP of the original thread has asked:

"Yes it's a domestic kitchen there is already a dedicated circuit with 6mm cable going from 32mcb to 45cooker switch then 45a cooker connection plate then 6mm cable to cooker. But we are getting a smaller single oven which is only 16amp but need be hardwired. So should I change 32mcb to 16mcb I'm consumer unit or just get electrician to wire it straight into connection plate with cable supplied".

So yet again OP if you are looking at this thread.

NO you don't need to change the MCB. It's purpose is to protect the 6mm cable not the oven on the end of it. The oven cannot draw more than its rated value. Any element fault (to earth) will trip the RCD which I hope you have. If not your money and time would be better spent getting an RCD fitted.

 

[bernardgreen]

The oven cannot draw more than its rated value.

Winston overlooks a possible cause of over current

A Live to Neutral fault will mean the oven will draw more than its maximum rated current

 

[SUNRAY]

And once again winston has offered incorrect advice

Once again the OP of the original thread has asked:


"Yes it's a domestic kitchen there is already a dedicated circuit with 6mm cable going from 32mcb to 45cooker switch then 45a cooker connection plate then 6mm cable to cooker. But we are getting a smaller single oven which is only 16amp but need be hardwired. So should I change 32mcb to 16mcb I'm consumer unit or just get electrician to wire it straight into connection plate with cable supplied".
And once again winston has offered incorrect advice
So yet again OP if you are looking at this thread.

NO you don't need to change the MCB. It's purpose is to protect the 6mm cable not the oven on the end of it.
And once again winston has offered poor advice
The oven cannot draw more than its rated value.
And once again winston has offered incorrect advice
Any element fault (to earth) will trip the RCD which I hope you have. If not your money and time would be better spent getting an RCD fitted.

 

[SUNRAY]

I think you will find (or would be able to find, had it not been removed!) that it was a very familiar looking message (including the usual image) about "MIs being wrong" which impaired winston's ability to continue posting to the other thread

Kind Regards, John

I don't know if you saw my reply but I had a PM £5 bet that the 16A fcu chestnut would be posted by 9am, sadly I lost by an hour or 2.

 

[SUNRAY]

Winston overlooks a possible cause of over current

A Live to Neutral fault will mean the oven will draw more than its maximum rated current

winston1 overlooks all sorts, especially common sense and experience and also dare I add competancy.

 

[winston1]

And once again winston has offered incorrect advice

THAT IS A LIE.

I never give incorrect advice.

A standard cooker circuit is 32 amp. If a cooker is in 2 parts, oven and hob, a 32 amp circuit is still used. If one of the 2 parts is not it makes no difference.

An over cannot draw more than its rated current. No one has yet explained how a live to neutral fault would occur. An element failure will invariably be live to earth which will trip the RCD at around 30mA.

Much of this has been explained in the original thread by various people.

 

[bernardgreen]

No one has yet explained how a live to neutral fault would occur

There would be no point in explaining it you as you seem incapable of learning.

But for other readers.... Some heating elements are bifilar and insulation failure can create an over current fault without the Earthed casing being involved.

 

[JohnW2]

But for other readers.... Some heating elements are bifilar and insulation failure can create an over current fault without the Earthed casing being involved.

As often discussed, that is the one sort of scenario in which something like a heating element can theoretically result in a 'non-negligible-impedance' L-N fault (i.e. an 'overload', rather than 'fault', current), without involving anything earthed. However, I suspect that is an incredibly rare occurrence.

Kind Regards, John

 

[SUNRAY]

THAT IS A LIE.

I never give incorrect advice.

A standard cooker circuit is 32 amp. If a cooker is in 2 parts, oven and hob, a 32 amp circuit is still used. If one of the 2 parts is not it makes no difference.

An over cannot draw more than its rated current. No one has yet explained how a live to neutral fault would occur. An element failure will invariably be live to earth which will trip the RCD at around 30mA.

Much of this has been explained in the original thread by various people.

winston1!

Please answer one simple question. If you are designing a circuit and conclude that 1.5mm² cable is the correct cable to use, what size MCB does it require?

 

[bernardgreen]

However, I suspect that is an incredibly rare occurrence.

I was talking to a person last night about the traffic management plan for an event. This was in the open air outside the gates of his house.

One of my concerns is that if a bus broke down in the access lane then traffic would be a standstill until the bus was recovered out of the lane.

It would be very difficult to recover the bus without a recovery truck on standby. The organiser thought the risk of a bus breaking down was very small and could be ignored.

I had to bite my tongue and not remind him that when he came out to meet me the electric gates across the drive would not open and he had to climb over the wall.

How often do electric gates fail to open ? Very seldom according the the person.

As I drove off he was still trying to get the gates open to get back to his house without the embarrassment of climbing over the wall.

 

[JohnW2]

... It would be very difficult to recover the bus without a recovery truck on standby. The organiser thought the risk of a bus breaking down was very small and could be ignored. .... I had to bite my tongue and not remind him that when he came out to meet me the electric gates across the drive would not open and he had to climb over the wall. .... How often do electric gates fail to open ? Very seldom according the the person.

The risk/probability of some events is obviously very small. What we (and those who 'regulate' us) have to decide is where to draw lines.

It always rather amuses (and, in some senses, saddens) me if I discover that someone concerned about some risk of incredibly low probability (whether in relation to an electrical installation of anything else) is someone who smokes, drinks appreciable amounts of alcohol, is obese or ..... !!

Kind Regards, John