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Manufacterer's advice/instructions

Been asked to connect up a used rangemaster all-electric cooker. No rating plate but model name is 'classic 90'. It has an induction hob.

Existing cable is 6.00mm on a 32A mcb.

Phoned the manufacturer who said it would be fine, since diversity could be applied but we would have to fit a cooker switch without a built in 13a socket and uprate the mcb to 40A.

I am a little troubled to say the least.

Comments welcome.

0 John Peckham over 5 years ago

`You cannot apply diversity to a single piece of equipment for sizing circuit protection and cable sizing. Diversity can be applied to individual items of equipment when considering the maximum load on a distribution circuit or an installation.

The cable and the circuit protection should be rated for the "Plated" load or the manufacturers instructions.
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0 broadgage over 5 years ago

John Peckham:

`You cannot apply diversity to a single piece of equipment for sizing circuit protection and cable sizing. Diversity can be applied to individual items of equipment when considering the maximum load on a distribution circuit or an installation.

The cable and the circuit protection should be rated for the "Plated" load or the manufacturers instructions.

In general I agree, but not in the case of cookers. A cooker typically consists of one or two ovens, several rings and perhaps a grill. The chance of all these components being fully utilised at the same time and for more than a couple of minutes is very small and an apparently undersized cable and MCB will almost always serve well.

If a single very large oven has a loading of 15KW then it needs a cable and MCB sized for 15Kw. If a cooker has a combined loading of 15Kw then it can use a smaller circuit.
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0 Former Community Member over 5 years ago

Remember that a cable (and a fuse or thermal element of an MCB) will take time to heat up - shove 50A or 60A down a 6mm² cable starting from cold and it'll take several tens of minutes to warm up to 70 degrees - by which time the oven thermostat will have started switching the oven off every few minutes and the pans will have started to boil and been turned down to a simmer setting. The '10A and 30%' rule has been used successfully for probably hundreds of millions of Christmas dinners by now (plus countless everyday meals) and seems to have been perfectly satisfactory.

How does 433.1 fare?

Regards

BOD
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0 Chris Pearson over 5 years ago

perspicacious:

How does 433.1 fare?

I thought that we were considering a big overload of short duration. ?

311.1
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0 Chris Pearson over 5 years ago

John Peckham:

You cannot apply diversity to a single piece of equipment for sizing circuit protection and cable sizing. Diversity can be applied to individual items of equipment when considering the maximum load on a distribution circuit or an installation.

The cable and the circuit protection should be rated for the "Plated" load or the manufacturers instructions.

Fair point!

If you were silly enough to turn on every single part of the cooker in one go, it would indeed draw gazillions of amps.

Problem in the OP is that there is no plate.

I fear that the problem is that one-upmanship encourages the manufacturers to declare the maximum possible power. However, it is perfectly reasonable for them to specify a smaller cable in the small print than may otherwise be expected.
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0 Former Community Member over 5 years ago

Is that the long and short of it Chris?

How long is the turkey in the oven for?!!!!!

Regards

BOD

PS check your PM.........!
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0 Chris Pearson over 5 years ago

perspicacious:

Is that the long and short of it Chris?

How long is the turkey in the oven for?!!!!!

Regards

BOD

PS check your PM.........!

Who said anything about fault conditions?

Don't know. I have never cooked one.

Back to the OP: what is the CSA of the cooker cable? That must give some indication as to the appropriate size of the fixed wiring.
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0 Former Community Member over 5 years ago

I fear that the problem is that one-upmanship encourages the manufacturers to declare the maximum possible power. However, it is perfectly reasonable for them to specify a smaller cable in the small print than may otherwise be expected.

And conversely, when I was doing a lot of pub PIRs (as they were at the time), it was quite usual to find an innocent looking twin basket deep fat fryer with two 13 A plugs prefitted when it was actually one appliance. The landlord saw nothing wrong with plugging it into the nearest double socket with the consequence of there being less than 3 kW left on the rfc in a very busy kitchen........

Regards

BOD
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0 Chris Pearson over 5 years ago

perspicacious:

And conversely, when I was doing a lot of pub PIRs (as they were at the time), it was quite usual to find an innocent looking twin basket deep fat fryer with two 13 A plugs prefitted when it was actually one appliance. The landlord saw nothing wrong with plugging it into the nearest double socket with the consequence of there being less than 3 kW left on the rfc in a very busy kitchen........

Let alone overloading the twin socket!
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0 Former Community Member over 5 years ago

Who said anything about fault conditions?

Ah, I was quoting out of the 17th: 433.1 "Every circuit shall be designed so that a small overload of long duration is unlikely to occur." and earlier editions echo the same.

My 18th isn't to hand so apologies if I've got the wrong Reg no.

Regards

BOD
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