New Cooker total Load 5.7KW - fuse rating ?

dak

I'm gettin a new Neff U15M52S3GB built in double oven next week ( replacing an existing De Dietrich) and just want to check the fuse rating.

Total Connected load is 5.7KW. From memory the Fuse Ampage is worked out by Load/Voltage = amp ie 5700w/240v = 23.75Amp fuse + 25% = 30Amp

I'm confused as one of the Websites selling this model has it rated as 20A.

Any Sparks that could explain ?

Thanks

Dak

2011

dak wrote: »

I'm gettin a new Neff U15M52S3GB built in double oven next week ( replacing an existing De Dietrich) and just want to check the fuse rating.

Total Connected load is 5.7KW. From memory the Fuse Ampage is worked out by Load/Voltage = amp ie 5700w/240v = 23.75Amp fuse + 25% = 30Amp

I'm confused as one of the Websites selling this model has it rated as 20A.

Any Sparks that could explain ?

Thanks

Dak

If you install a 20A B type MCB I would think that it will be suitable.
I don't know why you added 25%.
The full 5.7 kW load will only be applied while the oven heats up. A 20A B type MCB will not trip at 25A for quite some time. Once the oven is up to temperature the average current will be greatly reduced.

TPM

Is the purpose of the mcb/fuse not to protect the cable?

5700w/ 240v = 23.75A

Im not sure but I think 2.5 T&E is 25A,
the MCB should be rated below the max current rating of the cable
MCB are available in 20A, 25A and 32A
20 is below the cable max but also below the circuit design load
25A is not below the cable max so should not be used
Therefore a bigger cable size should be used

SO I would think the circuit should be
23.7s amp load-- 4sq T&E at (around) 35A max current protected by 32A MCB.

Its a long time since I did this and I am not sure of the cable ratings so I am open to correction

2011

TPM wrote: »

Is the purpose of the mcb/fuse not to protect the cable?

Yes.
But if Neff state that a 20A MCB is their recommendation then that is the optimum size.

The OP did not ask for a cable size or mention it so I did not mention it either.
However I agree that a 6 sq. T+E and a 4 sq. HR flex would certainly meet the requirements.

25A is not below the cable max so should not be used
Therefore a bigger cable size should be used

What cable max ???
Bigger than what ??

TPM

2011 wrote: »

Yes.
But if Neff state that a 20A MCB is their recommendation then that is the optimum size.

The OP did not ask for a cable size or mention it so I did not mention it either.
However I agree that a 6 sq. T+E and a 4 sq. HR flex would certainly meet the requirements.

Imo 20A MCB is too small for the load, if Neff said 10A I would assume it was a typo, same is possible of 20A.

Yea the cable size hadnt been brought up, I wasnt going to bring it up but it you cannot specify an MCB or fuse with out knowing it. And I was trying to give a (very) rough idea of the design requirements

2011 wrote: »

What cable max ???
Bigger than what ??

the 25A I refered to in relation to 2.5T&E (yes should have said is not below 25A the max current for 2.5T&E) my mistake

Bigger than the 2.5T&E that section referred to

TPM wrote: »

Im not sure but I think 2.5 T&E is 25A,
the MCB should be rated below the max current rating of the cable
MCB are available in 20A, 25A and 32A
20 is below the cable max but also below the circuit design load
25A is not below the cable max so should not be used
Therefore a bigger cable size should be used

SO I would think the circuit should be
23.7s amp load-- 4sq T&E at (around) 35A max current protected by 32A MCB.

Its a long time since I did this and I am not sure of the cable ratings so I am open to correction

Things always seem clearer in my head, I dont get them down too well some times

Bruthal

TPM wrote: »

I
Things always seem clearer in my head, I dont get them down too well some times

I know the feeling.

2011

TPM wrote: »

Imo 20A MCB is too small for the load, if Neff said 10A I would assume it was a typo, same is possible of 20A.

Have a look at the fusing characteristic for a 20A MCB and you would see that Neff did not make a typo.

Also remember this is a double oven, so the load will only be 5.7 kW with both ovens on until one of the stats kicks in.
According to the graph in the link above a current of that magnitude (less than 20% above the rating of the MCB) would not trip a 20A MCB for at least an hour. Within 1/2 a hour one of the stats would have switch off reducing the load to less than 20A.

Yea the cable size hadnt been brought up, I wasnt going to bring it up but it you cannot specify an MCB or fuse with out knowing it.

Normal practice is to select the protective device and then to size the cable, not the other way around.
I would agree that it is not good to install an MCB on a cable when you do not know the cable size, it is just that the OP asked something specific.

Things always seem clearer in my head, I dont get them down too well some times

Me too

M cebee

i wonder does that double oven have 3 heating elements
i wouldn't have thought they'd specify 20amp for 2 elements