2 hobs on a 6mm radial ????????

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rafsparkboy

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Hi guys,,

Can i install 2 x 6kw electric hobs on a 6mm radial circuit....ie a 6mm tail from each hob ( they are next to each other) going to the cooker outlet ( tight squeeze i know !!! ) . Both being isolated from the 45a cooker master switch on the wall, 30cm away...

havent got my book handy to look up diversity etc etc.....

Bloody kitchen fitters !!! they didnt tell me they were fitting 2 hobs, kitchen all tiled and flooring done !!!!!!!!!

cheers in advance

 
Hi guys,,Can i install 2 x 6kw electric hobs on a 6mm radial circuit....ie a 6mm tail from each hob ( they are next to each other) going to the cooker outlet ( tight squeeze i know !!! ) . Both being isolated from the 45a cooker master switch on the wall, 30cm away...

havent got my book handy to look up diversity etc etc.....

Bloody kitchen fitters !!! they didnt tell me they were fitting 2 hobs, kitchen all tiled and flooring done !!!!!!!!!

cheers in advance
Both on full whack 52A

Unlikely to need all that at once all on full

mmm

 
6000watts divided by 230volts = 26.09 Amps, so that makes 52 amps in total, now if my regs book is correct (red one ;) page 286 ) table 4D2A Multicore 70 degree thermosetting sheathed cable says a 6mm cable can take 46 amps so i would have to say NO as 52 into 46 = MELTING :^O :^O:^O:^O:^O

either 2 x 4mm or 2 x 6m cables need running in ;)

 
Sure i read somewhere about 100% demand/load of the first heating appliance and then a lower % for the second appliance.........not got my book handy ????

 
6000watts divided by 230volts = 26.09 Amps, so that makes 52 amps in total, now if my regs book is correct (red one ;) page 286 ) table 4D2A Multicore 70 degree thermosetting sheathed cable says a 6mm cable can take 46 amps so i would have to say NO as 52 into 46 = MELTING :^O :^O:^O:^O:^Oeither 2 x 4mm or 2 x 6m cables need running in ;)
but if the MCB is rated for the cable, the worst thatll happen is some nuisance tripping if both happen to be running full at the same time, which is unlikely. even if all hobs are on full, chances of them all drawing power at the same time is small

 
Sure i read somewhere about 100% demand/load of the first heating appliance and then a lower % for the second appliance.........not got my book handy ????
I'm in Badgers camp on this one, 2x hobs have been asked for by the client, so we have to presume they intend to use them at the same time or why would they have them, 2x cable runs IMHO

however based on the OSG, for diversity in domestic dwellings we have 10A+30% of fl in excess of 10A, which = 2.3kW+2.9kW= 22.65A (assuming 30% full load above 10A), having said that, should you treat this as more akin to a guest house, where you would more likely encounter two hobs?, for that it's 100%+80% = 10,800kW or 46.96 amps load, so 47A cable is too close for comfort

And just suppose at some stage in the future your installation fails under load, (at a peak time Xmas?) consider this, 1) you are protecting the client 2) protecting yourself since your name will be on the EIC

Robojin

 
You're not telling me that 6mm cable destructs at 47.1A! That's a safe working load.

10 minutes getting a load of pans boiling isn't going to melt the cable. May overload the MCB tho

I should have thought

 
I'm in Badgers camp on this one, 2x hobs have been asked for by the client, so we have to presume they intend to use them at the same time or why would they have them
A neighbour of ours has a similar arrangement and neither of them can cook more than a boiled egg :^O :^O:^O

The twin hobs are purely one-upmanship - they don't know how else to waste their money. They would be unlikely to trip a 10 amp MCB. :^O

 
You're not telling me that 6mm cable destructs at 47.1A! That's a safe working load.
Patch, no I guess we all assume the cable ratings are real safe numbers, perhaps 60-70% of the real load? :D , but if something fails catastrophically and the finger wagging starts, out will come the Red book, which is of course gospel in the eyes those who should be obeyed! ; \

Having said that the diversity load looks like 23A to me based on the OSG :)

 
Patch, no I guess we all assume the cable ratings are real safe numbers, perhaps 60-70% of the real load? :D , but if something fails catastrophically and the finger wagging starts, out will come the Red book, which is of course gospel in the eyes those who should be obeyed! ; \Having said that the diversity load looks like 23A to me based on the OSG :)
:) so red book happy then (I do take your point tho!)

 
A neighbour of ours has a similar arrangement and admin couldnt cook more than a boiled egg :^O :^O:^OThe twin hobs are purely one-upmanship - they don't know how else to waste their money. They would be unlikely to trip a 10 amp MCB. :^O
:eek:

 
Hi guys,,Can i install 2 x 6kw electric hobs on a 6mm radial circuit....ie a 6mm tail from each hob ( they are next to each other) going to the cooker outlet ( tight squeeze i know !!! ) . Both being isolated from the 45a cooker master switch on the wall, 30cm away...

havent got my book handy to look up diversity etc etc.....

Bloody kitchen fitters !!! they didnt tell me they were fitting 2 hobs, kitchen all tiled and flooring done !!!!!!!!!

cheers in advance
Obviously yes you can probably physically connect it up.

PUT it on a 40amp MCB

max 9200 watts 2800w short of max full load though

advise customer it may pop if they stick everything on! :(

if they don't want it popping... give quote for new cable! ;)

Each hob diversity 10a + (30% 16a) = 15.3 amp

total both with diversity 31 ish maps?

may just run..

AS LONG AS CORRECT MCB..

all that will happen worst case is....

power trip off half way though cooking big dinner!

BUT main questions...

what sort or premises is it?

how many people are there who are likely to simultaneously have every thing switched on?

What about OVENS?

are there any? Gas or Electric?

what about the overall MAX demand of the installation

i.e. how many electric showers.. other high power kit???

 
Great replies guys..........the situation is :

7 bedroom student property with 1 kitchen....the cable run is only 4m from cu to cooker master.

in reality students probably dont even know how to switch a hoover on let alone a cooker with variable controls !!!

And there is a `Subway ` 100m down the road !!

 
Great replies guys..........the situation is :7 bedroom student property with 1 kitchen....the cable run is only 4m from cu to cooker master.

in reality students probably dont even know how to switch a hoover on let alone a cooker with variable controls !!!

And there is a `Subway ` 100m down the road !!
Change the double hob to a Mikky wave job solved.

 
Have I missed something here but is diversity not supposed to be use to make sure the max demand of the WHOLE install is under the DNO's fuse rating.

Individual cable's and protective devices should be sized for the full expected load when designing, diversity has nothing to do with this stage of design.

The only way this circuit should go live is if the MCB is rated at less than the cable rating including any factors for the way it is installed (surface, buried etc.)

 
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