Two cooker hobs on one circuit (HELP)

[sparky1508]

Hi all

I am new on here and was wondering if it is possible to have to hobs on one circuit( side by side ). They are between 6.6 and 7kw depending which ones i go for. just wondering if i need to uprate the cable(not sure whether its 6mm or 10mm yet) if its only 6mm and also if i might need to upgrade the MCB on the consumer unit. Any advice would be greatly appreciated.

Thanks in advance

 

[PrenticeBoyofDerry]

A circuit rating exceeding 15A but not over 50A, can supply two or more cooking appliance if installed in the the same room.
If diversity was applied it could be possible, but the fact you need two hobs suggest that there could be overload issues when using diversity.
7kW and 6.6kW on individual circuits would need a 32A breaker 4.00 T&E can carry that current safely providing no issue over distance and route of cable.
If you combined the two then you are looking at 61A again distance and route would be a factor but a 10mm T&E can carry 64A. But this will be over the 50A maximum.
I would be concerned over the demand of your system though.
What is your supply fuse size/rating and what is your isolator rated at, also what circuits are currently on the board?

 

[Stoday]

Do your two hobs total 6.6 or 7kW? Or are they each 6.6 or 7kW?

I have two Domino hobs on one 32A circuit, no problems since a NICEIC electrician installed them 5 years ago.

 

[sparky1508]

Thanks for the reply, i'm not sure about the supply rating(i'm assuming you mean the main supply fuse) also unsure about the mcb on the cooker circuit. There is quite a few circuits on the CU as it is a big house with an extension so about 4 or 5 circuits for rings and about 3 for lights plus cooker and i'm sure there is a shower in the property too( maybe 2 ).Will have to do some more investigating to find out what is what on the whole CU. Thanks

 

[sparky1508]

Do your two hobs total 6.6 or 7kW? Or are they each 6.6 or 7kW?

I have two Domino hobs on one 32A circuit, no problems since a NICEIC electrician installed them 5 years ago.

They are 6.6 or 7kw each, 2 x 4 ring hobs.

 

[Taylortwocities]

You need to do some demand calculations on the existing installation before just bunging on and extra 13KW.

Although diversity may save your bacon on the hobs, you cannot do the same with those two instant heat showers .

I think you need to go away and collect a lot more information as asked for above and come back.
Who knows, there may be a three phase supply?

 

[sparky1508]

Ok so the CU has cooker on 32 amp mcb,immersion on 16 amp mcb, 3 lighting circuits on 6 amp mcb each and 5 ring mains circuits each on 32 amp mcb's. Couldn't get to the main fuse as couldn't get at the meter. The existing stove top and oven/grill i think are both on the cooker mcb but can't be certain as there is a cable(2.5 ring) that leads behind the cooker and i'm unsure where it goes. one thing i know for sure is the oven/grill IS on the cooker mcb. 3 showers in the house and no mcb for showers so assuming they are all mixer showers.

 

[PrenticeBoyofDerry]

So the three showers are not electrical.
I reckon you have a demand of about 133A. The mains fuse will not be greater than 100A could be 80 or even 60A. Although it highly unlikely your load will take a 100A out. Adding another 61A to the circuit could be a little naughty!

 

[sparky1508]

its not adding another 61 amps as there is already a ceramic hob installed which i would guess is between 6kw and 7kw so adding another hob of about 7kw would only add 29 amps(feel free to correct me if i'm wrong). also most of the ring mains circuits only supply 2 or 3 rooms which most sockets only running lamps apart from the family room which has 3 pc's and all the gadgets that go with a TV plus kitchen stuff on a separate ring with only 1 other room. Yes all showers not electrical and if they are they must have been spurred into ring somehow but all 3 showers have got mixer valves with hot and cold going in.

 

[PrenticeBoyofDerry]

I have already applied diversity to my calculation and that will take in to account only 40% of the full load of 4 of the 5 ring final circuits.
If you are as stated only adding on extra hob. Then the 61A will need adjusting to the value of your existing hob plus 30.5A
So the total maximum demand after diversity would be something like 103A

 

[sparky1508]

ok so here is another plan!!!!!!
At the moment there is a surface mounted grill type appliance 2.4kw which is wired into a fused switch which is part of the ring main for the kitchen.Is it possible to change the existing 4 ring hob for a new one therefore not adding any more to the cooker circuit and change the grill type appliance for a 2 ring hob rated at about 3kw. Surely that isn't going to put too much load on any of the circuits as they have been that way for years with no problems at all??????????

 

[ban-all-sheds]

Do the people employing you as a qualified professional know that you're having to ask on a DIY advice forum how to do the job?

 

[sparky1508]

There is nobody employin me as a professional but they do know i'm not an electrician nor do i pretend to be and i do not intend to do the work as it is notifiable work and has to be signed off by someone who is part P registered. I have told them that they will need an electrician to do the work but they have asked me to find out what is possible.They are very busy people and work away from home alot so not always easy for them to sort stuff themselves.Thats why i'm trying to get some info for them before they start having time off work for sparky visits and the like.Not once have i given the impression that i am going to be doing this work just asking for advice thats all.