Cabling for induction range cooker-a cautionary tale!

[HotCrossBunplease]

I’ve just had a fab new induction range cooker delivered. (Stoves brand)

It was replacing an existing Rangemaster installed 8 years ago as part of a full kitchen refurb. As the wiring was all done carefully and to regulations then, I rashly assumed that the new one could just be wired into the wall where the old one was removed.

Unfortunately my builder has just told me that we only have 6mm cabling from our fuse box (consumer unit) to the cooker circuit. The induction range has a much higher power load than my old gas hob/electric oven one, so I need 10mm cabling. And replacing that is not a 5 minute job as apparently 10mm is so much thicker than the 6mm that it can’t just be pulled through the same route that the 6mm wiring currently goes. He’s given me an electrician to contact to confirm but he’s pretty sure that connecting to the existing 6mm circuit will just trip the fuse.

NB the spec of the new cooker says Max power load 17.97-19.17 KW. Looking at the spec for my old Rangemaster, it was only 7.4 KW, a huge difference.

So my post is for 2 reasons:

1. to warn anyone getting a new cooker, particularly an induction one, to make sure you have the right wiring. I understand that 6mm in cooker circuits is quite common.
2. To ask if anyone else has had to upgrade from 6mm to 10mm and if there are any other issues I need to look out for?

I could send the cooker back but it is so lovely and I have my heart set on induction now ☹️.

Agreed. I’m sure it can be dealt with by an electrician and in a way I’m quite glad I don’t know in advance as I might have been put off buying it 😀

It was around £60 to get it fitted. Our electrician was a fireman and he is a fire risk assessment officer now.

If I were you, I would get three quotes from different electricians.

I think you would find it unlikely that someone would want to install it under those conditions. There is simply no upside to them doing so and plenty of downsides. But who knows. Hopefully an installer/electrician will be along in time to comment. In any case, the situation sometimes is never quite as dire as you think it is so it is worth getting an installer/expert to look at the problem and assessing what is possible and what isn't.

Thanks. It took me straight to page 2 which was all about Pampas grass and hot tubs, but I see what you were getting at 😀.

A 6mm cable can take 50-60 amps. You will only have a 32amp fuse in your consumer unit.. even if the cooker needs a 40amp fuse. In should be ok on 6mm. Im not an electrician amd one might suggest a 10mm and a 40 amp fuse. How many amps does the cooker pull ? Its a serious cooker if its trips a 32amp fuse.

The max rating is if everything is turned on full , but that’s unlikely to happen

our induction hob and cooker are on 13amp plugs on the kitchen ring. Iys never tripped yet. Its down to be rewired when we do the kitchen but still works fine.

Here is the spec

I remember being worried about the cooker red switch rating rather than cable size when I did the same. I changed from dual fuel range to a 90cm Stoves Induction range.

It was a 45A switch on a dedicated circuit, so the installer was happy to proceed. No idea of the cable size though.

Honestly OP, just speak to a qualified sparky on what is needed, not an internet forum. Its a big cooker, it needs a big supply straight to the board but a qualified sparky will tell you what is appropriate.

Does your house have enough power in to support it alongside other electrical usage?

For example we have upgraded our home to a 100amp supply as it only had 60 amp and we have a huge cooker plus a vehicle charger.

And by the way, your general builder won't know. He might think he does, but he won't.

@Ilovemyshed

I think you have misunderstood my reason for posting. I’m not asking the internet for advice. I said in my OP that I was speaking to an electrician. I also said that my builder had recommended specialist electrician advice.

I’m sharing my experience in case it benefits others, and asking if anyone else has encountered similar.

That kw figure on the spec sheet cant be right. If the cooker was using that much power it would need and 80- 100 amp fuse ????? The main service fuse on my house is only 60 amp !!!!!

He literally told me he didn’t. However it is his job to identify areas where additional specialist input is needed.

So your old hob/oven is probably fitted to a 32A breaker in your consumer unit (typical for a 6mm cable) - supports about 7.8kW I think. Easy to check visually though.

The max drawings on your range are:

Hob: 11kW (across all "rings")
Fan Oven: 2kW
Conventional Top: 1.4kw
Slow Cook: 0.17kW
Digital Oven: 3.1 kW (or Grill: 2.7 kW)

So if any combination of these tops 8kW your 32A breaker may trip.

Personally, I'd see if the electrician is willing to connect it to your existing wiring and see if it trips during normal usage, and upgrade the wiring only if you have issues (disclaimer, I'm not a sparky and up to speed on regs etc).

We changed from a free standing electric cooker with radiant rings,to double electric oven and 4 induction hob,we had to have new wiring 10mm and a new consumer unit, and,30amp fuse.

Thanks. We had a new consumer unit put in about 3 months ago so at least that part is already dealt with.

So the range is still sitting unconnected and only half unpacked in the kitchen.

Stoves customer service completely unreachable, line just disconnects after going through the menu. Online enquiry ignored.

I tried to call the retailer and was directed to a chatbot. It eventually directed me to fill in a form so I did that, and asked if they could call me to discuss an exchange to a less powerful appliance. They have instead emailed to say that they “have nothing in stock that can be connected to 6mm cabling”.

I find that hard to believe as their website includes the exact same dual fuel range that I just got rid of, after operating it without incident on my 6mm cable circuit for 6 years.

Next step is to get electrician to quote for 10mm cabling. I have 14 days to return the purchase if he says it’s impossible or quotes a crazy amount.

I am interested in the outcome !

Things I can think of that could possibly be issues :

Will the cooker isolator switch take the increased size wires and be rated high enough current ?

Will CU take an MCB big enough for the current and will that MCB take the increased wire size ?

From what I can tell CUs normally split into two separate circuits, each protected by an RCD. Will you need to swap out the RCD (often 63A) for a bigger one on the cooker circuit and if so will the CU take a 100A RCD (next size up I believe) ?

What main fuse rating do you have and will you need to contact the DNO to get a main fuse upgrade from current (maybe 63A) to 100A ?

Plus maybe more.

I did read some stuff on the net about how domestic circuits handle high currents and the concept of "diversity" which basically mitigates the supply contingency you need. However, it still looks to me like you will exceed the lower wire limit even taking this into account.

Anyway hopefully you can let us know what your electrician says. A learning experience.

Thanks @GasPanic , will be sure to update. Our main fuse is 100A, I checked that yesterday.

All the rest are good questions, but the original electrician (who was only consulted by phone previously) can’t come to our house till Tuesday so am now scrabbling about trying to find someone who can come sooner 🤯

Here’s the 100 Amp main fuse

I fear that the only question my husband wants to ask is “Which new gas range are we going to swap the induction for?”

But he never cooks so he doesn’t get to decide.

That's one bit of good news. The kind of bad news is that I think the DNOs often change them for free !

What’s a DNO?

I had my kitchen replaced in 2022, bog standard induction hob required full re-wire back to the fuse board which was old and not up to modern specs, was advised cost in the region of £1500 to rewire.

Distribution network operator. They are the people that own that fuse I believe.

Ah OK, like UK Power Networks? Thant’s right, they put that in for free. We had it upgraded from an old black one a couple of years ago. Why did you say it was bad news?

Consumer unit was replaced separately more recently.