Induction hob for preexisting 4mm T+E

[Jackster]

I have been told by a local spark that one can not run an induction hob on a 4mm T+E.

From my understanding, most induction hobs are 7-8kW and "require" 6-10mm T+E but our housebuilder only put 4mm because they are cheap.
Or maybe I am cheap for not coughing up £500 for a £150 induction hob "upgrade" when we bought...

Anyway, there is a 4mm T+E installed and I don't want my local spark coming and running new cable in my new build house. CBA with the mess.

I am aware of the 13amp ones but after using a full-power one at my old house, doubt a 13amp one will suffice my expectations.

So are there any mid-powered induction hobs models out there that can run on 4mm?

Note that a 2kW oven will have to be moved onto the kitchen circuit if I get this done.
We have a microwave, dishwasher, washing machine, kettle and Foodi Ninja (2kW pressure-cooker/grill machine).
All these devices won't be on at the same time so this should be okay on the kitchen circuit? B32 breaker in the CU.

Also, if 4mm should not be used on 32amp equipment. Why did my house builder put the 4mm T+E on a B32 breaker?

 

[Ian1981]

6 mm for a cooker circuit is a throw back to the older 3036 fuses, where 6mm on a 30 amp fuse was the norm as it dealt with the issue of the fusing factor of the 3036 fuses being 2 rather than 1.45 , I2 < 1.45 Iz.
So a 6mm for a cooker circuit has just been recycled down the line without any thought on actual design.
Considering that a 15kw load is fine for a 32 amp mcb with diversity taken into account, 4mm is quite adequate for a cooker circuit, obviously if the calculations allow it, the same as any other selected conductor.

 

[davesparks]

Its been done for decades, everybody knows a dedicated 32amp cooker circuit should be run in 6mm minimum.

But everybody knows that a 32A socket radial should be 4mm, so what's the difference? Same size OCPD, same calculation, different cable size?

'everybody knows' isn't always correct, it can just mean that a lot of people are wrong.

6mm is traditionally used for cooker supplies yes, but that is out of tradition, not calculations. It harks back to the imperial cable sizes where the size used for a 32A radial was nearer to 6mm and so people just started using 6mm.

 

[7029 dave]

@7029 dave , I would install 32A on 6mm too, just because it's always done that way. But I often wonder why? I could see 6mm being necessary for voltage drop concerns, or if using rewireable fuses. In the absence of these, and assuming method C, why wouldn't a 4mm conductor suffice?

The OP stated it is a new build so method C is out the window we have been told that, which will reduce the CCC thats why 4mm wont suffice.

 

[Ian1981]

The OP stated it is a new build so method C is out the window we have been told that, which will reduce the CCC thats why 4mm wont suffice.

Why is method C out the window?
Our company do new builds, method C is common to a lot of the circuits installed

 

[7029 dave]

But everybody knows that a 32A socket radial should be 4mm, so what's the difference? Same size OCPD, same calculation, different cable size?

'everybody knows' isn't always correct, it can just mean that a lot of people are wrong.

6mm is traditionally used for cooker supplies yes, but that is out of tradition, not calculations. It harks back to the imperial cable sizes where the size used for a 32A radial was nearer to 6mm and so people just started using 6mm.

I would use the term common sense other than tradition, out of interest given the info we have, what size cable would you select.?
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Why is method C out the window?
Our company do new builds, method C is common to a lot of the circuits installed

My understanding is that is a surface install.

 

[Ian1981]

I would use the term common sense other than tradition, out of interest given the info we have, what size cable would you select.?
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My understanding is that is a surface install.

No it’s cables clipped to a surface embedded in plaster as detailed in the installation methods in appendix 4

 

[pc1966]

Doh, I just double-checked the oven and it is 2,075 watts not 1900 watts.

Really that won't make any practical difference!

While it is recommended not to put any fixed loads over 2kW on a ring final circuit, a 13A socket is theoretically OK to 3kW but just don't use two heavy loads on a double socket as they are only rated to 20A (not the 26A expected from 2 * 13A outlets).