Single oven and induction hob both on 13a plugtop - connection

[Spreadsheetman]

I’ve got a 32a 6mm2 cooker supply in the re-wired kitchen which I plan to use for the single oven and induction hob. Both of these are 13a plugtop devices. The cooker isolator terminates in a 6mm2 t&e cable behind the units.

 

My thinking is to use 6mm2-capable wagos (773-173) in a Wagobox to split into 2x short 2.5mm t&e each connected to a single 13a socket in a pattress box in the back of a cupboard either side of the oven+hob.

 

Any of the sparkies on here know if that is acceptable under the regs?

[ProDave]

An induction hob on a 13A plug will be very disappointing.  Are you sure that is not just there as a test lead?  What do the instructions say?

[Mike]

13 minutes ago, Spreadsheetman said:

6mm2-capable wagos (773-173) in a Wagobox to split into 2x short 2.5mm t&e each

Not a sparky, but AFAIK you can't reduce cable size unless you have a fused connector to separate the different cables.

 

12 minutes ago, ProDave said:

An induction hob on a 13A plug will be very disappointing

+1.

[Spreadsheetman]

12 minutes ago, ProDave said:

An induction hob on a 13A plug will be very disappointing.  Are you sure that is not just there as a test lead?  What do the instructions say?

No, that is how they are (Bosch series 2 - a load of the Bosch and Neff hobs are like that). I fired it up for testing and it was pretty good for the kind of use we will put it to I.E. 95% of the time only 2 pans simmering.

 

You could cut the plugtop off and set the power to 16a in the config, but then I’d have to find some way of adding protection in-line.

[Spreadsheetman]

7 minutes ago, Mike said:

Not a sparky, but AFAIK you can't reduce cable size unless you have a fused connector to separate the different cables.

 

+1.

Yes, but the 13a plugtop intrinsically limits the current pulled via the 2.5mm2. There is a tiny chance of a cable fault sufficient to melt the 2.5mm2, but not trip the 32a type B mcb in the board, but I’d reckon that is very unlikely.

 

I have had an electrician suggest just cutting the plug tops off and connecting the cables together into the 32a! (and I have seen that done by a kitchen fitter using a bit of choc-block)

[Mike]

6 minutes ago, Spreadsheetman said:

Yes, but the 13a plugtop intrinsically limits the current pulled via the 2.5mm2

You can wire your power outlets in 6mm² (if the wires will fit) and plug in a 13A plug, but the regs don't permit you to reduce the cable size between consumer unit and outlet except via a fused connector.

 

Edited February 9, 2023 by Mike

[ProDave]

Set the hob to the highest power it can go, connect the hob (with a suitably larger cable) and the oven, both hard wired to a dual flex cooker outlet from the existing feed.

 

https://www.tlc-direct.co.uk/Products/AA45DCOP.html

[Spreadsheetman]

2 minutes ago, Mike said:

You can wire your power outlets in 6mm² (if the wires will fit) and plug in a 13A plug, but the regs don't permit you to reduce the cable size between consumer unit and outlet except via a fused connector.

 

I think I’m unlikely to get 2 x 6mm2 into 13a socket terminals. I could use wagos to split the cable to the 2 sockets though, 1 x 6mm2 usually fits a 13a. That’s probably the most compliant solution.

 

I could always stick a 2-module DIN enclosure with 2x 16a or 13a breakers in a cupboard to feed the appliances if I wanted to run 2.5mm2 and allow the hob a bit more current by hard-wiring it.

[Mike]

16 minutes ago, Spreadsheetman said:

I could always stick a 2-module DIN enclosure with 2x 16a or 13a breakers in a cupboard to feed the appliances if I wanted to run 2.5mm2 and allow the hob a bit more current by hard-wiring it.

I think that's your solution. No doubt a sparky will be along to confirm.

[Temp]

1 hour ago, Spreadsheetman said:

I’ve got a 32a 6mm2 cooker supply in the re-wired kitchen which I plan to use for the single oven and induction hob. Both of these are 13a plugtop devices. The cooker isolator terminates in a 6mm2 t&e cable behind the units.

 

I think it's possible to extend the 6mm^2 into the back of a cupboard to one side. There fit a switched double socket. The 13A plugs on the appliances are fused so that protects their cables. 

 

The double socket should be accessible but many people have them at the back of cupboards. 

 

The 6mm^2 needs extending correctly but I think it can be done with the appropriate sized connector blocks in a recessed box. 

 

Are the leads on the appliances too short to do this?

 

Check what your electrician says about this.

[andyscotland]

14 minutes ago, Temp said:

 

I think it's possible to extend the 6mm^2 into the back of a cupboard to one side. There fit a switched double socket. The 13A plugs on the appliances are fused so that protects their cables. 

 

I believe, unless it has changed since I trained, that BS1363-2 double socket outlets are officially rated at 13A across the pair, and are tested to 20A (16A one side and 4A the other).

 

For any sustained high load appliance I would fit a separate single 13A socket (if it absolutely had to be on a 13A plug).

[Mattg4321]

2 hours ago, Spreadsheetman said:

Yes, but the 13a plugtop intrinsically limits the current pulled via the 2.5mm2. There is a tiny chance of a cable fault sufficient to melt the 2.5mm2, but not trip the 32a type B mcb in the board, but I’d reckon that is very unlikely.

 

I have had an electrician suggest just cutting the plug tops off and connecting the cables together into the 32a! (and I have seen that done by a kitchen fitter using a bit of choc-block)

What potential danger would be caused by this given the loads are fixed. Overcurrent (not short circuit) protection can be omitted for a fixed load if necessary. 

 

2 hours ago, Mike said:

You can wire your power outlets in 6mm² (if the wires will fit) and plug in a 13A plug, but the regs don't permit you to reduce the cable size between consumer unit and outlet except via a fused connector.

 

Not true. It’s standard practice to fit an infused spur off a 32A ring final circuit using a cable only rated at 27A best case. Also standard practice to connect an oven/hob flex - perhaps 2.5mm2 or less, to a 6mm2 T&E on a 32A circuit with no further fuse. 

 

1 hour ago, Temp said:

 

I think it's possible to extend the 6mm^2 into the back of a cupboard to one side. There fit a switched double socket. The 13A plugs on the appliances are fused so that protects their cables. 

 

The double socket should be accessible but many people have them at the back of cupboards. 

 

The 6mm^2 needs extending correctly but I think it can be done with the appropriate sized connector blocks in a recessed box. 

 

Are the leads on the appliances too short to do this?

 

Check what your electrician says about this.

Double sockets are usually only rated to 20A, so this is a bad idea. 2 single sockets would be ok. 
 

Better still, just have your electrician fit a dual appliance outlet plate. 

[Spreadsheetman]

2 hours ago, andyscotland said:

 

I believe, unless it has changed since I trained, that BS1363-2 double socket outlets are officially rated at 13A across the pair, and are tested to 20A (16A one side and 4A the other).

 

For any sustained high load appliance I would fit a separate single 13A socket (if it absolutely had to be on a 13A plug).

This is exactly why I am looking at separate sockets.

[Temp]

1 hour ago, Spreadsheetman said:

This is exactly why I am looking at separate sockets.

 

Problem then might be getting two 6mm^2 into the terminals to connect them together.

[markocosic]

On 09/02/2023 at 20:40, Spreadsheetman said:

No, that is how they are (Bosch series 2 - a load of the Bosch and Neff hobs are like that). I fired it up for testing and it was pretty good for the kind of use we will put it to I.E. 95% of the time only 2 pans simmering

 

Link to the hob?

 

I'm interested in low power hobs and those with current limiters for renovating apartments with flaky power supplies 

[Spreadsheetman]

10 hours ago, markocosic said:

 

Link to the hob?

 

I'm interested in low power hobs and those with current limiters for renovating apartments with flaky power supplies 

This one: https://www.bosch-home.co.uk/product-list/cooking-baking/hobs/induction-hobs/PUG61RAA5B#/Tabs=section-technical-overview/Togglebox=accessories/Togglebox=manuals/Togglebox=accessoriesOthers/

[Thorfun]

30 minutes ago, Spreadsheetman said:

This one: https://www.bosch-home.co.uk/product-list/cooking-baking/hobs/induction-hobs/PUG61RAA5B#/Tabs=section-technical-overview/Togglebox=accessories/Togglebox=manuals/Togglebox=accessoriesOthers/

that's 3.7kW which, to my basic P=IV physics knowledge, that makes it need a 16A fuse? our sparky says that anything over 3.2kW needs a separate isolating fused socket (or something along those lines!)

[Spreadsheetman]

Check out the manual, there is a config parameter for maximum power draw. It comes configured to work from a 13a plug which is moulded on the captive power cable.

 

There is also a very useful parameter to change the conditions for the touch key beeping. This was pretty annoying by default as it did it for any key press and you can set it for just power on/off and faults instead.

[Spreadsheetman]

Just as a coda to the topic I started. I had a discussion with the supervising sparky of the team that were finishing off my kitchen 2nd fix and he agreed it is a slightly grey area, but if I couldn’t get a 2.5mm2 cable into the oven it should really be fused. I know the oven I’m using only really works with flexible 1.5mm2, so I can’t do that.

 

I’ve ended up with the 32a 6mm2 feed being split into 2x2.5mm2 t&e feeds (with wagos in a Wiska box), one goes to a 13a fused connection unit for the oven (which is hardwired in 1.5mm2 high temp flexible) and the other to a 13a single socket for the hob. Both of these live in the back of an adjacent base unit, so looks tidy. I’m happy with that solution and it is easy to change if I want to use different appliances.

[markocosic]

3 hours ago, Spreadsheetman said:

This one: https://www.bosch-home.co.uk/product-list/cooking-baking/hobs/induction-hobs/PUG61RAA5B#/Tabs=section-technical-overview/Togglebox=accessories/Togglebox=manuals/Togglebox=accessoriesOthers/

Thanks!

 

[Carrerahill]

On 09/02/2023 at 18:35, Mike said:

Not a sparky, but AFAIK you can't reduce cable size unless you have a fused connector to separate the different cables.

 

That is the ideal way to do it, but you can, in certain circumstances, use the BS7671 433.2.2 reg which states that the device protecting the cable against overload may be installed along the run of the conductor after the change occurs, that change is something that de-rates the cable, in this case the reduction in cross section, there is also a limit to 3m (this is interestingly where the DNO 3m tails rule typically sort of stems from) and there may be no other connections into the cable before this device etc. It also states that it should be installed in a manner so as to reduce risks.

 

@Spreadsheetman - If I was going to, I would split the 6mm using suitably rated terminals so I could get single 6mm² wires into my FCU or socket terminals. 

 

You could also, come in on 6mm² into a terminal, then go out on a piece of 4mm², then take 4mm² into socket 1, then back out and into socket 2 so you have a little 4mm radial. The protection would then come from the 13A fuse in the plug-top as the limiting factor, in fact I would probably fit 13A FCU's then come out of them into a single un-switched socket or cut the plugs off the appliance leads and wire in directly into my FCU's (what I did for my Bosch oven).

 

I cut plugs off appliances quite a lot, and on the occasion I needed to return a faulty oven I just removed the cable and installed a new cable c/w moulded plug of similar looking style to that which I had removed and Bosch were none the wiser. 

 

Another option may even just be to see if you could get an FCU that you could squeeze 2 x 6mm wires into each terminal and just run a 6mm radial. 

 

Essentially I can think of about 10 ways I could do this and comply.