Fitting two ovens where there was one

[johnty]

I'm looking to fit two ovens at home, one conventional and a smaller combi oven/microwave. They are both rated at 16A. The current supply is a 10mm cable from the consumer unit on a 32A mcb. What's the best way to connect the two ovens to this supply? Do I need to incorporate a 16A mcb into each connection?

 

[buzzlightyear]

Are both with plugs on the end?

 

[pc1966]

What do the instructions say?

Some EU style ones might assume a 16A or 20A MCB feeding them, others might allow a higher rating for protection.

 

[johnty]

Are both with plugs on the end?

Don't know - haven't purchased yet. They're both NEFF. Here's what the website says:
oven 1:
Energy consumption per cycle in conventional mode: 0.87 kwh
Energy consumption per cycle in fan-forced convection mode: 0.69 kwh
Number of cavities: Main cavity
Heat source: electrical
Cavity volume: 71 litre
Total connected load electric: 3.45 KW
Temperature range 40 °C – 275 °C
Length of mains cable: 120 cm
Nominal voltage: 220 – 240 V

oven 2: similar, but connected load is 3.6KW

 

[pc1966]

oven 2: similar, but connected load is 3.6KW

You would need to search for the NEFF instruction manuals for the models and read what it says about electrical connections.

Both are above 13A so need a dedicated supply (i.e. not off a 13A socket or related circuit), but if they can be protected by a 32A MCB you could simply power both from your existing circuit via some suitable isolation switch (probably already there for the previous cooker).

 

[pc1966]

Just to add that ideally they would have separate isolation switches so in the event of one being faulty you can quickly identify which one trips the circuit, and with it off you can still use the other until repaired/replaced.

 

[johnty]

You would need to search for the NEFF instruction manuals for the models and read what it says about electrical connections.

Both are above 13A so need a dedicated supply, but if they can be protected by a 32A MCB you could simply power both from your existing circuit via some suitable isolation switch (probably already there for the previous cooker).

Yes, although the website doesn't give connection details, (and delivery is likely to be many weeks, apparently, so getting an instruction manual isn't likely for a while), I wondered if the 32A breaker is good enough for both or if is necessary to protect each item individually with 16A breakers. But you think just two individual isolation switches is OK? Thanks for your advice.

 

[pc1966]

Yes, although the website doesn't give connection details, (and delivery is likely to be many weeks, apparently, so getting an instruction manual isn't likely for a while)

NEFF don't make it easy, but if you search around for the model and instruction manual terms you might find a PDF copy somewhere so can see before it arrives.

I wondered if the 32A breaker is good enough for both or if is necessary to protect each item individually with 16A breakers. But you think just two individual isolation switches is OK? Thanks for your advice.

It depends if the appliance is adequately protected by a 32A MCB.

Typically they will come with 1.5mm or 2.5mm cable which might not be protected against overload by a 32A breaker, but typically are safe against a high current fault as it will disconnect fast enough so the cable won't overheat.

You could have the existing (and presumably conveniently accessible) 32A+ isolation switch feed a small metal DIN enclosure with two 16A MCBs, and they would provide independent means of isolating a faulty appliance, but unless necessary it is a bit of effort and something to find a place for, and really a job for a professional electrician to do.

If they can be protected by 32A breakers then you could use a pair of 20A DP isolation switches to feed each, but they probably won't take the 10mm supply cable and a loop on 2.5mm+ to the 2nd switch, so it would mean a suitable joint and that is also above the size the usual 3-terminal Wago terminals, etc, will accept.

 

[pc1966]

There terminals would allow such a connection, but they are limited to 6-16mm cable so the feeds to each DP switch need to be in that sort of range:

RS PRO Commoning Block, 4 Way, 450 V | RS

uk.rs-online.com

6mm is the maximum that a typical 20A switch such as this can take:

https://www.NoLinkingToThis/p/mk-logic-plus-20a-1-gang-dp-control-switch-white/44956

So you are a bit limited in choice. Other terminals might be easier...

 

[pc1966]

You might find a wholesaler who will sell 6mm cable by the metre, otherwise it is kind of expensive to get 10m for the 0.5m or so you would need for the switch feeds:

https://www.NoLinkingToThis/p/prysmian-6242y-grey-6mm-twin-earth-cable-10m-coil/29733

 

[Dustydazzler]

Stick a 2 way board in the next door cupboard , feed this with your 10mm 32a supply. run a 4mm off a16a to a DP switch inside the cupboard and then wire the ovens into the switches

 

[timhoward]

It's a shame we don't have smaller 16A plugs and sockets in the UK. A small garage board and two 16A breakers and sockets would be job done except it would take up most of the cupboard!

 

[brianmoooore]

I'd rather use two 45A or 50A DP switches than 2 x 20A DP switches plus an external joint.

 

[pc1966]

I'd rather use two 45A or 50A DP switches than 2 x 20A DP switches plus an external joint.

Would make sense in case ever want to single 32A load, but I'm not sure may of them will be specified for 10mm plus another conductor. They might just accepts 10mm and 6mm, but might be a bit tight.

 

[brianmoooore]

Some are max. 10mm2, but most are 16mm2, so should be OK for 10mm2 in and 6mm2 to the second switch.

 

[Mike Johnson]

Just a heads up, I have this combination of two NEFF ovens (fan and combi) and the height of the enclosure needed in the cupboard is taller than normally supplied for a double oven, plus you need an additional shelf, you can't put one oven on top of the other, so you loose a drawer and need a make up piece to replace under the bottom oven, looked for a plate warming drawer to go in the space, but they are all too tall.