Two ovens on single cooker switch?

[Deuce]

Hi all,

I'm about to replace our kitchen and one of the upgrades is to install two full size ovens to replace the original twin over under counter unit.

The existing 45a cooker switch is in the right place but no convenient space for a second... Is there a reason I can't or should not connect both new ovens to this single switch? It's on a dedicated 32a circuit back to the CS so the circuit will easily take the two ovens, both of which require ~13a peak.

Thanks in advance for any help

 

[Dustydazzler]

No problem at all wiring both ovens to a single 45amp switch.
However the MI manual will probably request the oven is supplied via a 16amp supply fuse on its own circuit.

 

[Deuce]

No problem at all wiring both ovens to a single 45amp switch.
However the MI manual will probably request the oven is supplied via a 16amp supply fuse on its own circuit.

This is my question/concern really.. The circuit with existing protection and switch can obviously safely take the load of both ovens - but do regs state that the oven(s) must be individually supplied and protected as per MI? Or is it perfectly normal to just supply ovens with a 32a circuit regardless?

The house was only built in 2011 and the existing oven is also 16a, yet the spark who installed it used a 32a mcb - is that relatively standard practice?

There is actually space for a separate box I could feed from the oven switch where I could install a couple of 16a MCB's if it's really required. but it seems like a bit of a pointless ball-ache if it's not something a professional would even bother with!

 

[littlespark]

ovens are classed as a fixed load.... it cant possibly take more than 16A.... unless its a dead short which would take out the 32A instantly

You said in OP that they require 13A? does that mean it comes with a fitted 13A plug?

 

[Deuce]

ovens are classed as a fixed load.... it cant possibly take more than 16A.... unless its a dead short which would take out the 32A instantly

You said in OP that they require 13A? does that mean it comes with a fitted 13A plug?

The oven is 3.2kw, so slightly over 13a. Not fitted with a plug.

I understand that the 32a should be fine, as you say. Yet the manufacturers instruct that the circuit should be protected by 16a so my question is whether it's frowned upon to ignore that or if it's commonplace.

 

[mainline]

The oven is 3.2kw, so slightly over 13a. Not fitted with a plug.

I understand that the 32a should be fine, as you say. Yet the manufacturers instruct that the circuit should be protected by 16a so my question is whether it's frowned upon to ignore that or if it's commonplace.

I would just fit a dual outlet connection.

 

[Simon47]

Bear in mind that it's common to find a gas hob with the ignition supply (less than an amp, small cable, should have 3A fuse) connected directly to the 32A cooker supply ...
While not correct, I wouldn't be too worried about doing what you plan. You could fit a couple of MCBs if you wanted, but in practice you'd find both the 16A & 32A would trip in the event of a fault.
In practice, I thing the very worst case woukd be some internal faukt that was of sufficient resistance as to not trip the 32A MCB - but it's unlikely, the effects would be contained within the metal oven casing, and the heat produced would very quickly convert the fault into a dead short (MCB trips) or an open circuit. Such faults did happen with the old fashioned spiral element hobs, and the same type of element is still used for ovens. If a crack allows moisture into the mineral insulation, or there's a manufacturing defect, it can create a low resistance spot such that part of the element takes the full voltage and hence draws lots of current. Such faults don't last long - a LOT of heat is created at the defect, and this usually goes off with a bang. I recall years ago a friend showing me her favourite small pan with a hole blasted through the bottom - she was most concerned at having lost her "milk pan".

 

[Deuce]

Thanks so much for all the responses guys!

It seems that what I'm planning is nothing unusual or regs-busting. I'll hook it all up and have a local spark check what I've adapted and test the reinstated circuits to cover all bases.