Don't like how kitchen fitters have connected oven and hob

[Steve T]

Hi all,

Recently a mate had a new kitchen fitted, he's gone for an induction hob and pyrolytic oven, no gas at the property. At 1st fix a single 32A 6mm supply was installed to run both the oven and hob, the electrician already knew the exact specs of the appliances to be installed, and no issues there, with diversity both appliances are under 32A.
For info, the hob (neff T46FD53X2) is 6.9kW, the oven (neff B2ACH7HH0B) is 2.99kW.

So for the connection of the appliances the kitchen fitters 'electrician' has connected a click cooker switch with socket to the 6mm cable that comes from the above counter isolator. This has been shoved under the plinth with the 6mm cable and the hob cable just going through a rough hole in the (brittle) plastic backbox, so no cable restraint- first issue I think.
Then the oven cable has had a plug fitted and it's been plugged into the socket on the front of the cooker switch unit.

In my DIY opinion this isn't a good way of doing it. I would probably have expected a dual outlet plate to be used. However, having looked at the oven tech specs it may be the case that the oven should be protected by a 13A fuse, but I don't really like this as it's running at its max so can see the plug and fuse getting quite hot with the oven being on for a while for a Sunday roast or whatever.

So would please appreciate your views on whether the way they've been connected is acceptable?
And also your interpretation of whether the oven does actually need to be protected by a 13A fuse or would it be ok just on the 32A breaker?
And also depending on whether or not a 13A fuse is required, what's a better way of connecting them?

Thanks, and sorry for the long post!

 

[Steve T]

Tech specs for the oven where 13A fuse protection is mentioned

And the electrical connection instructions- very detailed!

 

[littlespark]

Spot on. Cooker switch to duel box, hob off outlay plate, oven off 13A unswitched fcu.

Reread the op…. Is there no accessible isolator, if the cooker switch is behind kickboard?

 

[kropaske]

Spot on. Cooker switch to duel box, hob off outlay plate, oven off 13A unswitched fcu.

Reread the op…. Is there no accessible isolator, if the cooker switch is behind kickboard?

According to op, there is one above the counter. The question is if the first electrician had all the specs why did he/she not install second supply for the oven. Or why did he/she not install appropriate isolators for both appliances instead just left the cable dangling under the cabinets?

 

[Lucien Nunes]

So would please appreciate your views on whether the way they've been connected is acceptable?

No. Your observations and comments are on the ball.

And also your interpretation of whether the oven does actually need to be protected by a 13A fuse or would it be ok just on the 32A breaker?

Now it gets complicated, because they don't say whether the prescribed 13A fuse is the minimum, maximum or what. The unusual terms 'protective contact plug' (=Schukostecker) and 'external conductor' (=außenleiter) are clear signs of direct translation from German instructions. German installations would conventionally have 16A or 20A protection and one might suppose the appliance was designed with this in mind. The reference to a 13A fuse suggests at least a moment's thought was given to UK practice, but I think it likely that they do not know about the problem of 13A plugs overheating behind-the-scenes on sustained 3kW loads because 16A plugs are less prone to this.

The UK is unusual in having large single-phase cooker circuits. On the continent it is more common to have say 16A single-phase for the oven and 16A 3-phase or the other two phases for the hob. Again, if that have just recycled the German instructions, it's possible no-one has thought to say whether a 32A MCB gives sufficient protection. That might require a call to their technical department and if that is in Germany it might take a couple of tries to get the English side of the operation to ask them the right question.

And also depending on whether or not a 13A fuse is required, what's a better way of connecting them?

Is there room for a 2-module DIN rail enclosure containing an MCB for the oven with the supply cable looping out to the hob and the oven cable glanded in?

 

[davesparks]

According to op, there is one above the counter. The question is if the first electrician had all the specs why did he/she not install second supply for the oven. Or why did he/she not install appropriate isolators for both appliances instead just left the cable dangling under the cabinets?

There's no need for a second supply for the oven, nothing in the regulations requires a seperate circuit per appliance.

 

[kropaske]

There's no need for a second supply for the oven, nothing in the regulations requires a seperate circuit per appliance.

Yes, you are right and I would not have a problem to connect both to 32A existing supply however having full kitchen refit including running new supply for the hob, it would be much wiser to run another cable and keep both appliances feed from separate circuits. This would give more flexibility for the client in the future and follow recommendations in section 314

 

[davesparks]

Yes, you are right and I would not have a problem to connect both to 32A existing supply however having full kitchen refit including running new supply for the hob, it would be much wiser to run another cable and keep both appliances feed from separate circuits. This would give more flexibility for the client in the future and follow recommendations in section 314

What flexibility does it offer?

All it does is waste materials and money.

Which part of section 314 are you referring to?

 

[Steve T]

No. Your observations and comments are on the ball.


Now it gets complicated, because they don't say whether the prescribed 13A fuse is the minimum, maximum or what. The unusual terms 'protective contact plug' (=Schukostecker) and 'external conductor' (=außenleiter) are clear signs of direct translation from German instructions. German installations would conventionally have 16A or 20A protection and one might suppose the appliance was designed with this in mind. The reference to a 13A fuse suggests at least a moment's thought was given to UK practice, but I think it likely that they do not know about the problem of 13A plugs overheating behind-the-scenes on sustained 3kW loads because 16A plugs are less prone to this.

The UK is unusual in having large single-phase cooker circuits. On the continent it is more common to have say 16A single-phase for the oven and 16A 3-phase or the other two phases for the hob. Again, if that have just recycled the German instructions, it's possible no-one has thought to say whether a 32A MCB gives sufficient protection. That might require a call to their technical department and if that is in Germany it might take a couple of tries to get the English side of the operation to ask them the right question.



Is there room for a 2-module DIN rail enclosure containing an MCB for the oven with the supply cable looping out to the hob and the oven cable glanded in?

Thanks for your detailed response, I did think the instructions weren't aimed at the UK market hence the unusual terms. And as you say there's no way it would ever be on a 13A fuse anywhere but the UK so think I'll give them a ring/email and see what they say. Of course connecting it via a 13A plug or FCU would be compliant but having seen my own 3kW kettle plug overheat in the socket doesn't exactly inspire confidence. Could install a separate 16A mcb in an adjacent cupboard, does seem like an overkill arrangement though, but if its the best way, that's fine.

Actually had a similar issue in my own house a few years ago, was putting a new oven in and instructions mentioned needing a 16A circuit with the oven being around 2.7kW, less than this one in question. The concensus on this forum was to just connect it to the 32A circuit with no further protection since the breaker isn't really meant to protect the appliance, only the cable to it, which it did since the oven was a fixed load. Reason I couldn't have just changed the MCB to 16A was because I couldn't find a suitable one for my consumer unit easily.

 

[Steve T]

Spot on. Cooker switch to duel box, hob off outlay plate, oven off 13A unswitched fcu.

Reread the op…. Is there no accessible isolator, if the cooker switch is behind kickboard?

There's a single isolator above the counter to isolate the oven and hob so local isolation is fine. They've basically used the cooker switch with socket as a connection unit under the plinth, obviously not its intended purpose.

Your suggestion there was actually something I thought of, just had the concern that a 13a FCU or plug would be prone to overheating if the oven is on for a while or certainly during its pyrolytic cleaning program where it would be pulling the full 13A for a long period of time.

 

[kropaske]

What flexibility does it offer?

If one of the appliance develop a fault and needs isolating you also loosing other cooking appliances. Not the case with 2 separate circuits

If fault in the wiring needs isolating the circuit you will loose both cooking appliances. Not the case with 2 separate circuits.

If client want to change for the new oven in the future and manual requires to be protected by16A PD then to follow MI you would need to install small CU. Not the case with 2 separate circuits. However it's worth to mention that there are different opinions on following MI and some electricians do that to the letter, some have more open interpretation and others just wipe their bottoms with it.

All it does is waste materials and money.

Few meters of cable in already made chase and mcb/rcbo in consumer unit. Fraction of the 5k or 10k or even more that possibly was spent on new kitchen.

Which part of section 314 are you referring to?

Every instalation shall be divided into circuits, as necessary, to avoid danger and minimize inconvenience in the event of a fault.

For some not having cooking appliance for unknown period of time because of a fault could be inconvenience.