Oven supply

[hard-work]

A quick one.

• A 6mm cable from CU to a local isolator with a 13A socket incorporated.
• 6mm cable to J box behind a 3.2 killowatt AEG oven.
• A 2.5mm heat resistant cable from j box to oven.
• The wiring is fine and not undersized.
• The mcb at the CU is 32A.
• The AEG oven states it needs a 16A fuse/mcb.
• This supply can be drawing approx 6.2 killowatts from the oven and 13A socket, which would trip a 16A mcb.

What size mcb would most fit in this situation?

thanks.

 

[EFLImpudence]

Does it definitely say 16A fuse/MCB (which it shouldn't) or a 16A supply?

 

[EFLImpudence]

99.9% of houses have a 30A fuse or 32A MCB and 6mm² cable which will be satisfactory for any domestic cooker.

 

[hard-work]

The AEG instructions state 16A. I forget the exact wordings.
Is this 16A for appliance protection only?
The 32A mcb will protect the 6mm cable for sure.
But will the 32A mcb protect the 2.5 flex cable, which I believe is rated at 33A, when in free vented air around it, which this will be?

 

[EFLImpudence]

The AEG instructions state 16A. I forget the exact wordings.

I suspect it is a minimum 16A circuit -what they have in Europe.

Is this 16A for appliance protection only?

No. It is (if I am correct) a minimum supply for it to work properly.
MCBs are to protect the circuit - not the appliance.

The 32A mcb will protect the 6mm cable for sure.
But will the 32A mcb protect the 2.5 flex cable, which I believe is rated at 33A,

Yes. It will protect it from fault current.
It's probably more like 25A and 6.2kW is 14.5A after applying diversity (25.83A before).
The oven cannot draw more than that and will be a lot less in normal usage (diversity).

 

[hard-work]

It is a fault condition that I am concerned about. What if the oven is drawing more than what the 2.5mm cable can handle due to a fault, which may be under the 32A protection of the mcb? You say 2.5mm flex heat resistant cable is under 32A rating. This cable is hanging free and in a ventilated space. Should the mcb be dropped to 25A to be sure? Then all bases are covered.

 

[EFLImpudence]

It is a fault condition that I am concerned about.

That's not what fault current is. It is a short from L to E or L to N in the flex (or oven) and the 32A will trip instantly.

What if the oven is drawing more than what the 2.5mm cable can handle due to a fault, which may be under the 32A protection of the mcb?

It can't. They are resistive loads and cannot cause an overload.
It is also possible that you cannot have all 6.2kW on at the same time.

You say 2.5mm flex heat resistant cable is under 32A rating.

It usually is.
If you are certain it is 32A then all is well.
If not, and you are (unnecessarily) worried then get 4mm².

This cable is hanging free and in a ventilated space. Should the mcb be dropped to 25A to be sure?

Easier to get 4mm² flex but there is no need to do either.

 

[ban-all-sheds]

If a 6mm cable from the CU a 40A mcb then a fuse to protect the 2.5mm cable rated at 25A.

Will you please explain why you think that fuse is needed. What kind of overcurrent events do you think it will prevent?