Which fuse size needed for my oven circuit?

[groovybug]

Hi everyone,

We have an appliance circuit for cooker and oven, this is connected directly to the consumer unit with a 32A MCB. However the cooker has been replaced with a gas cooker, and I have got a new 3.8kW oven. I wonder if I should change the fuse to a lower rating to better protect the oven?

Is 16A or 20A would suffice?

Thank you.

 

[JohnD]

No need.

 

[groovybug]

@JohnD: Thank you. Could you elaborate? I'm looking to learn, not just finding solution. Isn't leaving the fuse at 32A allow some small surge that could be still dangerous?

 

[SUNRAY]

This has been done to death on this forum, I personally would make the change. but the current regulations indicate the MCB/fuse is only to protect the cable and regs even single out resistive heating elements as not requiring such protection. Accordingly I'd say it's not worth the expense of making the change.
What does the manufacturers instruction say?

EDIT: What size cable is on the oven?

 

[EFLImpudence]

An oven will not draw more current than it's rating - 16A. Higher current does not get 'pushed through' because there is a 32A MCB.
A surge of higher Voltage, should it occur, will not be stopped by an MCB.

The internals of the oven will be the same as if it were pat of a cooker.


Having said that, it should be confirmed that the oven flex would be protected against Fault Current (Short Circuit or Earth Fault) by the 32A MCB.
It is virtually certain that it would be but we cannot tell from the internet.

So, perhaps it would be better to either change the MCB to 16A or 20A, as you say - or

change the flex for at least 2.5mm² (assuming it is smaller than that).

 

[groovybug]

@SUNRAY @EFLImpudence

The fuse is the mini plug-in type, so I imagine it's relatively simple to replace. However with appliance circuit, do I apply the diversity calculation (so 10A + 30% of 6A +5A for socket, so total of 17A, and needing a 20A MCB), or just go with maximum rating 16A? Another thing I want to ask is about the fused switch, which rating should it be at?

The electrical safety part in the manual is quite generic, without any specific information. I will make sure to go with 2.5mm2 cable.

 

[SUNRAY]

fused switch???? picture please.

 

[groovybug]

fused switch???? picture please.

I might have used the wrong term, what do you call the switch for the oven ? Connection unit, or fused spur? Sorry, total DIY beginner, but keen technical enthusiast otherwise.

 

[JohnD]

when you say you have a gas cooker, and a 3.8kw oven, I think you have a dual-fuel cooker, probably with a double oven or an oven and grill. Or perhaps you have a gas hob and a separate oven.

A 3.8kW oven must not be supplied through an FCU because it is only supposed to carry 3kW

A gas cooker, and some dual-fuel cookers with a single oven, can be supplied through a plug and socket. You can use an FCU if you want.

Cooker outlets on a 32A circuit usually have a noticeably larger switch, suitable for the greater current.

What have you got?

 

[SUNRAY]

cooker switch:

If you have one with a socket and change to 16A you may find it trips if you use a 3kw kettle at the same time as the oven.
connection unit/outlet plate:

often behind cooker

fused connection unit:

switched:

neither of which should be controlling an electric cooker or oven. if there is one for the gas hob igniter... use 3A fuse

 

[JohnD]

The fuse is the mini plug-in type, so I imagine it's relatively simple to replace

If its a Wylex Standard (it usually is) then, no, it's not very simple, because the base is designed to prevent a different rating fitting.

 

[SUNRAY]

If its a Wylex Standard (it usually is) then, no, it's not very simple, because the base is designed to prevent a different rating fitting.

 

[groovybug]

@JohnD Ah thank you. I've learnt alot today. Sorry I understand it can be frustrating explaining completely beginner stuff.

This is a house we've just moved in. It used to have an electric hob and electric oven on a 32A circuit, but the seller just replaced it with a gas hob, and took away the electric oven, leaving a bare circuit there. So what is currently there is not so relevant. I'm trying to see what is the safest and simplest way to connect a new oven.

So should I just use a double pole switch connection unit? Somehow I thought there is also 16A/20A fused switch for ovens? That would help me not having to change the MCB.

 

[Taylortwocities]

@JohnD

So should I just use a double pole switch connection unit? Somehow I thought there is also 16A/20A fused switch for ovens? That would help me not having to change the MCB.

No such thing as a fused switch more than 13A.
But, really, as mentioned before you do not need to change the MCB.

 

[JohnD]

it will also save you (or someone else) the effort of changing it back if you buy a double oven, or an electric hob, or an electric cooker, in future.

I just checked my double oven, and with both ovens heating, it draws about 4kW, and with the main oven plus the upper grill, about 5.5kW

It's a dual-fuel cooker so the hob is gas.