Oven connected into ring - EGBR says this is ok?

[HappyHippyDad]

I have just been asked by a customer if he can just plug his new cooker into a socket. I have said 'No' it needs to be on a dedicated circuit..

I then thought I'd do a bit of research as its only a 2.5kW oven and wanted to see it in black and white in the regs.

I didn't ecpect the Electricians Guide to the Building Regulations (Page 55 - 4.4) to say

"For lightly loaded circuits ovens of rating 13A or less may be connected into a ring final circuit"

Not sure if his kitchen is on its own ring, but if it is I guess its ok to plug in the oven?

Just doesn't seem right, especially after seeing all of Jason's entrys about having to be 2kW or less?

ps... I'll make this my last post for a bit, getting a bit carried away and a bit addicted to this electrics lark ...:rolleyes4:

 

[Octopus]

If it comes with a 13A plug on it, simply plug it in and walk away.

 

[telectrix]

if it comes with a fitted plug, then it's OK to plug it in.

 

[Sparky Ninja]

The dedicated circuit issue mainly revolves around loads of a constant deman, such as the immersion.

If it is a domestic appliance used irregularly then it makes little difference.

 

[Flanders]

If there an unused cooker outlet you could change it for a single socket and plug the oven into that,then you will have a dedicated circuit and the customer can use the existing cooker switch to turn it on and off if they so wish.

 

[Guitarist]

Agree with the others. If it's got a plug, plug it in.

 

[shocking_eg]

its no different to a kettle

either plug or FCU

 

[ayjay]

yo worry too much

 

[HappyHippyDad]

If it comes with a 13A plug on it, simply plug it in and walk away.

if it comes with a fitted plug, then it's OK to plug it in.

Agree with the others. If it's got a plug, plug it in.

Ok.. but if it doesn't have a plug?

Lets say it doesn't have a plug, the kitchen is on its own ring and its less than or equal to 13A?

 

[Sparky Ninja]

Ok.. but if it doesn't have a plug?

Lets say it doesn't have a plug, the kitchen is on its own ring and its less than or equal to 13A?

Then follow my advice above.

 

[shocking_eg]

Ok.. but if it doesn't have a plug?

Lets say it doesn't have a plug, the kitchen is on its own ring and its less than or equal to 13A?

much like most kettles and heaters run at just under 13A ???

 

[Guest55]

stick the oven flex into a sw spur if it makes feel happier

 

[Octopus]

Ok.. but if it doesn't have a plug?

Well... if its rated to 13A then the manufacturer MUST fit a plug in the factory. So if no plug is fitted I'd check the manufacturers instructions and the rating on the plate.

 

[HappyHippyDad]

Just thought I'd finish the thread. The original oven was plugged in, the new oven stated that it could have a plug fitted fused to 13A so thats what I did. The hob was confusing! It had 2.5mm flex on it and stated that it needed to be fused down to 23A (it was 5000W). The 45A cooker switch fed both oven and hob and was run with 6mm cable protected by 32A MCB.

I have removed the flex on the hob and connected the 6mm (that was previously feeding the last hob)directly into the new hob as there were 32A terminals in a box fitted into the underneath of the hob.

I didn't like taking off the flex as that is what it came with but I have to admit that I didn't know how to fuse down to 23A - I cant change the MCB as it feeds both oven/hob and needs to be 32A. Is there a FCU that is greater than 13A??

 

[Flanders]

You can get a 25 amp MCB and put it in an enclosure, ideally you need two supply's 1 for the oven and 1 for the hob . Don't think you should have that 2.5mm flex protected by 32 amp MCB its max current carrying capacity of flex is 25amps

 

[Flanders]

Sorry just realised you took the flex of hob This might affect the warranty.

 

[HappyHippyDad]

Thanks Flanders,

You're right it may affect the warranty but I just couldn't leave the 2.5mm on there knowing it was only protected by a 32A MCB. I cant see anything wrong with replacing smaller cable for bigger? Just seems crazy charging the lady hundreds of pounds for a new circuit when this is safe!

 

[GLENNSPARK]

Ok.. but if it doesn't have a plug?

Lets say it doesn't have a plug, the kitchen is on its own ring and its less than or equal to 13A?

use diversity here...
if its 3KW...then you can usually knock a KW off it....
think about it....if the oven has a grill...then the internal wiring will dictate that both grill and oven will not be on at once....

 

[Guitarist]

Just thought I'd finish the thread. The original oven was plugged in, the new oven stated that it could have a plug fitted fused to 13A so thats what I did. The hob was confusing! It had 2.5mm flex on it and stated that it needed to be fused down to 23A (it was 5000W). The 45A cooker switch fed both oven and hob and was run with 6mm cable protected by 32A MCB.

I have removed the flex on the hob and connected the 6mm (that was previously feeding the last hob)directly into the new hob as there were 32A terminals in a box fitted into the underneath of the hob.

I didn't like taking off the flex as that is what it came with but I have to admit that I didn't know how to fuse down to 23A - I cant change the MCB as it feeds both oven/hob and needs to be 32A. Is there a FCU that is greater than 13A??

A appliance actually stated to fuse it down to 23A?

 

[Geoffsd]

The 45A cooker switch fed both oven and hob and was run with 6mm cable protected by 32A MCB.

Nearly all of them are. You don't need a new circuit.

I have removed the flex on the hob and connected the 6mm (that was previously feeding the last hob)directly into the new hob as there were 32A terminals in a box fitted into the underneath of the hob.

4mm would do. Actually 2.5mm would probably do but that would require knowledge and test equipment.

I didn't like taking off the flex as that is what it came with but I have to admit that I didn't know how to fuse down to 23A - I cant change the MCB as it feeds both oven/hob and needs to be 32A.

Does it?

OPDs are there to protect the cable, not appliances.

Is there a FCU that is greater than 13A??

No. Do you think you should be doing this work?


You'd think there would be tradesmen around who knew how to do this sort of thing.

Goodness me, what if it was a COOKER with hob and oven stuck together?

 

[Flanders]

Thanks Flanders,

You're right it may affect the warranty but I just couldn't leave the 2.5mm on there knowing it was only protected by a 32A MCB. I cant see anything wrong with replacing smaller cable for bigger? Just seems crazy charging the lady hundreds of pounds for a new circuit when this is safe!

Yes the circuit is safe but...
The Hob is still protected by a 32 amp fuse so if there was a fault then would the internal wiring/connection unit cope with extra load before the MCB trips.

I have a 20 amp MCB protecting my hob and never had a problem

 

[GLENNSPARK]

Yes the circuit is safe but...
The Hob is still protected by a 32 amp fuse so if there was a fault then would the internal wiring/connection unit cope with extra load before the MCB trips.

I have a 20 amp MCB protecting my hob and never had a problem

the fuse/breaker protects the cable..
Happyhippy....crack on..its OK...

 

[Geoffsd]

Yes the circuit is safe but...
The Hob is still protected by a 32 amp fuse so if there was a fault then would the internal wiring/connection unit cope with extra load before the MCB trips.

How will a hob overload the circuit?

I have a 20 amp MCB protecting my hob and never had a problem

Precisely.

 

[HappyHippyDad]

A appliance actually stated to fuse it down to 23A?

Yes G, it really did say that, I'm not one to exagerate. You are one of the more experienced forum users and I would genuinely appreciate to hear what you would have done?

6mm cable fed from a 32A MCB to 45A cooker switch which splits (with 6mm) to a socket for oven (approx 2.5KW) and hob 5KW (which had 2.5mm flex attached).

Nearly all of them are. You don't need a new circuit.


4mm would do. Actually 2.5mm would probably do but that would require knowledge and test equipment.


Does it?

OPDs are there to protect the cable, not appliances.


No. Do you think you should be doing this work?


You'd think there would be tradesmen around who knew how to do this sort of thing.

Goodness me, what if it was a COOKER with hob and oven stuck together?

Yes :winkiss:

 

[Flanders]

How will a hob overload the circuit?


Precisely.

As stated the hob should be protected By a 23 amp fuse So I would say that if there is a fault with the Hob the internal wiring and terminal block of the hob can safely run at up to 23 amps were as the only over load protection for the hob is 32 amps So yes the circuit will take the load but will the Hob ??

 

[SPARTYKUS]

use diversity here...
if its 3KW...then you can usually knock a KW off it....
think about it....if the oven has a grill...then the internal wiring will dictate that both grill and oven will not be on at once....

yo Glenn

got caught out with this tuther day, they had a big posh cooker (4k) that came with its own 10mm2 3core heat resistant flex on it - turns out you can have the grill onat the same time as the oven.


for.....

PIZZA!!!

 

[GLENNSPARK]

As stated the hob should be protected By a 23 amp fuse So I would say that if there is a fault with the Hob the internal wiring and terminal block of the hob can safely run at up to 23 amps were as the only over load protection for the hob is 32 amps So yes the circuit will take the load but will the Hob ??

explain please which wholesalers i could get a 23A fuse from....
i want one for my collection...

 

[GLENNSPARK]

yo Glenn

got caught out with this tuther day, they had a big posh cooker (4k) that came with its own 10mm2 3core heat resistant flex on it - turns out you can have the grill onat the same time as the oven.


for.....

PIZZA!!!

the cable CSA would give the game away eh sparty....

 

[HappyHippyDad]

yo Glenn

got caught out with this tuther day, they had a big posh cooker (4k) that came with its own 10mm2 3core heat resistant flex on it - turns out you can have the grill onat the same time as the oven.


for.....

PIZZA!!!

I cant believe you are replying to this when Han Solo is at this very moment fleeing the imperial fleet!!!

 

[Leckie]

Is overload protection required for a resistive load such as a hob? The flex should not have been removed I suspect. Fault protection is of course required.

 

[DieselShunter]

Sorry just realised you took the flex of hob This might affect the warranty.

It might. But it won't affect your statutory rights, which are nearly always more effective than a warranty. Warranties, especially 12 month ones, are usually there to browbeat you into foregoing your rights under the SoG act.

 

[Geoffsd]

As stated the hob should be protected By a 23 amp fuse

That is presumably a misprint. Do you think, perhaps it should be 13?

Cooking appliance manufacturers state either:
It must be protected by a certain fuse - because that is needed to protect the (cheapest) flex they have fitted.
Or, without flex, it requires a certain amperage of supply - because that is required for it to work.

So I would say that if there is a fault with the Hob the internal wiring and terminal block of the hob can safely run at up to 23 amps

It will obviously be designed for its maximum load, whatever that is.

whereas the only over load protection for the hob is 32 amps

The hob cannot overload.

So yes the circuit will take the load but will the Hob ??

Neither it nor the cable will have to. Overload cannot happen.

Do you think the cabling inside cookers protected by a 30A BS3036 is all capable of carrying 42A, i.e. 6mm?

 

[Guitarist]

Yes G, it really did say that, I'm not one to exagerate. You are one of the more experienced forum users and I would genuinely appreciate to hear what you would have done?

6mm cable fed from a 32A MCB to 45A cooker switch which splits (with 6mm) to a socket for oven (approx 2.5KW) and hob 5KW (which had 2.5mm flex attached).


Yes :winkiss:

Well, for a start, I would contact the manufacturer directly and ask them where I can obtain this mythical 23A fuse. Sounds like they have simply decided that 5kw is about 23A, so that should do, without allowing for any diversity.

 

[SPARTYKUS]

I cant believe you are replying to this when Han Solo is at this very moment fleeing the imperial fleet!!!

Autopilot

 

[Flanders]

1. That is presumably a misprint. Do you think, perhaps it should be 13?

2. Cooking appliance manufacturers state either:
It must be protected by a certain fuse - because that is needed to protect the (cheapest) flex they have fitted.
Or, without flex, it requires a certain amperage of supply - because that is required for it to work.

It will obviously be designed for its maximum load, whatever that is.

3 The hob cannot overload.

4 Neither it nor the cable will have to. Overload cannot happen.

5 Do you think the cabling inside cookers protected by a 30A BS3036 is all capable of carrying 42A, i.e.
6mm?

1 .How can it be 13 amps when the unit is ratted a 5KW (about 22 amps at 230or 21 amps at 240) Apply a bit of diversity and a 20 amp MCB will be fine

2. So your saying the fuse is to protect the Flex not the appliance from overload ?

3. Why cant the Hob Over load??

4. So there was no need to change the cable to 6mm If the Hob can't overload ?

Here an example for you
There was 32 amp fork lift truck charger plug into a 32 amp socket protected by a 32 amp MCB , all ok
But then the folk truck charger was replaced by someone with a 16 amp ratted unit,using the same flex and 32 amp socket and was still and protected by the same 32amp MCB.

There was a fault on the fork lift charger coursing it to catch fire.
The customer asked why it did not trip the MCB first .
I told them it was because the MCB was overrated for the charger unit. Are you telling me that this was not the case ?


5. never though about that You may have a point

 

[Geoffsd]

1 .How can it be 13 amps when the unit is ratted a 5KW (about 22 amps at 230or 21 amps at 240) Apply a bit of diversity and a 20 amp MCB will be fine

We don't know. Perhaps the loads add up to 5kW but only 3kW can be switched on at once.

2 So your saying the fuse is to protect the Flex not the appliance from overload ?

Yes, definitely.

3 Why cant the Hob Over load??

It is a fixed load. It can't suddenly start drawing more current.

4 So there was no need to change the cable to 6mm If the Hob can't overload ?

No. 433.3.1.2(ii)

Here an example for you

Therewas 32 amp fork lift truck charger plug into a 32 amp socketprotected by a 32 amp MCB , all ok
But then the folk truck charger was replaced by someone with a 16 amp rated unit, using the same flex and 32 amp socket and was still and protected by the same 32amp MCB.

There was a fault on the fork lift charger coursing it to catch fire.
The customer asked why it did not trip the MCB first .
I told them it was because the MCB was overrated for the charger unit. Are you telling me that this was not the case ?

It may be different if someone has fitted the wrong plug to the charger and the charger is supposed to be protected by the MCB.

5 never though about that You may have a point

 

[Flanders]

So can there not be a fault with an appliance that courses an over load for example leakage to earth or neutral (not a dead short) I thought the fuse in the plug top were there to protect it ?

And Did you mean Reg 433.3.1(ii)

 

[Sparky Ninja]

It would cause an overcurrent called fault current.
An overload current will only occur in an electrically sound circuit.

 

[Flanders]

It would cause an overcurrent called fault current.
An overload current will only occur in an electrically sound circuit.

So the fuse is there to protect from Fault current, if there was a fault current coursed by the Hob would the 32 amp MCB trip out before any damaged is coursed to the Hob

 

[Geoffsd]

So can there not be a fault with an appliance that courses an over load for example leakage to earth or neutral (not a dead short) I thought the fuse in the plug top were there to protect it ?

That is not an overload but a fault current which will operate the 32A MCB in 0.1s. or less.

As long as the cpc can cope with fault current then all is well.
Hence the link to 434 in 433.3.1(ii) and my reference above to knowledge and test equipment.

A current leakage enough to overload a, say, 2.5mm conductor but not operate the 32A MCB would have to be very specific indeed - around a constant 6, 7 or 8Ω.
This isn't really possible, is it?, and we do not have to cater for it.
Such a fault would melt the internal wiring or element wire first anyway.

And Did you mean Reg 433.3.1(ii)

Yes.

 

[Geoffsd]

So the fuse is there to protect from Fault current, if there was a fault current coursed by the Hob would the 32 amp MCB trip out before any damaged is coursed to the Hob

Well, not really because such a fault can only be caused by a damaged part or

poking your screw driver around.

 

[Sparky Ninja]

So the fuse is there to protect from Fault current, if there was a fault current coursed by the Hob would the 32 amp MCB trip out before any damaged is coursed to the Hob

The fuse is there simply to protect the cable to the appliance from the over-current likely to occur in a fault.
The appliance is designed with a cable that will accommodate the full demand, and an overload cannot occur as it is a purely resistive load.
The fuse will operate in the case of a fault current flowing, but depending on the characteristics of the final circuit the circuits protective device may operate first.

 

[Flanders]

Fair comment Thanks For putting me straight

 

[HappyHippyDad]

A current leakage enough to overload a, say, 2.5mm conductor but not operate the 32A MCB would have to be very specific indeed - around a constant 6, 7 or 8Ω.
This isn't really possible, is it?, and we do not have to cater for it.

So are you saying it would have been ok to leave the 2.5mm flex on the hob which was protected just by the 32A MCB?

 

[Guitarist]

Whilst complying with regs, remember the prime directive of the current regs is to follow manufacturers instructions where they demand something specific. As I said, I would personally be getting in touch with the manufacturer to confirm that fuse rating. If they are adamant that a 32 amp OCPD is too high, then your only option is to fuse down. I realise that millions of hobs are wired into the main cooker outlet, but if hippy wants to cover his backside (and knowing him, sleep at night) then he will need to find a way of getting a 20A MCB supplying this circuit.

 

[Geoffsd]

A current leakage enough to overload a, say, 2.5mm conductor but not operate the 32A MCB would have to be very specific indeed - around a constant 6, 7 or 8Ω.
This isn't really possible, is it?, and we do not have to cater for it.

So are you saying it would have been ok to leave the 2.5mm flex on the hob which was protected just by the 32A MCB?

Yes, but you must ensure that it satisfies the fault current requirements.

Either way 4mm. would have done - max current 35A.
6mm. is only used because it is a left-over from 30A 3036 fuses when it was required - 30/0.725 = 41.4A.

 

[HappyHippyDad]

Whilst complying with regs, remember the prime directive of the current regs is to follow manufacturers instructions where they demand something specific. As I said, I would personally be getting in touch with the manufacturer to confirm that fuse rating. If they are adamant that a 32 amp OCPD is too high, then your only option is to fuse down. I realise that millions of hobs are wired into the main cooker outlet, but if hippy wants to cover his backside (and knowing him, sleep at night) then he will need to find a way of getting a 20A MCB supplying this circuit.

Never to have an impact on the internal development of a pre-warp alien state!!
Sorry Guitarist, I generally try and stay focused and sensible... but its one of my favourites!

 

[HappyHippyDad]

Yes, but you must ensure that it satisfies the fault current requirements.

Either way 4mm. would have done - max current 35A.
6mm. is only used because it is a left-over from 30A 3036 fuses when it was required - 30/0.725 = 41.4A.

Ok, thanks for a straightforward reply.

How do you ensure that it satisfies the fault current requirements?

Now take a deep breath and dont pelt me unless you really feel the need to...

 

[Leckie]

433.3.1(ii) refers to the omission of overload protection in certain circumstances and requires that adequate protection from fault currents assuming a fault of negligible impedance, I.e. a short circuit. The flex fitted by a manufacturer should not be replaced as the warranty will probably become invalid. The fixed resistive load cannot draw a higher current that ohms laws equates to, partial faults are not considered only faults of negligible impedance. If you have a short line to earth or line to neutral it will operate the CPD. All completely different for other load types, eg a fluorescent light fitting. Then the nature of the load, i.e. a ballast can become faulty and draw a current higher than the load rating of the equipment. Same with other inductive loads. So you need to protect the cable as required by BS7671 and the equipment in accordance with the manufacturers instructions.

 

[Geoffsd]

How do you ensure that it satisfies the fault current requirements?

The same as is done for any circuit.

You need to determine that the fault current is sufficient to operate the opd in the required time (should already be done) and then work out if the cpc is large enough to take this current without damage.

Having said that, if you are using 2.5mm flex with 2.5mm cpc then it will.