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:

 

[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.

 

[HappyHippyDad]

Got it!!

Its the same prinicipal as using 16mm tails on a 100A cut out fuse. It needs to meet regulation 434.5.2 then its fine....

I'm ashamed I didn't do that when I was there now, I just thought of that reg with regards to tails but of course it applies to all fault current protective devices. I shall return and do my Zs and make sure that K[SUP]2[/SUP]S[SUP]2 [/SUP]is greater than I[SUP]2[/SUP]t. If it isn't then I will cry...

 

[oldtimer]

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

Can see where he is coming from as a couple of years ago they did come with a lead and plug on them not so much now or have I been unlucky as I quoted a guy for replacing his oven and took the lead and moulded plug off the old unit as they were taking it away on the same day and yep oven turned up same size and load but no lead ?

 

[Geoffsd]

Can see where he is coming from as a couple of years ago they did come with a lead and plug on them not so much now or have I been unlucky as I quoted a guy for replacing his oven and took the lead and moulded plug off the old unit as they were taking it away on the same day and yep oven turned up same size and load but no lead ?

Ah. I thought I was just unlucky.

Fitted really small (low power) oven recently - no flex or plug.

 

[oldtimer]

Ah. I thought I was just unlucky.

Fitted really small (low power) oven recently - no flex or plug.

That why I remove the old one as customer appreciates not having to pay the extra cost so its good PR plus if you notice they have stopped useing philips screws and now use anti tamper or Allan keys

 

[Guitarist]

Ok, thanks for a straightforward reply.

I thought that my answer had been straightforward... Guess not what you wanted to hear.

 

[IzzyS]

Just thought I'd finish the thread.

Good try What was the make and model of the oven? Perhaps the instructions had a typo, as previously stated.