MCB max load for an oven (EICR)

[NigelD01]

I want to check the rules when doing an EICR for MCB size for ovens. My mate says i should fail an installation because there is a 40 amp MCB on an oven rather than a 32 amp. Is he right?

 

[DPG]

I want to check the rules when doing an EICR for MCB size for ovens. My mate says i should fail an installation because there is a 40 amp MCB on oven rather than a 32 amp. Is he right?

Nope, a 40A MCB on a cooker feed is not an automatic fail. Why does he say it is?

 

[Rockingit]

No, he's talking ball hooks. If the cable is sufficiently sized for the CPD it can be any rating you want!

 

[Rockingit]

NB - lots of newer large range ovens with 5-6 induction hobs now require 40A and I've even seen 63A MCB's on 10mm cables

 

[NigelD01]

Nope, a 40A MCB on a cooker feed is not an automatic fail. Why does he say it is?

I'm not sure. Made no sense to me. I'll ask him tomorrow and post his reply. That's why I wanted to check the rules to see if it had something to do with the max consumption of the oven. Has anyone got a link to the rules so I can have a read?

 

[DPG]

I'm not sure. Made no sense to me. I'll ask him tomorrow and post his reply. That's why I wanted to check the rules to see if it had something to do with the max consumption of the oven.

Well, like any circuit, it depends on cable type, routing and device requirements

 

[loz2754]

Has anyone got a link to the rules so I can have a read?

Industry Books | CEF

 

[telectrix]

your MCB rating is determined by the size of the load and the ccc of the cable feeding the load from the MCB, having allowed for any derating factors .

 

[telectrix]

Ib<In<Iz is the answer . (all the right symbols, but not necessarily in the right order. just checked. they are).

 

[timhoward]

Ib<In<Iz is the answer . (all the right symbols, but not necessarily in the right order. just checked. they are).

Subtle! Nice! Andre Preview would approve....

 

[telectrix]

just received a "like " from Eric's tomb.

 

[NigelD01]

He said that because it’s not to regulation having a 6mm cable on a 40a MCB.

I actually found this answer below to a similar question on my builder.com (Is 6mm cable with a 40 amp MCB sufficient for a 8.5 kw electric shower? - MyBuilder - https://www.mybuilder.com/questions/v/38684/is-6mm-cable-with-a-40-amp-mcb-sufficient-for-a-85-kw-electric-shower), so it looks as though he's right.

"6mm twin and earth cable (which this almost certainly is) can be backed up by a maximum of a 32a MCB, even lower if other factors are involved. You'll need that 10mm cable and a 40a MCB unfortunately as your shower is going to draw over 32a. Whoever fitted the 40a MCB onto the 6mm cable originally was in the wrong."

 

[DefyG]

The tabulated CCC for 6mm t&e (Clipped Direct) is 47A (Table 4D5)
There are other factors to consider and is not B&W, but its possible it is compliant!

 

[telectrix]

he's wrong. 6mm cable ref. method C is rated up to 46A, so a 40A MCB is correct (if the shower/cooker draws > 32A but < 40A). only if cable is derated by refe.methof (insulation) does it warrant a 32A fuse, or even lessif need be.

 

[DPG]

Surely anybody carrying out an EICR doesn't consult mybuilder.com to see if things comply?