16amp b type breaker for oven.

[julianacb]

Hello all, excuse my bad grammar spelling etc. today i had the people from building control around to sign of my cu change
at my house,here is my question. My mum had her oven changed a little while ago and it has a design current of around 10.5 amps, the old fuse protecting was a 40 amp wired in a 10mm t+e, i have since replaced this with a 16 amp breaker and put connecters at old cooker switch and a blank plate. I done this as section h of osg states you can do this and dont need a switch if the circuit breaker is to be used as one. The inspector told me this is not Good and my interpretation is wrong. And i need a local isolation switch. I want to know what others opinion was on this he also said the oven is not fixed equipment? If im wrong fine but how do i remedy the situation its a double box do i just put the old cooker switch back on. I did do a little search before posting but could not really find what i was looking for. Any advice greatly appreciated!

 

[Octopus]

Anyone connecting fixed equipment to a CU with RCD's and not having DP isolation is a fool IMHO.

 

[jaypp]

we always put an isolator in. what did the inspector advise? if to re-instate isolator then do that. job done!

 

[HandySparks]

What was your thinking behind removing the switch?

 

[julianacb]

Looking back now pretty stupid move thanks for replys

 

[julianacb]

And another reason i queried is that an electrician that i worked with done a kitchen extension and all appliances were done this way, but the fuse box for extension was actually in the kitchen, is this more acceptable or still not good practice?

 

[telectrix]

it's always good practice to provide double pole isolation for any item of fixed equipment. as murdoch said. an earth fault will take out an RCD, so isolation of both L and N is recommended.

 

[HappyHippyDad]

And another reason i queried is that an electrician that i worked with done a kitchen extension and all appliances were done this way, but the fuse box for extension was actually in the kitchen, is this more acceptable or still not good practice?

Hi Julian,

I've looked at many threads on local isolation and functional switching etc etc and there seems to be differing views, but the main theme seems to be that it is pretty bad practice not to provide local ioslation and in your case it probably doesn't comply with BS7671 (see below) because a MCB is not DP:

Page 45 OSG (ii)
ISOLATION
"The device must switch all live conductors in a TT system and all line conductors in a TN system."

Probably best just to put the 45A DP cooker switch back on :wink_smile:

 

[telectrix]

it's not just that, happy. if the cooker had a N-E fault tripping the rCD, it's much easier to isolate the cooker with a D/P switch than leave a RCD that might also supply sockets and lights off till a spark can attend.

 

[Geoffsd]

I've looked at many threads on local isolation and functional switching etc etc and there seems to be differing views, but the main theme seems to be that it is pretty bad practice not to provide local ioslation

The switch is not required for isolation.
It depends whether you think emergency switching is required for an oven.

and in your case it probably doesn't comply with BS7671 (see below) because a MCB is not DPage 45 OSG (ii)
ISOLATION
"The device must switch all live conductors in a TT system and all line conductors in a TN system."

OK for TN, then. MCB, that is. Section 537 & Table 53.4.

Probably best just to put the 45A DP cooker switch back on :wink_smile:

Yep.

Why do people keep quoting the OSG instead of the actual regulations?

 

[julianacb]

Hi Julian,

I've looked at many threads on local isolation and functional switching etc etc and there seems to be differing views, but the main theme seems to be that it is pretty bad practice not to provide local ioslation and in your case it probably doesn't comply with BS7671 (see below) because a MCB is not DP:

Page 45 OSG (ii)
ISOLATION
"The device must switch all live conductors in a TT system and all line conductors in a TN system."

Probably best just to put the 45A DP cooker switch back on :wink_smile:

Thanks all for replies nails are in the coffin

 

[jaypp]

And another reason i queried is that an electrician that i worked with done a kitchen extension and all appliances were done this way, but the fuse box for extension was actually in the kitchen, is this more acceptable or still not good practice?

probably rcbo's? but my limited knowledge is in line (no pun intended) with other replies.

 

[julianacb]

probably rcbo's? but my limited knowledge is in line (no pun intended) with other replies.

No 15 way split rcd board no rcbos

 

[GLENNSPARK]

now..

i`v seen this in renteds...where the only means of isolation for the cooker has been the MCB..

i thought it was crap then and i think its crap now....

this kind of install is only performed by them offering the cheapest of cheapest quotes...in fact in my mind it aught to be made a requirement to have a means of local isolation for such equipment...as on the 2 previous occasions where i have come across this..the dis-board was in the cellar below the kitchen area...

really poor...

 

[jaypp]

are regs, good practice and common sense 3 different things?

 

[GLENNSPARK]

sometimes...

depends on who it is...

 

[overskilled]

I always fit an isolator switch for any appliance in kitchens...mentioning things going faulty and catching fire tends to sway most of them to my way of thinking...
Though lost one job as the clients wife was doing the interior design on a rented property and "didn't want those ugly switches on show" and they "all have to be in the back of the cabinets hidden out of sight"...no chance...he saw the point, i think she threw a fit as I've heard nowt since sticking the quote in weeks ago....
Got a job on tomorrow...re-lay a cooker supply....as previous owners rejigged the kitchen, put in a gas cooker and their spark just extended the ring for the cooker igniter and turned the old cooker/oven supply into a socket with random spur....not what I was hoping to find...was hoping it was just the usual cooker outlet plate previously swapped for a single socket...
I really hate crawling under newish build house floors (no room to move as the builders backfill them with crap and ends up like being on an assault course)...and I have to lift laminate in a cupboard to cut a hatch (Though owner is ok with it getting wrecked if thats what it takes to get access to the floor below..says he'll get a carpet if needs be for the cupboard so one saving grace)...'kin hell....this is going to be a LONG day tomorrow....still work is work...

 

[HappyHippyDad]

The switch is not required for isolation.
It depends whether you think emergency switching is required for an oven.


OK for TN, then. MCB, that is. Section 537 & Table 53.4.

Sorry, just checked my definitions. I thought of 'live' conductors as including neutral, but realise 'line' does not include neutral!

Yep.

Why do people keep quoting the OSG instead of the actual regulations?

I guess its because BS7671 is pretty scary and reads like a law book! I should have said 537.2.1.1, but seeing as though that says it doesn't need to be DP, we'll just say 'It's good practice so just do it'

 

[GLENNSPARK]

its really poor form not to be fitting localised isolation....

 

[Geoffsd]

.
I agree but in answer to the OP -

The inspector told me this is not Good and my interpretation is wrong.

It is not good but you're interpretation is not wrong.

he also said the oven is not fixed equipment?

Is it screwed to the base units?