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Discuss 32amp MCB and cable to 20 amp oven in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

R

RogerTerry

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Hi,
Installation has 32amp MCB to 32amp cable to exisiting cooker. Cooker is to be replaced by one rated 20 amp. Can anyone advise whether the regs require that the the 32amp MCB be replaced by a 20 amp MCB?
Thanks
 
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S

Spudnik

  • Thread Starter Thread Starter
  • #2
If the oven is rated at 20A then personally, i would swap out the 32A and put a 20A MCB at the front end, although im sure it will be fine as is.
 
K

kung

  • Thread Starter Thread Starter
  • #3
I would swop as well
Hello and welcome RogerTerry
 
S

suburban

  • Thread Starter Thread Starter
  • #4
Hello, I would also go down to a 20a mcb.
 
R

rob1967

  • Thread Starter Thread Starter
  • #5
I would down grade the mcb to a 20amp mcb, but to be honest it doesn't matter as the cooker will only pull a maximum demand of 20amps..................
 
M

maddfridge

  • Thread Starter Thread Starter
  • #6
Hi,
Installation has 32amp MCB to 32amp cable to exisiting cooker. Cooker is to be replaced by one rated 20 amp. Can anyone advise whether the regs require that the the 32amp MCB be replaced by a 20 amp MCB?
Thanks
hi there

everyone seems says down grade fine if you consider both the load and the current capacity of the cable as this is existing i think you should be ok as cookers are getting more efficient these days

cheer all
 
Last edited by a moderator:

Des 56

-
Arms
Esteemed
Why downgrade the 32 amp mcb which is correct for the existing circuit and install a 20 amp mcb to a cooker with a rating that matches that mcb
It is better to leave the 32 amp which is well capable of running at 20 amp far better than a possibly fully loaded 20amp
Heat generated in the mcb will not help its cause
If a fault of negligable impedence occurs the instantaneous tripping of the mcb will be to all intents and purposes no different 20 or 32 amp
 
D

daver

  • Thread Starter Thread Starter
  • #8
Leave the 32 as is. You may move house in 6 months and new tennants bring in there super big rangemaster. Cable fine but MCB would not be. It makes no odds with the smaller load.
 
J

johnnyb

  • Thread Starter Thread Starter
  • #9
I would keep the 32a in as the other lads said, due to the cable thats feeding the cooker is rated at 32a, and would still trip in a fault condition.
 
W

WayneL

  • Thread Starter Thread Starter
  • #10
hi,

might seem like a daft question but what's a 32A cable -

I'm being taught at the moment that current carrying capacity depends

on how it's fixed, where it runs, ambient temp etc etc - so I just don't

get the 32A cable bit:)

Maybe someone can enlighten me.

Wayne
 
J

johnnyb

  • Thread Starter Thread Starter
  • #11
Yeh your right but i think in this instance its got to be a house you would have thought, but take yer point, i again would also think that in the cable run it won,t be a massive run and clipped in air and possibly run through lagging, but all in all the cable is protected by the breaker in this case a 32a so i am guessings its a 6mm t&e why change the breaker to a 20a. I know that the load is 20a but thats surely being right on the loads limit then, just a thought.
 
W

WayneL

  • Thread Starter Thread Starter
  • #12
Yeh, I agree with that.

If the breaker was sellected to suit the cable when the were installed

then there is no need to down grade the breaker - the load is irrelevant

unless it exeeds the cable or breaker ratings.

Wayne
 

Des 56

-
Arms
Esteemed
" Household cooking appiance

the first 10A fo the rated pus 30% of the remainder of the rated current
(plus 5A if there's a socket incorporated in the control unit)


so 10A + 3A = 13A

10A + 3A + 5A for unit with socket

so id put in a 20A breaker
The cookers rating is 20 amp Just to repeat my post
Why downgrade an mcb on a circuit which has a correct mcb fitted so that the mcb will now become fully loade when it need not be so
 
L

Lew1s

  • Thread Starter Thread Starter
  • #14
Assuming you're fitting a B class breaker, changing it to a 20A would be fine, especially as you're going to be allowing for diversity. This is more down to personal preferancce than regs, 32A is also fine as you're allowing for future tenants (I assume its a house) to use a bigger cooker if they wish so. Lol @ the guys coming like "omgz mayn 20a is the load of teh cooker aswel it cud trip da mcb!!!!11". You see that little letter on your mcb's next to it's current rating? Research in to that, then get back to me ;)
 
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