Discuss Sizing Cooker fuse / diversity...confused in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

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aaronstuart

Replacing cooker 32A mcb.
New is rated at 9kw = 39.1 Amps.

Been reading through other posts and some say I can use existing fuse because of allowing for diversity.
I was led to believe that diversity was for calculating tails / main fuse etc.

Will the 32A mcb be ok or should I uprate it to a 40A?

Having problems getting the mcb, mainly cost......Crabtree sb6000 40A.

Thanks Aaronstuart.:confused:
 
As above but remember that your mcb is to protect the cable so a combination of diversity, current carrying capacity and installation method will decide.


Chris
 
32A should be fine diversity is only a guide unless you are having a big party (am I invited:)) I doubt that you will be having any problems.



Chris
 
Dont really beleive what i am reading! Since when was putting in a smaller protective device to get over cable size acceptable?

Every circuit shall be designed so that a small overload of long duration is unlikley to occur

Co-ordination will only be met when regulation 433.1.1 is met. i.e Ib<In<Iz

1. The rated current of the protective device (In) is not less than the design current (Ib)
2. The rated current will not exceed the lowest ccc (Iz) of the circuit

What you are suggesting by "bang in a smaller breaker it will be all right mate" can lead to a potentialy overloaded circuit:confused:

And the post about diversity is utter rubbish
 
Last edited by a moderator:
What you are suggesting by "bang in a smaller breaker it will be all right mate" can lead to a potentialy overloaded circuit:confused:

And the post about diversity is utter rubbish



That part.!
 
What you are suggesting by "bang in a smaller breaker it will be all right mate" can lead to a potentialy overloaded circuit:confused:

And the post about diversity is utter rubbish



That part.!

Ok, From the BRB we are told to comply with reg 433.1.1 by putting in a smaller protective device than the design current we do not.

If you follow your calculations through It=In/CaCgCiCc
using a reduced value if In your Value for It is incorrect, leading to the incorrect selection of cable size
Incorect cable size of course will affect you disconnection time

Zs=Ze(R1+R2.Cf.L/1000)
 
Last edited by a moderator:
wotsit

will the 32a mcb be ok was the question
most people gave common sense answers for things to try to help the guy out
its all well and good quoting the regs and we shoulld follow them
however nobody said he should try anything dangerous just saying he could try the 32a and see how it goes
before he gets invoved with possible new circuits
another example of this must be shower upgrades im sure there are many on a cpd that is underated but run perfectly ok because these thing seldom run at full load


ps this is what the forum is here for discussion and debate and your post is as valid as any of the others
 

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