MCB Not tripping

[fire]

i have come across two showers in different houses where they have installed 32A mcb on a 9.5Kw shower. switched the shower on full and measured how many amps is drawing which was well over 32A but the mcb doesnt trip. any ideas as to why?

 

[Richard]

Seen this quite alot. Most MCB's won't pop at their stated ratings. I forget the factor, but I know they will take alot more than stated.

Rich

 

[SirKit Breaker]

i have come across two showers in different houses where they have installed 32A mcb on a 9.5Kw shower. switched the shower on full and measured how many amps is drawing which was well over 32A but the mcb doesnt trip. any ideas as to why?

This is normal, have a look at the trip curves for the particular type of protective device in the back of the good book, and factor in your operating current.

From the info in the table and the current you are running at, you will be able to work out how long the shower needs to be on for to make the MCB operate in overload condition, not short circuit. It should disconnect within 0.4 second in short circuit conditions.

Cheers..........Howard

 

[Specialist]

Type B will pop at 3 - 5 times the FLC
Type C at 5 - 10 times
Type D at 10 - 20 times
So in the event of a S/C they should Trip within their rated times but will actually hold a lot higher load than they're rated for, for quite a while.

 

[Guest123]

A current of 160A would be needed to operate a 32A B type MCB instantaneously.

It would hold on for an hour at around 47A.


The graphs are in app 3.

 

[i=p/u]

did i see someone type 1.45 times the rated current or am i making this up.. and for 1 hour

 

[SPARTYKUS]

1.13 all day for a type B 60898

so for a 32A thats just over 36Amps

So... if the voltage is for example 254Volts at the shower, thats nearly 9 & a 1/4 kWatts. Not quite sure what the 'current use graph' is for a shower but doubt it runs at full tilt all day.

 

[Deleted member 9648]

1.13 all day for a type B 60898

so for a 32A thats just over 36Amps

So... if the voltage is for example 254Volts at the shower, thats nearly 9 & a 1/4 kWatts. Not quite sure what the 'current use graph' is for a shower but doubt it runs at full tilt all day.

You've not met my missus have you?

 

[Engineer54]

You've not met my missus have you?

Well at least you have a ''Clean'' missus wirepuller!!

 

[Deleted member 9648]

Well at least you have a ''Clean'' missus wirepuller!!

She's better dirty:tounge_smile:

 

[SPARTYKUS]

Ok it might run at full tilt all day especially in certain extreme conditions :tounge_smile:

 

[Specialist]

She's better dirty:tounge_smile:

If she reads that, you better sleep with 1 eye open tonight mate

 

[Engineer54]

She's better dirty:tounge_smile:

Ahhhh, but a Clean Dirty missus!! got to be better than a Smelly Dirty missus ....surely?? :tounge_smile:

 

[Specialist]

:rofl:

Ahhhh, but a Clean Dirty missus!! got to be better than a Smelly Dirty missus ....surely?? :tounge_smile:

:rofl:

 

[Superspark23]

would you say its acceptable to have a 9.7kw shower on a 32a mcb? Surely this could be a no no espicially if the cable is 6mm or 10mm run under insulation.