Main Fused Switch isolator

[Sparky10]

Came across this on an install today and wondering if its correct,

Main Fuse was 100A, cables going into a meter then from a meter into a 63A switched fused isolator, Then 16mm Armoured from isolator into fuse board about 15m away.

now i'm confused as to why its 100A Main fuse - 63A isolator then back to 100A (Main switch in CCU) or is this normal and ok.

Then was confused as to why water needed to be earthed if its plastic - copper - plastic all over the place

 

[Andy78]

I see you're in training right ?

What function do you think the main switch in the CU is capable of ?

 

[MJPD29]

100a main switch is not for protection, it is an isolation switch rated at 100a

 

[Sparky10]

I see you're in training right ?

What function do you think the main switch in the CU is capable of ?

I am yes, 100A main switch im assuming is the maximum loading the whole board could take (although never heard of that tripping) but in this case would never get to that as there is a 63A isolator before it...

 

[Sparky10]

100a main switch is not for protection, it is an isolation switch rated at 100a

So having this 63A wylex switch before the board is normal practise? i tried to find it in the regs book but i couldn't ;(

 

[MJPD29]

I am yes, 100A main switch im assuming is the maximum loading the whole board could take (although never heard of that tripping) but in this case would never get to that as there is a 63A isolator before it...

Main switch won't trip, 100a is just the maximum current it is rated to allow before things go wrong. It is solely for isolation. The fuse is for overcurrent and short circuit protection of the cable feeding the board

 

[MJPD29]

It is because of the length of the cable feeding the board . I think it might be covered under 434.2.1, but I don't have the big book to hand so don't quote me on that lol

So having this 63A wylex switch before the board is normal practise? i tried to find it in the regs book but i couldn't ;(

 

[Andy78]

So having this 63A wylex switch before the board is normal practise? i tried to find it in the regs book but i couldn't ;(

It is providing overcurrent and fault protection to the distribution circuit, same as you would provide for any circuit.

There are times you can exclude this for tails ..... see the reg Matthew quoted and 433.2.2

 

[Sparky10]

Thank you so much in pointing me in right direction, Have no idea how you guys know this book by heart!

 

[JAWS]

Thank you so much in pointing me in right direction, Have no idea how you guys know this book by heart!

I read replies from Members on here and think these all know their stuff big time.

 

[ipf]

Thank you so much in pointing me in right direction, Have no idea how you guys know this book by heart!

It's more of an understanding and experience matter than knowing the book by heart.
In a few years, when you've finished your training and been in the job for a while, you'll be wondering why you even asked the question.

 

[KentSparky]

Thank you so much in pointing me in right direction, Have no idea how you guys know this book by heart!

Never be scared to ask when you are unsure and never think you know it all.
The only stupid question is the one you don't ask