Supply to a 63A RCB

[Spike1947]

Hi

I need to put a 63A RCB 6 way weatherproof consumer unit ( Garage unit ) with 2x6A , 2x20A , 1x32A MCB's, in my workshop at my farm , now the supply to it, comes from the Main 83A 3 phase fuse box on the other side of the wall where I want to mount this unit , the length of cable would be around 500mm max .

Question , with it being such a short length of cable for the feed could I use a 6mm2 cable ! , as I have loads of it, but no 10mm2 .


cheers


spike

 

[Spike1947]

I meant to say , 2x16A , 2x6A , 1x20A .

 

[bigspark17]

What ocpd are you putting on it at supply end.?

 

[Spike1947]

There is no ocpd on the supply , apart from the main 3 phase 83A 30mA RCD trip switch coming into the Farm , basicly I am wanting to know if a short length 400mm of 6mm2 cable will take the load of a 63 amp 30mA double pole RCD trip switch .

 

[Leesparkykent]

Sounds like a bodge..

 

[The Ghost]

Just get some 10 mm² from wholesalers they do cut it.

 

[Spike1947]

Attached BS7671

 

[Spike1947]

Sounds like a bodge..

Can you not just answer my question ! .

 

[HandySparks]

Question , with it being such a short length of cable for the feed could I use a 6mm2 cable ! , as I have loads of it...

If you calculate that it needs 10mm², then that's what you install. Just buy what you need:

6242Y 10.0mm² Grey Twin & Earth Cable 100m & Cuts - https://www.tlc-direct.co.uk/Products/CA10G.html
6181y 10.0mm² Tails Brown 50M - https://www.tlc-direct.co.uk/Products/CA10TBRslash50.html

 

[HandySparks]

Attached BS7671

View attachment 33739

But that's for 90 deg C cable.

 

[HandySparks]

BTW, an RCD isn't an OCPD.

 

[bigspark17]

83A rcd is your protection??? So as this isnt an ocpd you must be relying on DNO for ocpd on this submain? i think you need rethink your design, whats the earthing arrangement.?

 

[Leesparkykent]

Can you not just answer my question ! .

No as you don't seem to understand the basics so IMO would be dangerous to give you advice

 

[Richard Burns]

You describe no overcurrent protection at the supply, this would be best before it goes through the wall as otherwise you are relying on the DNO supply fuse which will not be suitable for a 6mm² cable.
The cable is running through a wall so is not in free air, there is a significant limitation to the heat loss.
You have a total maximum load of 84A from the sum of circuit breakers, though this is not the design current.
You are reading the wrong table for the the cable type.

Overall, no, 6mm² cable is unsuitable for this application. Depending on your supply fuse size 16mm² or 25mm² cable would be more appropriate.

 

[The Ghost]

Your question was answered

 

[Spike1947]

Hi

Thanks for your feedback , the lights (lights 60W ) are only for the Tack room x1 and grain store x1 , chicken room x2 , the sockets are for these rooms only , they are part of the main workshop ( but they are separated ) it all was the Cow shed !.

The Main workshop wiring is fine ( off the blue phase ) , anyway what I have done is :

Have changed the Main supply fuse feeding the 63A RCD from 83A to a Lawson 63A ,( this is off the Yellow phase , house is off the Red phase ) and used a 10mm2 cable to supply the 63A RCD , yes I know I really should put in 16mm2 tails ! , needed it doing today

ps: I would not do anything until I was 100% sure it was right , that is why I am asking the questions , maybe stupid questions but if I get the correct answer at the end that is what I will do ! , not before .
I am not a Electrician as you have guessed , I am a time served mechanic so I do have a bit of savvy about me , not a lot but a bit ! , as they say in my trade you learn something everyday ! .

spike

Read more: Supply to a 63A RCB - http://www.diynot.com/diy/threads/supply-to-a-63a-rcb.467722/#ixzz4Ltk1uUJ4

 

[bigspark17]

Well being as its a grain store you have now got to be very carefull with ip rating of everything in that vasinity,may be worth reading DSEAR. So after everybody telling you NO its not ok to use 6mm cable youve used it anyway?? Why dont you post a pic of the incoming 3phase set up and maybe we can give more accurate advice.

 

[Richard Burns]

It would have been cheaper, safer and legal to have bought the right size cable.
Choosing to work illegally and unsafely for greater cost it not generally the best approach.
However you are unlikely to overload any parts with the set up as you have described.

 

[Spike1947]

You describe no overcurrent protection at the supply, this would be best before it goes through the wall as otherwise you are relying on the DNO supply fuse which will not be suitable for a 6mm² cable.
The cable is running through a wall so is not in free air, there is a significant limitation to the heat loss.
You have a total maximum load of 84A from the sum of circuit breakers, though this is not the design current.
You are reading the wrong table for the the cable type.

Overall, no, 6mm² cable is unsuitable for this application. Depending on your supply fuse size 16mm² or 25mm² cable would be more appropriate.

It is not fed direct from the DNO fuse , this feed come via a 63A RCD 30mA from the DNO fuse box ! .

Well being as its a grain store you have now got to be very carefull with ip rating of everything in that vasinity,may be worth reading DSEAR. So after everybody telling you NO its not ok to use 6mm cable youve used it anyway?? Why dont you post a pic of the incoming 3phase set up and maybe we can give more accurate advice.

No not 6mm2 , I am using 10mm2 as I have just stated ! .

 

[Spike1947]

You describe no overcurrent protection at the supply, this would be best before it goes through the wall as otherwise you are relying on the DNO supply fuse which will not be suitable for a 6mm² cable.
The cable is running through a wall so is not in free air, there is a significant limitation to the heat loss.
You have a total maximum load of 84A from the sum of circuit breakers, though this is not the design current.
You are reading the wrong table for the the cable type.

Overall, no, 6mm² cable is unsuitable for this application. Depending on your supply fuse size 16mm² or 25mm² cable would be more appropriate.

It is not fed direct from the DNO fuse , this feed come via a 63A RCD 30mA from the DNO fuse box ! .

Well being as its a grain store you have now got to be very carefull with ip rating of everything in that vasinity,may be worth reading DSEAR. So after everybody telling you NO its not ok to use 6mm cable youve used it anyway?? Why dont you post a pic of the incoming 3phase set up and maybe we can give more accurate advice.

No not 6mm2 , I am using 10mm2 as I have just stated ! .