Outside Power using RCBO please advise Ask questions and find answers to many subjects relating to electrics and electrical work

[JAP]

Can someone please advise if this set up is correct (will get an electrician to check over prior to using the circuit).

I have a 6mm SWA (Steel wired armoured) cable radial circuit protected by a 32 Amp 30mA Single Module SP RCBO.

The 6mm SWA cable connects to my garage and goes into a metal clad socket. As 2 x 6mm cables would be tight to connect in the same socket, to continue the radial circuit I have used a 2.5mm cable to connect into a 30amp junction box, i.e, I have now changed the size of the cable on the circuit from 6mm to 2.5mm in the metal clad socket so we now have a 6mm cable and a 2.5mm cable in the metal clad socket.

The 30 amp junction box has 3 connections:

1. The obvious connection which continues the radial circuit from the 1st matal clad socket mentioned above.

2. A weatherproof cable 2.5mm that connects to an outside MK weatherseal socket.

3. Final connection is another 2.5mm cable which goes to a MK Metal Clad Switched Connection Unit (Spur) and then from the spur 1.5mm cable to the fluorescent light. (I will protect the light with a 5amp fuse in the switched connection unit (spur)

I would like to clarify please

1 - Is the 32 Amp RCBO the correct size for the circuit?

2 - Is it ok to change the size of the radial circuit from 6mm to 2.5mm any issues or problems with this?

3. Are there any concerns with the above set up, i.e, is it safe and will it pass the appropriate electric regs etc.

Thank you in advance to any constructive posts

[ericmark]

As I read your post it seems you have 2.5mm cable protected by a 32 amp rcbo the 2.5mm should be protected with a 20 amp device unless in a ring.
The rules do not allow a change in cable size without a overload device being fitted within 3 meters of the change. Although one does need some common sense here and if the whole lot was from a 20 amp overload then I would not really be too worried on change of size. The lights I assume on a fused spur unit with no more than 5 amp fuse. Most light fintting are only rated at 5 amp so even if the cable can take more it still needs 5/6 amp protection.
One problem is any new circuit will come under part p and although electricans can sign off their own work they can't sign off someone elses work and it would need to go through local authority building control so I would approch an electrician first before you do anything and let him design and although you may still do donkey work he can then sign it off.
Eric

[JAP]

ericmark,

Many thanks for you reply.

The problem is the circuit and sockets etc are already installed and just waiting on the final connection i.e. fitting the 32amp RCBO into the consumer unit by an electrician. Wasn't aware about the local authority so will have to check this and hope I can find an electrician to pass the work who may be ameniable to putting his name down??

With regards to the light yes you're right the lights are on a fused spur unit with a 5 amp fuse.

If I understand you correctly if I was to change the RCBO to 20amp then it would be ok to leave the 2.5mm cable in situ? Is that right?

Alternatively as I have had the RCBO for some time (need to look for the receipt) say I was to change the cable size to 6mm or 4mm as 2 x 6mm would be a bit tight to get into the metal clad socket could I still use my 32amp RCBO?

So in other words I would now have :

6mm SWA from consumer unit to 1st socket in garage

From 1st socket 6mm or 4mm to 30 amp junction box

From 30amp junction box 6mm or 4mm weatherproof cable to the outside MK weatherseal socket.

and finally 6mm / 4mm cable to fused spur for the light (protected by 5amp fuse)

Would such a set uo then be ok i.e, would it be safe and pass the appropriate part p regs (albeit I do get someone to pass the work)

Please let me know what you think on this.

regards

J.A.P

[ericmark]

Page 363 of 17th Edition and the update which is available on iet web site as free down load does say 4mm can be used on a 32 amp mcb.
Hope you find someone to sign. I don't like the part p regs but they are law.
All best Eric

[JAP]

ericmark,

Thanks very much for your advice appreciate it.

best wishes
J.A.P

[JAP]

Hi EricMark/ Anyone Else Have Any Thoughts Please

Sorry to be a pain but run into another problem,

I have changed all the cables in the garage to 6mm right up to the fused spur as recommended.

However the only issue is with the cable that feeds the outside MK weatherseal socket. This was a very short connection around 10 inches. I was using 2.5mm Hituf - Protected Cable from the junction box in the garage basically drilled through the wall to feed the outside socket, but Hituf don't do a 6mm version and I don't think anyone makes any 6mm cable for outside use that is not SWA - If I use 6mm SWA I can gland to the MK Weatherseal socket but what do I do with the connection that goes to the 30amp junction box?

Obviously I will not be able to gland to a standard round 30amp junction box. Does anyone have any ideas please on what to use ? I need a junction box to connect 3 x 6mm cables with the ability to gland to it.

Or can I use a standard metal box e.g.

http://www.awin1.com/awclick.php?mid=12 ... -4-x-4-x-2

I could then gland to such a box and continue the cable through one of the cut outs to the 30amp junction box.

The other option is not to gland at the end that connects to the 30amp junction but doubt this is correct and would meet the part p regulations.

Any advice is appreciated.

regards
J.A.P

[ericmark]

Go to whole sale outlet and ask. You can get adaptable boxes and din rail with proper connections and link bar and do a proper job or simply a backing box with lid and some chock block there are loads of options.
Eric

[JAP]

Many thanks again Eric,

Once again your advice is really helpful. Believe it or not before posting I spoke to a local wholesaler but didn't get decent advice.

So just to clarify I can go with a : Adaptable Box 4" x 4" x 2" 20mm. Pre-galvanised Steel Adaptable Box with knockouts, this has got a lid on it. I can then gland into the metal box, and if I understand you correctly by chock block I can use a 30amp Terminal Strip to connect 3 x 6mm cables placing this inside the adaptable box. Would this be correct?

Best Wishes

J.A.P

[JAP]

Had a thought that I would like to run past the forum please regarding
connecton to the consumer unit.

Want to use 6mm SWA cable to connect a 32amp RCBO to my consumer unit.

I was initially thinking of glanding direct into the consumer unit but rather than risk cracking the base of the consumer unit could I not use a metal adaptable Box say a 4" x 4" x 2" 20mm, Pre-galvanised Steel Adaptable Box with knockouts, this has got a lid on it.

link below is to the item:

http://www.awin1.com/awclick.php?mid=12 ... -4-x-4-x-2

I can then gland into the adaptable metal box, and then place a 30amp terminal strip inside the box to connect 2 x 6mm cables, 1 cable being the SWA and the other onwards to the RCBO in the consumer unit.

Or do without the terminal strip connection glanding into the adaptable metal box but leave the swa cable long enough to use the inner cable to connect direct to the consumer unit I could protect the inner part of the swa cable with conduit. Is this a better option then using the terminal strip?

Does anyone have any thoughts on this please? Any potential problems? Will it meet part p regulations when coming to inspection?

regards

[ericmark]

I would use a metal clad backing box and a blanking lid much smaller and neater. No blanking plates shown in screw fix but see http://www.screwfix.com/prods/15151/Ele ... Metal-Clad for an example of box. These are available in most good whole sale outlets with blank instead of switch.
Eric
PS a barrel nut as used to connect to lengths of conduit and two brass male sorry forget name will connect box to consumer unit very well.
I have even used a stuffing gland and removed rubber internal bits in past. Big one of course.

[JAP]

Thanks again Eric

best regards

J.A.P

[JAP]

Hi Eric,

I have had a look round on the net and can see what you mean re : the metal clad box and blanking lid e,g :

However I am having difficulty finding any info on what you are referring to when you state :

[i]PS a barrel nut as used to connect to lengths of conduit and two brass male sorry forget name will connect box to consumer unit very well. I have even used a stuffing gland and removed rubber internal bits in past. Big one of course.[/i]

You don't happen to have a internet URL link to the item/items please.

I can gland the 6mm swa cable into the metal clad box as suggested but apart from using a 30amp terminal connection strip I am having difficulty picturing the type of connector/connectors you are referring to to join the the other standard 6mm twin and earth cable that needs to go onwards to the RCBO into my consumer unit.

I just have a standard wylex split load plastic consumer unit like :

regards

J.A.P

[JAP]

Hi Eric, Forum

I have had a look round on the net and can see what you mean re : the metal clad box and blanking lid e,g :

However I am having difficulty finding any info on what you are referring to when you state :

[i]PS a barrel nut as used to connect to lengths of conduit and two brass male sorry forget name will connect box to consumer unit very well. I have even used a stuffing gland and removed rubber internal bits in past. Big one of course.[/i]

You don't happen to have a internet URL link to the item/items please.

I can gland the 6mm swa cable into the metal clad box as suggested but apart from using a 30amp terminal connection strip I am having difficulty picturing the type of connector/connectors you are referring to to join the the other standard 6mm twin and earth cable that needs to go onwards to the RCBO into my consumer unit.

I just have a standard wylex split load plastic consumer unit like :

regards
***********************************************************

Does anyone have any thoughts to the above posting please if I was to use the metal clad box and blanking lid fto gland the 6mm SWA cable does anyone foresee a problem with just using a 30amp terminal connection strip to then connect to the 32amp RCBO in the consumer unit.

[ericmark]

The barrel nut or coupler see http://www.qvsdirect.com/Galvanised-Cou ... 19102.html will take two brass bushes see http://www.qvsdirect.com/Male-Brass-Bus ... 19110.html which allows good connection between box and consumer unit. I would not try to connect in the box but run cable straight through box to consumer unit. The box is only to stop gland pulling on consumer unit and bending plastic a conduit box would do same thing. Sorry I got a post saying you had replied but when I looked nothing there then on second post there were two shown think Sysop is a bit slow can’t understand why they inform there is a reply before releasing it to be read but seems that’s the way it works.
Eric

[JAP]

Thanks again Eric for all your help

best regards

J.A.P