lights in outbuildings....

[JimK]

A friend has acquired a few ramshackle sheds and erected them approx 10ft from his existing mains equipped outbuilding. Theres a modern rcd equipped cu in the outbuilding with 2 unused mcbs.

What is required to get light to the sheds? He doesn't want sockets just a bulb and switch for each shed.

I can easily help him wire the internals (lights & switches), but is a full new lighting circuit needed or is daisy chaining allowable and why/not?

Also whats required to span the 10ft gap overhead between buildings?

Is surface mounting ok for the wiring? It won't be hidden any time soon and there's an rcd on the cu....

Any other gotchas to beware?

TIA

Jim K

[meow2222]

cable, clips, switch, backbox, lampholder and...

what's the difference?

...catenary wire or bamboo

why not?

The rules on external T&E have tightened up in the 17th, if that matters to you

NT

It won't be hidden any time soon and there's an rcd on the cu....

[JimK]

/ Snip like/q

Sounds like it'll be a learning experience for you too :-)

Jim K

[ARW]

Well that is news to me.

[ARW]

Cable.

Daisy chaining is called a radial and is allowed. Your call.

Catenary wire plus a couple of other bits to fix the catenary wire.

Yes

[Tim Watts]

He could chain them from a suitable existing RCD protected circuit (like a 6A protected lighting circuit in the first outbuilding).

Vehicular traffic under the wire or not?

If not personally a bit of catenary wire well mounted between the two buildings should be fine.

And run some suitable cable along that. If it were me I'd run HiTuf cable along that - but I expect others might be happy with T+E. In either case leave drip loops at each end, partly, well, to drip water off and partly to leave some slack to dissipate flexing fatigue when the wire sways in the wind.

Don't see why not. Just be aware of whether it is likely to get hit or not but people walking past carrying stuff.

The only one I can think off - are any of these buildings metal? Or with metal framing? That might lead to complications with respect to the earthing arrangements - something I'm not going to attempt to offer any opinion on if they are!

[JimK]

Cable.

Daisy chaining is called a radial and is allowed. Your call.

Catenary wire plus a couple of other bits to fix the catenary wire.

Yes/q

Thanks Adam.

If radial is used and number of lampholders is say 5, and max length of radial would be say 50m, would I be better with 1 or 1.5mm2 cable?

If switch cables ran externally (to correct IP rated switches), any special requirements for those cables' protection? or anything?:-)

Cheers Jim K

[Tim Watts]

should help you :)

What's the over current protection? Type B 6A breaker with RCD protection? This will also have a bearing - the ability to clear a fault within 0.4s with the fault on the furthest end of the circuit.

Whilst an RCD would guarantee that a L-E fault will be cleared on a mile long bit of wet string, you need to clear a L-N fault before the cable suffers damage.

Is it 50m back to the breakers? What's the run from there back to the main CU like?

[John Rumm]

A cable. SWA if he wants to bury it, or something like HiTuf if suspended.

You mean extending the lighting circuit from the existing shed? Yup that is ok so long as the implication of a trip taking out all the lights is not a problem. (i.e. it depends on what is going on in the sheds)

Yup that's generally fine - but again it depends on the use of the buildings and how likely one is to damage the exposed wiring.

More details here:

Main things to think of are voltage drop, overall loop impedance, and the type of earthing and whether you are exporting an equipotential zone.

[John Rumm]

Could you clarify?

[JimK]

Could you clarify? /q

+1 That would be helpful...

Jim K

[JimK]

/He could chain them from a suitable existing RCD protected circuit (like a 6A protected lighting circuit in the first outbuilding).

Vehicular traffic under the wire or not? /q

No vehicles under.

/ If not personally a bit of catenary wire well mounted between the two buildings should be fine.

And run some suitable cable along that. If it were me I'd run HiTuf cable along that - but I expect others might be happy with T+E. In either case leave drip loops at each  end, partly, well, to drip water off and partly to leave some slack to dissipate flexing fatigue when the wire sways in the wind. /q

Understood thanks.

/> Is surface mounting ok for the wiring? It won't be hidden any time soon and there's an rcd on the cu....

Don't see why not. Just be aware of whether it is likely to get hit or not but people walking past carrying stuff.

The only one I can think off - are any of these buildings metal? Or with metal framing? That might lead to complications with respect to the earthing arrangements - something I'm not going to attempt to offer any opinion on if they are/q

No 99% wooden or masonry.

Thanks a lot

Jim K

[JimK]

/

should help you :) /q

Will peruse :-)

/What's the over current protection? Type B 6A breaker with RCD protection? This will also have a bearing - the ability to clear a fault within 0.4s with the fault on the furthest end of the circuit.

Whilst an RCD would guarantee that a L-E fault will be cleared on a mile long bit of wet string, you need to clear a L-N fault before the cable suffers damage.

Is it 50m back to the breakers? What's the run from there back to the main CU like? /q

Er mcbs are in cu?

Cheers Jim K

[Tim Watts]

Where's the over current protective device? In the house CU? Or in a local mini CU in the outbuilding?

And what is protecting this particular circuit you wish to extend? Type B MCB with RCD (in or behind the MCB)?

[JimK]

/Where's the over current protective device? In the house CU? Or in a local mini CU in the outbuilding?

And what is protecting this particular circuit you wish to extend? Type B MCB with RCD (in or behind the MCB)? /q

The outbuilding has a 3 phase supply.

Not sure as yet what there is between that and the recent 6? way mini cu with RCD & mcbs in, 2 of those MCB ways are unused but have 16a & 32a MCBs in currently, so could have any type of 6a MCB put in as necessary for a new circuit.

Extending existing lighting circuit is currently not on his wish list for some reason, that is protected by a 6a MCB (all in the same mini cu with RCD), not sure what type at present.

Cheers Jim K

[Brian Gaff]

I'd be careful about using wire to carry the weight. Some so called stainless i used some years ago only lasted a couple of years. The best version I ever did used plastic pipe.

Brian

[JimK]

Thanks for all pointers and assistance so far, looks straightforward enough.

But..... Do normal cheapo bulkhead light fittings provide enough room to take 3 x 1.5mm cables ? Or are we going to be titting about with junction boxes for every light too?

And are all 6a MCBs the same size/fitment? or are they proprietary and 'unique' to each manufacturer &/or cu?

The

Jim K

[ARW]

The starting point is the maximum known load. Five lights assuming 20W CFls and not 500W halogen etc is f*ck all and you would be looking at a couple of hundred metres before you have to start calculating votage drop.

You are always better off using 1.5mm instead of 1.0mm

[John Rumm]

They normally have knockouts that will take a 20mm threaded conduit connector, so getting the wires in is not difficult. There is *usually* terminal space, but that will depend on the actual make and model of fitting. However you could always crimp / use wagos internally.

Somewhere between the two. Generally its best to find the same make and version the CU was designed for (not only does it make sure it fits, it also means the CU's type approval is still valid). However its not always and option.

We did have a bash at a device interchangeability table some years back

- its out of date now:

Contactum for example now have two versions of their CUs and MCBs etc - they have slightly different live busbar entry positions that require a copper shim to be used when mixing generations.

[meow2222]

I though it was no longer to clip T&E to the wall behind plants & leave it.

NT