4 Core SWA linking two legs of a ring circuit

[Chris Packet]

Hi folks, I'm recently qualified so be nice...

I'm preparing a quote for the wiring of a dozen up and over garages which are in two rows of 6 and face each other with an 11m gap. One double socket per garage and fcu for a single 1500 fluorescent fitting. I was planning to wire them all as one ring circuit and use swa 2.5mm 4 core to link the two rows. Singles and pvc conduit for the wiring in each row of garages and then wiska box for the connection to the swa.

The armour would be the cpc so it wouldn't be a ring as such. I couldn't find anything in the regs which says it's a no no but I'm open to anyone opinions on this. It's obviously cheaper than running 2x 2.5mm swa cables but would it still be classed as a ring circuit?
I was hoping to use this job for my part p assessment so it has to be a perfect job. Feedback welcome.

Thanks!

 

[Sintra]

I would be more inclined to install 2 radials.

 

[Plonker 3]

As Sintra said, if someone decideds to overllad the circuit at least you have the ability to still have the lights working rather than losing everything in the garages.

 

[telectrix]

as they both said. ^^^^^

 

[guest119]

What is an up and over garage?

 

[davesparks]

Probably a garage with an up and over door

 

[cornishboy]

Separate radial to each garage with a 2 way garage unit with rcd in each unit controlled from one board least that way if u ever have to meter each one separately u can , don't think I would really like to rely on the swa for coc if they are rented out if people fiddle all the other units may loose the earthing too, garage units no more than 25 to 30 quid now and control gear and bg do a good one

 

[ipf]

Who'd be paying for the juice ?

Area of more than 100m2, too, I'd imagine.

 

[Pete999]

who is going to pay the electricity bill???

 

[Knobhead]

Run two lollipop rings, one for each row of garages.

I was going to make a suggestion but at a guess this is a cheap job not quality so I’ll not bother.

 

[Octopus]

1 ring? 2 radials? 12 seperate garages - are they used by multiple owners?

 

[Knobhead]

The whole setup sounds cheap and nasty to me. it would be interesting to know where this is fed from.

 

[Engineer54]

As usual, far too little information about the installation to give any meaningful advice!! We don't even know the construction material of these garages (metal, prefab concrete, brick, etc) or the supply source and earthing system to be used??

At the moment rather than being perfect, it could well end up a perfect cock-up!! lol!!

 

[7029 dave]

All tapped off the local street lighting.

 

[Guest77]

Hi folks, I'm recently qualified so be nice...

I'm preparing a quote for the wiring of a dozen up and over garages which are in two rows of 6 and face each other with an 11m gap. One double socket per garage and fcu for a single 1500 fluorescent fitting. I was planning to wire them all as one ring circuit and use swa 2.5mm 4 core to link the two rows. Singles and pvc conduit for the wiring in each row of garages and then wiska box for the connection to the swa.

The armour would be the cpc so it wouldn't be a ring as such. I couldn't find anything in the regs which says it's a no no but I'm open to anyone opinions on this. It's obviously cheaper than running 2x 2.5mm swa cables but would it still be classed as a ring circuit?
I was hoping to use this job for my part p assessment so it has to be a perfect job. Feedback welcome.

Thanks!

Yes we can see that, how about some info then, amount of sockets, length of runs, OCPD, earth arrangement, calculations regarding volt drop etc etc etc.

 

[Chris Packet]

Thanks for your replies. I'll ignore the rude/uselesscomments and respond to the more constructive ones. The garages are 1970'sconcrete block construction. At themoment one row of garages is supplied with 4mm swa on a 32A RCBO put in by aprevious sparky which goes to a single outside socket. It's fed from a small dbin the electrical room at the base of the flats.

This does limit me as the client has asked for power andlighting in each garage plus 2x security lights outside. So that will be 12sockets, 12 fluorescent lights and two security lights minimum. Two radialcircuits seems to be the way to go, I just thought a ring circuit would giveeach garage a better choice for extra sockets in the future. I'll use fcu forthe lights in the garages and the security lights.
I'm planning to fit a meter box with a garage cu with rcdmain switch and wire a radial circuit for each row on a 20A. Or maybe RCBO eachrow of garages. I'd change the 32A feed rcbo to an mcb.
I've calculated volt drop with 2.5mm cable and it's ok witha load of 9A. That's with a cable run of 40m which is being generous. I can'tsee anyone plugging in anything larger than a 2kw heater.
It's a block of flats so all the residents will be payingfor this hence why only one socket per garage and it will be used occasionallyhopefully.
TNS earthing arrangement at the flats but I was planning toinstall an earth spike and make the garages a TT system. Don't shoot me down!Everyone seems to have a different opinion on this.

 

[Engineer54]

One thing i wouldn't do, and that's TT'ing this installation, that will achieve Nothing!! Keep with the far superior TN-S earthing system, unless you can guarantee TN Ra results that is...

I'll let others comment on the proposed installation itself!!

 

[davesparks]

Why on earth do you want to ditch the TNS??

Why did you calculate VD with a load of 9A? It's a socket circuit which could have any load up to its OCPD rating plugged in to it.
Did you include the existing supply cable in the VD calculation ? And what % VD did you use for compliance?

 

[VoltzElectrical]

Thanks for your replies. I'll ignore the rude/uselesscomments and respond to the more constructive ones. The garages are 1970'sconcrete block construction. At themoment one row of garages is supplied with 4mm swa on a 32A RCBO put in by aprevious sparky which goes to a single outside socket. It's fed from a small dbin the electrical room at the base of the flats.

This does limit me as the client has asked for power andlighting in each garage plus 2x security lights outside. So that will be 12sockets, 12 fluorescent lights and two security lights minimum. Two radialcircuits seems to be the way to go, I just thought a ring circuit would giveeach garage a better choice for extra sockets in the future. I'll use fcu forthe lights in the garages and the security lights.
I'm planning to fit a meter box with a garage cu with rcdmain switch and wire a radial circuit for each row on a 20A. Or maybe RCBO eachrow of garages. I'd change the 32A feed rcbo to an mcb.
I've calculated volt drop with 2.5mm cable and it's ok witha load of 9A. That's with a cable run of 40m which is being generous. I can'tsee anyone plugging in anything larger than a 2kw heater.
It's a block of flats so all the residents will be payingfor this hence why only one socket per garage and it will be used occasionallyhopefully.
TNS earthing arrangement at the flats but I was planning toinstall an earth spike and make the garages a TT system. Don't shoot me down!Everyone seems to have a different opinion on this.

This is totally unacceptable. What happens when someone sets up a growing room in their garage. Is everyone going to split the bill?

This is potentially a major source of conflict and I wouldn't touch it with a bargepole. The landlord is well out of order instructing this setup.

 

[Guest77]

Thanks for your replies. I'll ignore the rude/uselesscomments and respond to the more constructive ones. The garages are 1970'sconcrete block construction. At themoment one row of garages is supplied with 4mm swa on a 32A RCBO put in by aprevious sparky which goes to a single outside socket. It's fed from a small dbin the electrical room at the base of the flats.

This does limit me as the client has asked for power andlighting in each garage plus 2x security lights outside. So that will be 12sockets, 12 fluorescent lights and two security lights minimum. Two radialcircuits seems to be the way to go, I just thought a ring circuit would giveeach garage a better choice for extra sockets in the future. I'll use fcu forthe lights in the garages and the security lights.
I'm planning to fit a meter box with a garage cu with rcdmain switch and wire a radial circuit for each row on a 20A. Or maybe RCBO eachrow of garages. I'd change the 32A feed rcbo to an mcb.
I've calculated volt drop with 2.5mm cable and it's ok witha load of 9A. That's with a cable run of 40m which is being generous. I can'tsee anyone plugging in anything larger than a 2kw heater.
It's a block of flats so all the residents will be payingfor this hence why only one socket per garage and it will be used occasionallyhopefully.
TNS earthing arrangement at the flats but I was planning toinstall an earth spike and make the garages a TT system. Don't shoot me down!Everyone seems to have a different opinion on this.

2 mistakes IMO, that double socket in the garage will have 2 multi extention leads plugged into it, a heater, a lawnmower, freezer and wood working machine plugged in to start haha