SWA problem

[Vilasalvas]

Hi, I wonder if someone could answer this one? Due to a mistake, the garage at the bottom of the garden (80mts away) had 3 core 4mm SWA run to it. When this mistake was discovered by the contractor he ran a second 4mm SWA to the garage (when it should of been a 10 or 16mm cable). Anyway the upshot of all this is, one of the electricians (both part P) would like to run 2 separate 4mm supplies using the 3 cores as live, neutral and earth. The other, however, is looking at using one SWA with all three cores running a LIVE and one SWA with all 3 cores running a NEUTRAL and the earthing being covered by BOTH steel armour covering. Garden has been al landscaped now a third! cable is out of the question. Cheers.

 

[jamie-spark]

Deleted

 

[HandySparks]

What equipment / loads will this supply be used for?

 

[kingeri]

Do both cables follow exactly the same route?

 

[Brightspark2]

Line, neutral, CPC in each SWA is the correct way to do it. Not the other way.

Providing certain conditions are met they could be connected in parallel. This would be your 'electricians' decision.

 

[11kstanton]

Drop me put! Get another contractor, this contractor is a 2 bob c£$€

 

[11kstanton]

Spelling mistake ... Drop me out **

 

[D Skelton]

The other, however, is looking at using one SWA with all three cores running a LIVE and one SWA with all 3 cores running a NEUTRAL and the earthing being covered by BOTH steel armour covering.

BAD idea. Without going into huge amounts of scientific detail, this way of doing it will induce current into the armour/earth and potentially create excessive heat at the termination ends (assuming the cables are terminated into a steel enclosure of some sort). This idea needs binning off and so does the electrician that proposed it because he hasn't a clue what he's doing!

 

[SparkyJoe]

The other, however, is looking at using one SWA with all three cores running a LIVE and one SWA with all 3 cores running a NEUTRAL and the earthing being covered by BOTH steel armour covering.

Take 3 steps back, get a run up, and kick him in the nuts.

names not graham is it lol

 

[Engineer54]

Absolutely nothing wrong with paralleling cables so long as they follow the same route (same length)are of the same size and type etc. In this case however, i'd be concerned with volt drop over the 80 odd meters. Off hand i think 4mm has a value of around 12 or 14 mV so 2 X 4mm will give you 6 to 7 mV, you can do/check the calculations yourself to see if it complies.


As for this numbty electricians idea, Mr D has the right idea what to do with him!! lol!!

 

[Octopus]

What exactly are you planning to do/use in your garage?

 

[joelypops]

Take 3 steps back, get a run up, and kick him in the nuts.

names not graham is it lol

I've had several 'experiences' with a graham too lol

 

[Engineer54]

Another problem, if it's a PME supply to the house, is if the garage has any extraneous earthed metal parts, such as a metallic water supply!! Then it will have to be a 10 mm 3 core cable or a separate 10mm bonding cable taken out to the garage. Failing that, the dreaded UK TT solution!! ...lol!!

As this is the builders electricians mistake, any remedial costs will be against the builder!!

 

[Vilasalvas]

Thanks for all the comments, to answer the questions, both supplies are run along side each other and underground. They both are connected to a consumer unit in the house and a metal box with service connectors in the garage. There are two buildings next door to each other at the end of the 85mt run. One is a hobby garage with strip lights small ring with 3 double sockets on. Normal hand tools drills grinders etc. There is a MIG welder and a compressor which has not been used or tried yet. The other building is a music studio with tons of equipment i.e. mixing desk (3-400 watt) computers, tape decks, amps, 5 or 6 Led spots but there is not really a situation where all the equipment is powered up at the same time. I will not be working in the garage and the Studio at the same time either, hope this helps.

 

[Tiny Spark]

Are these cables run in some kind of ducting?
If so get the guy to pull them out and replace them with the right damn cable!!

 

[SirKit Breaker]

BAD idea. Without going into huge amounts of scientific detail, this way of doing it will induce current into the armour/earth and potentially create excessive heat at the termination ends (assuming the cables are terminated into a steel enclosure of some sort). This idea needs binning off and so does the electrician that proposed it because he hasn't a clue what he's doing!

i know what i wanted to say, but didn't know how to say it. Cheers…………..Howard

 

[HandySparks]

You're going to run into voltage drop problems, especially if you put a heater or two on in the cold weather.

Not much more than 12A per 4mm² cable to drop 5% over that distance.