Wiring – What are the 4-wire cables use for

lightingwiring

I am trying to figure out what's the best way to get electricity from my garage to the garden. In the garage, I have the normal 230 V outlets/lamps, and the power gets there via 1.5 or 2.5 mm^2 (still need to check) 3-wire (line, neutral, ground) cable. I was planning to connect another cable to it, lay it in the garden and connect to the lamps/water-proof outlets there. In the shop, I've discovered the dedicated cables for the outdoor use. But they also have a 4-wire cable. I wonder what the purpose of this cable may be. In the photo below I show it next to the normal 3-wire cable.

enter image description here

Best Answer

enter image description here

Those cables have totally different applications. On the left, you have common household power cable in the modern EU (IEC) colors:

  • Ground: mandatory green/yellow
  • Neutral: mandatory blue (today; older installations use other colors)
  • Hot: by common practice, brown

The American equivalent is bare-white-black. These colors in 14-2 Romex (jacketed cable; 14 gauge; 2 conductors +ground) is used all over the place in every US home.

The right is for three-phase power, specifically "delta" power (which by definition does not have a neutral.) That is why there is no blue "neutral" in the bundle. This is bigger power, for heavier loads such as factory lighting or air conditioning in a large retail store.

It'd be an odd duck in residences — while three-phase "wye" power comes down your street (230 V to neutral, 400 V phase to phase), it's rare to pull all 3 phases into a home. Probably more common in a townhouse (mansion) or a 12-unit apartment block. Because of its notable lack of neutral, this cable would only be useful for running large motors or heating units, say to deliver 400 V delta to a large air conditioning unit of 5 kW capacity. Here are the IEC color codes:

  • Ground: mandatory green/yellow
  • Phase 1: Brown
  • Phase 2: Black
  • Phase 3: Gray

Black is no longer legal for neutrals in the UK, and unless the cable is pre-2004 old stock, it is certainly intended for 3-phase delta, since the colors are just right for it.

What I hear from Euro folks is this is how normal 3-and-earth is sold, and you are expected to re-mark one of the phase wires to be neutral (if you need neutral). I would re-mark the black, since you should take it "out of play" as it's not a valid neutral color anymore, so that'll reduce confusion.

Note: North American people can never re-mark or re-sleeve wires, *except in cables, they can re-mark a white (neutral) wire to be a phase/hot. In wiring where only certain wires are always-hot, the remarked white must be used for the always-hot.

Related Topic