1mm or 1.5mm for lighting?

Discussion in 'Electricians' Talk' started by Deano070578, Dec 10, 2005.

  1. Deano070578

    Deano070578 Member

    Can anyone tell me why some lighting circuits use 1mm cable and some use 1.5mm.

    What is the maximum number of battenholders can you have connected using either 1mm cable or 1.5mm??
     
  2. Lokkars Daisy

    Lokkars Daisy New Member

    Rule of thumb is 10 per circuit I usually use 1.0mm for a domestic installation gives more space in the switch boxes,many use 1.5mm though. It depends on other factors but in a domestic installation I have never found an instance where I had to use 1.5mm instead of 1.0mm
     
  3. Trip-Lock

    Trip-Lock New Member

    Yes LD is right.

    allow about 1100w load per lighting radial, and with each light taken to be 100w, that's 10 -11 units.

    Always use 1.5mm meself, as it's got abit more meat.

    Triplock
     
  4. Deano070578

    Deano070578 Member

    I've got a 500w floodling on one 6A MCB, so I'm guessing I shouldn't put any more than 5 Battenholders on the same radial?

    On the other 6A MCB, I know that each battenholder won't consume 100w though as I have all energy saving bulbs - don't suppose it would meet regs if I put any more than 10 battenholders on my other circuit though!
     
  5. Trip-Lock

    Trip-Lock New Member

    No,, because at a future date, someone could fit 100w bulbs
     
  6. unphased

    unphased Screwfix Select

    Hi Deano

    All circuits should really be designed to satisfy Regs. Its all very well using "rule-of-thumb" but I think this isn't good advice and should not be used for lighting circuits. The 100W per light fitting is a design minimum to enable initial cable sizes to be obtained. You count up the number of fittings, multiply by 100W then divide by 230V to get the current in amps. This will give initial cable size. Then you have to look at length of cable route and other factors that will determine actual cable size. In domestic situations there are few light fittings so 1.0mm2 is usually ample. However, 1.5mm2 is used where loads are greater and cable runs are longer. Also if light fittings are chandaliers all the load could be taken up by as little as one, two or three fittings then you have to start increasing cable size and dividing up circuits.

    UP
     
  7. Ripped Off

    Ripped Off New Member

    No,, because at a future date, someone could fit 100w
    bulbs

    You can only design for today, who's to say the next owner doesnt put in 50+ halogen lights in place of your single 100 pendants? After all it will have be wired correct with 1.0mm cable.
    Look at what you need work out the current with diversity factors then install whats required not might happen.
    Next owner might go for 1000W halogenss in every room, now thats loading it up a bit
     
  8. Rabbit Rabbit

    Rabbit Rabbit New Member

    I usually wire the loop-in/out in 1.5mm and the switch cable in 1.0mm it helps in identification later on.
     
  9. I usually wire the loop-in/out in 1.5mm and the
    switch cable in 1.0mm it helps in identification
    later on.

    Ahhhhhhhhh....., Now thats opened up a kettle of worms (what ever that means ?). Although you see a mix of 1mm and 1.5 quite often it is wrong to design and install like that as you are downsizing the cable at the switch drops. Also the two way switching is probably the longest run on the lighting circuit (when you add the length of the strappers and common)so there is no point in wiring in 1.5 (although i see where your coming from, loading etc)
     
  10. Lokkars Daisy

    Lokkars Daisy New Member

    I usually wire the loop-in/out in 1.5mm and the
    switch cable in 1.0mm it helps in identification
    later on.

    That's innovative :)
     
  11. Kai

    Kai New Member

    What size for that circuit do you put down on the EIC then?
     
  12. ­

    ­ New Member

    What size for that circuit do you put down on the EIC
    then?

    1.25 obviously ;)
     
  13. sinewave

    sinewave Screwfix Select

  14. Ripped Off

    Ripped Off New Member

    What size for that circuit do you put down on the EIC
    then?

    Just an X after all its the X factor
     
  15. Cornish Crofter

    Cornish Crofter Active Member

    I tend to stick to 1.5mm. It can be a bit of a squeeze in some instances.

    I once fitted 2.5mm to a bathroom light, as I had no 1.0 or 1.5. As I'm not Part P registered I had to get this approved by a BCO who said "Better that way around". He was OK with that provided I could secure the conductors etc into the connectors, and secure the cable grip on the fitting.

    CC
     

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