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Thread: House wiring questions

  1. #1

    Red face House wiring questions

    I am finishing a flat at home and am doing the electricals myself while getting an electrician to inspect and provide the cert...

    Two questions I have:
    1) Is 2.0mm twin and earth within spec for 16a plug circuits? Or does it have to be 2.5mm?
    2) Can I have one circuit for regular lights and plugs if there is very little on it (1x ceiling fan, 1x plug socket, 1x light, 1x extractor fan)?... i.e only one circuit for the basics (separate to the geyser - and stove is gas)

    I will have a small DB with my earth leakage, mains isolator, 16A circuit breaker, geyser isolator... the lights and plugs to be connected to the 16A breaker.

    What exactly needs to be passed? Is there an insulation certificate I need? I guess I need to let them inspect before I close the ceiling up since it will be a tight squeeze after the fact (low flat roof)...

    Any advice is appreciated...
    Last edited by Terrabiticfossilite; 11-06-2009 at 05:57 PM.

  2. #2

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    I would suggest that the plugs and lights be put on seperate circuit breakers. Even a single plug can be overloaded very easily.

  3. #3

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    1) 2.5mm^2 for plug circuits with 5 outlets per circuit
    2) Don't mix plug and lights circuits for no reason, as UP said.

    The geyser can go on a 25A circuit breaker and you should have an isolator near the geyser anyway. The water piping to the geyser must be earthed also.

    as for the cert, most importantly everything must be earthed, make sure
    the cables all the contacts in the DB and at the points are screwed in as tight as possible.

    Twin is *** to work with
    Last edited by Drake2007; 11-06-2009 at 06:25 PM.

  4. #4

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    The CB protects the wire. So if your 2.0 mm^2 wire is rated for more than 16 A, you should be fine. Remember, finely stranded wire is not legal for fixed house wiring. Single strand and 7 strand is OK. Where on earth you got hold of 2.0 mm^2 wire and 16 A CB's I don't even want to know. Geyser must be isolated in the DB and at the geyser. 20 A is fine for 150 l (3kW), 25 A only if it's a 200 l or 250 l (4kW). Keep lights and plugs separate.
    Quote Originally Posted by PeterCH View Post
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  5. #5
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    What they said.

    Use 2.5mm^2

    Your plugs need to be on an Earth Leakage unit. Your lights don't need to be.

    - Put your lights on a 10A 1P breaker 5kA rating. (2.5kA is junk)
    - Put your plugs through a 23A E/L and then through a 15A 1P breaker 5kA rating.
    - Don't put more than 8 plugs on a circuit. Rather just add another breaker. It'll save you a ball ache as well when one trips.
    - If you have a dedicated computer room, you might even want to put a dedicated plug circuit down, to make sure that the girlfriend doesnt trip your pc with the kettle/iron/hairdryer.

    Again - I'm not a big fan of giving electrical advice on these forums as it's very easy to make a mistake that can cause severe injury to someone in the future.
    Chicks are car guards. Kick 'em inna panty!

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  6. #6
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    plug and light circuits have to be separate, I would put them both on the circuit board.

  7. #7

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    Thanks guys, you've been great help... a couple more questions and points:
    - 16A breakers - I haven't got any, but I assume from the post further up that they are not available, so 20A is next?

    - about lights not needing earth - what does one do when you have a ceiling fan... or when you upgrade to a ceiling fan...? Do people add earth, or replace the whole cable? What about the circuit it's on, can it share the light's breaker? I assume they don't chew more than 120W...

    - What is 2.0 mm^2 wire? I have 2.0mm twin and earth (single core)... is it the same thing?

    - Agreed that twin and earth is *** to work with - esp. when conduit is used... If I opt to go straight twin and earth and skip the conduit, is it OK?

    Thanks again, you guys are awesome...

  8. #8

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    Don't you need a wireman's license to install those things?

    AFAIK an Electrical engineer won't give you a certificate unless you have a wireman's license. Just an educated guess though

  9. #9

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    Quote Originally Posted by mbp View Post
    so 20A is next?

    - about lights not needing earth - what does one do when you have a ceiling fan... or when you upgrade to a ceiling fan...? Do people add earth, or replace the whole cable? What about the circuit it's on, can it share the light's breaker? I assume they don't chew more than 120W...

    - What is 2.0 mm^2 wire? I have 2.0mm twin and earth (single core)... is it the same thing?

    - Agreed that twin and earth is *** to work with - esp. when conduit is used... If I opt to go straight twin and earth and skip the conduit, is it OK?

    Thanks again, you guys are awesome...
    Earth on twin is the centre (not copper) wire. Lights and the switches must be earthed but not neccesarily go through the earth leakage as far as I understand it.

    Wire is specified in cross sectional area or guage, not its diameter.

    If you're running conduit why not use house wire instead especially when it comes to wiring the light switches, also with the lights you can use 1.5mm^2 wire (cheaper).

    Ceiling fans are no problem on the light circuit.

    Another thing is you can not generally fish wires through conduit with more than 3 bends in unless you have a good fishtape, and with norsc cable it gets that much more difficult to pull through after.

  10. #10
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    Quote Originally Posted by mbp View Post
    Thanks guys, you've been great help... a couple more questions and points:
    - 16A breakers - I haven't got any, but I assume from the post further up that they are not available, so 20A is next?

    - about lights not needing earth - what does one do when you have a ceiling fan... or when you upgrade to a ceiling fan...? Do people add earth, or replace the whole cable? What about the circuit it's on, can it share the light's breaker? I assume they don't chew more than 120W...

    - What is 2.0 mm^2 wire? I have 2.0mm twin and earth (single core)... is it the same thing?

    - Agreed that twin and earth is *** to work with - esp. when conduit is used... If I opt to go straight twin and earth and skip the conduit, is it OK?

    Thanks again, you guys are awesome...
    Based on the questions you asked, and please - I'm not trying to sound demeaning as we all have our different talents, I would highly recommend you get an Jnr. electrician to do it for you. It will cost a bit more, but it will be done right & your house won't burn down - and if it does, your insurance will actually pay out.

    Quote Originally Posted by Pitbull View Post
    Don't you need a wireman's license to install those things?

    AFAIK an Electrical engineer won't give you a certificate unless you have a wireman's license. Just an educated guess though
    Electrical engineers have nothing to do with it. The qualified electrician signs the Certificate of Compliance based on tests he performs on the installation - regardless of the installer, because once he signs for it - he becomes responsible.
    Chicks are car guards. Kick 'em inna panty!

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  11. #11

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    Quote Originally Posted by Pitbull View Post
    Don't you need a wireman's license to install those things?

    AFAIK an Electrical engineer won't give you a certificate unless you have a wireman's license. Just an educated guess though
    Wireman's licence is to certify it, but yes you shouldn't stick fingers in the DB unless you know what you're doing i.e. trained electrician, or being supervised by one at least.

  12. #12

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    Awesome, thanks guys...
    About the DIY thing, I am totally for paying a qualified lekkie to do it but in this place I live, it can take 6 weeks just to get a quote... service in SA has absolutely dropped in recent years. That aside, since it's a small job and since I will be expanding in 6 months time, I will do this first leg myself and get the board in, then get someone in the second time around when I add on the lounge. I am confident and OK with the actual tech side of the work and the general understanding of the principals of AC, but what I struggle to find are the SA standards with regards proper wiring... I know there are certain things that need to be taken into account - # of plugs on a circuit, double insulation, etc. etc.... I would love to know if there is some place on the net where one can get those specs...

    As I said earlier, you guys are stars - your input is much appreciated. Voicy, you make a valid point on the insurance - probably the most compelling reason for me to have it passed by a licensed wireman... Drake, your knowledge is appreciated man - you obviously know your stuff.

  13. #13

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    The standard is SANS 10142; don't think it's available on the net, but the SABS will sell you a copy at a reasonable price (half price for students).
    Quote Originally Posted by PeterCH View Post
    Windows is ok in general, and sometimes it's necessary

  14. #14

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    Quote Originally Posted by mbp View Post
    Drake, your knowledge is appreciated man - you obviously know your stuff.
    See there's the danger with internet, I actually know next to nothing and only what I've picked up with wiring a few houses with my Bro who is an electrician.

  15. #15

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    Drake, don't undervalue yourself man

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