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Thread: DB Wire Size

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    DB Wire Size

    Hi Guys

    I just wanted to confirm if 10mm2 wire is OK for mains use (60A). I noticed that my mains wires feeding into the mains 63A MCB is 16mm2, but from there feeding into the Earth Leakage again from the EL into the first breaker it is all 10mm2. Everything else seems fine though. 2.5mm2 for all plugs and geyser (20A MCBs), 4mm2 stove (32A MCB) and 1.5mm2 for lights (10A MCB). The house has had two different COC's done over the years by two different companies. My earth wire coming into the house is oddly 10mm2 compares to 16mm2 for the live and neutral.

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    10mm is correct wire size yes.the overall Installation is correct for stove and plugs according to wire size.

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    Quote Originally Posted by Lindley View Post
    10mm is correct wire size yes.the overall Installation is correct for stove and plugs according to wire size.
    Thank you, I was just wondering since on another forum a member claimed that 10mm2 will fail a COC because it is only rated for 52A. https://powerforum.co.za/topic/2303-...&comment=37743

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    Wire size is relative to several factors, not just the load in Amps. The installation method, the wire/cable type and the length of the circuit should also be taken into account. A 4mm wire on a 32A breaker and a 10mm wire on a 63A breaker are a bit undersized from memory but I'd need to check the table in the regs when I'm in my office to confirm.
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    I agree with Andy that 10mm^2 are to small. If im correct your electrician have the option to increase the wire size to 16mm^2 or to decrease the breaking current of the mains breaker to 40 amps.

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    Thats interesting ... table 6.27
    10 amps - 1 mm
    16 amps - 1.5 mm
    25 amp - 2.5 mm ... I remember it being 20 amp - 2.5 mm ... I see a lot of aircon installations with 25 amp MCB's ( been looking at my SANS book a lot lately )

    If you look at the manufacturers table ... 10 mm can carry 61 amps ... but then there are other factors which need to be considered

    https://www.voltex.co.za/wp-content/...-and-Wires.pdf

    I have noticed prepaid meter installations popping up all over town using 10 mm to connect between the DB and the meter ... some dodgey looking installations ... I suppose you allow a R600 budget for an electrician to drive to site ... chase the wall or drill into the side of the DB ... mount the meter and connect ... you cant expect a COC and a quality installation ... you get what the supplier pays.
    Comments are based on opinion...not always facts....that's why people use an alias.

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    A note - calling the ECA is not going to get you an investigation unless the contractor is not an ECA registered member (they look after their members)

    I assume you need to contact the AIA or DOL ( dont know that they have suitably trained/qualitfied staff to tackle investigations ... hence the appointment of the
    AIA ? )

    Maybe someone who is up to date with this kind of stuff can comment ... I gave up with the ECA more than 10 years ago ... I think Brian Bilton got tired of all the calls back when I actually gave a shyte about this industry ... you can only flog a dead horse for so long.
    Comments are based on opinion...not always facts....that's why people use an alias.

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    Here is the table from the regs for single core PVC insulated wires. The table seems to be for longer runs of wire since the installation methods listed are all about how the wires are fixed. But I'm assuming that the "direct clipped" method in the table will suffice as a worst-case scenario compared to how they are installed in a DB board. According to the table then, 10mm2 should be able to carry 65A in a single-phase installation?

    Click image for larger version. 

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    Since back when we didnt even have TV's ( a flippen long time ago)

    I would use the general rule for wire size

    1.5 mm - 10amps
    2.5 mm - 20 amps
    4 mm - 30 amps
    6 mm -40 amps
    10 mm - 50 amps
    16 mm - 60 amps
    25 mm - 80 amps
    35 mm 100 amps

    I dont know of any issues ... i am still doing work for customers since tha 90's

    I have identified more issues (thermal) with loose connections and and dogdey equipment than under rated wire size ... make no mistake i do have find issue with under size wiring ... in fact today ... the aircon which was relocated last week ... the wire size is only 1.5 mm between the indoor unit and compressor ... it is showing signs of over heating ... by discolouring on the copper core and the plastic is not as felxible and the sheat is difficult to remove ... I will create a report and email it to the customer.
    Comments are based on opinion...not always facts....that's why people use an alias.

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    Diamond Member AndyD's Avatar
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    Quote Originally Posted by recre8 View Post
    Here is the table from the regs for single core PVC insulated wires. The table seems to be for longer runs of wire since the installation methods listed are all about how the wires are fixed. But I'm assuming that the "direct clipped" method in the table will suffice as a worst-case scenario compared to how they are installed in a DB board. According to the table then, 10mm2 should be able to carry 65A in a single-phase installation?

    Click image for larger version. 

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    The length or the run becomes a problem because of volt-drop. Yes, if the cable doesn't enter conduit anywhere along its run then and no there derating factors are applicable then a 10mm cable will suffice for a 65A load.
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