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Thread: DB Wire Size

  1. #11
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    Quote Originally Posted by AndyD View Post
    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.
    Talking about derating ... I had to do the calculations for an 800 amp supply ... 150 metres long ... everything was on track until the cables got to the underground duct ... that 30 m piece in the ducts makes a huge difference to the cable calculation.
    Comments are based on opinion...not always facts....that's why people use an alias.

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    Interesting questions, am I aloud to use silicone insulated wire or panel flex in a db? Some people reckon than you only allowed to us gp wire.

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    Quote Originally Posted by Frans400 View Post
    Interesting questions, am I aloud to use silicone insulated wire or panel flex in a db? Some people reckon than you only allowed to us gp wire.
    I dont see why you cant use panel flex (so long as it is rated for the the voltage).

    There is some confusion with flexible cables ... panel flex ... welding cable ... automotive cable ... its all about the rating (voltage) some cables are only insulated for up to 50 V other cables up to 1000 V and higher.

    YOu can use flexible cables for just about anything so long as it is correctly rated for the applications ... you can wire inside the DB to motors/ pumps / controls ... you can even use flexible busbars.

    Maybe one of the smart fellas could do a write up expalining the difference.
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  4. #14
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    Attached is an example of welding/flexible cable you cannot use for 230/400 VAC applications ... not in a DB or any other application with a voltage rating of over 100 VAC/VDC.

    https://www.l-osales.co.za/download-...ding-cable.pdf
    Comments are based on opinion...not always facts....that's why people use an alias.

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    Click image for larger version. 

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    Ok, so I measured the cross sectional area of the commercially available busbars pictured above.

    On the left is for dinrail. Top section between breakers 7mm sq.
    Pins going down into breakers 4mm sq.

    On the right is for samite. Top section between breakers 18mm sq.
    Pins going down into breakers 10mm sq.

    So from the above, as far as dinrail is concerned, It seems as if self made bridges using 6mm sq house wire will do a better job than the commercially available buzbar, I also know that if a product has been especially designed for a certain purpose, then it should be used.

    What sayeth the other toppies ?

    Peace out ... Derek

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    Something to consider ... the time frame the load is present on the bussbar or any cable for that matter.

    Installing a 6 mm cable for a stove for example ... which is used maybe a max of 2 - 3 maybe 4 hours a day (unless like one of my customers who does baking for a shop) ... and only 10-20 % of the rated load ...etc etc etc ... In all the years as a sparkie I personally have never seen a 6 mm stove wire burnt due to overloading ...only burnt at the connection.

    How often is a 60 amp supply to a house under full load ... not very often ... I have been running load profiles for solar/inverter installs ... I can tell you that we hardly ever see anything over 30 amps.

    From my experience .. .you more likely to see a burnt out terminal on a circuit breaker than a overloaded wire ... the last fire I went to ... it started at the connector block the aircon tech used to extend the calbe to the plug ... it completed guttered the granny flat ... thats where it gets interesting ... does the insurance company pay out and sue the aircon company ... what if the installation was done by a non registered installer ... the entire building was burnt ... yet the place the fire started was as clear as daylight ... you could actually see the V up the wall from the connector.
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  7. #17
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    Quote Originally Posted by Frans400 View Post
    Interesting questions, am I aloud to use silicone insulated wire or panel flex in a db? Some people reckon than you only allowed to us gp wire.
    Not sure why you'd want to use silicone insulated wire, it would work out expensive and is unnecessary from a temperature rating point of view...

    The regs mention the voltage rating of the insulation must be higher than any voltage found in the DB, they don't specify it must be PVC as far as I know.

    The problem with using silicone wire or any panelflex type wire would be that it's fine stranded conductors which may be against the manufacturers instructions for the types of wire the circuit breaker cage clamp terminations or the neutral bar screw terminations are suitable for....although using it in conjunction with bootlace ferrules may be acceptable.
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