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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

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  1.  
    If the plug on the end of the cable is rated as 250v/6a would it be deleterious to use an equivalently rated cable? Or 2 x 3 core 250v/6a cables
    • CommentAuthorRex
    • CommentTimeDec 25th 2019
     
    I know I am getting flak on the basis that since I don't understand this topic, I should get a professional to do it. There was a time when i didn't understand driving either, but have never had an accident, so am happy to try and understand cables.

    A trailer company gave me two samples, both 7 core. The 8.5mm o/d one has copper wire cores at around 1mm o/d which computes as 0.78mm2, which is the same as the old cable. The larger has an o/d of 11mm and a twisted core o/d of 1.6mm giving an are of about 2mm2. It is unlike I can fit the larger diameter cores into the plug.

    But my question, what is the difference between this heavy duty 6 core, 2mm2 cable designed for trailers with a max of 24v and normal electrical cable designed for 250V? Such as the one in the link above, where the 0.75mm2 is good for up to 750V.

    The Chinese supplied one in the link is possibly the one I need as it is multi-stranded tinned copper so very flexible.
  2.  
    Posted By: RexBut my question, what is the difference between this heavy duty 6 core, 2mm2 cable designed for trailers with a max of 24v and normal electrical cable designed for 250V? Such as the one in the link above, where the 0.75mm2 is good for up to 750V.

    IMO it is going to be the standard of the insulation - or rather the standard to which the insulation is tested/rated. The 24v cable's insulation will be rated for lower voltage than the 250v

    In addition AC will need a higher insulation level than DC (for the same voltage) so the type of voltage needs to be taken into account.

    Having said that you don't know what the manufactures used for the 24v cable. It could be that it is the same as the 250v cable because it may not be worth changing the material if the cost doesn't justify and no one cares if the 24v cable has a higher spec than needed, just that the insulation must meet the spec of the required standard - on the other hand the 24v insulation might have cheaper insulation = weaker electrical strength.
    • CommentAuthorRex
    • CommentTimeDec 26th 2019
     
    Interesting and thanks for your answer. I am surprised that for the average Joe (me?), cable is cable is cable. Who would ever have thought the nature of the insulation could be so important?

    I don't think I can use the trailer cable because although it is multi-strand, I should at least use similar 9tineed copper / 20 strand) as it will have greater flexibility. Not that I will be using it much, but it does need to be wound to pack away, and needs to be sufficiently flexible that when in use, hangs loosely so that the natural 'bend' does not overpower the stability of the lighting stands.
  3.  
    As I suggested above 2 x 3 core my be an alternative to a 6 core - if sourcing 6 core is problematic.

    Also if the plug (and presumably the socket) is rated as 250v 6A then using an equivalently rated cable could be justified (IMO)

    And regarding insulation, my electric fence cable has an OD of 6mm and a wire dia. of 1.5mm so quite a thick layer of double insulation, but this is to contain 10,000V (and negligible amps) and if you think about a car spark plug wire, this is also has thick insulation surrounding a fairly thin conductor. Thickness/quality of insulation is needed to contain the volts whereas thickness/quality of the conductor (wire) is needed to carry the amps. High voltage needs thick insulation regardless of the amps, high amps needs thick wire regardless of the volts (a bit simplified)
    • CommentAuthorgyrogear
    • CommentTimeDec 27th 2019
     
    Posted By: RexWho would ever have thought the nature of the insulation could be so important?


    don't mind me, but I consider that to be an insulant question...

    gg
    • CommentAuthorMatBlack
    • CommentTimeDec 27th 2019
     
    Posted By: RexI know I am getting flak on the basis that since I don't understand this topic, I should get a professional to do it. There was a time when i didn't understand driving either, but have never had an accident, so am happy to try and understand cables.

    A trailer company gave me two samples, both 7 core. The 8.5mm o/d one has copper wire cores at around 1mm o/d which computes as 0.78mm2, which is the same as the old cable. The larger has an o/d of 11mm and a twisted core o/d of 1.6mm giving an are of about 2mm2. It is unlike I can fit the larger diameter cores into the plug.

    But my question, what is the difference between this heavy duty 6 core, 2mm2 cable designed for trailers with a max of 24v and normal electrical cable designed for 250V? Such as the one in the link above, where the 0.75mm2 is good for up to 750V.

    The Chinese supplied one in the link is possibly the one I need as it is multi-stranded tinned copper so very flexible.



    Cross sectional area of cable is chosen for the current it can handle. Theres adiabatic equations for how long insulation will last before setting on fire due to fault current. 2mm2 will take more current than 0.75mm2.

    Cant remember if the top of my head but I think normal flex cable is rated to 1000v anyway. If youre sure of the cross sectional area ( stamped on the side?) And it exceeds the old cable csa it should be sound. Again, check the current draw of the device.
    •  
      CommentAuthordjh
    • CommentTimeDec 27th 2019
     
    Posted By: Peter_in_Hungarymy electric fence cable has an OD of 6mm and a wire dia. of 1.5mm so quite a thick layer of double insulation

    All the electric fences I have seen use uninsulated wire. I'm not sure why it would need insulating?
  4.  
    Posted By: djh
    Posted By: Peter_in_Hungarymy electric fence cable has an OD of 6mm and a wire dia. of 1.5mm so quite a thick layer of double insulation

    All the electric fences I have seen use uninsulated wire. I'm not sure why it would need insulating?

    Insulated wire is used to carry the charge from the fence unit to the fence and to carry the charge across gates, in both cases this is often underground.
    •  
      CommentAuthordjh
    • CommentTimeDec 27th 2019
     
    Ah , OK. Cable associated with the fence but not actually part of it :)
    • CommentAuthorrevor
    • CommentTimeJan 1st 2020
     
    The spec of HO7RNF may suit have a look. Don't think it is done in 6 cores but you could double up on 3 core making sure you connect correctly the ends. Google the cable reference and here is one to start.

    https://www.cef.co.uk/catalogue/categories/cables-and-accessories-ho7rn-f-rubber-flexible-cable

    CEF will sell by the cut length. I have used the cable to wire external LED floods in a coastal exposure environment. It is very flexible. (It is used in high quality power tools and industrial extension leads).
    • CommentAuthorRex
    • CommentTimeJan 3rd 2020
     
    Thanks for all the advice and Happy new Year to all.

    After much head scratching, I have ordered 5m of the 6 core, 1mm2 section cable that DJH linked to in the second post of this thread. Since it is rated up to 750V and is a larger cross section than the existing (0.75mm2) I hope there will not be a big 'BANG!' When I have replaced the crumbly cable, I will post back the result.

    The next issue which I have found some links to, is the fact that since the flash unit as not been used in a considerable time, the capacitors will need to be re-formatted. I have found some methodology so will follow when re-cabled.

    If all works, I will replace the cable on the other two flash heads. And may be start using it again.

    I hate to throw the unit away, but the total replacement cost of cable will be around £75 and I doubt that I would get that for the whole unit when working on an eBay sale.

    Toodle pip
    • CommentAuthorgyrogear
    • CommentTimeJan 3rd 2020
     
    I for one wish you a FULL (i.e 365 days...) and happy new year !

    gg
    •  
      CommentAuthordjh
    • CommentTimeJan 3rd 2020
     
    Posted By: gyrogearI for one wish you a FULL (i.e 365 days...) and happy new year !

    What year are you living in? That's short-changing him! There are 366 days this year :)
    • CommentAuthorgyrogear
    • CommentTimeJan 3rd 2020
     
    eek - apologies !

    yes, leap-year, I never could count...

    gg
    • CommentAuthorRex
    • CommentTimeJan 17th 2020
     
    A heads-up!

    Received the 6 core cable fro China, and yes, with the silicone insulation, is very flexible. It does not feel particularly robust, but as it will have little use and only ever dragged across a carpeted floor, I think it will do the job.

    Re-wired the head, and have spent the last couple of days reforming the capacitors using a 150w bulb in the income live to act as a resistor. Been following a 'reform' regime, there has been quite a lot of clicking from the flash-pack, no smoke, no bangs. The ready light now comes on, have been hitting the flash button and the caps are recharging.

    Long time since I used it but sounds pretty much as I seem to recall; nothing getting hot so believe I have managed to revive the unit.

    Now to find something to photograph!
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