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Radial Voltage Drop Calculation?... By Load or MCB Rating?

Nano Brewery
I'm doing the calculation for total voltage drop.  I have 14 radials/ways going out.  As I understand it, that would equal a max allowance of 0.285% voltage drop per radial/way.  Or some sort of mixture throughout not exceeding the 4% drop allowance overall.  Firstly, is this correct? 


Secondly, should I be doing my calculations based on actual Load or the MCB ratings of the individual radials/ways? 


Thanks in advance!
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    Also, Broadgage, LED lighting is not ohmic in response, so this too should not be a problem They are not a few LEDs in series with a resistor, even a simple light bulb has a full-on feedback stabilized switch mode power supply, so all bulbs at any reasonable voltage should be the same brightness. Dimmable ones are a bit different they modify the feedback by the mains peak voltage, to make them dim at all!
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    Thanks all!


    On a side note.  Would you say that it would be suitable to use un-armoured cable for these radials?  I am intending to run cable tray all around the building, then clip direct for the run down from the cable tray to the sockets, enclosures or junction boxes...  Was wondering if I can get away with using NYY or N2XH instead of SWA?
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    yes, OK if the mechanical/ environmental  arrangements mean it cannot be damaged easily -  depends what is moving about - trolleys or furniture can quickly scuff a cable, but then wooden battens beside it at key points may be the way forward, as SWA does not do much better, its just that the first thing you reach is the earthed armour, not a live core.


    A note against DZs comment above:

    Many  cheaper lower wattage LED fittings do not contain a regulated supply,  but a series capacitive dropper and bridge rectifier. They are cooler running more reliable and cause less of an EMC issue than some of their expensive counterparts. Apart from that they have nothing in their favour.
    a5aa07cd668fef36b99f3e4d74c99e96-original-led_lamp.png

  • 0
    Hi all.  Hope all's well!


    So, I'm looking to order the cable in the next week.  Was wondering if H07RN-F would also be suitable option?  I would classify the mechanical/environmental damage risk as very low as it's:


    All internal.

    Run around on tray.

    All wiring and sockets are mounted on perimeter walls no lower than 110cm.

    All equipment is static - Cask's/Keg's will be moved around, but only in centre of room/work area.


    The only slight concern to me is the Hot Liquor Tank and Kettle/Boiler Elements - These are fixed to the vessels at approx 30cm from the floor - Again, I would say low risk of mechanical damage, but should I be ticking some additional boxes here by using CY or SWA?  I personally feel that NYY or H07RN-F would be adequate.


    Look forward to your feedback/advice/help!


    Cheers!
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    broadgage:

    0.285% Voltage drop seems a remarkably low allowance.

    5% is commonly allowed, though remember that this is the TOTAL voltage drop from origin to point of use. So if most of this has already been used in a sub main such a low allowance is possible.

     


    5 % is only for equipment not covered by a product standard (525.201), or, perhaps socket-outlets for general use - specific equipment (standards or manufacturers instructions) may well be different. See preceding Regulation, and the first one under 525, Regulation 525.1:

     



    525.1 In the absence of any other consideration, under normal service conditions the voltage at the terminals of any fixed current-using equipment shall be greater than the lower limit corresponding to the product standard relevant to the equipment.





    For example, BS EN 61851-1 for EV charging equipment specifies total - 10 % below nominal, i.e. 4 % in the installation in the UK, not 5 % ... although a manufacturer may permit more.


    Appendix 4, section 6.4, volt drop limits (along with Regulations 525.202 and 525.203) applies to Regulation 525.201, equipment not covered by a product standard ... and is "informative" ("guidance") not "normative" ("requirement of the standard").


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    RE: Choice of Cable Type, given your earlier description, I wold go NYY. A good rule of thumb  - although not scientific in any meaningful way - is that anything below 1 metre in horizontal height from the floor should really have some mechanical protection via armour/metal trunking/conduit etc.

    NYY should see you right for most of your installation, but take special care when choosing cable for heatars/hot areas.
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    Was wondering if H07RN-F would also be suitable option?

    Flex isn't often used for fixed wiring - partly because it's more expensive and harder to dress neatly, but also because the finely stranded conductors may need special preparation (e.g. ferrules) for use in some types of terminals. It's more usual to use a rigid conductor system for the fixed wiring and then transition to flex for the final span to the appliance where flexibility or heat resistance is required. Immersion heater normally require heat resisting flex for example.


    Other considerations on choosing a wiring system might include whether future changes/additions are anticipated (in which case singles in trunking/conduit might be advantageous), hygiene (what sort of cleaning processes will go on, does the system have to minimise nooks and crannies that can trap dust and dirt, will it have to be resistant to water ingress from washing down etc.) and whether the system is likely to come into contact with grease or oil.


    Also consider EMI/screening - especially if you have controls that might be chopping up the normal a.c. waveform into something more spiky (for speed or temperature control perhaps) .

     
    Run around on tray.

    How are you attaching the cables to the tray? Bear in mind that supporting cables only using plastic devices (e.g. nylon cable ties) is no longer permitted.


       - Andy.
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    For example, BS EN 61851-1 for EV charging equipment specifies total - 10 % below nominal, i.e. 4 % in the installation in the UK, not 5 %

    Presumably 4% as 6% might already be lost in the distribution system (230V+10%-6%)


    That can't be good for our continental cousins where their incoming supply is I think 230V +6% -10% - so their 10% allowance has already gone and they'd have to achieve zero v.d. in the installation to comply.


       - Andy.
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    Run around on tray.

    How are you attaching the cables to the tray? Bear in mind that supporting cables only using plastic devices (e.g. nylon cable ties) is no longer permitted.




    Cheers Andy.  Cables will be on top of horizontal tray, I understand that plastic cable ties are fine for attaching in this situation?  Is that correct?  Any vertical or horizontal cable runs without tray support will be clipped direct using metal wall cable clips.

    Re Cable choice - what options would you personally go for?

    Main cable runs to power sockets and/or isolators around perimeter on tray and clipped direct, all above 1m from ground - NYY?  SWA?

    Secondary cable runs from Isolator (1m above ground) to Element (30cm above ground) -  CY?  NYY?  SWA?


    Cheers!


  • 0
    whjohnson:

    RE: Choice of Cable Type, given your earlier description, I wold go NYY. A good rule of thumb  - although not scientific in any meaningful way - is that anything below 1 metre in horizontal height from the floor should really have some mechanical protection via armour/metal trunking/conduit etc.

    NYY should see you right for most of your installation, but take special care when choosing cable for heatars/hot areas.




    Cheers WH! 

    Re Cable choice - what options would you personally go for?

    Main cable runs to power sockets and/or isolators around perimeter run via tray and/or clipped direct, all above 1m from ground - NYY?  SWA?

    Secondary cable runs from Isolator (1m above ground) to Elements (30cm above ground) -  CY?  NYY?  SWA?


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