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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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  • 0
    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!




    Very difficult to say - I'm not able to see the overall situation remember.


    If the robustness of SWA isn't necessarily needed, I might consider BS 8436 types (which goes under various brandnames, but often have "shield" in the name) - much easier to dress and gland off than SWA, but you still get some decent protection from shock if the cable is damaged (unlike all-insulated types), easy to get a decent IP rating using simple stuffing glands, and you get some reasonable screening thrown in too. But that's just thought to add to your list - rather than a recommendation.


    If the heaters are similar to domestic immersion heaters, there's likely to be a requirement for heat resisting cabling - so heat resisting (HOFR) flex would be my first thought - but again that can't be a recommendation. Hopefully the heater's installation's instructions give you a clue to what's actually required. Likewise the heater's boss might constrain your choice (is it fitted with a 20mm threaded inlet or a cord grip that'll only accept flex for instance?)


       - Andy.


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  • 0
    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!




    Very difficult to say - I'm not able to see the overall situation remember.


    If the robustness of SWA isn't necessarily needed, I might consider BS 8436 types (which goes under various brandnames, but often have "shield" in the name) - much easier to dress and gland off than SWA, but you still get some decent protection from shock if the cable is damaged (unlike all-insulated types), easy to get a decent IP rating using simple stuffing glands, and you get some reasonable screening thrown in too. But that's just thought to add to your list - rather than a recommendation.


    If the heaters are similar to domestic immersion heaters, there's likely to be a requirement for heat resisting cabling - so heat resisting (HOFR) flex would be my first thought - but again that can't be a recommendation. Hopefully the heater's installation's instructions give you a clue to what's actually required. Likewise the heater's boss might constrain your choice (is it fitted with a 20mm threaded inlet or a cord grip that'll only accept flex for instance?)


       - Andy.


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