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How to supply a 20A Distribution cct?

Farmboy
Sorry if this is too simplistic a question but I'm wondering what you think, given I've had conflicting views from a trade assoc tech dept and Hager tech dept.


A 65m, SP+N, 20A (estimated, but could be subject to some increase) distribution cct, fed from within a commercial setting (an osteopathy/acupuncture service provided in a converted ground floor flat), is to supply a shed/summerhouse with a couple of sockets (for a kettle and TV) and a couple of LED bulkheads (via cb's in the shed CU), sited at the end of the garden. How would you supply the distr. cct at the meter position?

- From a henley block in the existing tails:

              - Its own modular enclosure containing DIN rail mounted main switch and 20A fuse carrier.

              - A rotary handled 20A fused switch disconnector.

- From a 20A cb in the existing CU.


From the trade assoc., one said from the CU, another said it's got to have its own main sw, another said no problem with the modular encl and fuse carrier. While Hager said its got to be the rotary type, not the fuse carrier.


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  • Former Community Member
    0 Former Community Member
    If it's only a 20A supply then you wouldn't need anything bigger than 6mm² to carry that, a 16mm² is properly overkill (that's including volt drop and power requirements etc.)


    I'd take it from a 20A RCBO in the existing CU on a bit of 6mm² SWA (unless it's already on an RCD incorporated into the existing CU. I'd make sure it's going onto an RCD/RCBO just to be safer, but an MCB is fine as long as all requirements are met and the board in the shed incorporates additional protection in case anyone decides to use a radio in the garden or a lawnmower etc.)


    Reason I'd go for a 6mm² is that it has a capacity of 53A (ref method D) and you'd have a volt drop of only about 4%. You could use a 10m² but I think it's overkill for what you're suggesting will be required.
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  • Former Community Member
    0 Former Community Member
    If it's only a 20A supply then you wouldn't need anything bigger than 6mm² to carry that, a 16mm² is properly overkill (that's including volt drop and power requirements etc.)


    I'd take it from a 20A RCBO in the existing CU on a bit of 6mm² SWA (unless it's already on an RCD incorporated into the existing CU. I'd make sure it's going onto an RCD/RCBO just to be safer, but an MCB is fine as long as all requirements are met and the board in the shed incorporates additional protection in case anyone decides to use a radio in the garden or a lawnmower etc.)


    Reason I'd go for a 6mm² is that it has a capacity of 53A (ref method D) and you'd have a volt drop of only about 4%. You could use a 10m² but I think it's overkill for what you're suggesting will be required.
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