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Cable size

  • 06-12-2023 3:00pm
    #1
    SD_DRACULA
    Registered Users, Registered Users 2 Posts: 2,416 ✭✭✭


    I'm thinking about relocating the inverter to the shed, it is in the attic now with a 15m cable run to the CU and 6mm2 cable.

    The new location will be about 35m and I need to find out what cable size to use to avoid AC loses, was thinking 10mm2 but not sure if that's enough for the 35m run.

    Any suggestions?



Comments

  • #2
    Water John
    Registered Users, Registered Users 2 Posts: 21,808 ✭✭✭✭Water John


    What's the max output of the solar panels?



  • #3
    SD_DRACULA
    Registered Users, Registered Users 2 Posts: 2,416 ✭✭✭SD_DRACULA


    Well the inverter size is about 8kw so based on a quick calculator online seems like 10mm2 is about right:

    image.png




  • #4
    Buffman
    Registered Users, Registered Users 2 Posts: 2,862 ✭✭✭Buffman


    Ye, 10mm2 for that sort of distance. Have you actually got 8Kw of panels serving the inverter? Are you moving it closer to or further away from the panels? If the latter, you'll have to keep in mind the DC cable losses also.

    FYI, if you move to a 'smart' meter electricity plan, you CAN'T move back to a non-smart plan.

    You don't have to take a 'smart' meter if you don't want one, opt-out is available.

    Buy drinks in 3L or bigger plastic bottles or glass bottles or cartons to avoid the DRS fee.



  • #5
    munsterfan2
    Registered Users, Registered Users 2 Posts: 415 ✭✭munsterfan2


    As we're here, what size cable ( is there a site / equation ) for DC cable runs. I have some ground mount, side closest to shed is maybe 6m, far end of row is closer to 18m from inverter. 6 x 360w panels ?



  • #6
    graememk
    Moderators, Home & Garden Moderators Posts: 6,384 Mod ✭✭✭✭graememk


    https://www.boards.ie/discussion/comment/121462060#Comment_121462060

    standard 4mm2 is fine.



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  • #7
    SD_DRACULA
    Registered Users, Registered Users 2 Posts: 2,416 ✭✭✭SD_DRACULA


    https://www.boards.ie/discussion/comment/121461981#Comment_121461981

    Hmm closer to one string, away from two others but that's the exact same distances I have now, shed string is on a 12m DC cable and house strings on 5m, the distances would probably flip the other way around except the shed string will probably be 2m from inverter now and the house ones 15m away. On 4mm dc cables currently. Strings are 4kwp each.



  • #8
    Buffman
    Registered Users, Registered Users 2 Posts: 2,862 ✭✭✭Buffman


    https://www.boards.ie/discussion/comment/121462320#Comment_121462320

    Ye, 4mm should be fine, obviously the old saying bigger is better is still true but I don't think it's worth replacing the 4mm with 6mm for a small reduction in loss.

    https://www.boards.ie/discussion/comment/121462060#Comment_121462060

    4mm sounds fine for it off the top of my head. There are lots of DC cable sizing tools online, here's a random one:

    https://www.solar-wind.co.uk/info/dc-cable-wire-sizing-tool-low-voltage-drop-calculator


    FYI, if you move to a 'smart' meter electricity plan, you CAN'T move back to a non-smart plan.

    You don't have to take a 'smart' meter if you don't want one, opt-out is available.

    Buy drinks in 3L or bigger plastic bottles or glass bottles or cartons to avoid the DRS fee.



  • #9
    slave1
    Moderators, Sports Moderators Posts: 19,266 Mod ✭✭✭✭slave1


    Will you really be outputting 8kW? Can your panels feed 8kw? 10mm2 is a bitch to manoeuvre, what does the calculator say for 6kW



  • #10
    SD_DRACULA
    Registered Users, Registered Users 2 Posts: 2,416 ✭✭✭SD_DRACULA


    https://www.boards.ie/discussion/comment/121462470#Comment_121462470

    In summer for sure from PV but also batteries can supply the 8kw no probs, and there's a rating for cables whether they're in trunking or not, to do with heat, etc.

    Inverter spec sheet says 6mm2 for the grid supply but probably not over 35m



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