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Sizing the inverter

edited 21 August 2022 at 1:20PM in Green & ethical MoneySaving
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  • ispookie666ispookie666 Forumite
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    With the current lead time for installs, DNO would not be the limiting factor  
    I am also with UKPN.  
    They will upgrade fuse to 100A for free. 
    “Don't raise your voice, improve your argument." - Desmond Tutu

    System 1 - 14 x 250W SunModule SW + Enphase ME215 microinverters (July 2015)
    System 2 - 20 x 330W Jinko Panels + Enphase IQ7+ microinverters (Jan 2022) + Givenergy AC Coupled inverter + 2 * 8.2KWh Battery (May 2022) + Mitsubishi 7.1 KW and 2* Daikin 2.5 KW A2A Heat Pump
  • BrimbleBrimble Forumite
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    Thanks for all the continued support.

    So above, both @70sbudgie and @Martyn1981 have suggested that an export-capped inverter and AC battery might be the best solution. But why an AC battery? Why wouldn't the solar panels be able to charge a DC battery before sending anything to the inverter? What about a 'hybrid inverter' with a DC battery, would that be more or less appropriate for the system I'm proposing?

    (By the way, I'm not 'pro DC' or 'anti AC', I'm just not sure I understand which would be better for me and why).
  • Martyn1981Martyn1981 Forumite
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    Brimble said:
    Thanks for all the continued support.

    So above, both @70sbudgie and @Martyn1981 have suggested that an export-capped inverter and AC battery might be the best solution. But why an AC battery? Why wouldn't the solar panels be able to charge a DC battery before sending anything to the inverter? What about a 'hybrid inverter' with a DC battery, would that be more or less appropriate for the system I'm proposing?

    (By the way, I'm not 'pro DC' or 'anti AC', I'm just not sure I understand which would be better for me and why).
    Good question. I may be wrong, but with a DC side battery (hybrid inverter) I think there's less choice, and you might not be able to expand the battery size as large. But I could be completely wrong, and offerings may have improved.

    Actually, thinking about it, there's the Givenergy systems which are good looking, and have a 5kW hybrid offering that can cope with 6.5kWp of panels. Hopefully others who know a hell of a lot more than me on batts, will be able to help.
    Mart. Cardiff. 5.58 kWp PV systems (3.58 ESE & 2.0 WNW)

    For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
  • QrizBQrizB Forumite
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    Brimble said:
    What about a 'hybrid inverter' with a DC battery, would that be more or less appropriate for the system I'm proposing?
    I'm pretty sure @Reed_Richards has a Goodwe(?) hybrid inverter with export limiting.
    N. Hampshire, he/him. Octopus Go elec & Tracker gas / Voda BB / Lyca mobi. Ripple WT2 member.
    2.72kWp PV facing SSW installed Jan 2012. 11 x 247w panels, 2.5kw inverter. 29MWh generated, long-term average 2.6 Os.
    Kinda busy right now but I try to pop back to the forum every so often. Drop me a PM if you need me!
  • Reed_RichardsReed_Richards Forumite
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    QrizB said:
    Brimble said:
    What about a 'hybrid inverter' with a DC battery, would that be more or less appropriate for the system I'm proposing?
    I'm pretty sure @Reed_Richards has a Goodwe(?) hybrid inverter with export limiting.
    That's true but I only have a 4.8 kWp set of panels and my Goodwe inverter is rated for a maximum 3.68 kW export (though I could make it less in software if I choose).  There is/was another model with a higher maximum export capacity in the range.
    Reed
  • BrimbleBrimble Forumite
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    With the current lead time for installs, DNO would not be the limiting factor  
    I am also with UKPN.  
    They will upgrade fuse to 100A for free. 
    Just reading back through this thread, I'm not sure I understand the 100A fuse bit.

    I've read elsewhere that 3-phase supply might cost several thousand pounds to install, so presumably that's something different? Are you talking about a 100A fuse but still on single phase power? Sorry for my ignorance of electrical matters, but what will that 100A fuse enable me to do that I can't do without it? Is it about DNO approval, or is it about what I can power in my home?

    On my consumer unit fuse box, the double-size main red switch says 100A, so does that mean I already have the thing you are saying I might need? (House was built in 2007, so quite new, if that makes any difference to what it is likely or unlikely to have). Might it mean that I actually need MORE than 100A fuse (if the house already needed it before my plans to install PV I mean)?
  • edited 24 August 2022 at 10:56AM
    Reed_RichardsReed_Richards Forumite
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    edited 24 August 2022 at 10:56AM
    If you are exporting or importing anything less than about 15 kW then a 60 A fuse (which was the standard) will be sufficient.  The consumer unit will not tell you what size your mains fuse is, just what its maximum current rating is.
    Reed
  • edited 24 August 2022 at 11:31AM
    QrizBQrizB Forumite
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    edited 24 August 2022 at 11:31AM
    Brimble said:
    Just reading back through this thread, I'm not sure I understand the 100A fuse bit.
    On my consumer unit fuse box, the double-size main red switch says 100A, so does that mean I already have the thing you are saying I might need?
    Before your consumer unit is the electricity meter, and before the electricity meter is the main DNO fuse. This fuse is generally* the limiting factor in how much power you can pull from (or feed into) the distribution network.
    Common sizes are 60A, 80A and 100A.
    • A 60A fuse limits you to 13.8kW (at a nominal 230V).
    • An 80A fuse limits you to 18.4kW.
    • A 100A fuse limits you to 23kW.
    If you want more than 23kW, you tend to need three-phase where you get three separate cables each capable of supplying the same 100A.
    * There's also the matter of the meter tails. 100A needs 25 sq. mm. tails but 16 sq. mm. are often used and might need replacing if you get a larger fuse fitted.
    House was built in 2007, so quite new, if that makes any difference to what it is likely or unlikely to have.
    I would hope that a house built in 2007 would have at least an 80A main fuse.
    N. Hampshire, he/him. Octopus Go elec & Tracker gas / Voda BB / Lyca mobi. Ripple WT2 member.
    2.72kWp PV facing SSW installed Jan 2012. 11 x 247w panels, 2.5kw inverter. 29MWh generated, long-term average 2.6 Os.
    Kinda busy right now but I try to pop back to the forum every so often. Drop me a PM if you need me!
  • Reed_RichardsReed_Richards Forumite
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    The man who came to change my mains fuse told me that they are pretty slow to blow so you might be able to exceed the rated fuse current for a while.
    Reed
  • BrimbleBrimble Forumite
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    QrizB said:
    I would hope that a house built in 2007 would have at least an 80A main fuse.
    I do indeed - I looked in my box outside where the meter is, and there is a single fuse with a sticker on it say 100A - thanks for your guidance on that. :smile:
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