Sizing the inverter

ispookie666

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. 

Brimble

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).

Martyn1981

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.

QrizB

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.

Reed_Richards

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.

Brimble

ispookie666 said:

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)?

Reed_Richards

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.

QrizB

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.

Reed_Richards

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.

Brimble

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.