Solar install with two consumer units

[JohnD]

However, I think now due to project constraints it may be worth me running appropriate cable in place now rather than destroying walls to run it in the future.

You can more likely run conduit yourself ready to have the appropriate cable drawn in by the installer. Mine is is a utility duct, and in the garage it is exposed, and the conduit looks like 20mm convoluted flexible. Might be 25mm.

 

[dungargon]

Yes it can


In a simplified way, yes.
Voltage from the inverter is higher than the grid supply, energy from the inverter will be used before anything is taken from the grid.

Hi, sorry to resurrect this thread but I have this same situation and it seems like the second consumer unit is bypassing the solar and only using mains power. Solar was already connected when the second consumer unit was added, and the electrician who did wasn't sure whether it would work or not... Does something need to be changed to get solar to consumer unit too?

Thanks in advance for any wisdom

 

[DetlefSchmitz]

The only issue I can see is the labeling of the meters. The one next to the inverter would usually be called a generation meter. The one nearest the supply would be an import meter and would be what you would pay based on. The other one doesn't do much unless you are on some scheme I don't know about.
Basically the generated mains would find its way to whatever wanted to use it rather than go through the import meter.

 

[dungargon]

Thanks @DetlefSchmitz. That’s my error on the labels.

It’s weird though, the battery is full, but when I use anything on the second consumer unit my smart meter says it’s coming from the grid

 

[Why Not Indeed]

This doesn't add up, the junction box cannot "know" to somehow let energy flow from the import meter to CU2 but not from CU1 to CU2, unless it is not merely a junction box [I don't know the word for what such a thing would be].
I assume the battery hangs off the inverter? Not that it would make any difference to the question.

As an analogy, think of the wiring as a series of tubes carrying fluid, and the two sources of power in the circuit as sources of pressure. The tendency is for the fluid to flow from high to low pressure areas until they balance out.
The more "pressure" contributed by the inverter, the lower the difference in pressure between either side of the import meter, and the less fluid that flows into your house through it.
I'm not sure if this analogy helps you, but it's all I've got

 

[StephenStephen]

Thanks @DetlefSchmitz. That’s my error on the labels.

It’s weird though, the battery is full, but when I use anything on the second consumer unit my smart meter says it’s coming from the grid

You have a battery? (Curious as I don't see it on the circuit sketch)

 

[dungargon]

This doesn't add up, the junction box cannot "know" to somehow let energy flow from the import meter to CU2 but not from CU1 to CU2, unless it is not merely a junction box [I don't know the word for what such a thing would be].
I assume the battery hangs off the inverter? Not that it would make any difference to the question.

As an analogy, think of the wiring as a series of tubes carrying fluid, and the two sources of power in the circuit as sources of pressure. The tendency is for the fluid to flow from high to low pressure areas until they balance out.
The more "pressure" contributed by the inverter, the lower the difference in pressure between either side of the import meter, and the less fluid that flows into your house through it.
I'm not sure if this analogy helps you, but it's all I've got

This is a fantastic analogy, thank you! Makesnit a lot clearer.

It’s a “double pole connector block”
https://www.ccmsupplies.co.uk/100a-double-pole-connector-block.html, but sounds like basically a kind of tube that should let the electricity across.

The battery hangs off the inverter as you said.

It doesn’t add up somewhere though… I’ve seen it exporting back to the grid from the PV at the same time my smart meter says I’m using 5 kwh.

I’ll experiment again tomorrow if the sun comes out!

Thanks for sharing your wisdom with me

 

[dungargon]

You have a battery? (Curious as I don't see it on the circuit sketch)

Sorry, I was trying to keep it simple

 

[Adam_151]

Is there a CT anywhere, battery systems generally meter the incomming supply and will (depending on settings) set the output to minimise power imported (as far as reaonably practicable given both the loading and the amount of stored energy and generation available) as oppsed to non battery systems that just feed verything they have into the grid.

If the CT is on the supply to DB1 rather than the main incomming tails then the system will be trying to match its output to load pulled through this board, rather than the instalaltion as a whole

 

[DetlefSchmitz]

I’ve seen it exporting back to the grid from the PV at the same time my smart meter says I’m using 5 kwh.

Could you describe in detail what you where looking at and reading to come to this conclusion. (I'm assuming you meant 5kW.)

 

[dungargon]

I have solarman app connected to the inverter. It doesn’t ‘see’ any consumption on consumer unit 2, but it gives consumption on 1, generation, battery, and export.

When I first looked it said generating 3.02kw, send 1.58kw to battery as below.

At the same time, my smart meter said I was taking 1.21kw from grid.

I then turned the oven on (consumer unit 2). Battery charge had gone up a bit, and draw from grid went to 6.42kw.

It seems maybe the inverter prioritising the battery over usage? I didn’t notice in January, but now the days are longer the battery fills up early afternoon. and I’ve paid for a bunch of electricity at the same time.

 

[DetlefSchmitz]

Do you know where in your diagram the measurement current transformer(s) are? I get the impression they are not positioned correctly. Mostly because the import doesn't show the same as your smart meter.

 

[dungargon]

Is that the current transformer the thing in the pic below?

The cable runs from a port in the inverter for current transformer and this widget is around the live cable to consumer unit 1 as it leaves the junction box.

 

[DetlefSchmitz]

Yes, I would have thought this should be round the live at the smart meter.

 

[dungargon]

Yes, I would have thought this should be round the live at the smart meter.

Thanks, that makes sense... I suppose it was until the junction box was added, and then it placed on the wrong side. Is this something I can unclip and move, or does it need an electrician?