Constant Draw From Grid

[SolarBrit]

Hello Everyone,
I have a Fox system which consists of the Fox ECS battery storage system and 2 X Fox H3 inverters. It's a large system with both inverters being at 12kw each and a large battery backup.

For some reason I just cannot figure out and try and reduce the constant pull from the grid. My battery is at over 95% when the attached picture was taken and I am still pulling over 0.1kwH from the grid. This is adding up since I've used over 100 units of energy on my electricity meter in 3 days, even though I have maintained over 40% battery at all times throughout the night and I am fully charged up in a few hours in the morning.

Why the constant draw from the grid? How can I stop this completely or reduce?

Thanks in advance.

[SolarBrit]

Here is another image taken just now.

[calum]

Firstly, you need to know that all "grid tied" inverters pull a small amount of power from the grid at all times to check that the grid is still connected and "active". This is because they are required to shut down in the event of a power cut, to avoid making the cables "live" and endangering anyone working on them. On my H1, this is probably about 10W on average.

Second, be aware that the data you see on the web portal is a snapshot taken every five minutes, it may not be representative of what is happening "in between times" as it were. If you turn on a large load there is a fraction of a second delay before the inverter increases production of power to match that demand, and during that fraction of a second, a large amount of power may be drawn from the grid, albeit for a very short period of time. If the 5 minute reading is taken right then, it can appear that you are using more power than you are.

All that said, it is possible for misconfigured devices to pull power from the grid unnecessarily. If you can log on to https://www.foxesscloud.com with the same details as you have used for the app, you will be able to find the Inverter Details page where you'll be able to see how much power you are / are not pulling from the grid.

In the example I've just taken from my own system, you can see the grid consumption line is very close to zero until 2.30am, when it starts to charge the battery from the grid (labelled "1" on the screengrab). At about 3.20am you can see the consumption increases to nearly 6kW, this is because the dishwasher was finishing the drying cycle at the same time as the battery was still charging. At 3.52am (labelled "2") you can see the charging stops, as the battery had reached the MaxSoC I'd set it to. Then at 4.30am the grid consumption line drops back to almost zero again, because that's when the charge period I'd set ended.

If your grid consumption line strays away from zero without good reason, then something's up. Otherwise, you're maybe just seeing the effects of only taking a reading every 5 minutes - it can be misleading.

[SolarBrit]

That's very interesting. I have just logged in and pulled the following 2 screenshots from today and yesterday.

Does this look normal?

The spikes in usage are due to the immersion being switched on.

Thanks in advance.

[calum]

You need to be looking at the "Inverter Details" rather than the "Site Details" (see the tab name at the top in green):

"Inverter Details" - shows power to and from grid

"Sites Detail" - doesn't help you as no grid trace

[SolarBrit]

I think I have it now:

[calum]

Looks fairly normal to me, ie your system is pulling from the grid at certain times of the day, but not all the time. Do the times it's pulling in grid power make sense to you?

[SolarBrit]

These surges are in line with my timer controls on the immersion heating. Although, I'm concerned that if I'm mainly pulling from the grid for whatever reason at these times instead of from the solar panels or battery, I can't see the point of using the immersion. From the graphs it looks like the grid pull actually continues for the entire duration.

[canton7]

The only time I see you pulling from the grid is in your first screenshot around 6am, and that's presumably because you depleted the battery: suddenly the discharge power drops and you switch to the grid, and remain on the grid until solar picks up.

Add the battery soc to the graphs, and you'll see for sure.

[calum]

This shows what that looks like , unfortunately it squashes the scale for the power traces a lot, but you can see where the battery starts charging overnight at 1.30 (marked "1"), then it stops at "2". The heatpump decided to heat up the hot water tank right after the battery finished charging so there's another peak there. Then the charge period ends at 4.30 and the house goes back to running on the battery, although you can't make out the difference between the battery and grid lines.

By the way, this is (roughly) the same period taken from my Home Assistant Grafana dashboard. It takes data every few seconds rather than every five minutes, so you get a far better idea of what is going on.

[MikeUK]

I get similar issues but it only started when batteries were added:

- Intermittent draw from the grid when there is sufficient power from the panels and batteries for consumption ~0.1 KW. This is displayed on both the Fox Inverter Tracking and the totally separate SmartMeter supplied by my Energy Supplier

I also have power sent to the grid even when the batteries are not fully charged

[calum]

I don't actually think SolarBrit necessarily has an issue. They've not posted any new graphs with the SoC on to confirm (or otherwise) what's going on, but from what they have posted, they are not seeing "constant draw from the grid" other than the handful of watts that the inverter draws to confirm that the grid is still "up".

Are you able to post screenshots of the graphs from the app or website showing the behaviour you're concerned about?