A\C Inverter, 8.2kw battery, Storage heaters - Load doubling

Am wondering if anyone can shed any light on some figures I am getting from the dashboard. Have an 8.2kw battery with A\C Inverter installed and run storage heaters. Have only 1 storage heater turned on at the moment which has a 2.4kw max load \ import on the off-peak circuit starting at midnight .

On the odd mornings I have charge in the battery carried over from the previous day the dashboard shows the load at midnight double to 4.8kw, the battery discharging at 3kw and the import staying the same minus our normal 200W background load. Once the battery has drained the dashboard shows 2.4kw load \ import as expected.

On the mornings that I have battery charge I expected the load to stay at 2.4kw not double and the import to reduce to zero whilst the battery is dischargng however this does not happen???

The only draw on the off-peak circuit at this time is the 1 storage heater. We have a hot water immersion but this is on the normal circult and timed by an Eddi to run after 5am so does not affect anything.

Any pointers anyone can give me would be appreciated. I emailed technical a couple of days ago with no response. I can load images of the dashboard when I figure out how.

jeff The inverter is set to support house demand from battery (ECO mode). This means that when the storage heater or immersion starts heating, the inverter will supply that load from battery, supplemented from grid as necessary. If you don't want it to do this, set the Givenergy inverter to a timed charge for those durations. The battery will charge to whatever you have set the Charge to %, so if you don't want to actually charge the battery, set the Charge to % to be whatever you expect to have in the battery that night.

However, since your E7 tariff will be less than your standard rate tariff, you might as well put some charge into the battery off-peak and consume it during the day. You'll effectively be extending your E7 use outside the E7 period. You could charge the battery up to 100% each night but if you have any PV, you may not be able to divert it to your battery. So if you charged it up to say 50% or maybe 75%, it would reduce your peak-rate consumption (at the cost of off-peak charge) but still leave battery capacity should you have a good solar day.

jeff the load at midnight double to 4.8kw, the battery discharging at 3kw

This looks like your grid CT might be on the wrong way round? The best way to test this is to do a charge now on your inverter and see what the portal shows. It should show a grid import equivalent(ish) to the battery charge. Then do an export now and see if the opposite is shown. An AC-coupled will have two CTs; the grid one for minimising grid import/export by discharging/charging the battery and one for each PV system you have so that the PV input is displayed in the portal.

Thanks for the responses so far. Am now able to load a photo of the dashboard readings which may explain my circumstances better.

or just paste https://flic.kr/p/2o1icL6 in to your google search

2022-11-11 Battery empty. Storage heater comes on at 00:00 with a load of 2.4kw
Dashboard Load and Imports says 2.4kw which is correct.
NB: Around 5am the battery charges using off-peak and the immersion is timed to come on.

2022-11-13 Battery 40% charge. Storage heater comes on at 00:00 with a load of 2.4kw.
Dashboard load now says 4.8kw rather than 2.4kw, Battery discharge 3kw and Imports says approx 1.8kw rather
than 0. When battery fully discharged dashboard Load and import revert to 2.4kw which is correct again.

2022-11-16 same as 22-11-13

So big questions,
1) Why is dashboard doubling the reported load from 2.4kw to 4.8kw?
2) Why isn't the battery discharge being used by the storage heater?

is there a boost function on the storage heater?, ie second element?

jeff
I'm curious to see where this goes, as I think I see a similar effect on my system (power in matches load when the battery is flat - but a big imbalance when the battery is discharging).

I had always assumed it was because we have two AC3.0 inverters in parallel (each with a single battery), and that the software could not properly account for that. But if you only have a single AC inverter, I am wondering if we both have one of the CT clamps in the wrong place.......

if so then the battery ct clamp would be the one but the OP says all was fine until a certain date.

positor1

hi. There is a boost element but cannot be the cause. The immersion is now controlled by an Eddi device on the normal circuit. The Eddi is setup so that the Boost comes on at 5:30am to heat the top of the tank Mon-Sun and to heat the bottom of the tank 4-5:30am saturdays only. I still only have one storage heater switched on, its been a warm November, and there are no other devices that could account for the 2.4kw rise at that time of the morning. The 2.4kw rise always only seems to be when the Storage heater is on and the battery is discharging in the morning. I have several other examples where it has done the same thing.

Sorry Positor1, had immersions stuck in my head. Yes there is a boost on the storage heater however this feature is not switched on. The storage heaters are modern Dimplex Quantums where the stored heat is emitted by fan according to a timed schedule. The boost is an additional 1kw element which can be used when the stored heat has gone however this feature is not swiitced on.

Here is a picture showing the CT clamp positioned between the 100A fuse and the meter. The other CT after the fusebox is for the Eddi so it can send any surplus PV to the immersion tank

https://flic.kr/p/2o1id6j

I have had the A\C Inverter and battery installed for over a year now and monitor the readings closely. I only noticed this when it started getting colder and switched a storage heater on. I am assuming this must be a 'feature' due to the storage heaters being on the seperate off-peak circuit from the meter but it still doesn't make a lot of sense to me.

jeff and @ToothyChris
An observation which I don't need an answer to but: why deplete the battery from at the start of your off-peak period and then charge it up later? You're introducing inverter losses. Simply set the inverter to do a timed charge to match your off-peak window with your Charge to % set at whatever you want in the tank when the period finishes (50% on the 16th for example).

Where is your second CT connected and does the magnitude of output recorded in the Givenergy portal look "right" when compared to your PV inverter data? The reason for asking is that on your chart, the battery charges from PV starting at <70%, rising to 100% on the 16th. However, the magnitude of the values doesn't look right. When (presumably your separate FIT) PV is charging the battery the PV looks to be about 1kW whereas battery charge looks to be about 2kW.

I think the root of the problem that you originally posted about is that your myEnergi Eddi CT is not measuring export and so will not divert surplus PV to the immersion. It is measuring energy flowing out of the consumer unit. During the day, this will be export but at night it is measuring the battery output to your storage heater. When the Eddi sees this, it diverts the "surplus" to the immersion heater and therefore you actually are consuming the energy displayed in the chart. To solve this, unclip the Eddi CT from where it is and clip it to the Live connection between the DNO fuse and the energy meter. If there's not enough room, you can clip it to the Neutral connection coming out of the energy meter but the arrow has to point the other way (pointing away from the consumer unit towards the meter).

Thanks Tim. Yes you were correct, its the Eddi causing the load to double. I had started to think that myself, the extra load had to be going somewhere....... just couldn't understand why. The battery was up above 50% so I stayed up last night to watch and the Eddi diverted power in to the immersion as soon as the off-peak circuit became live. It was interpreting the battery discharge as export. I switched off the Eddi at the wall and the battery supplied the storage heater load as expected.

https://flic.kr/p/2o1vD5m
NB: The Inverter wasn't particularly efficient at supporting the load though! Load 2360W and battery power 2773 which makes 413W inefficiency if the dashboard is to be believed.

I will move the Eddi CT as you suggest, though see later comments. I had not thought it was the Eddi as I had a long conversation with GivEnergy Tech support about diverters, CTs, batteries and priorities when the battery was installed. I showed them pictures of the already installed immersion diverter's CT where it is now after the meter and they did not pick up on any potential issues. Oh well you live and learn.

re. your other comments.....

I had been playing around with the Inverter settings battery charging time when I discovered the load issue and became sidetracked. Originally the battery charged from 00-00 to 07:00 like you suggested but long term am attempting to spread my load across the off-peak period. Everything (6 storage heaters, battery charging and immersion) coming online at midnight in the depths of winter takes me close to my 100A fuse limit and I would like to fit an EV charger at some point. Have moved the immersion to after 5am when the storage heaters are mostly finished and with some Inverter Setting fettling I should be able to get the battery to charge later in the morning as well without the issue that caused this thread.

Well spotted for noticing the PV data does not look right. Am missing an EM115 meter on my 2nd set of solar panels. We have been waiting 8 weeks for it so far and still no sign of it. It means the PV readings only reflect the1st of panels however the Inverter has been charging the battery and the Eddi diverting in to the immersion fine without it. Didn't want to complicate things by mentioning it here.

Thanks for all the comments eveybody. If Tech Support respond to my email I will let them know the resolution.

jeff coming online at midnight in the depths of winter takes me close to my 100A fuse limit

If you want to reduce the impact of the Givenergy battery charge on your import, leave the timed charge window to the same as your E7 tariff, set the Charge to 100% and reduce the charge power to say 900W, or whatever you want, to get the right amount of charge in the battery by the end of the charge window. You could delay the start by an hour or so, but if you have the same window as the storage heaters, the inverter will prevent discharge to the storage heaters for the whole period. Of course, you will probably want to increase the charge power to soak up the PV during the day, but if you didn't, it would just divert to the immersion, so wouldn't be lost.

We used to have storage heaters and did blow our DNO fuse at one point, after many years use, and they replaced it with a 100A fuse. They are BS1361 and so can carry 1.25 x Full Load Current for up to 4 hours, although I'm not suggesting that you overload the consumer unit at all. There are two things that you could do to secure your supply better. One would be to get a sparkie to install an 80A fused isolator after the meter and before anything else. That way, if you exceeded 80A for any length of time, your 80A fuse would blow and you could replace it at your convenience rather than having to call out the DNO. Another thing you could do is ask your friendly sparkie to put some of your storage heaters on a separate consumer unit and energise that with a contactor on a time switch so that it comes on a couple of hours after the first set. The idea here would be to allow half the storage heaters to start charging at midnight and then start the others charging at say 2am when the first batch had had at least some charge. Obviously with this scenario, you'd probably want to put the larger heaters to come on at midnight and start the smaller ones later in the night. Also, EV chargers (at least our Zappi) can be configured to limit the charge to the EV so that the total import from grid is kept below a threshold that you can set. This means that if you are pulling 70A and you've set the threshold to say 80A, the EV will charge at 10A until heaters get to temperature and switch off, at that point the EV charger should ramp up its output to keep the grid import at 80A (or below).

It's the ability to flex these parameters (when you're asleep at night hopefully) according to a set of rules which suit your lifestyle that leads to home automation, ultimately, for most of us.

jeff missing an EM115 meter on my 2nd set of solar panels

Are your two PV systems connected independently to your house consumer unit with separate MCBs or are they connected to a "solar" consumer unit with one connection to your house consumer unit? If the latter, then you can move the CT to be on the one connection to the house consumer unit. If they are independent of each other, then independent EM115s are needed, unless the CT happens to be within the consumer unit and it's feasible to pass the two live conductors from the inverters through the same CT.