High load showing when generation is high?

Hey,

So my panels were only in for a week before I went on holiday and I felt like my app readings looked strange for household usage. Being away meant that I could monitor this more closely as my house load was flat (disclaimer; I have a vivarium light that comes on 8am-8pm). As you can see from the attached picture as solar generation increases, the household load increases almost in direct correlation. The base load when the Viv is on is an average of 160w, however when the solar was producing 2411w the household load increased to 600w!! Even if we say the base load was at 200w at that point (both fridges and freezer had all kicked in at the same time for example) that's still 400w additional usage just because the solar output is high. This indicates that the inverter is running at less than 84% efficiency, which seems madness when GivEnergy advertise it as over 99%. Can anyone help me understand these figures? Does everyone see these spikes when generation is high? Is sub-85% efficiency to be expected?

It's worth pointing out this is not a single occurance and the same pattern of increasing load as solar gen increases can be seen on every single day.

The inverter is a HY3.6 hybrid. No battery installed yet as GivEnergy keep cancelling the delivery date with my installer. Another issue we won't get into here!

Any help.or advice appreciated!!


PHughes sounds like it could be the CT clamp the wrong way round, you should be able to change this yourself to check.

That graph looks reasonable to me, you’re generating 2800 and using 600 then exporting 2200 (ish).

Which bit do you think is wrong?

kram He is suggesting that as he isn't in the house the load should be fairly consistent throughout the day but it appears to increase significantly when the sun is out.

Cdent is this the CT clamp in my meter box on the live into the property?

This was installed the wrong way around initially, as I was getting crazy readings initially. I figured it out when my household use exceeded solar the app basically soft crashed (household use dropped to zero, no indication on electricity flow) so I turned it round and the figures started making sense. So I'm 99% sure that CT clamp is the correct orientation. Is there another CT clamp anywhere?

kram Ra is correct, the house was empty so the base load should have remained flat throughout the generation period.

Obviously come minor fluctuation is expected with fridges and freezers coming on and off, but the load tripleing EXACTLY when solar gen is at its highest is too suspicious to me. I also have the half hourly usage figures from my last holiday, and the house never reached anything near 600w

PHughes no, this should be the only CT clamp that feeds your inverter. The only thing I can think of if you don't have something on a solar diverter, is that the data points in the app are every 5 minutes and it's seeing spikes in usage due to viv light/appliances, etc. and reporting it. Do you have access to GivTCP to get more granular data?

Cdent I won't lie, I don't even know what that is! 🙂 I get what you're saying, about it being a snap shot, but it seems highly unlikely that the exact same pattern can be seen for 7 solid days when the property was empty. Unfortunately, I don't have a IHD unit for my smart meter, but I do use Loop which shows me consumption half hourly via an app. The Viv uses a 60w bulb, there are two fridges, a freezer, my smart heating hub (heating was off) and my router. In addition to the solar gubbins. Everything else was off and unplugged whilst we were away, so 600w draw at any single time should be impossible.

The loop figures tally reasonably nicely with the GE app when there is none/little solar, but obviously when there is high solar Loop shows zero usage as I'm not drawing from the grid.

From what I can gather, the home usage figure on the app is simply calculated. It looks at generation, deducts export or adds import and reports that figure. Therefore the only explanation I can see is that the inverter is using a significant proportion of the generation (poor efficiency) or the export figure is not being recorded correctly thus assuming household usage is higher than actually is.

The CT clamp was (and still is) quite poorly fitted. When I had a look to see if I could easily turn it initially, it came unclipped simply by touching it. When I refitted it I tried to secure it better but the clip is just poor quality and doesn't 'snap' into place. Could this be the issue?

I have an export meter, is the info on this fed by the CT clamp or is it measured more directly? Could I take the export reading before the sun's up, then once solar is down and compare this to GV figures for export for the day to see if this is the cause?

EDIT: Also, nothing on solar divert... Yet

PHughes I do use Loop which shows me consumption half hourly via an app.

If you have access to your DCC data via this app, you should be able to add your smart meter export MPAN and see that data too. The CT clamp not being secure could lead to weird readings, but probably only lower than actual import/export readings.

The fridge/freezer loads won't be constant. They will be a kick of 800-1200W for say ten minutes every hour as the thermostat switches on the compressor until it falls below the set point. On average, your base load will be whatever it is but there will be peaks and troughs caused by the fridge, freezer, boiler (our combi-boiler draws about 150W for a few minutes each hour while it keeps the internal hot water buffer at temperature). The only constant loads will be things like a router, PC, lighting. The 30 minute readings will be good for seeing what the caseload is and if/how it varies during the course of the day.

Tim I don't think I have a export meter MPAN yet, as I am still awaiting my MSC cert to sign up for an export tarrif. I believe when I first sign up I will then get an MPAN?

Completely agree with what you're saying, but I just felt like whenever I checked the app whilst away and solar was high, home usage was also high. I never went on and saw solar gen over 2kw and home usage under 500w, whereby I regularly saw sub 200w usage when solar was low or not generating. It all just seems too highly coincidental to me.

How 'snug' should the CT clamp be on the cable? I'm no expert, but if I had to hazard a guess I'd say the clamp was intended for a larger cable as there is significant room inside the clamp between the cable

PHughes I think a call to your installer is required in this case, could be they wired something wrong on the inverter

PHughes How 'snug' should the CT clamp be on the cable?

It's better if it is close to the insulation but the key thing is that it should make a complete ring around the conductor. The alternating current in the conductor induces a proportional change in magnetic flux in the ring magnet which then induces a current to flow in the secondary conductor wound around the magnet, which is then measured. If the ring is not complete, the change in magnetic flux will not happen, or it will be a poor indicator of the primary current.

Cdent well they still need to fit the battery when it finally arrives so I will.get them to recheck everything

I mean I think two fridges and a freezer could happily pull 600W.

However have you looked at the fact if your use is very low, the inverter losses are going to look bigger?

Tim well it looks like the CT clamp fitting was the issue. After securing it as best possible and wedging it in place as best I could, readings today are looking much more sensible (again, house is empty today so stable load expected)

https://photos.app.goo.gl/ffHdZzrHN9QjMJTK6

You seem to imported your total useage, exported you generation and lost about 300W in that last picture.

kram well that's just the daily peaks isn't it, consumption and import match as I had the dishwasher on overnight on the cheap rate tarrif 🙂 That was my highest draw of the day and as it was 1am there was no solar so it was all import.

I was more pointing out that the graph shows usage as stable through the day and not following the same curve as generation, as it has previously every day

kram
Hi PHuges,

Any chance you can post a picture of your CT clamp, as it is now? I also suffer similar symptoms, but always put it down to us having a pair of AC3.0s running, each with their own battery. But after your success, I am wondering if we have the same problem?

Did you do anything to try and make sure the two halves of the ferrite ring were clamped together well? e.g. with a cable tie, or with tape or an elastic band??

ToothyChris I'll post a picture up tomorrow when it is light.

I thought about a cable tie, but I didn't want anything too permanent at this stage.

I ensured the clamp was sitting squarely, then I forced the flimsy clip down over the catch to see if it would hold a bit better, then I wedged the clamp up on a few stones to ensure the was no hanging weight on the crappy clip. I'll throw a quick pic up tomorrow