Inverters & "Ramp Rate"

Yup, I have noticed as well that the ramp rate means that for ten minutes or so you buy energy. I cannot imagine this is very good for the supplier either: When they come back from an outage, all the solar people who were happily running close the taps, and run from the grid for 10 minutes.

(You can change the grid code to “other” and avoid all that of course… :slight_smile: ).

There are two other things that cost me. I have about one quarter of my PV AC-coupled directly to the grid. Of course I lose this, which means between 2kWh and 4kWh lost. MY own fault for taking the cheap route and not wiring it to the output of the Multi.

And then, the bundling up of loads. Things that were scheduled to run at different times and maximise PV use now run at the same time, pushing the peak higher. Example, pool pump. Early morning first the heat pump runs (after morning showers). Then the washing machine runs. Then the tumble dryer. Then starts the pool pump (around noon, so the heating mats can also work optimally). And so forth. But now, things run simultaneously and more has to be imported from the grid.

Then, when you have a 4-hour slot late afternoon into the early evening, and then another one in the early hours of the morning, and a weather forecast that says not to bargain on sun… that means recharging. At an 85% discharge efficiency, and a 90% charge efficiency, so you pay another 25% extra for charging back from the grid.

Now while this sounds like a complaint, which it some ways it is, I understand that I should be thankful for my blessings. I mention these things because sometimes we forget that even though we have the backup, there is still a cost to the outages.

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Many of those costs I mitigated, albeit manually, with my “doomsday switch”. Since we are anyways conditioned to work within the limits of the Multi, I can flick it (given sun is available) and run all the non-criticals during LS that I normally would.

I think you should be able to do the same to get your PV inverter online and run those extra loads, unless your Multi isn’t big enough for the loads…

In theory I can just plug it into a wall socket that is conveniently next to it. In practice, that puts it on the wrong side of the RCD, and I have it on good authority that the ABB PV-inverters trip RCDs when you do that (they also do a relay test when they start up).

It would seem this ramp can be set to a 60s minimum within the ZA grid code:


I don’t think the NRS allows minimum of 60s. I’ll try and attach an extract:

For controllable generators, a maximum of 10% per minute after reconnecting after 60s. So full power after 600 seconds/10minutes after reconnection.

I suspect the intended meaning there is that the power exported to the grid must be ramped up over 10 minutes. Limiting the power generated for own consumption for a period of 10 minutes after reconnecting to the grid doesn’t make a lot of sense.

I agree, when interpreting ambiguous regulations, I find I interpret them to suit myself, and I sleep very well.

It makes sense to me though: If I’m a utility and had to shutdown down supply to you for whatever reason, I’d like to know what the true demand is and whether I can stably provide it, since I can’t actually rely on the generators in the grid that I don’t know about and control. In reading the non-controllable generators bit, it seems to be what they are trying to achieve.

But yeah, might be flawed thinking as I have no technical background in this. I just looked up the NRS in order to understand Victron’s grid code settings.

I’d love it if I’m allowed to take it to 0 seconds ramp rate without affecting compliance.

That’s one thing I tried explaining to a friend this weekend. I may have a nice blue inverter running the whole house as normal during loadshedding, but as I don’t have PV I’m now paying more than before as I’m always recharging from the grid. But I don’t just pay for what I used during loadshedding as I also have to pay for the charge and discharge (in)efficiencies.

And then you have the weather we’ve had in Johannesburg for the last couple of weeks. I’m typing this while looking out the window and it feels like a Cape Town winter (with less wind).

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That inefficiency. Every night I check the weather. If there is sun tomorrow, no problem. Inverter can run the battery right down to 25% SOC for all I care. If not, then the settings needs to be adjusted.

The most difficult weather to deal with is what we currently have. The app says “partly cloudy”. OK, so does that mean a few clouds will sometimes obstruct the sun, or does it mean near-full-cloud-cover will occasionally let the sun through? So then you check the temperature. If it says partly cloudy, but the temperature is high 20s, then there will probably be some sun.

If there is no load-shedding ongoing, then getting it slightly wrong doesn’t matter. Right now, with a 4AM-8AM slot yesterday and 6AM-8AM again today (right around the time breakfast has to be made), I had to err on the side of keeping the batteries charged, which again has additional costs…

Not complaining. Just stating some forgotten realities that comes with this :slight_smile:


100% agree. Definitely not complaining, but all the little intricacies that comes with this wonderful journey adds up :wink:

I realized the same thing. I had a 6AM-8AM yesterday with an 8AM-12PM today (and CityPower likes to take as much of the 30minute restoration as they can). With the heat pump switching on at 06:00, the pool pump at 08:00 along with some washing I realized there’s some balancing needed when PV arrives.

I’ll most likely just play it safe. Incorporate the EskomSePush API to bump up the min SoC and maybe also add something like a CBI Astute and switch the pool off if the SoC drops (aka no sun). But bumping the min SoC along with the weather means more from the grid which, like you said:

The amount of planning required of people without the backup must be utterly staggering. I mean, the three big items that still needs to be planned around is the washing (because we basically tumble dry the bulk of things, and have to in this weather), the pool pump (which needs 3 hours every day), and supper always has to be planned so that nothing that needs the oven is planned for those evenings (stove top is LPG). But at least I don’t have to worry about charging my phone in time, boiling water and putting it in a thermos in time, downloading something to watch onto a phone or tablet… etc etc… the internet stays up, the inconveniences really are minor, comparatively.

In fact, I am thankful that they are still there. I think getting too out of touch with the rest of the country is not a good thing. You know, when the masses with the torches and pitchforks show up… :slight_smile:


Also checking the weather combined with early morning LS.

I got really tired of this thing called “costs” to automate things, which leads to even more complexities.

So much so that all I care about now is the real critical loads like PCs, lights etc.

The SOC must just increase the whole day to 100% at 6pm’ish, and not to drain the batts in bad weather, use inverter max watts to manage that.

If I get really gatvol of this “weather thing” coinciding with this “LS thing”, the blerrie altering schedules all the time, I just leave the system on Keep Charged till the weather improves.

Wife went to kuier in Harties, her Dad has a generator, but it is too much effort he says. So with LS, they simply go to bed. Daytime they don’t care, so what the TV is off.

What got my wife good though was access to her clients. LS and the cell towers, even fibre goes down.

That was messy.

Ditto, also a point to ponder on methinks.

As a matter of fact, some outside lights had a Day/Night sensor failure, I did not replace it, why advertise we have lights?

Oh, definitely. We’re talking about making sure that we can run the washer / dryer & pool whereas I was on the phone with a friend who said he needs to hang up to go charge his phone before loadshedding hits.

We had this conversation last night. We went to bed just after 23:00. I looked at my phone and saw an EskomSePush notification. Loadshedding 20:00 - 00:30. I looked at my wife and said I didn’t even know we’re being load shed at the moment and we spoke about how we would have most likely gotten a good night’s rest earlier this year as we would have just gone to bed.

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LS is very bad for businesses, but for home users, there are subtle benefits yes.

So we can use the kettle, MW, but we refilled the camping gas bottles and cooking tops recently and started cooking on that at times, even coffee.

It is good enough for when we camp right? So why keep it packed away, then go out and spend more on “convenience”?

Slippery slope, Rabbit hole came to mind for me.

The longer our system runs, and it is really boring, it works … the less I care about convenience, as long as the PCs operate.