Inverter fridge protection

Last year I purchased a 1000VA Line Interactive UPS for my home theater amp as the Multiplus II transfer time wasnt fast enough and the amp would shutdown and reboot. The UPS has sorted that nicely now.

My question is, I have replaced my fridge in the last couple of weeks after the main control board blew on the old one. The new fridge is an inverter fridge and I was wondering if I shouldnt get another UPS for the fridge as well?


I’m dealing with that now.
My one 700va APC UPS has surge protection ports that go off when LS happens, the other ports keep stuff on, work nicely on the fridges/freezers. Got it for free, cost R5.5k otherwise.

Then one gets plugs for fridges/freezers, but one needs to keep in mind the 30mA limit.

I’m now getting this, between the main DB and inverter/critical loads:

I like reading manuals for stuff like this :slight_smile:

AVS Manual

Yes, saw that before, scanned it.

Was asked to please install one, by my preferred Victron Dealer/Repairer. Hence I tend to just do. :slight_smile:

My plan is as follows, anyone please critique it:

  1. If volts drop below 210v AC, disconnect the inverter/Critical Loads.
  2. If Eskom comes back on, or volts stabilize, wait 10min before reconnecting the inverter/Critical loads.
  3. 30amps is fine, I think, as it is ±7.2kw - inverter is maxed at 4kw, Critical loads DB breaker is 25a.

Main DB has surge protection already, as has the Critical loads DB.

What is left on the main DB is the kitchen, geysers, etc, the sensitive stuff being on Critical loads, as are the fridges/freezers.

@TheTerribleTriplet I’m actually very keen on having an AVS30 installed as well, please keep us updated on your progress.

Could you share the link to where you bought yours? Do you have it in hand yet?

Segen solar.

Arriving on Tuesday. Have NO idea what “next day” means when it comes 6 days later. But ag, who cares, I don’t have to drive. :man_shrugging:

EDIT: DB parts also arriving on Tuesday, so yeah, “groot geld”.
But, the AVS30, does not fit in a DB, soooo … maybe I can make a plan to be able to “swap” inverters easier. Will keep you updated.

The first part is here - had to open it.

Cannot be mounted on DIN rails, only external, as it has lights to show one what is potting.

I’m actually wondering if a voltage relay (and more in this case) will act faster than a MultiPlus to disconnect in case of loadshedding…

I’m still getting this "Overload L1: Alarm" as load shedding hit every once in a while, same as @MongooseMan. If such a relay could disconnect the grid before the MP goes to overload it would be very nice.

I often get the same overload error as load shedding hits and there is only around 500W load on the system.

I cant find the cause so I have written it off as an annoying bug. My Multiplus II is running the latest firmware as well.

@plonkster @JacoDeJongh

What are your opinions on the AVS30?

Jaco have you installed any on your installations?

Plonkster my understanding is a Victron distributer recommended this be fitted so no issues there I assume?

It looks like your standard “disconnect the power for x secods if the voltage is out of range” device. They do the job. It’s a bit different to the original question you asked, whether you need a UPS for the fridge. And I don’t really know the answer to that.

My understanding of an “inverter” appliance is that it runs a VSD (variable speed drive), which means it takes the incoming AC, rectifies it into DC, then changes it back into AC of a different frequency so that it can drive an induction motor at a different speed/power level. That means the very first thing these devices always do is change the incoming AC into DC. And one side effect of that is that they can take a wide range of input voltages, which means I would actually expect this new fridge to be a little more resistant to voltage fluctuations.

But you blew a control board. Now either that happened just because the thing didn’t like constantly being turned on and off, or because there was a surge. So my gut feeling is you should simply put a good surge arresstor on the Eskom side (before the inverter). But that’s a gut feeling only.

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It was recommended to me by my favourite Victron repair center in George, who even asked me before I installed the loan unit, to get it installed ASAP.

Here is the thing, I want to disconnect from the grid BEFORE the grid volts drop, like at 215v.
Or over 250v, disconnect.

And when it comes back, wait 10min.
And after 10 min, the volts are still not right, keep off for another 10min.

In other words, I’m regulating my Eskom input to within my parameters.

I also deduced that it should put less strain on like i.e. fridges and all that, as all they now have to contend with, is the 20ms break before Victron takes over.

EDIT: Also less strain on the inverter, as it is a “clean” break. The lights flicker quick, not like lately, at times they dip quite pronounced.

Apologies, I wasn’t very clear initially and should have provided more information.

The first question should have been, will an inverter fridge run safely on a modified sine wave UPS for the few milliseconds it takes the Multi to switch? The answer appears to be yes, it appears to run fine with hopefully no long term ill effects. There is no change in the sound from the compressor and the LED lights inside dont dip either.

My old fridge would kick the compressor on every time the inverter took over from Eskom after the initial dip. I have no idea if that contributed to its demise, the fridge was roughly 12 years old. I highly doubt it was a surge as no other devices were effected and the surge arrestor inside the DB board did not blow :man_shrugging:

The second question should have been, as TTT correctly read between the lines, how can I prevent a similar situation in the future. I like the AVS30 solution and may just go ahead and implement it anyway.

Now you might ask, what brought this on? My insurance policy was updated a day before the fridge failed to include an excess for any power surge.

If it weren’t for my bad luck, I wouldn’t have any luck at all…

Inverter appliances tend to not care about what the waveform looks like, precisely because they turn it into DC before inverting it again. So the answer here would be yes, it should be fine.

In an ESS system, the Multi is synced with the grid, so when it takes over the waveform is synced with what was there before. Your typical induction motor can ride out the 20ms gap easily.

I would be more worried about a cheaper UPS that simply kicks on a 50Hz sine wave starting just anywhere. I would think that is a lot more jarring on an induction motor.

Of course I think the bigger issue here is the control board. That probably runs from some kind of switch mode power supply, with electrolytic caps that slowly dry out or get baked… and then fail when they suddenly have to handle some inrush current.

I’m just guessing here, speculating. Unless out of range voltages is actually the reason the thing blows in the first place, adding a device that works around that is going to do nothing :slight_smile:

Just to clarify, this has nothing to do with an inverter and the errors it gave.

The Victron dealer/repairer is dealing with quite a few damaged units, because of Eskom. So I’m following good advice based on actual repairs done to Victron inverters, by adding some more parameters to be checked.

Repeated continuous SA electrical woes are causing havoc, insurers, as @Thaelian also noticed, is a good benchmark now too, of how bad it has become. Mine sent out a notice months ago.

Grid-tied inverters are not designed to protect against woes Eskom can send down the lines. What I see, the moment Eskom comes back on, the power passes straight through the inverter. I want to avert that, let Eskom settle a bit. Or, Victron must not link to the grid at all when it comes back, for a User Determined period.

I’ve lost 2 x screens already, and many many LED bulbs, I can hear my fridge motors rattling at times when Victron takes over, they are new A+ freezers. I also see frequent pronounced dips of the lights at times.

The insurer replaced my screens, but not going forward UNLESS one has protections added. Also lost many many LED bulbs.

Grid-tied inverters cannot protect against this. Not their function.

Looking at my grid voltage input on VRM for the last month, I think a device like the AVS should be beneficial?


Is that the voltage measured as the voltage falls away?


EXACTLY what I saw too. Hence, below ±215v, let Victron step in.

Others have seen >260v.

that is insane :astonished:

That is normal. Check yours?

When the grid drops, comes back on, inverters are taking the strain the best they can.

The voltages shown I think are the gradient of the graph and not very accurate over a longer span of time, a month is too long.

Here is the last week which I suspect is a better indicator. The dip shown was not load shedding: