Using AC-Out-2 while AC in (grid) is not available (loadshedding)

Is anyone making use of AC-Out-2 while AC in is not available and more specifically how do you have it set up?

In my case:
As long as there’s enough battery (based on SOC, Volts, Used Watts or something) and the combined AC out is not approaching the inverter’s limit (let’s say 3500W on a 5kVa) I’d like to use AC-Out-2 even if AC1 is not available and disconnect it if it’s no longer the case.

  • Combined AC out value might be difficult to properly do, but would be ideal to disconnect it before an ovarload

What I’ve found might work:

  • Programmable relays (not really documented and apparently a little difficult when multiple parameters comes into play)
  • Aux input using GX relay (Don’t quite understand it, but sounds easy-ish)

You can use the AUX inputs on the multiplus to control the outputs including AC-OUT 2, you can wire AUX input to GX relay to control AC-OUT 2. You won’t need to buy anything.

Any thoughts and/or comments on how to go about getting this set up? Or examples?

I don’t know if any of you will remember the time before you got the blue stuff, but I’m running 320 different scenarios etc. through my head while waiting on some quotes.

I initially had the idea of simply having the whole house on AC-Out-1 on a 5kVa Multiplus-II as our peak usage generally is not that high, but today we peaked at 6550W with a perfect storm (oven, microwave, coffee machine, pool pump & heat pump) which made me rethink things as I don’t want to have to struggle with overload and/or trips.

As easy as it is to simply move the 2kW oven over to AC-Out-2 and know that it won’t be there when the grid drops I would still like to be able to use it if the inverter and battery allows especially if the Sunday roast is on the go, the sun is shining and there’s no other loads. I will also throw the heat pump over to it as an extra in case a hair dryer gets thrown into the mix.

I’m like a dog with a bone with this scenario: Some loads will be more critical (essential) than others. So the least critical loads need to be switched off to prevent overloading…

I’m 95% with you on that. I’ve got no issue with moving the oven and heat pump breakers over and acting like they don’t exist if there’s no mains. I also thought about putting in a manual changeover to bring them back if/when needed if there’s an extended outage where we know what’s going on and can manage the loads.

But if there’s a way of having them around a little longer during short outages while ensuring no overload I’d like to have the possibility even if I don’t end up doing it.

You can definitely do this.

I would basically do what you described:

  1. Using Ve.Configure, setup an assistant to toggle programmable relay using the AC-Out2 output based on an aux input in on-off scenario.
  2. Wire the aux input to the Cerbo relay output, and then setup your parameters there using the Generator wizard.

You could also put in a ON-OFF-ON switch between the Cerbo and the Multi that could be used to hard override the input on or off if you wanted to quickly bypass the relay setup on the Cerbo.

This way it is easier to change the settings than programming the Multi all the time. For first prize, I would setup 2x relay assistants, possibly using the General Flag as a go-between with the 2nd assistant configured with a hard inverter power limit. Otherwise the delay before the Cerbo notices the peak might be too long.

If you download Ve.Configure you can test some of this by selecting the demo input as the COM port. I’m not on a Windows machine right now, so can’t do screenshots unfortunately.


@plonkster wrote up about 60% of what you need to do here (but with a different goal).

Yeah, the reason why I didn’t reply to this thread yesterday, is though I know it is possible in principle, I also remember vaguely in the back of my head someone complaining because it didn’t quite work as he expected (something about a 4 minute delay or such). That is to say, the relay on AC-out-2 already acts in a certain way by default, and this overrides it with an assistant. I cannot remember if the issue with the interaction between the two was completely solved… I assume it was.

Were you able to solve the problem? In VRM there is an on/off switch for AC out 2. Does that work?

I ended up getting it installed as follows:

  • Everything on AC-Out-1
  • Separate changeover for oven & outbuilding geyser (normally connected to grid)

If there’s loss of mains everything except the oven & outbuilding’s geyser keeps on working.
If the oven is needed we can flip the changeover to keep it going.

The main reason for doing it this way is that the inverter is installed ~10m away from the DB, so it was easier, neater (and cheaper) to put in a small DB with a changeover compared to running another big hump of AC cabling. As I already have an ET-112 that would have gone to waste we use it to power these with PV / battery. PV install is still pending, but it would have used PV / battery on AC-Out-2 in any case, so keeping the ET-112 and doing it this way just keeps that available.

I think in the ~6 months since installation I’ve only flipped the switch twice. Once because of something in the oven that had to continue, but the second time I couldn’t find a lighter to light the gas stove (spark connected to the oven).

I am looking at getting a CBI Astute Smart Controller and switching the pool pump with Node-Red, but will see if it’s needed when PV goes in as the setup is currently only used for backup power (thank goodness we had it installed when we did)


This is pretty much what I call my “doomsday switch” and I use it all the time. This time of the year, naturally there is more sun than I can use, so my changeover keeps the pool pump and aircon running when Eskom is out.