Essential Loads disconnecting on power cut with MultiPlus-II 48/8000

Q&A and troubleshooting
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1

Hello,

I have a problem with essential loads (AC Out1) dropping off on mains failure. After looking through all settings, I can’t find anything wrong, hence I decided to post the question here while awaiting visit from electricians that installed and commissioned the system (I may be waiting some time for that).

My setup consist of the following components:

  • MultiPlus-II 48/8000/110-100
  • 3x Pylontech US3000C
  • MPPT RS 450/200 (with 8.8kWp connected in E-W configuration)
  • External grid meter (measuring directly after main house breaker and connected by modbus to Cerbo)
  • Cerbo GX

The installation location is Spain, the MultiPlus is configured to use Spanish grid code. The system is configured as ESS and works for just over a year now, and it works well - using solar to charge batteries, feed loads, export, import when needed to support load and/or charge batteries if requested - all as expected.

However when the system was commissioned, the essential loads output was brought back to my main electrical board, terminated on the breaker and left unused (re-wiring the board was not in scope in the installation).

I finally decided to make use of it, with notification of upcoming 1/2 day power disruption in my area being a good motivator. I now have all loads separated nicely - 2 RCDs with everything I consider essential connected to critical load (AC Out1) and all heavy loads (heat pumps, water heating, oven etc) remaining unprotected - these loads are connected before MultiPlus, on AC In, AC Out2 is unused.

As far as Cerbo screen and VRM reports, it all looks good - the ‘precious’ part of my load now shows as ‘Essential Loads’ and reminder as ‘AC Loads’.

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Here is where everything good ends and comes the problem and the question. After re-connecting the power and giving MultiPlus few minutes to synchronise with the grid and return to normal operation, with battery charged to c. 60%, I pulled the main incoming breaker down hoping the house remains powered. I got disappointed as everything dropped offline. I was so puzzled that I pulled the breaker back up without checking the status of the MultiPlus, but I can obviously do it again if that’s of any use.

I had another 2 short power disruptions since (caused by grid issues) and on both occasions the same happened. First time I wasn’t home and the second time the interruption was few seconds long, so I didn’t manage to get to the inverter in time, but I was watching the screen showing only unprotected loads supplied until the magic relay clicked few minutes later to bring the lights back.

Summarising, what I achieved now is that my house remains dark 5 mins longer than the entire neighbourhood as it takes so long for Essential Loads to re-connect after the power is back.

While I am not confident I have been through all posts reporting similar problem, I did fair bit of searching and I found nothing that would help me resolve the problem.

Is there anything someone here can suggest I should check, try or test?

While I am not certified electrician, I have background in electronics and telecoms, so I have good understanding of electrical basics. I also have the MK3 cable, so I can download/check the config from MultiPlus.

Thank you in advance.

Regards,
Sergiusz

2

Since you have VRM setup you can use the advanced page to show various tiles, for example the VE.bus monitor which will show you the MPs states it was in

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The cable on the ACout was installed back when the Victron system was installed, but was never actually used until recently. Are you sure its connected to ACout1 and not to ACout2 by accident? This would be the simplest cause

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Hi Chrigu,

Thank you for your answer.

I can take off the cover of terminals tomorrow and take a look, but I go by the fact that since I started using the essential loads breaker, VRM/screen started reporting load in “essential loads” box, which for a year sat at 0. The load it indicates matches what I’d expect it to show taking into account what’s drawing power on my 2 protected RCDs at any time. I guess it wouldn’t show that load in the essential loads box if it was connected on AC Out2, right?

Good point on the state graph for the inverter, I didn’t think about it. Here it is. I don’t know why it shows ‘Bulk’ most of the time, including now when my inverter is sitting in ‘External Control’ state. The ‘Inverting’ state matches the time when it returned after power outage and before it synchronised with the grid. On 2nd loss of power today, I briefly manually flicked inverter to off and back on to see if this makes essential loads re-connect sooner as I was under some pressure coming from wife and kids waiting for the TV to come back. Not sure what ‘sustain’ indicates.

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I also did not mention in my original post - the only alarm Cerbo logged on both events today were ‘Grid alarm: Grid lost’. No overload, no battery low - everything looking healthy.

Thank you again.

Regards,
Sergiusz

4

Its the same output measurment, ACout2 simply has another relay. The MP can not distinguish how much of the output power goes to ACout1 or ACout2.

External control means that the MP is not controlling itself, but in your case its the Cerbo due to the ESS setup. Same for Bulk, it will mostly stay in that state since the Cerbo is controlling the charge parameters. Looks ok to me

5

Ok, thank you again. That’s very helpful info. I assumed ‘essential loads’ means exactly what it says, ie. stuff connected to ‘AC Out1’. Good to know it’s not the case. And would load connected to ‘AC Out2’ also remain disconnected until after MP2 synchronises itself with the grid? Are both relays closed only after its phase synchronized?

6

ACout1 is the output of either the transfer relay or the inverter directly, depending on whether the unit has mains or not. Apart from that it is not switched. If everything goes well, then even a mains failure will not cause an outage on ACout1.

ACout2 is the same output, but with an additional relay to further control when its switched on. By default ACout2 is on as long as mains is available and off as long as mains is not available. But you can change that behaviour if desired. See “Two AC outputs”

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Again, thank you. I’ll check the connections tomorrow and report back on what I found. I really hope it’s that simple and I can run on solar/batteries when the mains is gone for 6 hours tomorrow.

8

Good morning chrigu,

You were so right with your diagnosis! I feel somewhat stupid that I didn’t check it, but then I also blame Victron a bit for mislabelling the box… what’s connected to AC Out2 should not be reported as Essential Loads!

In any case, that was the problem, electricians connected AC Out2 and labeled it critical load. Moved the wires across and after re-powering my house lit up, despite the entire neighbourhood being with no power until this afternoon.

Thank you so much, your help is greatly appreciated!

Regards,

Sergiusz

9

That’s what happy power outage day looks like :slight_smile:

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