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johnjaymack asked

Difference between warning levels and alarm levels on a Multiplus II 2x120 for load shedding

I feel that I must fill in some background. I have an all electric Newmar Ventana coach. I have converted its 12 volt house system to a 24 volt system and I am running two Multiplus II 2x120 inverts in parallel. This gives us 4800 watts when off of shore power and up to a 4800 watt boost when on shore power. The system has been in operation since December 2022 and for the most part has worked well, but there have been a couple of problems that I believe that I have a solution for.

Our system has shutdown unexpectedly a couple of times for very legitimate reasons. In one case, we lost our 50 amp shore power connection when the pedestal breaker tripped. Another time, the electrical power company dumped power due to a transformer malfunction. We also lost power because of a high temperature alarm. Now each of these issued caused a legitimate shut down after producing a warning and an alarm.

I am looking at using Node Red to control relay 2 on the Cerbo GX. Relay 1 is configured for Automatic Generator Control. What I intend to do is use relay 2 to activate a Power Shedding Relay that I will install. In simplest terms, I will run certain higher wattage loads such as electrical water heat, one of the AC units, etc. through a power relay controlled by the power shed relay. When the power shed relay is triggered, the load shed relay will open reducing the loads on the inverters. My theory is that if the loads are reduced quickly enough, then the inverters will not have to go into emergency shutdown.

Now to my questions. Using "Temperature Alarm L1" as an example, the three states are 0-OK, 1-Warning, and 2-Alarm. I need to know:

1) whether the Multiplus shuts down on the Alarm immediately or whether there is a short delay,

2) how close to the maximum is the warning level set,

3) is there a way to show the current state of relay 2 as a node red display ( I can see the output change by going to the GUI and looking, but I am lazy, and, finally,

4) how can I inject a test to my setup to simulate a warning or an alarm condition. I know that I can inject a test signal, but I would like to know if the actual warning or alarm levels can be adjusted temporarily to simulate the operation while actually operating.

Any thoughts or suggestions are most welcome.


multplus 2 gx
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Mike Dorsett avatar image Mike Dorsett commented ·
Traditionally load shedding would be done on battery voltage (or state of charge). Although linking this to other warnings like temperature and overload is probably a good thing to do.

I think that the multi's shut down immediately on alarm condition, so use of the 'warning' state should be used for load shedding.



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johnjaymack avatar image johnjaymack Mike Dorsett commented ·
Thank you for the reply. I have had a couple of shutdowns that did not relate to battery SOC , etc. I have been connected to 3600 watt shore power sources. For loads above this amount, the two Victrons supplement an additional 4800 watts. While most of the time this is plenty, occasionally a combination of circuits all kick in at the same time an overload the system. I think that I cam use the Warning to trigger the Cerbo GX relay #2 via Node Red and use that to disconnect the high power circuits before the system shuts down.


Based on your answer, I will use the Warning and not the Alarm for my trigger.

Do you know if the Waring level can be adjusted? And at what level does the warning appear? For example, for a rated 4800 watt inverter, would the warning occur at and above the 4800 level, of just before it, say at 4700 watts?


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5 Answers
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johnjaymack answered ·

I found the Node Red Relay module so now I can monitor the status of Relay 2. Lazyness solved.

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johnjaymack avatar image
johnjaymack answered ·

I am setup, currently, with 4 Victron Node Red VE Bus System nodes. On my system, only the Multiplus II show up. I have them configured, so far for:

1) Temperature Alarm L1,

2) Overload Alarm L1

3) Overload &

4) Grid Lost Alarm

For 1,2, & 4, I have possible outputs of 0-OK,1-warning ,2- Alarm. Overload only gives 0 & 2..

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zl2fae avatar image
zl2fae answered ·

I used to use alarms but now trigger actions based on actual measurement thresholds such as when the load goes over a set wattage or the system or battery is over a certain temperature. I find that my system responds much faster than with alarms.


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johnjaymack avatar image
johnjaymack answered ·

Thank you for the suggestion, @ZL2FAE. I am still very new to some of this. Do you use Node Red to program your measurement thresholds?

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johnjaymack answered ·

Following up on the suggestions that @ZL2FAE made, I have been trying to determine what Node Red modules might be used to set up a wattage watch. I maybe just missing a point.

Here is the issue that I have seen. I travel in an RV and may connect to shore power sources from 15 amp to 30 amp on Leg 1 only, or to 50 amp fed to both leg 1 and leg 2. I set my input current limit based on the shore power source that I connect to.

When the output power requirements exceed the input current limit, my Multiplus II begin to assist. Since I am running two Multipluses in parallel, I can get an assist of up to 4800 watts. What I am not seeing is a single setting that reports only the inverter assisting output. Ideally I would be able to set up an Inverting maximum wattage setting so that anytime the load on the inverter reached the set point, an alarm would be triggered or an automatic load shed would occur.

As a specific example, let's assume that the needed AC output is 5500 watts. If not connected to shore power, an immediate load shed would be required. 4800 watts maximum on inverter only. If connected to 30 amp, the shore power would provide 3600 watts, and the inverter would assist with 1900 watts. Everything is fine. If connected to a 50 amp service, the entire load is supplied by shore power and the inverter would not be assisting at all.

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