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johnjaymack avatar image
johnjaymack asked

Controlling relays on MultiPlus II with Node Red

Some background. I live fulltime in a 44 foot motorhome. Other than the engine, it is basically all electric. When not connected to shore power, my inverters carry the loads.

I have two MultiPlus II 2x120 connected in parallel connected to a Cerbo GX. I am using Relay #1 on the Cerbo for generator control using Guimods. Most of the time, the system works well. Today, the outside temperature was above 105F and I had a complete system shutdown. My shore power connection, 50-amp, shutdown without warning pushing the entire load onto the inverters. They carried the load for a while and then shutdown on L1 Overtemperature or Overload, I believe. Since they are such work horses, I did not realize that shore power had dropped until all AC power disappeared.

I am looking at creating an automatic load shedding capability. I can independently disconnect certain loads to reduce the overall load on the system based on a signal input.

I know that I can use Node Red to look at various conditions and trigger the Cerbo #2 relay. But I would like to get better control of the possible problems.

Each MultiPlus has a K1 open collector relay control, and an Aux relay. What I would like to do is control each of these relays separately. For example, maybe use Inv #1, K1 to control a small relay and use that relay's contact to turn on a fan in the inverter bay. Maybe use the Inv #1 Aux relay to signal loss of Grid power inside the coach. On Inv #2, I could program its two relays for additional functions such as shedding loads one at a time until the warnings are reduced or eliminated..

It appears that I could use the VE.Bus System Configurator and Assistants to program the inverter K1 and Aux relay but that seems to be less convenient than a Node Red solution.

So, to make the question straight forward, can Node Red control the MultiPlus K1 and Aux relays on each inverter independently, or are they only controlled through the VE.Bus System Configurator and Assistants?

Any other thoughts or suggestions are welcome.

Multiplus-II
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3 Answers
derrick thomas avatar image
derrick thomas answered ·

The multi's relays can only be controlled from assistants or virtual switch within each inverter. You might look into adding an external relay module which can then be controlled via node red. Alternatively you can connect non-critical loads to the ac output 2. In standard out of the box configuration ac output 2 is only powered when shore power is available, and disabled when inverting. If you want more control over the ac output2 relays (other than simple on/off according to shore availability) you can use assistants and turn on/off based on SOC or other parameters.

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johnjaymack avatar image
johnjaymack answered ·

Thank you @derrick thomas for your response. I had hoped that I had missed something. I have already placed certain loads on AC2 so that they are automatically disconnected if shore power is lost.

Our problems have occurred when we are on shore power, we have various circuits in use such as Air Conditioning and kitchen appliances in use, and shore power drops, or due to elevated outside temperatures, we begin to approach temperature alarms or high L1 power. When everything is connecting and working, no problems. If we lose shore power and do not know it, we overload the inverters.

When boondocking, we actively monitor our loads because we know that we have limited inverter power.

Thanks again

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Gabriel avatar image
Gabriel answered ·

I am also looking for extra relay to control heater and fan for LFP battery. Would Multiplus relays be activable from Nodered?
The Cerbo relays are already used for generator and water heater...

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derrick thomas avatar image derrick thomas commented ·
Multiplus relays are only accessible from assistants or virtual switch, not from the cerbo.
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