pganguet avatar image
pganguet asked

Backfeed relay failure?

So two 12v/3kw multiplus in parallel. Used System configurator to allow two separate inputs. Worked fine for a couple years. Today had a heavy load going on one multiplus input (46A). It dropped the grid input and went to invert. Troubleshooting showed there was power within spec at the AC-in terminals. Backfeed relay would click every few seconds, trying to connect to grid but never does. Troubleshot by applying grid power to other Multiplus (with the same configuration file), which connects to grid and operates fine.

I'm near certain the backfeed relay is dead (burned contacts). Just to verify my troubleshooting, anyone have any other ideas what went bad? Is this common?

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1 Answer
Paul B avatar image
Paul B answered ·

I am presuming that your multiplus is the 50 amp pass through version and that you are NOT exceeding the 50 amps pass through otherwise it will also turn off


This is only a guess and somewhere else to look at,

the other posable cause is if you have a ignor AC in selected in a assistant or in the virtual switch andf then there is a issue with the control thats activating that programed feature.

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pganguet avatar image pganguet commented ·

Hmm, I do have an ignore AC input assistant. My initial assumption of the process was that inverter sees qualified AC in and syncs frequency then energizes the relay. Then at the same moment the inverter ceases output as soon as the relay closes. Then because the relay is not making contact, the inverter senses a voltage drop and starts inverting and de-energizes the relay. But if somehow the assistant was interfering, that could have the same net effect. I can certainly delete the assistant to rule it out. Thanks for the idea.

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