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Old 12-29-2014, 10:14 AM   #1
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Magnum inverter "AC Backfeed" fault

The Magnum inverter is tripping and giving a "AC Backfeed" fault message. Any ideas on how to trouble shoot this or suggestions on what to check would be appreciated. I have shut off all the breakers it feeds and still get the the problem.
Thanks!
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Old 12-29-2014, 10:42 AM   #2
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I have a MagnaSine inverter and have had a few periodic issues with it, however that is not one of the fault messages I have seen! Do you have the manual for your remote? If not, here is what the manual says about this particular fault:

AC Backfeed:
This fault message causes the inverter to shut down because AC voltage from an external AC source has been detected on the inverter’s AC output. An inverter reset or power reset will be required to resume operation (see Sections 6.2 & 6.3).

Remedy:
This fault usually occurs because the AC output wiring is connected to (or able to be connected to) the incoming AC source. When this fault happens, all system wiring should be re-checked to ensure the incoming hot and/or neutral wires are not able to be connected to the AC output.


Not sure if that helps at all - the manuals for these units are available online at magnumenergy.com
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Old 12-29-2014, 11:06 AM   #3
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I occasionally get that same error message on my Xantrex/Heart Interface inverter. In my case, this occurs only when I am switching between shore and genset power, and only sometimes. I have yet to figure out what the cause is.
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Old 12-29-2014, 03:16 PM   #4
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I occasionally get that same error message on my Xantrex/Heart Interface inverter. In my case, this occurs only when I am switching between shore and genset power, and only sometimes. I have yet to figure out what the cause is.
I'm having that same issue as we speak (AC feedback code). Will let you know how it works out, but up to now, I've only been able to detect a low battery (10.8 volts) coming out of one of the 8D house banks. According to the manual, the Inverter will not put out unless it has a 12 volt feed., but the message remains (AC feedback).
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Old 12-29-2014, 05:09 PM   #5
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I once witnessed an electrician get a shock while working on a shore power pedestal. He had turned off the main breaker at the shore transformer but a boat with an inverter was back feeding into the system. Get a qualified (ABYC certified) marine electrician immediately.
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Old 12-29-2014, 05:42 PM   #6
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Old 01-05-2015, 07:31 AM   #7
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Quote:
Originally Posted by Kenmaki View Post
The Magnum inverter is tripping and giving a "AC Backfeed" fault message. Any ideas on how to trouble shoot this or suggestions on what to check would be appreciated. I have shut off all the breakers it feeds and still get the the problem.
Thanks!
If you have two 30 amp cords might try unplugging one not on inverter buss to see if fault goes away. Possibly another small standalone inverter somewhere aboard or in a piece of equipment?
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Old 01-05-2015, 08:57 AM   #8
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One place the neutral and ground are connected is via the polarity reversed detection circuit. I'm not positive how they work but think that is supposed to be a high impedance bulb across the two wires but if the inverters circuits are very sensitive it just might be enough.
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Old 01-05-2015, 09:24 AM   #9
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If you are still having a problem call them, I have and have gotten good advice.
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Old 01-05-2015, 09:37 AM   #10
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I'd call Magnum, but will place my $.25 bet on this being the result of an electric motor being turned off and momentarily acting as a generator while it spins down. That little bit of back current looks like a backfeed, because it is.
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Old 01-05-2015, 10:42 AM   #11
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I'd call Magnum, but will place my $.25 bet on this being the result of an electric motor being turned off and momentarily acting as a generator while it spins down. That little bit of back current looks like a backfeed, because it is.
My money is on your theory and it may explain my own periodic backfeed faults.
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Old 01-05-2015, 11:27 AM   #12
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My money is on your theory and it may explain my own periodic backfeed faults.
The real challenge is how to fix it. I think it will either take some programming in Magnum's part to make the device more tolerant, or judicious and magical application of capacitors. My half-joking theory over the course of my 30 year career in electronics was that all hardware problems are solved by the addition or removal of capacitors. Nobody ever proved me wrong :-)
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Old 01-05-2015, 11:43 AM   #13
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Kenmaki:

What electrical devices are on when the trip occurs?

Two years ago it was our microwave that started back feeding through an older MSW inverter into the instruments. Not always, just sometimes. A new PSW Magnum inverter/charger cured the issue. Is your Magnum MSW or PSW?
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Old 01-05-2015, 04:30 PM   #14
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The real challenge is how to fix it. I think it will either take some programming in Magnum's part to make the device more tolerant, or judicious and magical application of capacitors. My half-joking theory over the course of my 30 year career in electronics was that all hardware problems are solved by the addition or removal of capacitors. Nobody ever proved me wrong :-)
I second the capacitor theory.

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