Reverse Polarity RV Plug on Bluetti/Ecoflow/Goalzero?? Is this a problem?

Will Prowse

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Hey everyone. I had a lot of people email me this week about concern over bluetti/goalzero/ecoflow products having a reverse polarity RV plug.

I don't think it's a problem at all. There is no exposed case on these units, and it's a floating system. It is only considered "reverse polarity" when using the other receptacles as a reference as to what "hot" and "neutral" is considered. It's alternating current though, so it doesn't matter. What does matter is if the reference potential of grounding conductors across ac outputs is bonded. And after testing this five seconds ago, they are. So I don't see any safety issue either.

If the outputs were in parallel to increase capacity (with some way to sync the waveforms), the relative "polarity" of the inverters output would matter.

But in this instance, I don't see an issue at all. I also can't imagine how electrical engineers from multiple companies could all be wrong in the same way. It is possible, but highly unlikely.

If you disagree with my reasoning above, please explain your thoughts below.
 

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smoothJoey

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A trick I've seen people do to get a neutral/ground bond is to make a dummy nema5-15 plug that just bonds neutral to ground inside the plug.
That could yield a nasty surprise for the RV circuit.
 
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Will Prowse

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We don't even have polarized plugs on mainland Europe, and equipment needs to work no matter where phase/neutral are in the socket. I can't imaging there be many products even in the States that rely on the polarity...
I think people are freaked out because they were checking continuity of the ac outputs. But it simply does not matter. And yes exactly, alternating current circuits are just that. The polarity does not matter.
 

Will Prowse

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Good to know!

I took my comment down because I need to look up the tesla charger circuit and figure out why it has ground fault monitoring. I was going to rewrite that comment, but you replied before I was able to. I would imagine if a garage where a tesla is stored were to flood, it needs its own GFCI, similar to a hot tub.
 

time2roll

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Is it truly reverse polarity or floating neutral? What is the voltage measure hot-ground vs neutral-ground?

GFCI detects an imbalance of power between hot and neutral. 5mA will trip.

True reverse polarity in an RV can cause a hot skin issue and the user can feel a tingle or worse when touching the RV and standing on the ground outside. There is no GFCI to protect the entire RV.
 

smoothJoey

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True reverse polarity in an RV can cause a hot skin issue and the user can feel a tingle or worse when touching the RV and standing on the ground outside. There is no GFCI to protect the entire RV.
I may be wrong but the hot skin issue occurs because current gets back to the source(transformer) because the transformer is bonded to the planet.
The skin is hot and your body completes the circuit.
rv_skin->human->planet->transformer
 

time2roll

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I may be wrong but the hot skin issue occurs because current gets back to the source(transformer) because the transformer is bonded to the planet.
The skin is hot and your body completes the circuit.
rv_skin->human->planet->transformer
Yes. Bad ground connection and/or reverse polarity combined with leakage creates several combinations to have this issue or mask other issues. Water heater, fridge heating element and converter all are suspect of leaking current to ground (chassis).
 

smoothJoey

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Yes. Bad ground connection and/or reverse polarity combined with leakage creates several combinations to have this issue or mask other issues. Water heater, fridge heating element and converter all are suspect of leaking current to ground (chassis).
The point I didn't quite make was, If the solar generator is properly isolated the current can't get back to source via the planet.
 

Will Prowse

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Hot skin to ground issue when connected to an rv wouldn't occur because it's a floating system. None of these units have a true earth ground connection. Check out the ecoflow deltas ground for the ac receptacles, there is none.
 

smoothJoey

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Hey everyone. I had a lot of people email me this week about concern over bluetti/goalzero/ecoflow products having a reverse polarity RV plug.
When you say its reverse polarity you mean relative to the nema 5-20 outlets, confirm?
 

FilterGuy

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Polarized plugs and Neutral-Ground bonding are related, but separate things.

My understanding is that the Polarized plug in the US originally came about as the result of the old Edison Screw-in light bulb socket. The polarized plug and properly wired lamp would ensure that the 'hot' is the little button contact at the bottom of the socket and the neutral is the threaded part of the contact. This made it far more difficult to accidentally touch the hot contact of the socket.
If the power source is isolated from earth ground (such as the Bluetti), touching the 'hot' has no effect so this is not an issue.

The NG bond is there for two reasons:
1) Clear a fault
2) If the ground wire is connected to the earth, it prevents the circuit from floating to some potential other than earth.

For a Floating system (such as the Bluetti), the 2nd purpose does not come into play and if Hot and Neutral are reversed, the system will still clear a fault if there is a short between Neutral and Ground.

Where things could get wonky is with more modern equipment that actively checks for the N-G bond (Such as the Tesla Charger) If it expects the bond to be between two specific wires, it may not be happy with reversed polarity.

The other area that would need to be checked is what RCDs or GFCI breakers will do with Hot and Neutral reversed. (I don't know)
I had a lot of people email me this week about concern over bluetti/goalzero/ecoflow products having a reverse polarity RV plug.
If they are all doing it (and not just copying designs), there must be a reason. I wonder what it is.
 
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FilterGuy

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My understanding is that the Polarized plug in the US originally came about as the result of the old Edison Screw-in light bulb socket. The polarized plug and properly wired lamp would ensure that the 'hot' is the little button contact at the bottom of the socket and the neutral is the threaded part of the contact. This made it far more difficult to accidentally touch the hot contact of the socket.
BTW: A three-prong plug achieves a polarization of the plug. I imagine that they considered requiring 3 prong plugs on lamps but realized there were too many houses wired without ground so they opted to make the two-prong plug polarized. NEC worries about cost as a secondary issue to safety, so it does not directly drive their decisions, but polarizing the plug is cheaper than requiring 3 prong plugs.
 
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