Generator/Reverse Polarity
Hi everyone, looking for a bit of advice please. I have a Honda EU20i which I want to use for battery top up in my motorhome. When I plug into the generator the reverse polarity light keeps flickering on the motorhome panel. Would it rectify the problem if I change the plug to a reverse polarity.
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I’ve no idea but I sincerely hope you won’t use it on site. Have you considered a solar panel?
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If he was on a club site he’d almost certainly have EHU so not need it.👍🏻
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Wow. Miles off subject in two posts. Is that a record?
I doubt that the generator polarity is reversed the problem you are seeing is simply one that happens with small units, especially the less expensive types. If you need to check it get a mains tester plug and try it in the 230v socket on the generator.
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You’re right, Brian.
Apologies to Michelina.
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If the polarity was reversed then the light would stay on so I am inclined to agree with the other posts that it could just be the nature of the waveform from the generator. A poor Earth could also cause a problem.
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If there is nobody close to you use it, or if there is, just ask if it is alright to use it. You will soon be told if it is an annoyance. You must have a reason as to you wanting to use a generator, don't be put off by others that don't know your reasons. .
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Our Swift manual says that the RP light coming on may happen with some generators because (as I understand it) the live and neutral conductors are each approx 110V above Earth i.e. the Earth is connected to the centre of the windings which each generate 110V giving a total of 220V between them.
This is done so that the maximum voltage above Earth is 110V (safer)
The fitted RCD inside should be tested regularly and aims to prevent any risk of electric shock by assuming that any difference between current flowing in Live and Neutral conductors is going through a person therefore it shuts of the supply.
Therefore RP light on is not a big worry but...
If I were using a generator, I think I'd expect to find an Earth post on the generator and drive in a suitable metal stake (Id make it at least a foot long, or more?) to act as an Earth but of course, following the makers instructions (from the EU20i manual, there does appear to be an Earthing point on the control panel)
Always ready to hear other justified views.
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Definitive answer?:
https://caravanchronicles.com/guides/understanding-generators/
The bit headed Update explains it well (IMHO)
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Interesting article which raises some issues which I had never had a reason to think about as I have never owned or contemplated buying a generator. Clearly, without the EHU connected, the “earth” of the van or motorhome is floating, as is the neutral. If you plug in a generator you would expect the generator metal work to be used as an “earth” and connected to its neutral. The van Earth would be connected to the generator Earth through the Earth wire in the connected cable. If the generator doesn’t have the neutral connected to the earth then there is no return path to allow an RCD to work
All I can conclude from this is - read the generator manual carefully to find out how it’s connected and what is recommended. An Earth spike for the generator may be sensible and can’t do any harm.
As I mentioned earlier, a flickering reverse polarity light could indeed relate to earthing problems.
In my career I worked on many types of electrical systems; the USA and parts of Southern Europe can be quite different. The point being that it is difficult to give definitive advice without knowing quite a lot about the equipment you are dealing with.
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I'm fairly sure that modern RCDs measure currents going in via Live and out via Neutral and if there's any difference over their design trip current (can be 30mA) they assume that difference is going through a person down to Earth and cut off the supply therefore no Earth actually needed?
Of course if you touch both Live and Neutral conductors then it won't trip so I'd not recommend that!
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Yes, an RCD detects imbalance between live and neutral which occurs if current is "diverted' via an earth, however, the earthed metalwork needs a connection back to the neutral of the supply or no current can flow. In fact, if you had a genuinely isolated earth you can't have an earth fault and you cannot get an electrical shock because of the lack of return path to the supply. The "earth" (bonded metal, dirt, mud and rock) act as a conductor to take the current back to the supply neutral.
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A previous post appears to have disappeared?
I have discussed this area with an expert friend and, based on this document:
https://www.hse.gov.uk/foi/internalops/ocs/400-499/oc482_2.htm
Focus on getting all appliances and the installation in a good state by visual inspection and any problems noted during use.
A PAT test on appliances would be the next step but visually is often at least as good.
Don't worry too much about earthing of generator and don't make any mods to it without getting a professional to assess it and make any changes.
Earthing rods need to be tested with specialised equipment and start at 1m length!
Test the RCD regularly but be aware that this only tests the mechanical integrity and cannot guarantee the electrical characteristics (tripping currents and times)
Otherwise, don't have a false sense of security and get an expert for your application.
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Interesting article. Thanks. I have designed many systems with independent generation but a permanent large generator is very different to a small plug-in temporary supply. It seems to suggest that you can run with the neutral isolated which is fine but, as I said, the RCD won’t work. Bear in mind that this paper is talking just about the generator, not the van that you are connecting to. Earth rods used for a specific purpose have to have a maximum resistance to earth as defined in the IET Building Regs. Last one I was involved with was several meters long so I’m not a great fan. Also the caravan/motorhome isn’t earthed except through the Earth cable back to the supply.
Like all advice, the article has if’s and but’s and suggests getting professional advice which, of course, is impractical. Best suggestion is to do what it says in the generator instructions.
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