Posted on 14/10/2020 17:01
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.
Posted on 19/10/2020 11:06 by DougSI'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!
Posted on 19/10/2020 15:57
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.
Posted on 22/10/2020 14:12
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.
Posted on 22/10/2020 14:12 by DougSA 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.
Posted on 23/10/2020 08:05
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.
Michelina
Motorhomer