aandncaravan Posted October 4, 2017 Share Posted October 4, 2017 We worked on a vehicle recently that had a 2,000watt Inverter fitted to run various 230v appliances. Nothing unusual there, but this installer thought he would wire it into ALL of the vehicles 230v sockets using a 'home made' auto switching device that disabled the EHU input, when running on the Inverter. The switching device was quite clever, but when he had finished, none of the 13amp sockets had an Earth when a tester was put into the socket. If the system was 'switched' back to straight EHU the Earths all 'appeared', as soon as the Inverter was started, all the Earths vanished.. The Inverter he had bought was a budget device with no Earth output to the 230v output socket. When we found the instructions they specifically stated only appliances classified as 'Double Insulated' should be used with the Inverter because it had no safety Earth capability. Not sure how common this is, but something to consider? Also the voltage at the sockets was 265v, but this dropped slightly under load. Don't assume your Inverter is delivering a solid 230v, check it with a voltmeter. We will add this warning to the 'Inverter webpage' : http://www.aandncaravanservices.co.uk/inverters.php Link to comment Share on other sites More sharing options...
Tracker Posted October 4, 2017 Share Posted October 4, 2017 We used one of these permanently plugged into the inverter mains outlet, or could be used on any other socket had we ever used ehu. https://www.amazon.co.uk/UK-Mains-Earth-Present-Tester/dp/B00780WFHQ Cheap enough to gain peace of mind as there can be enough shocks to owning a van without electric shocks too! Link to comment Share on other sites More sharing options...
Charles Posted October 4, 2017 Share Posted October 4, 2017 Inverters and generators have floating earths. It's nothing to be concerned about. The output current won't flow to earth even with a dead short. Read this: https://en.m.wikipedia.org/wiki/Floating_ground Link to comment Share on other sites More sharing options...
Charles Posted October 4, 2017 Share Posted October 4, 2017 QUOTE "If the system was 'switched' back to straight EHU the Earths all 'appeared', as soon as the Inverter was started, all the Earths vanished" It's not the Earth connection that's disappearing, it's the live from the inverter that's not 'interested' in flowing to earth, giving the misleading conclusion that the earth isn't there. Link to comment Share on other sites More sharing options...
aandncaravan Posted October 4, 2017 Author Share Posted October 4, 2017 In this instance the Earth was not wired up internally. The output on the centre 3 pin plug was open circuit. Opening the box revealed no connection to the Earth Pin at all, hence going on a hunt to find the instructions of operation. Although it had a 3 pin 13a socket on the end of the Inverter, it was wired for 2 pin plug operation for double insulated devices only. Because the 'switching' device 'broke' the EHU cable, for obvious reasons, Earthing WAS lost, it wasn't me being as stupid as you seem to think. A few questions before contradicting my post, as you so often seem to do, might have been an idea? Link to comment Share on other sites More sharing options...
Charles Posted October 4, 2017 Share Posted October 4, 2017 The Earths are never connected in an inverter, they are always like this. Or am I missing something? Floating earth = not connected. When using the inverter earth is not needed. As you say it's double insulated. When using ehu earth is needed because mains power is a TN (Terra Network) system. https://en.m.wikipedia.org/wiki/Earthing_system Sorry if you think I'm being rude I'm just stating the facts. Link to comment Share on other sites More sharing options...
aandncaravan Posted October 4, 2017 Author Share Posted October 4, 2017 Charles - 2017-10-04 12:50 PM QUOTE "If the system was 'switched' back to straight EHU the Earths all 'appeared', as soon as the Inverter was started, all the Earths vanished" It's not the Earth connection that's disappearing, it's the live from the inverter that's not 'interested' in flowing to earth, giving the misleading conclusion that the earth isn't there. Your second response is different to the above where you intimate a physical Earth will be there, "just not visable". Now you say a physical Earth will NEVER be there? I am not getting into another, "Sorry Allan but I am going to prove you wrong" argument, so regardless of whether there is an imaginary Earth or not, can we suggest everyone checks their Inverter is safe for your needs? As we point out in the original post, this one was only designed to be safe with Double Insulated devices, which some may not be aware of, I didn't expect to see that in the instructions. . . Link to comment Share on other sites More sharing options...
Tracker Posted October 4, 2017 Share Posted October 4, 2017 I have no techy education on electricity, what it does and how it works but I'm trying to think it through. When an inverter is fitted it is fed from the battery + and - and obviously with no earth facility to connect it to. As long as only two core cable double insulated appliances like chargers or hair driers with totally enclosed plastic casings are used I presume there is no risk of shock, or am I wrong? But if the inverter is used to power say a microwave or anything else metal cased there can't be any earth return unless an ehu is hooked up, in which case you wouldn't need to use an inverter, so should you earth an inverter, and if so how would you do it? Link to comment Share on other sites More sharing options...
monique.hubrechtsgm Posted October 4, 2017 Share Posted October 4, 2017 I am looking forward to a battey pack assisred motorhome. Not even a hybride is there. Solely a electric driven mororhome and not any of combustion engines.That clears up all the amperes problems you have above. By the way an electric car has no floating earth. Link to comment Share on other sites More sharing options...
Brian Kirby Posted October 4, 2017 Share Posted October 4, 2017 Might there be an element of cross-purposes, here? Forgive the ley explanation, but my understanding of the need for a safety earth is that the high voltage mains electricity transmission lines (i.e. the grid) are only positive conductors. The three groups of wires are not line, neutral and earth, they are the brown, black and grey phases of a three phase alternating supply. There are no HV neutral, or earth, wires as such. The "neutral" and "earth" conductors only originate further down the system, at the step-down transformers, where high voltages are reduced to feed the low voltage power cables that deliver electricity to consumer installations. So far, we have a supply to the consumer, but no return. To ensure a return path to the generator, both the neutral and earth conductors of the low voltage power cable are connected to a common terminal (a metal spike driven into the ground) at the step-down transformer, and thence literally via the earth. Safety earth connections are required where it is possible for an individual to come into contact with a live item, such as a metal part of an appliance with a fault. Without an earth connection, a person touching such a live part would provide the path to ground for the live current, and so be electrocuted. With an earth connection, the live current will flow immediately to ground via the earth wires, which will cut (fuse/MCB/RCD) the supply before anyone can touch the live part. It is a fail-safe system, but it is only necessary where the common return path for electricity is via the ground. This is why "double insulated" appliances have no earth wire; they have no potentially live parts that can be touched, so provide no path to ground. OTOH, with a battery driven inverter, that merely converts 12V DC to 230V AC, there is no earth wiring, and no risk to earth, because all return current flows via the neutral circuit. So, (at length :-)), if an inverter fed power system is tested with a conventional test plug, which "looks" for an earth connection as well as a neutral, it will "see" only a neutral, because although the earth wiring is present at the power socket, it is terminated at the mains consumer unit, which has no electrical connection to the inverter. This should not indicate a risk, as it should be normal. Were an earth to be detected, OTOH, there may be a risk, as both mains and inverter fed circuits will have somewhere been connected. With the installation described, in principle, its behaviour, as Charles suggests, would seem to indicate a "safe" installation on both mains and inverter power, but a detailed examination of the circuitry would seem to be desirable, to ensure that there is no possibility of both mains and inverter feeding the circuits simultaneously - and I have no idea of the potential consequences should that happen! Fireworks? :-D Link to comment Share on other sites More sharing options...
Tracker Posted October 4, 2017 Share Posted October 4, 2017 Brian Kirby - 2017-10-04 5:20 PM Without an earth connection, a person touching such a live part would provide the path to ground for the live current, and so be electrocuted. So if said person were not able to provide a route to ground, like if he were in a vehicle suspened from the ground by 4 big rubber inulators that we would call tyres he could not be electrocuted? Thanks Brian, nice try but for making it even more complicated than it needs to be!! Link to comment Share on other sites More sharing options...
Charles Posted October 4, 2017 Share Posted October 4, 2017 Spot on Brian. And yes Tracker, ie he would not get a shock, his whole body would be 'live' but no current would flow to earth, he wouldn't feel a thing. Link to comment Share on other sites More sharing options...
Brian Kirby Posted October 4, 2017 Share Posted October 4, 2017 Tracker - 2017-10-04 5:32 PM Brian Kirby - 2017-10-04 5:20 PM Without an earth connection, a person touching such a live part would provide the path to ground for the live current, and so be electrocuted. So if said person were not able to provide a route to ground, like if he were in a vehicle suspened from the ground by 4 big rubber inulators that we would call tyres he could not be electrocuted?............. When electricians work on live installations, for exemple inside electrical cabinets, it is usual for them to stand on a rubber mat to avoid accidental electrocution. So yes, rubber provides protection against electrocution. But, to answer your supplementary question, of course he could be electrocuted - if he were stupid, or unlucky, enough. For example (assuming said vehicle is a motorhome), he would need a vehicle on EHU with no earth connection, and he would have to stand with one foot on the van, and the other on the ground, while touching the live part, so by-passing the insulation provided by the tyres. But I don't quite see your point. The issue was whether a tester should see an earth connection at mains sockets when mains power is replaced by inverter power, not whether it is possible to electrocute one's self in a van, or whether the tyres would insulate the van from earth. Am I missing something else? Link to comment Share on other sites More sharing options...
Tracker Posted October 4, 2017 Share Posted October 4, 2017 Brian Kirby - 2017-10-04 6:30 PM But I don't quite see your point. The issue was whether a tester should see an earth connection at mains sockets when mains power is replaced by inverter power, not whether it is possible to electrocute one's self in a van, or whether the tyres would insulate the van from earth. Am I missing something else? The original question was 'inverters - is your's safe' and on that basis of safety it is possible to get an electic shock when using an inverter then clearly it is not safe and that is the point. There has been plenty of waffle and opinions posted and my sumation has not changed in that it appears to be safe as long you use only double insulated appliances when using mains power via an inverter as there is no earth circuit to take away deadly current to earth. Link to comment Share on other sites More sharing options...
Charles Posted October 4, 2017 Share Posted October 4, 2017 Tracker - 2017-10-04 6:44 PM Brian Kirby - 2017-10-04 6:30 PM But I don't quite see your point. The issue was whether a tester should see an earth connection at mains sockets when mains power is replaced by inverter power, not whether it is possible to electrocute one's self in a van, or whether the tyres would insulate the van from earth. Am I missing something else? The original question was 'inverters - is your's safe' and on that basis of safety it is possible to get an electic shock when using an inverter then clearly it is not safe and that is the point. There has been plenty of waffle and opinions posted and my sumation has not changed in that it appears to be safe as long you use only double insulated appliances when using mains power via an inverter as there is no earth circuit to take away deadly current to earth. The ONLY way you can get a shock from a STANDARD inverter is to touch both live wires coming out of it at the same time(there is no neutral) You cannot, on a STANDARD inverter, get a shock to earth, by touching either of the 2 live outputs (As long as you don't touch them both at the same time you won't feel a thing) Link to comment Share on other sites More sharing options...
aandncaravan Posted October 5, 2017 Author Share Posted October 5, 2017 As they say, you learn something new every day. I am happy to admit I know nothing about Inverters, hate their ability to chew up batteries so won't have anything to do with them. As you will read on our Inverter webpage. Link to comment Share on other sites More sharing options...
StuartO Posted October 5, 2017 Share Posted October 5, 2017 Charles - 2017-10-05 4:46 AMThe Earths are never connected in an inverter, they are always like this. Or am I missing something? Floating earth = not connected.When using the inverter earth is not needed. As you say it's double insulated. When using ehu earth is needed because mains power is a TN (Terra Network) system.https://en.m.wikipedia.org/wiki/Earthing_systemSorry if you think I'm being rude I'm just stating the facts. People who claim to be correct because they are quoting facts are often, at best, stating their interpretation of some facts, or maybe even a something which is merely published information and not necessarily facts at all. They are therefore merely expressing their conflicting opinion. Sometimes they do this tactfully and respectfully but sometimes they seem to be merely insisting that their opinion is the correct one (and claim it, wrongly, to be a fact) and what they are really doing is insisting someone else is wrong. Instead of being a helpful contributor, they thereby cast themselves as clever clogs. Link to comment Share on other sites More sharing options...
Charles Posted October 5, 2017 Share Posted October 5, 2017 That's the problem with forums, it's just a load of opinions, facts and rubbish all thrown in and mixed up. We all use them together with Web sites when we want to know something. So when I see something I know from experience is wrong or misleading I speak up! I think to myself how many people must be reading this rubbish (posted by someone who later admits to knowing nothing about the subject) and are being mislead. Oh and to top it off he's then upset because I explained there was nothing to worry about! Priceless! Link to comment Share on other sites More sharing options...
Tracker Posted October 5, 2017 Share Posted October 5, 2017 Perhaps if you boys can stop the 'I can pee higher than you' contest and get back to the topic without all the hysterics and blame game we would all be happier? Like many others I am no expert but I am able to learn and I appreciate their time in posting their views, but not the posturing - thanks! Link to comment Share on other sites More sharing options...
Brian Kirby Posted October 5, 2017 Share Posted October 5, 2017 Tracker - 2017-10-04 6:44 PM............................summation has not changed in that it appears to be safe as long you use only double insulated appliances when using mains power via an inverter as there is no earth circuit to take away deadly current to earth. Double insulated is not really relevant to appliances fed from inverters, Rich. Try looking at it a different way. As I tried to explain above, the electrical energy generated at a power station is + (Line, or live) only. But, to do work, that energy needs a path back to the power station. With mains installations, the way it gets back is literally through the earth. So, if you touch something that is live and you are in contact with the earth - directly or indirectly - the current will use you as its route back to the power station. You will be electrocuted. With an inverter powered from a battery, the electrical energy produced flows only through wired circuits. There is no connection to earth, literally or figuratively. Here, the only way to become electrocuted is, as Charles infers, by allowing your body to provide a connection between the line and the neutral conductors. If you do that, the electricity will use you as its return circuit and you do risk electrocution. However, were you to touch "line" only, in the absence of an earth, the electricity has no path back, so cannot flow through you. Hope this helps. Link to comment Share on other sites More sharing options...
aandncaravan Posted October 5, 2017 Author Share Posted October 5, 2017 To get the Post back to being the useful informative item that was originally intended, lets change it slightly. The warning about voltages still applies, we have seen a few with higher than normal volts which may or may not be an issue for the appliances used? The one we saw above was putting out 265v, that might be fine for a kettle but maybe not for a TV? Suggest you don't just assume it will be 230v - 240v, as this unit we saw above was quite poor quality and there may be more out there? If you check the output of an Inverter with a conventional socket tester and it shows things amiss, you can ignore any abnormalities in relation to the Earth, but maybe investigate further if the tester shows other issues. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.