Recently bought a cheap 12v->240ac inverter for the car. It has no earth and as a far as I can tell no RCD.
How safe are these units? The environment in which they are being used presents many risks - spilt drinks, wires trapped in metal doors, wires pulled out, children up to no good etc...
I've not heard of any problems with inverters, but then it only seems to be in the last couple of years that they become really popular/cheap.
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An RCD would be of no use whatsoever. They trip when the current in a pair of wires is different due to earth leakage (like house wiring where you grab a live wire and an earthed tap - so the current in the live wire is more than the neutral wire).
If you grabbed live and neutral in a house circuit while stood on a rubber mat, then the current in both cables would still be the same so the RCD would not trip and you could well peg it. The same applies to your inverter if you grab both wires.
Your inverter has no earth - so if you grab a single wire then there is no circuit back to earth so no lethal shock.
This is one of the principles that the yellow transformers on building sites works on.
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I would have though the biggest danger with these is people over loading them, and they do seem to get very hot. Would they not use the cars ground as the earth? I personaly would only ever use low voltage stuff with them such as laptops and would never use something like an electric kettle (which would overload most of them anyway).
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they are very safe to use.
Even though they run warm-ish, they do have safety cut outs to stop anything going bang.
regarding getting shocks, the 230 volts only wants to go from one pin (live) to the other pin (neutral).
So if you were to touch the live of the inverter you would get a shock but I will put your life in danger.
I wouldn't advise touching the live though.
Its quite different from the mains electric in the house.
As other posters have said a RCD would not work as they need an earth path to measure earth leakage current. Inverters do not use an earth
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Thanks for the replies and link to previous post.
So in summary, it seems they are very safe, the exception being to never touch both the live and nuetral at the same time - hopfully not something that will ever happen!
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The inverter does not have an earth because the car does not have an earth.
RCD would still work because it measures difference between phase and return - i.e. what is going through you. They don't need an earth wire to work.
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I invested in a 150W inverter. It cost an astonishing 20 Euros and allows me to run a cheap inkjet printer from the car which is proving a godsend. They are as safe as anything CE marked and electrical, but they are not idiot proof. If you stick your finger in the live terminal it will be able to supply enough juice to give you a nasty shock.
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The inverter does not have an earth because the car does not have an earth. RCD would still work because it measures difference between phase and return - i.e. what is going through you. They don't need an earth wire to work.
Ok, so there are two conflicting replies about wether a RCD would work.
If the electricity is passing through someone, where is it going to?
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a 20 euro inverter must be made of plastic squeegy bottles and a bit of tin though
i have one of those usb 240 volt mains chargers for my pen camera (only use it for blackmailing) anyway, the first one broke so i took it to bits as you do and learnt a valuable lesson,i wouldnt leave the thing unattended ,i bought another from hong kon-k and it was a £1 plus £2.80 postage or something daft so just be aware they may be eu approved but that doesnt mean to say they are safe ( i seem to remember a lot of these type things were removed from the market last year due to fire hazards)
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If you are in the car, you will be pretty well insulated from earth, so a shock is most unlikely to be fatal, unless you touched one wire with each side of your body/arms so that it passes through your chest. It is not likely to pass in any magnitude down a single arm through your heart and into your feet or saddle. I dare say that running the unit or an appliance outside of the car (such as at a picnic) would pose a greater risk.
Edited by Hamsafar on 11/06/2009 at 12:38
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Rattle>>This is one of the principles that the yellow transformers on building sites works on.
Err, the main benefit of using 110V on a building site is that the maximum electric shock to earth (the most likely route) is 55V, which is very unlikely to harm you.
As for RCD, they measure leakage to earth. So if you put yourself between the live and neutral, and insulate yourself from earth, then you would be just like a laptop, and utilise the energy.
Fortunately plugging something into an RCD doesn't make it trip...
Edited by Mapmaker on 11/06/2009 at 12:50
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Mapmaker... could you elaborate on the 55V thing?
I found this on the net:
Two principle types exist, the smaller ones have a single phase primary winding to suit the normal single phase supply of 230/240 volts. The secondary winding is single phase 110 volt nominal with an earthed center tap.
This ensures that the maximum voltage to earth is only 55 volts, thus almost eliminating the risk of dangerous electric shock.
Such transformers are generaly portable and fitted with a short length of cable and a 240 volt plug. Common ratings are from 500 watts up to 3,000 watts, though larger units exist.
I don't understand why the maximum voltage to earth is 55v, is the 110v measured from peak to trough on the waveform, and if so, how does the equipment "see" 110v and not 55v?
Cheers,
David.
Edited by David Horn on 11/06/2009 at 13:56
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Don't worry, just figured it out. :-)
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