electric shock from chassis

[Steve_5078021]

I have recently returned from Holiday, whilst on one site I experienced very mild electric shock tingling whilst kneeling on ground and touching the chassis or aluminium shell of the van. I obviously resolved to have this checked out on my return.

My quandry is this... when I moved to a second site the problem was not present and no matter how hard I tried I could not recreates it - Could it be that the problem lay with the site electrics?

Any advice appreciated - Steve

(needless to say I will mention this on the next service anyway)

 

[Rod_5041370]

Did you check the polarity and earthing at the site where you felt the tingle?

 

[GrahamW]

Steve

Are you sure it was not just a static charge?????

 

[BrianStAlbans]

Had the same at home when plugged into outside socket ,turned out to be a loose earth ,so probably a fault with the sites electrics. Might be worth phoning them to check it.

 

[Icemaker]

was your holiday on the continent ?. if so you could have had reverse polarity on the supply. if you did then the neutral wire would have been live and the earth could have passed a small current.

 

[WatsonJohnG]

It sounds like a faulty earth in the site electrics or your equipment.

Its worth using a polarity tester even in this country as I have found wires that have worked loose in this way.

 

[ProfJohnL]

Hello Steve,

As the problem did not ocurr on all sites, it points very strongly to a site fault, however, it would be wise to have your caravan and mains cable checked as well.

 

[rob_jax]

Steve,

It could have been static electricity, but you wouldn't have received a mild tingling - it would have been a definite zapp. and it would only have happened once - unles you were running around in nylon shorts and rubbing baloons on your head.

And I think the answer is in your description of a mild tingling, most people believe that the 240 volts AC is all on the live wire and no volatge at all on the neutral.

Well that's not true, there will be a voltage difference of 240 V between the live and the neutral, but depending where you are in the supply system the neutral can be at a potential difference of anything upto 30 volts.

If the camp site earth was not in a good condition or incorrectly wired, it may be that your van was not earthed, but at neutral potential.

Most people perceive contact with 20V to 30V AC as a mild tingling.

Regards, Robert

 

[Gary_5075845]

Hi Steve,

I had exactly the same experience on my 1993 sterling finesse at home on the drive while hooked up to the electric. I was just taking the wheel clamp off and I had a short sleeve teeshirt on and my arm was just touching the aliminium body of the caravan and I felt what you described. At first I thought my arm was rubbing something sharp but I soon realised that I was actually getting a mild shock. My first though was a bad earth somewhere so I went round to the other side of the van and found an earth strap that had one end screwed to the shell and the other end went to the chassis. Both the screws looked rusty so for a qick fix I undid them then re-tightened them and sprayed them with a drop of WD40 and this seemed to solve my problem. I do intend to replace the screws this weekend before we go away. Infact, thank you for reminding me because I had forgotton all about it.

Regards

Gary

 

[ProfJohnL]

To Gary and all.

I believe there are some misconceptions being aired in this thread and Steve's original question is not being addressed safely.

Back to fundamentals, for an electric current to flow and operate an appliance, there has to be a circuit made from the power supply and back again. This only requires two wires, and in UK terms this is Live and Neutral. The third wire in the UK is a safety device commonly known as the "Earth" but its correct name is a 'Continuous Protective Conductor'

The CPC connects all exposed metal parts of appliances to the earthing point of the supply. Manufactures have to go to considerable lengths to ensure that the CPC is correctly installed and it has to offer a very low resistance path from any exposed conductive surface back to the earth point.

Under correct operating conditions, there should be no contact what so ever between either the Live or Neutral circuits and the CPC. If a contact is made there is a fault, and the fact that the CPC provides an easy path back to earth means that you should not receive a shock, as the current will preferentially flow in the CPC rather than you.

Now if Steve is receiving a shock, it means that his caravan is not properly earthed. That is a fault. It could be in his caravan, or in the site supply. An electrician should be able to establish where the fault lies by testing.

If he always receives a shock whichever site he is on, then it points to a fault in his caravan, but if the shock is site specific, then it points to the site wiring.

Steve's shock is indicative of a wiring fault, and somewhere either in the caravan or the site an appliance has developed a fault to allow current into the CPC circuit. The polarity of the supply is not relevant to this, but it is a separate safety issue

With modern caravans and the equipment supplied, the polarity of the supply should not affect the safety of the CPC. Polarity is important to ensure that on /off single pole switches will disconnect the Live conductor to safely turn off appliances. Some appliances now use double pole switches which are the safest approach because they isolate both Live and Neutral, but not the CPC.

Steve get you caravan checked by an electrician. If he shows no fault with the van for other peoples safety contact the site where you got your shock and report it as a safety issue.

 

[WatsonJohnG]

Agree with what you are saying John and testing with a polarity tester that shows earth faults would show if there was a problem with the site wiring/cable/van wiring and would alert the user to check further.

I have written to Caravan magazine as they say in August's edition "Just to clear up one point our European neighbours use double pole switching,so there is no such thing as reverse polarity.With new British caravans also using double pole switching,reverse polarity also not a problem."

Firstly my two year old Ace does not have double pole switching and I have pointed out that it would make no difference if it had and I was using any UK appliance such as a table lamp that was single pole switched as the lamp would be switched at the fitting rather than on the socket.If this was in an awning with direct contact to moist earth etc etc. Later Ace vans have no switches at all on mains sockets.Reverse polarity at French sites means that a proximity tester will show that the cable to the van is live but the equipment will not work if the site trip in the neutral is tripped out.

 

[ProfJohnL]

Agree with what you are saying John and testing with a polarity tester that shows earth faults would show if there was a problem with the site wiring/cable/van wiring and would alert the user to check further.

I have written to Caravan magazine as they say in August's edition "Just to clear up one point our European neighbours use double pole switching,so there is no such thing as reverse polarity.With new British caravans also using double pole switching,reverse polarity also not a problem."

Firstly my two year old Ace does not have double pole switching and I have pointed out that it would make no difference if it had and I was using any UK appliance such as a table lamp that was single pole switched as the lamp would be switched at the fitting rather than on the socket.If this was in an awning with direct contact to moist earth etc etc. Later Ace vans have no switches at all on mains sockets.Reverse polarity at French sites means that a proximity tester will show that the cable to the van is live but the equipment will not work if the site trip in the neutral is tripped out.

Hi Watson(John G),

You are correct to say that polarity is important as many UK fittings still only use single pole switching, so the potential for a fitting to remain Live when an MCB or fuse has tripped is still there if the supply polarity is reversed.

However even if it is reversed your two year old caravan should be fitted with a double pole RCD, which if tripped would disconnect both live and neutral. The RCD should prevent a lethal shock to an adult if some one was to to touch a live, but it is less certain for a child.

I fully agree with your suggestion that a supply should be checked when you get on site with a relatively cheap and simple detector (about

 

[WatsonJohnG]

Hi Watson(John G),

You are correct to say that polarity is important as many UK fittings still only use single pole switching, so the potential for a fitting to remain Live when an MCB or fuse has tripped is still there if the supply polarity is reversed.

However even if it is reversed your two year old caravan should be fitted with a double pole RCD, which if tripped would disconnect both live and neutral. The RCD should prevent a lethal shock to an adult if some one was to to touch a live, but it is less certain for a child.

I fully agree with your suggestion that a supply should be checked when you get on site with a relatively cheap and simple detector (about

 

[Steve_5078021]

Wow... What a response, thanks everyone for your shared experiences and advice in particular the technical response from John L. I will of course follow this sound advice I had already considered contacting the site.. we have experienced different issues with their supply before (which is a little old and decrepit). Just to be safe I will also have my van checked. Rob_Jax, no it was definately not static and there was not a balloon in sight - but your comment made me chuckle all the same!

 

[WatsonJohnG]

Just as an aside its quite common to get a tingle when connected the Sky dish up .Presumably this is not related to your problem ---or is it?

 

[Steve_5078021]

Just as an aside its quite common to get a tingle when connected the Sky dish up .Presumably this is not related to your problem ---or is it?

No John, we dont have a sky dish - only an aerial on a pole (even the status has gone - see my other posting on duty of care, not that it worked that well anyway)