Help with testing to find why I'm getting shocked when on EHU

[TravellingSmurff]

Hi guys,
I have a converted crafter that I didn't convert.
When in France the other week, I went on ehu and touched the underslung gas tank and got a shock. Same when I touched the metal in the garage part under the bed.
I do not have an inverter.
I have two UK mains plug sockets
I have a battery charger connected to the ehu

I understand that when on ehu, the chassis and plugs should be connected to the ehu earth and that when I got the shock, I was laying on wet grass and I was the conductor to earth, rather than it going back to the ehu.
How and what do I test? I have a multimeter. And I understand there should be some resistance between the earth on the ehu and the things connected to it, including the chassis. Do I need to make up a long lead, touch the earth on the ehu IN and then start measuring the resistance on appliances?

If you think I should hire someone to have a look, then who and anyone know at what cost roughly?
Taking it back to the people that did the conversation is a possibility but they're the other end of the country and was hoping to save some time, money and effort really.
Thanks for your time
Danny

 

[Tigger-Tim]

I use a Megger 420 these days. It's a serious piece of kit, at about £1700. But I'm testing a lot of kit, a mixture of 110v, 230v and 415v.

I still use a little multimeter for some fault finding activities - often working out what's wrong after something has failed on the big tester ahead of a retest.

I'm pleased that travellingsmurff is taking it back to the converter to get it looked at properly.

 

[autorouter]

I'm pleased that travellingsmurff is taking it back to the converter to get it looked at properly.

The other way of looking at it is, he is taking it back to the people who did the original wiring, and maybe made a mistake in the design and installation. I'm not sure I'd want them looking at the wiring of my camper van.

Another thing, I'd like to know if there is an RCD fitted in the mains box, alongside the MCBs. Or maybe an RCBO or two. And if there is, why didn't it trip? And if there isn't, there absolutely should be an RCD in there somewhere. Maybe TravellingSmurff could post a picture,

 

[Bodoge]

The other way of looking at it is, he is taking it back to the people who did the original wiring, and maybe made a mistake in the design and installation. I'm not sure I'd want them looking at the wiring of my camper van.

Another thing, I'd like to know if there is an RCD fitted in the mains box, alongside the MCBs. Or maybe an RCBO or two. And if there is, why didn't it trip? And if there isn't, there absolutely should be an RCD in there somewhere. Maybe TravellingSmurff could post a picture,

Hopefully when the converters have diagosed the fault and the necessary remedial works carried out,we shall all be informed. I agree, a trip, if there are any, should have tripped, but it would also depend on where and how the leakage is occurring. Having read through these posts and comments prompted me to check moho's circuit breakers, low and behold i found an ac circuit breaker, protecting a dc circuit, an obvious replacement, now remedied.

 

[activecampers]

I am no expert but the chassis etc acts as Earth for the vehicle 12 volt systems.

I do not believe that the chassis or vehicle parts should be used as Earth for the 240 volt EHU power.

Earth should be the Earth connection at the EHU post and all earths should connect back to that.

If you are getting shocked then there is a mains short/leak to the chassis.

The consumer unit must be earth bonded to the chassis with thick cable, 6mm2 iirc minimum. Yes, also goes back to post but the chassis would this be connected to earth. It's the only way you'd get RCD protection if wiring fault made van live. That's why tent type hookup extension leads must not be used in van as if the cable splits and touches chassis then you will get shock

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[TravellingSmurff]

The other way of looking at it is, he is taking it back to the people who did the original wiring, and maybe made a mistake in the design and installation. I'm not sure I'd want them looking at the wiring of my camper van.

Another thing, I'd like to know if there is an RCD fitted in the mains box, alongside the MCBs. Or maybe an RCBO or two. And if there is, why didn't it trip? And if there isn't, there absolutely should be an RCD in there somewhere. Maybe TravellingSmurff could post a picture,

 

[autorouter]

The left-hand trip switch is an RCD, which protects against electric shock. It is the standard 30mA trip current. The '25A means it is suitable for all circuits up to 25A. It is not an overcurrent protection device.

The right-hand trip switch is a double-pole MCB, which protects against overcurrent. The 'C13' means it will allow any current up to 13A. This combination of RCD and MCB is exactly right for a motorhome mains supply.

One simple test is to press the test button on the RCD. The one at the top marked 'T' . If the hookup is not connected, nothing should happen. If the hookup is connected, it should trip. Note that it should trip even if there is a missing earth, it only tests the internal trip mechanism of the RCD, not the earth. If it doesn't trip with the mains connected, then either there is a problem with the connection (most likely), or the RCD trip mechanism has failed (less likely but possible).

 

[TravellingSmurff]

It tripped. And it tripped the one in the house that's connected to the garage socket from where I connected the lead

 

[Tigger-Tim]

I'm surprised you are still plugging the van into the mains. It needs to get to an electrics person ASAP.

You still have some wiring issues. The chassis of your van should not be live. And the chassis of your van should be connected to the EHU earth. It is dangerous and needs to be repaired.

 

[TravellingSmurff]

Yep just to test whenever someone on here asks. But then disconnecting. It's booked in at the end of October and we are not using it with ehu until then

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[Ian Bosman]

I am no expert but the chassis etc acts as Earth for the vehicle 12 volt systems.

I do not believe that the chassis or vehicle parts should be used as Earth for the 240 volt EHU power.

Earth should be the Earth connection at the EHU post and all earths should connect back to that.

If you are getting shocked then there is a mains short/leak to the chassis.

the mains wiring should be totally independent of the vehicle but a solution is to wire an earth connection such that a probe can be literally earthed into the ground. A piece of copper pipe cane be easily soldered up to an earth wire capable of conducting 16 amps at least pushed into the ground will be most effective. as to why you a getting shocked though sounds like faulty mains wiring somewhere. look for brown(live wire) or blue (neutral) which has chafed against the vehicle chassis or has been hooked up to the chassis in error.

 

[autorouter]

To clarify this bit about chassis earthing and conducting through the chassis.

On the 12V side, the chassis is used as a common negative return conductor. Positives go from the battery, through the device, and the negative from the device is attached to the nearest point on the chassis. The negative return current then flows along the chassis metal, through the earth strap, and back to the negative battery terminal. The benefit of this is it saves the weight and expense of the copper wire negative returns. This is often referred to as an earth or ground, but technically it isn't, it's a common chassis negative return.

On the 240V side, that's not how the mains supply to the motorhome works. The live and neutral are always isolated from the chassis and any exposed metal parts. A protective earth wire connects all the earth terminals of the sockets, and all the earth terminals of any appliances connected directly without sockets. The protective earth cable is kept separate from the live and neutral throughout the whole of the motorhome, and at no point is the neutral wire and earth wire connected together.

All exposed metal parts, including the chassis, in the motorhome should be bonded to the earth cable. However these exposed metal parts should not be used to carry any earth currents. So they are not 'earth return' connections, just 'earth bonded' connections.

When testing this, at the motorhome inlet there should be insulation between all the three conductors. There should be continuity between any exposed metal parts or metal chassis parts and the earth conductor.

If you only have a standard multimeter for testing, 'Insulation' means higher than the highest measurable resistance on the highest range of an ordinary multimeter. 'Continuity' means a very low resistance, well below one ohm, which is just about measurable on the lowest range of most multimeters.