Using Mobile Power unit as an EHU Earth question.

[turtle2121]

Hi,

I have a mobile camping power unit (4 sockets, rcd and mcb in one). I was thinking of repurposing it as an EHU. The thinking seems to be that it should be earthed to the body.

So my question to the fine folk of the forum is, if the power unit is close and wired to a charger which is permanently connected to the battery. Won't that be earthed to the body through the battery negative? (edit: added a schematic for interest)

 

[Salty Spuds]

Theoretically you still need to earth the mains side to the van. If you look at your drawing, the 12V earth is isolated from the mains via the transformer. You should connect the incoming mains earth to the van. If you got a mains earth fault, you could end up with the van body live & not know until someone touched it that was stood on the ground. Don’t forget the van is isolated from earth by the 4 rubber things at each corner.

 

[Dellmassive]

@turtle2121 this is an interesting one.


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what "mobile camping power unit" have you got (post some pics) - the fact you say its mobile implies that it has no connection to the grid or real earth ground.

if its a mobile unit that has a battery & inverter inside the opinion is that no chassis/earth bond is needed as no connection to the grid.

if you have both external and mobile EHU then a transfer switch and chassis earth is required.






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a mobile system with an external earth chassis bond can actually be more dangerous:




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as @Salty Spuds says - if the van is connected to the grid at any point, the chassis needs to be bonded to ground.


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The charger question is an interesting one too . . .

the schematic you show above certainty does show the main earth as connected to the chassis and neg side of the battery.

however that schematic is from an old style metal box analogue dumb style charger - more of a power supply really.

nearly all modern chargers are smart and micro processor controlled,

and


they are almost all double insulated - meaning they have no earth connection.

so i would believe that the schematic above would not be relevant.

as an example i have around 10 chargers around me from all different manufacturers and all are double insulated,

apart from the Victron IP22 that has an alu metal body . . . but even with this the earth pin on the mains plus IS connected to the ALU case . . . but NOT connected to the

chargers NEG output - so again effectively isolated.




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more info here:

https://www.victronenergy.com/upload/documents/Wiring-Unlimited-EN.pdf

page 55 onwards - 7. Ground, earth and electrical safety

 

[Salty Spuds]

I’m assuming that the OP has one of the tent hookup jobbies, a trailing lead that plugs into a EHU & has a box on the tent end with a RCD & 4 sockets.
Something like this
Eurohike Mobile Mains Kit, Brown, One Size https://www.amazon.co.uk/dp/B0714L1...i_i_7Y22MQ2Z2J6F9C35HCBW?_encoding=UTF8&psc=1



Edit ..

Pic added.




.

 

[turtle2121]

Thank you all, amazing information. It is a case of me trying to save twenty quid by using the the eurohike plug, rcd and sockets pictured above. After this education, I think I will take an earth from the charger 3 pin plug and bond to the body.

 

[BoroBoy]

So just for clarity.
The earth wire from the hook receptacle has to be earthed in the consumer box and the van body?

 

[Dellmassive]

@turtle2121

can you post a pic of the mobile thing you are referring too.

Just to avoid confusion.

 

[Dellmassive]

So just for clarity.
The earth wire from the hook receptacle has to be earthed in the consumer box and the van body?

If the van is connected to external 240v grid power, then yes.

Earthing must be continuous from chassis to consumer unit to EHU post/ grid conection.

If stand alone inverter then no.

 

[BoroBoy]

If the van is connected to external 240v grid power, then yes.

Earthing must be continuous from chassis to consumer unit to EHU post/ grid conection.

If stand alone inverter then no.

OK understood.

 

[BoroBoy]

OK understood.

 

[turtle2121]

@turtle2121

can you post a pic of the mobile thing you are referring too.

Just to avoid confusion.

Hi @Dellmassive. It is similar to the Eurohike one that @Salty Spuds kindly posted above. Should fit nicely in the rear quarter. (full size bed). I plan to run charger to a battery under the bed (I'll take the earth from this socket) and another socket to the pod, which will run the fridge and gadget chargers. The benefit of this install is I could remove it if needed. Your guides have been invaluable to me, so I'll take this opportunity to say thanks!

 

[Salty Spuds]

Hi @Dellmassive. It is similar to the Eurohike one that @Salty Spuds kindly posted above. Should fit nicely in the rear quarter. (full size bed). I plan to run charger to a battery under the bed (I'll take the earth from this socket) and another socket to the pod, which will run the fridge and gadget chargers. The benefit of this install is I could remove it if needed. Your guides have been invaluable to me, so I'll take this opportunity to say thanks!

View attachment 158180

All you need to do is make sure the incoming earth from the mains is securely bonded to the van body. There’re a couple of ways to do it. You could have a 13A plug with a length of earth cable (I’d use something like a Tri-rated 2.5mm ) connected to the earth pin in the plug & to an earth stud on the van body. When you use the hookup box, plug the earthed plug into one of the sockets on the EHU box. This will connect the van to mains earth. The other way would be to wire an earth flying lead out of the EHU box & somehow connect that to the van with something like a large crocodile clip or welding earth clamp, probably not as elegant as option 1. Another option would be an earth spike connected to the van & hammered into the ground when you pitch. What you’re aiming for is to provide a better earth for any fault current than a person would provide.
The last option is do nowt & hope nothing goes wrong, which in truth it probably won’t, until…..

 

[Rioja John]

Hi @Dellmassive. It is similar to the Eurohike one that @Salty Spuds kindly posted above. Should fit nicely in the rear quarter. (full size bed). I plan to run charger to a battery under the bed (I'll take the earth from this socket) and another socket to the pod, which will run the fridge and gadget chargers. The benefit of this install is I could remove it if needed. Your guides have been invaluable to me, so I'll take this opportunity to say thanks!

View attachment 158180

I have installed the same as above and today I’ve run an earth from inside the unit down to one of my Van King bed bolts that are secured to one of the latching points.

John.