Recommendations for an earthing strap on inverter generator

[Nikki]

I've seen that the suitcase gennys don't come with an earthing strap, but do have an earth terminal
Any of you made your own? If so what with please
Many thanks

 

[autorouter]

I don't have a generator, but you can get earth braid (plaited stranded wire, very flexible)

Earth Braid - 19mm² 130A

Tinned copper earth braid suitable for low voltage automotive and marine applications. 130A, 19mm², 16/16/0.30mm, 7.2mm dia. Round cross section.

www.12voltplanet.co.uk

You can crimp some terminals onto it. Choose the ones to fit the bolts it will connect to.

Copper Tube Terminals - 25mm² Cable

Closed copper tube terminal for 25mm² max. cable. Bell-mouthed entry & inspection hole. Can be crimped or soldered. Available with 5/6/8/10/12mm holes.

www.12voltplanet.co.uk

You can get readymade ones at places like Halfords. Maybe you can get a garage to crimp the connectors onto the braid (a 10-second job with the right crimp tool).

 

[JJ]

I have never ever used an earth strap on my genny...

...but then, I drive in Spain with bare feet and have never weighed my van or had a habitation check.


JJ

 

[Lenny HB]

Normally generators have a floating output if you want to earth them the correct way is to drive a metal stake 1 m into the ground and water it if the ground is dry.

Edit:
I must be in a good mood, not normally very civil when people ask questions about noisy horid generator things

 

[MANGOFORTH]

I have never ever used an earth strap on my genny...

...but then, I drive in Spain with bare feet and have never weighed my van or had a habitation check.


JJ

That made me laugh ?

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[PhilipPrice]

I saw this article in the MMM magazine yesterday about not earthing the generator but connecting the caravan earth to the neutral terminal, no idea if it is a good idea though.

 

[Nikki]

Yes I have seen similar to the article above, but am not brave enough to tinker with it!

 

[pappajohn]

Earth wire needs to be 16mm2 and earth spike needs to be driven 1mtr into the ground.....
Then the van itself will need earthing in the same way to complete the return path to earth.
Why bother, the generator already has a centre tap floating earth.

 

[Richard n Ann]

Earthing it won't do anything unless you connect one of the generator outputs to it, this is then called the neutral and it's why the current from the other output (now called live) wants to flow to it.

Our house supplies want to flow to earth because neutral is earthed at the local substation.

Basically leave the generator alone, it's safe as designed, neither of the outputs will flow to earth ?

 

[tonyidle]

Basically leave the generator alone, it's safe as designed, neither of the outputs will flow to earth

You can but MMM is right (only on this one thing and only this month!) that if you want your van protection to work as though it was on EHU you need to connect earth and neutral together at the generator. Earth spikes will do nothing.

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[DBK]

View attachment 338875
I saw this article in the MMM magazine yesterday about not earthing the generator but connecting the caravan earth to the neutral terminal, no idea if it is a good idea though.

It's electrically and technically correct as the neutral wire in your mains at home is also connected to the earth at a local substation. This doesn't mean you can connect the neutral and earth together in your house as the neutral to earth voltage can be 20 or 30 volts or more depending on how balanced the three phases are locally.

There's probably a Wiki article about all this.

 

[Silver-Fox]

I have never ever used an earth strap on my genny...

...but then, I drive in Spain with bare feet and have never weighed my van or had a habitation check.


JJ

?

You’re just a free spirit arnt you ?

 

[Nikki]

Thank you everyone, it's very interesting and a bit mind boggling for me, but I get the basic principles
I think as some have said, that if I'm just using it to top up batteries via the charger, I will leave alone
If I were also running things off the mains sockets at the same time, when the RCD may be used, I would think differently
That's my very basic thoughts

 

[Pausim]

I am getting confused (easily done). I thought modern RCDs monitored the balance of current between positive and negative and that the earth was no longer used for this purpose. With polarity often being unknown I can see that an RCD that switches off both positive and negative connections is essential but what is the role of the earth?

 

[tonyidle]

I am getting confused (easily done). I thought modern RCDs monitored the balance of current between positive and negative and that the earth was no longer used for this purpose. With polarity often being unknown I can see that an RCD that switches off both positive and negative connections is essential but what is the role of the earth?

L / N current is as you say balanced. To become unbalanced there has to be a connection or leakage from one or the other. That connection or leakage has to connect to something to exist and what it connects to is the Earth connection.

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[Pausim]

L / N current is as you say balanced. To become unbalanced there has to be a connection or leakage from one or the other. That connection or leakage has to connect to something to exist and what it connects to is the Earth connection.

OK got that but what changes when the earth and neutral are connected together?

 

[Richard n Ann]

OK got that but what changes when the earth and neutral are connected together?

It encourages live to flow to earth. Before you do so it wouldn't be interested ?

 

[Richard n Ann]

Simple diagram time ?
This is an unmodified generator, you can't get a shock off it's outputs unless you touch them both at the same time...

This is it modified so the RCD can work...

The current from the Live output wants to flow to earth because earth is tied to it's other output, in reality you probably wouldn't feel a shock because of your shoes/carpet etc. Plus the RCD should trip anyway ?



Disclaimer: This is in no way meant to be patronising ?

 

[tonyidle]

OK got that but what changes when the earth and neutral are connected together?

Until the earth WIRE is connected to something no current will flow under fault conditions - it's simply an unconnected wire.

Before the RCD (at the generator) there are three wires: the L and N carry the current used by anything switched on in the van. The E, despite being connected to the N does nothing, because inside the van it is only connected to the van metalwork and each appliances chassis or other exposed metal part. If a fault occurs within the motorhome and L becomes connected to earth via, say, the human body current will flow. Sufficient current to cause danger to the person involved but nowhere near enough to trip a breaker or blow a fuse. The RCD spots this minute current and switches off the supply.

 

[tonyidle]

Simple diagram time ?
This is an unmodified generator, you can't get a shock off it's outputs unless you touch them both at the same time...
View attachment 339010

This is it modified so the RCD can work...
View attachment 339012
The current from the Live output wants to flow to earth because earth is tied to it's other output, in reality you probably wouldn't feel a shock because of your shoes/carpet etc. Plus the RCD should trip anyway ?



Disclaimer: This is in no way meant to be patronising?

The earth wire needs to pass through the RCD for that to work ?.

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[Richard n Ann]

The earth wire needs to pass through the RCD for that to work ?.

Ive never seen an RCD with an earth connection ? what makes you think that?

 

[SuperMike]

Earth wire needs to be 16mm2 and earth spike needs to be driven 1mtr into the ground.....
Then the van itself will need earthing in the same way to complete the return path to earth.
Why bother, the generator already has a centre tap floating earth.

Uncle PPJ is being generous. I was always taught the point of the 3/4” spike should be at least 8ft into the ground. Happy SuperMike ‘cos it’s lump hammer time.

 

[Pausim]

Right, I am sitting in my Faraday Cage with no hook up and no generator but I do have an inverter running. The inverter is connected to dedicated sockets via a separate twin pole RCD. Am I safe or should I be connecting the neutral to the earth?

 

[Richard n Ann]

Right, I am sitting in my Faraday Cage with no hook up and no generator but I do have an inverter running. The inverter is connected to dedicated sockets via a separate twin pole RCD. Am I safe or should I be connecting the neutral to the earth?

Safe. That's how ours is ?

 

[tonyidle]

Ive never seen an RCD with an earth connection ? what makes you think that?

Sorry - badly put. The earth connection from the generator (linked to N at generator) needs to pass the RCD to the consumers inside the van. The actual earth (the ground itself) won't guarantee a path.

To those suggesting earth spikes: as has been pointed out it is impractical, the van stands on (possibly conductive) tyres, and there's still no link to Neutral to encourage the RCD. Richard and Ann s drawing makes what is needed to maintain RCD function very clear.

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[joka250]

Surely the definitive answer is to ban generators.!!! Helmet at the ready.

 

[pappajohn]

Uncle PPJ is being generous. I was always taught the point of the 3/4” spike should be at least 8ft into the ground. Happy SuperMike ‘cos it’s lump hammer time.

Never seen or used an 8ft earth spike Mike.....and I've hammered my share of em.
Usually 1.2mtr with a brass tip to penetrate hard rocky ground.
Lightning conductor earth spike is 8ft long though..... But that's carrying umpteen gigawatts.

 

[SuperMike]

Never seen or used an 8ft earth spike Mike.....and I've hammered my share of em.
Usually 1.2mtr with a brass tip to penetrate hard rocky ground.
Lightning conductor earth spike is 8ft long though..... But that's carrying umpteen gigawatts.

Your probably right, Uncle, its a long time since I drove one in. You know what it's like, the old boy who taught me said so and you did as you were told, and it stuck, there was no google to check what he said.

If you wanted your little brown envelope, apprentices money, at the end of the week, the only answer was "Yes Mr Smith" (Yikes, i've forgotten his name).