Caravan Earthing, Higher impedance?

[whitenight639]

So I have a static caravan that has a hookup to the house, And I wanted to improve the earthing by installing one specifically just for the caravan,

So I have driven in around 4ft of copper pipe and used 30a capble to earth both the chassis of the caravan and the metal exterior, but upon checking the continuity and resistance the earting I have installed seems to have increased the resistance, Measuring with my new earth disconnected from the ground rod it measures 30 Ohms from an earth in a socket to the the caravan shell / exterior sheeting, with my new earth rod connected it measures 60 Ohms, now the hook-up runs around 15 metres to the garage and then into the house.

If electricity follows the path of least resistance than surely my readings must be wrong, right?

I don't have any fancy earth testing equipment just a multimeter, I'm not an electrician, I just wanted to improve the earth in the caravan mainly to add additional safety and protection from lightning / EMP.


Either there is a principle I am yet to understand or I am measuring it wrong, or have faulty reading, what do you guys think, and what should a good earth measure in Ohms or isnt it that simple, It's very strange because I added salt and water around the earth rod to check it and the resistance went from 60 Ohms to around 55 Ohms.

 

[markc123]

You either buy yourself an earth electrode tester, or you can do it using an earth fault loop impedence tester (not prefered)

And please don't add water around the rod again, testing should be done when the ground is least favourable.

 

[alancoulson]

blimey where to start !! forget testing with a multimeter you need an impedance tester and the knowledge to use it.
have you run a 2 core from the house supply and then earthed the van using an earth stake ?
im not gonna go into how you test the resistance for the earth stake which will give a Ra reading etc etc. maybe you should ask a sparky to carry out the correct testing.

 

[whitenight639]

blimey where to start !! forget testing with a multimeter you need an impedance tester and the knowledge to use it.
have you run a 2 core from the house supply and then earthed the van using an earth stake ?
im not gonna go into how you test the resistance for the earth stake which will give a Ra reading etc etc. maybe you should ask a sparky to carry out the correct testing.

No the Caravan is supplied by 3 core so is earthed through that connection, the earth I have added is additional, I can't see how spending £900 on a fancy earth tester is worth it for one job, especially when my multimeter is capable of measuring impedance (I know im gonna get stick for this, so bad), obviously impedance is proportional to current and voltage but I can soon unplug everything and connact a 12v battery to the van and measure the current and impedance of the earth?

 

[telectrix]

first consideration is the earthing system at the house. TN-S or TNC-S?

 

[markc123]

No, i agree earth electrode testers are pricey if you don't use them regular.

Thats why you can now rent them for the day.

 

[telectrix]

as my old man use d to say. " if it flies, floats, or fornicates, then rent it".

 

[44ALLAN]

How do you know the earthing needs improving?

 

[whitenight639]

first consideration is the earthing system at the house. TN-S or TNC-S?

TNC-S

No, i agree earth electrode testers are pricey if you don't use them regular.

Thats why you can now rent them for the day.

as my old man use d to say. " if it flies, floats, or fornicates, then rent it".

Sparky wisdom, love it, I think I will give my sister a ring, who works at HSS.

How do you know the earthing needs improving?

I don't But I have sensative electrical equipment in here and would like it to be as safe as possible, I would like to think I could provide a better earth as our house was built and wired years ago, Also the long length of cable for the hook-up dosn't inspire me, it seems logical to provide a local earth for this van.

 

[markc123]

I'm not being funny - but you're wanting to make it as safe as possible but you don't really know what you're doing?

Just ring an electrician.

And another thing, good look complying with BS7671 - TNC'S is forbidden for what you're wanting to use it for. 708 Special locations, read it.

 

[whitenight639]

I'm not being funny - but you're wanting to make it as safe as possible but you don't really know what you're doing?

Just ring an electrician.

And another thing, good look complying with BS7671 - TNC'S is forbidden for what you're wanting to use it for. 708 Special locations, read it.

You asked the earth scheme at the house. TNC-S, but the van has its own RCDs and earth so will be more like TT which is desarable. I want to understand the science of it, I care little for the regulations as only I use the place, when I say safety I mean from fire / lighting strikes and EMP etc.

 

[markc123]

You asked the earth scheme at the house. TNC-S, but the van has its own RCDs and earth so will be more like TT which is desarable. I want to understand the science of it, I care little for the regulations as only I use the place, when I say safety I mean from fire / lighting strikes and EMP etc.

Oh dear. That's not a clever thing to say. For one, if you were wanting an EICR on the install and the leisure accommodation vehicle has a TNC'S supply (regardless whether its doubled up with a TT) then it'll fail.

Do it properly, pay the extra and it wont bite you in the arse further down the line.

 

[MDJ]

have you run a 2 core from the house supply and then earthed the van using an earth stake ?
.

How is the cable from the house protected?

 

[whitenight639]

Oh dear. That's not a clever thing to say. For one, if you were wanting an EICR on the install and the leisure accommodation vehicle has a TNC'S supply (regardless whether its doubled up with a TT) then it'll fail.

Do it properly, pay the extra and it wont bite you in the arse further down the line.

No I do not want an eicr, this is not a leisure accommodation vehicle, its a meth lab (Joking).

How is the cable from the house protected?

it's 3 core armourflex burried 12ft deep and protected by laserbeams and tiny dragons, This forum is useless

 

[markc123]

No I do not want an eicr, this is not a leisure accommodation vehicle, its a meth lab (Joking). This forum is useless

I know you don't want an EICR - im saying for the future, if you were ever to have one done, it would fail. Then it'll be a bigger cost at the time to put what should of been installed correctly in the first place.

And yes it is a leisure accommodation vehicle regardless as what you're using it for. A static caravan = a leisure accommodation vehicle.

This forum is a great learning resource.