Chalet/Caravan Earthing?

[pwdrive]

Yes, that's what I would do, split before house CU etc, but I'm a bit skint at the moment, if all goes to plan the chalet will only need to be used for a few weeks so I'll have to put up with the present set up (two 30 ma RCD's cascaded) until a later date as funds allow.

Lawrence.

[ppppenguin]

Sounds like your earth loop impedance is already safe enough if it trips on a 7k rsistor.

I just thought up this idea so it may be utter rubbish but it seems to make sense. You can do a more sensitive test by finding the highest value resistor that will trip the RCD when connected from L in to N out. Or N in to L out. This is what the test button does but you are trying to find the trip threshold. Then find the highest value that will trip when connected from L to the earth rod. This should be lower than the value found in the first test. To a fair approximation the difference is the earth loop impedance.

[pwdrive]

Jeffrey, I was thinking more cave man style, shunt the RCD's, light bulbs to the earth rod, measure the drop   Only joking folks.

Just got word that the loop tester Mrs ordered for me has been dispatched.....tomorrow or Monday with a bit of luck.

I shall report.

Lawrence.

[ppppenguin]

Not as daft as it sounds. If you work carefully without gefingerpoken und spitzensparken you'l be fine

[boater sam]

The cascaded RCDs should be OK. On our mooring site because of the way the power is split through the farm we have up to 4 RCDs of various current and trip current ratings from 100A, 500mA trip to 16A 30mA trip in cascade.
There are occasions when the higher rated RCD will trip when the littluns don't. But it is still a safe instillation. There is literally hundreds of yards of SWA buried.

We have multiple earth rods on the ends of the distribution to the boats to try to ensure that hull corrosion due to galvanic action is minimised, every connection is RCDed separately, we have an awful lot of switch boxes!

If you have problems with bedrock, you can drive earth rods in at an angle, it is the contact area and soil condition that matters. Under a rainwater spout is a great place!

[pwdrive]

In the end I got the Martindale EZ2500 as opposed to the EZ150, it gives a more accurate read out, anyways it arrived today so I gave it a go, looks well made as does the IEC lead and the carry case.

So....re connected the earth rod to the earth terminal in the chalet, plugged in the loop tester and powered up, readings displayed at the chalet are given below:

Mains supply = 241 vac @ 49.9 hz.

Phase earth loop impedance = 61.5 ohms, PFC = 4 amps, that's not too bad for a first attempt with the earth rod.

Phase neutral impedance = 0 .44 ohms, PS(S)C = 525 amps, I'm happy with that.

For the relatively low cost of a couple of earth rods/connector etc I think I'll try and sink another earth rod down to 2.4 meters about 3 metres from the one I put in the other day, connect them up and see how much the 61.5 ohms is reduced.

For the above test all SMPS's in the house and chalet were disconnected.

The camera is in use by Mrs at the mo' I'll try and post some pics tomorrow.

Lawrence.

[ppppenguin]

If you're getting about 60 ohms earth loop resistance then you've solved it. Why bother with more rods.

[pwdrive]

If you're getting about 60 ohms earth loop resistance then you've solved it. Why bother with more rods.

Just for the hell of it Jeffrey, it's the sort of nutty stuff I do.....

Lawrence.

[ppppenguin]

60 ohms is ******** good for an earth rod. Be thankful you have nicely conductive soil. More likely very wet soil.

I'm thinking I ought to get one of those little testers. They tell you a lot with little effort.

[pwdrive]

60 ohms is ******** good for an earth rod. Be thankful you have nicely conductive soil. More likely very wet soil.

I'm thinking I ought to get one of those little testers. They tell you a lot with little effort.

They claim the test the tester does will not trip a 30 ma RCD, that was one of the reasons I got it, the other as you say is little effort required, the EZ150 is under half the price of the EZ2500 that I got but the earth loop impedance read out is less indicative so to speak.

The test I just done was at a wet time of the year and the ground is soaked at the moment, I will check it again during a dry spell, the first few weeks of Autumn is usually the best time down here for the water content of the ground to be low at depth.

Lawrence.