Domestic electrical advice? - Earthing stake

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Steve Wright
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Domestic electrical advice? - Earthing stake

Testing the Power of Blatchat again, any electrical engineers able to offer advice?

Our dishwasher packed up. The Hotpoint engineer plugged in his tester before starting work and advised that the earth impedance was too high for him to work safely on the machine so he went away.

I've tried good old Google and it looks as though we must have a TT system i.e. the earth is supplied by an earth spike rather than via the supply cable. We have an earth spike near the front door.

The bit I have trouble understanding is how a device plugged into a wall socket can detect this "high" impedance.

Also wondering if I can do anything to improve the earthing to get round the problem. I guess removing the paving blocks and driving in a new and maybe longer stake might do it? I'll photograph the top of the stake when it gets light tomorrow if it helps.

Any thoughts welcome as always, it's good to chat.

Thanks.

Steve

SM25T
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Getting the lightning conductor tested at our Saxon church, there were doubts expressed regarding the earth spike. Seems it depends on how wet the soil is at the time of measuring. A long dry spell means trouble. I guess that won't be your problem at this time of year.
Derek Batty
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Hi Steve was electrician before retired six years ago ,you need to get an electrician round to test it , if it’s been there a while poss have 6 mil cable to it  ,,now needs upgrading , not sure now  what size they req ,or reading as it keeps. Changing , just make sure electrician you get is redg,,, it should just be a call out charge and quick easy test ,plus price to put right ,,if you don’t no good electrician poss ask round friends or put on BC

dsrek  

Derek Batty
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It’s a simple  job to just plug tester in to give reading ,,from what  I remember it had to be below 200  ohms ,,earth rods now are  a lot thicker , and you can just screw one onto other if poss to knock in further go get good reading , it can sometimes be a nightmare if ground is hard or sandy , rods are usually one meter long the most I have had to extend is five to get a good reading 

good luck 

derek

SM25T
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Don't pierce a drain, or gas or water supply !
CaterBram
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The issue with earth rods is they don't have a great surface area contact so can be susceptible to the ground drying.

We used to install rod networks for generator earthing, but now it works out more cost effective and better to excavate a 750mm wide trench, lay a series of linked copper lattice earth mats and cast the whole thing in Bentonite.

However as detailed above get an electrician to do a Condition Report of the installation to BS7671:2018 and you can then make some decisions based on the outcome.

TT installations are fairly rare these days unless you are in the wilds or on a private transformer as 99.999% of the time you will get either TN-S or PME 

Chris Bramall - Deep in the YoSDeNS area...

Member Since Aug 2009 

Steve Wright
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Thanks for the prompt replies chaps! Very helpful.

The Hotpoint man did mention 200 ohms and it being over that. I have a multimeter and can measure it, but wondered what you would measure it against i.e. one probe on the earth stake or maybe the earth pin on a socket but where would the other multimeter probe go? Just thinking in case I decide to drive a longer stake in the ground. Need to make sure it's safe.

I'm guessing I may have to get an electrician her in order to meet safety requirements. Part B certificate I think they called it when we had some work done a few years ago?

 

 

Norfolk AR - Member since 1996
Derek Batty
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Best to get an electrician in to be honest Steve you need a good meter to test ,,nearly all old houses on iom are TT systems criss ,, new sites now diff ,and tns , pme from what remember years ago in   uk ,, they put a link from neutral to earth terminal ,,,,but don’t do it on iom 

derek

Steve Wright
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Blimey, two more replies while I was keying #7.

OK, I see the point, need to get it done properly and certified. A job for tomorrow to find a good local electrician. 

Many thanks everybody.

Steve

P.S. good point SM25T re doing a DIY job and piercing other supplies!

Norfolk AR - Member since 1996
Derek Batty
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The bills in the post Steve

ddrek

Steve Wright
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Thanks Derek I'll look out for the post. It's not very reliable round here though...

Steve

Norfolk AR - Member since 1996