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Checking Appliance Earthing.

Zoomup
Today I spoke to the manager of a local chain of domestic appliance retail shops. The chain sells and installs appliances like cookers and ovens etc. I asked the manager if they carry out an earth fault loop impedance test to confirm adequate earthing of the supply circuits and good earthing of appliances like cookers. He said that they did not. He asked me what test gear is used to carry  out the tests. I was shocked by this. People are having appliances installed by unqualified installers and the earthing effectiveness is not being tested.


Also his shop has nuisance tripping of the R.C.D. when several appliances are turned on. In particular washing machines cause tripping. Probably down to the 50 appliances each leaking a small current to earth via their internal mains filters. Get the cheapest quote. That''ll do. That's Norfolk for you.



Z.


Z.
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    At the level of Dangerous Dave's Domestic Appliances Installed Daily  (*), a continuity check with a  wander lead from the new cooker or new light fitting to the earth pin on a nearby socket would be within the capability of anyone who can read a multimeter and do their own car electrics. It does not need a £1000 multi tester, at a push a torch bulb and battery would do, and would be an easy 2 sentences to add to the fitting instructions.

    We don't honestly need an ELFI value accurate to 3 significant figures,  - that was presumably designed to be right at some earlier point, we just need to know it is not open circuit now because the screw has fallen out.


    (*) Apologies if that is anyone's real company, like the Far Eastern Dangerous Toy and Lawnmower Import Company I used in another post,  any resemblance is unintended and accidental.
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    It's an interesting question. Is it really the appliance supplier/installer's responsibility to check the adequacy of the installation's earthing? (rather  than just their connection - which at a push could probably be adequately checked with a look and a tug).


    If we'd been a bit more organised in the past and come up with a plug & socket arrangement for cooker connections would anyone really be expecting anyone to do a loop test before plugging a cooker in?


       - Andy.
  • 0
    I was called to a cooker installation a while ago because curries had refused to connect, stating that the property had no earthing. On arrival it turned out the property was a TT system all test readings adequate and RCD in place.

    I called the installers on behalf of the client and asked them to explain their refusal. The guy I spoke to had no idea what I was talking about when I explained to him that the installation was fine.
  • 0
    Amusing but probably better than the other way about, and suggests they  mostly do connections in towns and cities.
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    mapj1:

     At the level of Dangerous Dave's Domestic Appliances Installed Daily  (*), a continuity check with a  wander lead from the new cooker or new light fitting to the earth pin on a nearby socket would be within the capability of anyone who can read a multimeter and do their own car electrics. It does not need a £1000 multi tester, at a push a torch bulb and battery would do, and would be an easy 2 sentences to add to the fitting instructions.

    We don't honestly need an ELFI value accurate to 3 significant figures,  - that was presumably designed to be right at some earlier point, we just need to know it is not open circuit now because the screw has fallen out.


    (*) Apologies if that is anyone's real company, like the Far Eastern Dangerous Toy and Lawnmower Import Company I used in another post,  any resemblance is unintended and accidental.




    The continuity test from cooker exposed conductive parts and the earth pin of a nearby 13 Amp socket confirms that the two items are connected together electrically, BUT are the two connected effectively to Earth? They may not be.


    A torch bulb and battery may confirm that a few milliAmps can pass through  the route but will not prove that the route is good enough to carry a large fault current sufficient to operate a protective device like a fuse or M.C.B. The circuit may only be hanging on by a strand or two of fine copper or a loose screw terminal.


    Z.

  • 0

    Zoomup:

    The circuit may only be hanging on by a strand or two of fine copper or a loose screw terminal.




    In which case the Zs will be elevated by a tiny amount because of the tiny length of inadequate CPC. Which, perhaps, is why we inspect and test.

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    The question is not however can we eliminate all possible faults however unlikely, but more can we be reasonably confident that the cooker swappers have not left the installation dangerous by their actions. I agree there are a whole raft of things that those of us with access to a full suite of test gear and more knowledge may choose to do, but if we think it is not reasonable for the cooker to be swapped and no verification at all, then at least confirming a connection to some form of CPC will eliminate the most dangerous errors that could leave it live relative to the rest of the metalwork in the kitchen is worthwhile.

    I agree the CPC may pass and yet be hanging by a thread, but the non-RCD trip testers also suffer this weakness, and it is no worse.
  • 0

    I suppose that is the going rate these days Fitzi if the job is to be done correctly. It is a blanket cost to cover most eventualities I suppose. My local installer charges £60.00 plus VAT to wire up a cooker, including cable, and claims that customers won't pay any more.  20 per cent VAT makes the job even more expensive.


    Z.


     




    We just charge our usual hourly charge to do it (to the nearest half hour). It's usually done and dusted in under 30mins even with hob+oven and cleanup under the oven and round the hob.  25 quid. (I think we under charge but it sure brings in the money). We do indeed test for polarity and function and earthing. I even set the clock!

  • 0

    MHRestorations:




    I suppose that is the going rate these days Fitzi if the job is to be done correctly. It is a blanket cost to cover most eventualities I suppose. My local installer charges £60.00 plus VAT to wire up a cooker, including cable, and claims that customers won't pay any more.  20 per cent VAT makes the job even more expensive.


    Z.


     




    We just charge our usual hourly charge to do it (to the nearest half hour). It's usually done and dusted in under 30mins even with hob+oven and cleanup under the oven and round the hob.  25 quid. (I think we under charge but it sure brings in the money). We do indeed test for polarity and function and earthing. I even set the clock!


     




    Twenty five quid including materials? Plus VAT? 


    Z.

  • 0
    Inc Vat, we're not registered, but no materials, labour only.  :)

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