Garage earth rod or not.

Discussion in 'Electricians' Talk' started by Woodster1, Jul 12, 2019.

  1. Woodster1

    Woodster1 New Member

    Morning, I’ve seen a few similar questions relating to garage electrics but nothing specific. My question - do I need an earth rod off the garage circuit or not.

    Electrician (now retired) rewired our whole house and garage including consumer unit around 7 years back. The garage was supplied with armoured cable from the main box to a small consumer unit supplying sockets and lights. This had an earth cable going to an outside rod.

    Garage has been replaced as part of a new extension and the new electrician has run a new 10mm armoured cable to the new garage (15m from the house). He has said we don’t need the earth rod (I kept it) as it’s handled by the house.

    Is this okay?

    Cheers.
     
  2. Comlec

    Comlec Screwfix Select

  3. Tony Goddard

    Tony Goddard Screwfix Select

    Sounds absolutely fine to me, the method of using a rod at the garage is fine, safe and appropriate in some cases, but by far the most common method is to do as your new electrician has done, if he says it's OK (assuming he is qualified etc. and knows his business) then I would have no reason to doubt him.
     
  4. Woodster1

    Woodster1 New Member

    Perfect, thanks for the confirmation. He/his company is fully qualified, I was interested if the requirements had changed or if there was a better way of doing it.
    One copper earth rod to the scrap man.
     
  5. Tony Goddard

    Tony Goddard Screwfix Select

    Its not copper, it's steel jacketed in copper, so the tip is a better option unless you have another ton to go with it!
     
  6. Woodster1

    Woodster1 New Member

    Cheers gents.
     
  7. Bob Rathbone

    Bob Rathbone Screwfix Select

    To answer you question fully you should consider a CCU in the house with circuits of mixed disconnection times, ie fixed and portable services. By extending a common CPC to the zone outside that protected by the equipotential bonding you may contravene the regulations concerning disconnection times for circuits outside the equipotential zone. As you will have sockets in the garage, the disconnection time for these will be 0.3 seconds or less. Your local RCD will ensure this on a local basis. However, assume that a fault to earth occurs in the house on a 5 second disconnect circuit, then it is possible, as you have shared a common CPC, that the CPC in the garage and any metalwork connected to it, will become live for up to 5 seconds while we wait for the fault in the house to clear. This clearly does not comply.
    Their are 2 solutions, 1 install local bonding in the garage, perhaps to the re bar in the floor and any services such as water. 2, do as you did before an use the earth rod as a clean earth, with a 30mA RCD.
    Many will say this is over the top, but they may not have considered carefully all of the implications of extending the CPC outside the equipotential zone. The CPC is not benign.
     

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