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Shower with no RCD or supplementary bonding

MrJack96

I have been round to a relatives flat and seen he has an old Wylex board with MCBs. His bathroom has no supplementary bonding from what I can see and no RCD protection for his electric shower. how potentially dangerous is this? I know the circuits are fairly short and can see main bonding in place Can only really think if the R2 values are low enough touch voltages should end up being kept low? 

 

 

 

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    Can you please explain, for instance, the current path of a fault and how the 50V between an exposed-c-p and an extraneous-c-p is calculated or achieved.

    Calculation (current path and assumptions)

    Step 1 decide the maximum current that may flow to earth (live to CPC )without operating ADS quickly.

    (if say  breaker is 40A perhaps a 50A current) 

    Step 2 measure the resistance between the CPC and the non-bonded part.

    (let us assume the non bonded part is connected to the MET by some moderate resistance)

    Step 3 Assume (an this is the biggy)  that in the worst case fault, all the current in step 1 flows in the resistance of step 2, and multiply both numbers to get a maximum voltage.

    perhaps the cpc is 1 ohm from fault point to the MET and the point of fault rises 50V relative to MET during fault.

    less than 50 ?

    more than 50  ?

     In reality this over estimates the problem, as the unbonded part may not be connected to the MET at the other end of the CPC, so the resistance may not be the full R2..

    Mike

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  • 0

    Can you please explain, for instance, the current path of a fault and how the 50V between an exposed-c-p and an extraneous-c-p is calculated or achieved.

    Calculation (current path and assumptions)

    Step 1 decide the maximum current that may flow to earth (live to CPC )without operating ADS quickly.

    (if say  breaker is 40A perhaps a 50A current) 

    Step 2 measure the resistance between the CPC and the non-bonded part.

    (let us assume the non bonded part is connected to the MET by some moderate resistance)

    Step 3 Assume (an this is the biggy)  that in the worst case fault, all the current in step 1 flows in the resistance of step 2, and multiply both numbers to get a maximum voltage.

    perhaps the cpc is 1 ohm from fault point to the MET and the point of fault rises 50V relative to MET during fault.

    less than 50 ?

    more than 50  ?

     In reality this over estimates the problem, as the unbonded part may not be connected to the MET at the other end of the CPC, so the resistance may not be the full R2..

    Mike

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