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Main to out building

Face plate
Sorry to bring up this old chestnut but just seeking clarification as it was in 2005 that it was first raised. I am now retired and my last update was C and G 2008

I have been asked to maintain a small sewage tank system for 6 houses. This consists of air pump and controls and lift pump.The pump controls are situated approx 200 metres from the incoming main and earthing / supply is an armoured  cable with cpc which is connected to a TN C S (PME) at origin.

The only metalwork in the tank is a 25mm pipe from lift pump to outlet and internal blower pipework.

Is it allowed to export the PME system in this case or should it have been a TT system with RCD at origin ?

Many thanks FP

  • 0
    Hi just to expand, I visited the site yesterday and the origin of the circuit is in fact a 30ma RCBO and all the CPConductors connected to the metal Hager unit and then connected to the PME terminal. So PME with the circuit fed via an  RCBO. Should an earth stake at origin also be fitted?

    Thanks FP
  • 0
    If the armour is protected by the PME earth, then you could have the RCD at the load end if you prefer.

    Is it credible that a person can be in good contact with terra-firma earth and the TNCs supply derived one at the same time?


    Even if so , it is an acceptable risk to do so if this is only occurring occasionally, so perhaps consider if  this is any more frequent than say contact with a lamp post, or a light fitting in a metal frame bus stop, on a PME supply - which is acceptable.

    Something like a milking parlour or a building site has regular hand and feet contact time - I suspect this is not the case here.


  • 0
    Are there any extraneous conductive parts; and if so are they anywhere a person may come into contact with them?
  • Former Community Member
    0 Former Community Member
    Face plate:

    Sorry to bring up this old chestnut but just seeking clarification as it was in 2005 that it was first raised. I am now retired and my last update was C and G 2008

    I have been asked to maintain a small sewage tank system for 6 houses. This consists of air pump and controls and lift pump.The pump controls are situated approx 200 metres from the incoming main and earthing / supply is an armoured  cable with cpc which is connected to a TN C S (PME) at origin.

    The only metalwork in the tank is a 25mm pipe from lift pump to outlet and internal blower pipework.

    Is it allowed to export the PME system in this case or should it have been a TT system with RCD at origin ?

    Many thanks FP

     


    Hi! Do you have any pics of the installation that you could post? 


    Also is there any previous documentation available, such as An EIC, manufacturers instructions, etc? I am interested to know why there is a 30mA RCBO supplying a communal waste water system, and who carries out the regular pressing of the test button?


  • 0
    Reviewing the existing installation all appears to be in order unless I am advised differently.

    1 Requested EIC from contractor

    2 The houses are all under one management system so my maintenance schedule will advise on frequency of pushing test button on rcbo.

    3 There is no extraneous conductive parts/metalwork so PME extended is fine.

    4 RCBO at circuit origin is extra protection to the PME line and covers commando outlet for pump

    6 No entry to electrical panel without authorisation

    7 PME is first circuit from 11kv transformer and crimped lines.

    8 Log book to be used on all service /maintenance issues.


    Thanks for replies



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