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Topic Title: crabtree elcb
Topic Summary: replace?
Created On: 02 May 2013 09:35 PM
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 02 May 2013 09:35 PM
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bak1950

Posts: 85
Joined: 24 June 2009

Have to work on one circuit on a TT system.Only protection is an old crabtree elcb can you just RCD the circuit in question. Or should the ELCB be replaced with an upfront RCD. Customer does not wish to upgrade consumer unit.

Thanks.
 02 May 2013 09:55 PM
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AJJewsbury

Posts: 11553
Joined: 13 August 2003

What sort of ELCB - current or voltage operated? (does the earth connection go through it?) - and is it still functioning?

- Andy.
 02 May 2013 10:00 PM
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bak1950

Posts: 85
Joined: 24 June 2009

Yes and yes
 02 May 2013 10:05 PM
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DOUGIE1000

Posts: 4168
Joined: 13 August 2005

Replace it for rcd and leave a quote for board change,

-------------------------
Dougie
Power Plus Electrical.co.uk

My mission is to live as long as possible......so far so good!
 02 May 2013 10:37 PM
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daveparry1

Posts: 6246
Joined: 04 July 2007

If it's voltage operated replace it with a 30m/a rcd,

Dave.
 02 May 2013 11:50 PM
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dg66

Posts: 1675
Joined: 11 January 2008

Just RCD the circuit/or part of that you're working on as thats all you are responsible for,recommend UPFRONT RCD, and let customer decide.
Of course if you add an upfront RCD then according to some(see CU change thread) you will then be responsible for the entire installation and will have to carry out an EICR

-------------------------
Regards

Dave(not Cockburn)

Edited: 03 May 2013 at 07:53 AM by dg66
 03 May 2013 07:41 PM
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jcm256

Posts: 1895
Joined: 01 April 2006

Just RCD the circuit/or part of that you're working on as that's all you are responsible for,recommend UPFRONT RCD, and let customer decide.
Of course if you add an upfront RCD then according to some(see CU change thread) you will then be responsible for the entire installation and will have to carry out an EICR
....................................................................................................................................

Whilst this idea is a very simple to carry out in practice, there is a meaty feast of irregularities why you should not. One would be , the earth electrode connected to a fault voltage operated protective device is in series with the trip coil , therefore the earthing circuit for the operation of an additional residual current operated protective device would be MET (called F frame)- coil -earth electrode. If you fitted another earth electrode for the additional RCD it would be difficult to separate this one earthing system and MET from all other installation earthing and the effects of parallel earth paths.

Note: the basic earthing circuit for FVOD is exposed conductive parts and extraneous conductive parts of an installation is connected to earth via terminal 'F'
(Frame) though the trip coil to terminal 'E' and the earthing conductor to the earth electrode.

There is a lot of facts on parallel earth paths, a water pipe for example simply becomes a parallel earth path on the installation. The voltage sensitive element will still operate if a voltage above a preset level appears between protective metalwork and earth. The device does not, however, limit the magnitude of current obtainable.




.

Edited: 04 May 2013 at 08:51 AM by jcm256
 07 May 2013 08:46 PM
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dg66

Posts: 1675
Joined: 11 January 2008

Originally posted by: jcm256

Just RCD the circuit/or part of that you're working on as that's all you are responsible for,recommend UPFRONT RCD, and let customer decide.

Of course if you add an upfront RCD then according to some(see CU change thread) you will then be responsible for the entire installation and will have to carry out an EICR

....................................................................................................................................



Whilst this idea is a very simple to carry out in practice, there is a meaty feast of irregularities why you should not. One would be , the earth electrode connected to a fault voltage operated protective device is in series with the trip coil , therefore the earthing circuit for the operation of an additional residual current operated protective device would be MET (called F frame)- coil -earth electrode. If you fitted another earth electrode for the additional RCD it would be difficult to separate this one earthing system and MET from all other installation earthing and the effects of parallel earth paths.



Note: the basic earthing circuit for FVOD is exposed conductive parts and extraneous conductive parts of an installation is connected to earth via terminal 'F'

(Frame) though the trip coil to terminal 'E' and the earthing conductor to the earth electrode.



There is a lot of facts on parallel earth paths, a water pipe for example simply becomes a parallel earth path on the installation. The voltage sensitive element will still operate if a voltage above a preset level appears between protective metalwork and earth. The device does not, however, limit the magnitude of current obtainable.









.[/q
Dont see the problem myself,fitting an upfront RCD and using the existing electrode,disconnect all earthing from the VOELCB and use it as a double pole isolator, or just add an RCD to an existing circuit.No additional electrodes.

-------------------------
Regards

Dave(not Cockburn)
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