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CONSUMERS TAILS IN THE OSG

John Peckham
I have just been having a scan read of the latest edition of the OSG. On page 20 it says in respect of consumers tails, " Polarity should be indicated by the colour of the insulation and the minimum cable size should be 25mm".


Alongside this statement is a reference to 514.3.1. I am OK with the requirement in 514.3.1 for the colour of the insulation but where  does the requirement come from for the CSA to be 25mm?


I do know some DNOs representatives may require a minimum CSA of 25mm but I suspect that this is a personal preference. My thinking is this is one of the myths and legends of electrical installation work that has been repeated so often that it has become fact. My view is the tails need to be sized to take the maximum load and they also need to be co-coordinated with the supply fuse. In addition some older consumer unit terminals will not take a 25mm tail.


Can anyone direct me to a reference source that requires the minimum CSA of meter tails to be 25mm?


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    Several years ago I went to a NAPIT trade association meeting and John Peckham was the guest of honour, in return for tea and biscuits he gave us an earthing and bonding CPD, this was followed by a Q&A session.


    The subject of requirements for 25 mm meter tails came up and was the debated.


    My comment was that I had stopped worrying about it, as I had attended a electric meter box fire to reinstate the customers damaged, totally wrecked, main switch and tails and metering services installed 16 mm tails as the replacements.


    I had actually used 25 mm tails. then metering services arrived to install a new meter and make the connection to the new cut out installed by WPD and used 16 mm tails. I queried the use of 16 mm tails and was told that meets the requirements and actually is all that is needed with the standard 60 amp fused supply that you get.


    So on new work I still use 25 mm though the DNO side of the meter may be 16 mm, on existing jobs if there is 16 mm tails I don’t break into a sweat about it and I definitely won’t be phoning the DNO to try and get the tails upgraded, a couple of years ago I tried unsuccessfully to get a neutral meter tail that had been rubbed by a garage door exposing the copper replaced and gave up leaving it bound up with insulation tape along with instructions to the customer to try and get it replaced. Bear in mind had it been the live phase there would have probably been a body on the floor.


    If I couldn’t get a damaged tail replaced I don’t stand a cat in hells chance of getting 16 mm tails upgraded to 25 mm on the grounds that they are dangerously undersized.


    Pick your battles, and this is not one worth fighting.


    Andy Betteridge
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  • 0
    Several years ago I went to a NAPIT trade association meeting and John Peckham was the guest of honour, in return for tea and biscuits he gave us an earthing and bonding CPD, this was followed by a Q&A session.


    The subject of requirements for 25 mm meter tails came up and was the debated.


    My comment was that I had stopped worrying about it, as I had attended a electric meter box fire to reinstate the customers damaged, totally wrecked, main switch and tails and metering services installed 16 mm tails as the replacements.


    I had actually used 25 mm tails. then metering services arrived to install a new meter and make the connection to the new cut out installed by WPD and used 16 mm tails. I queried the use of 16 mm tails and was told that meets the requirements and actually is all that is needed with the standard 60 amp fused supply that you get.


    So on new work I still use 25 mm though the DNO side of the meter may be 16 mm, on existing jobs if there is 16 mm tails I don’t break into a sweat about it and I definitely won’t be phoning the DNO to try and get the tails upgraded, a couple of years ago I tried unsuccessfully to get a neutral meter tail that had been rubbed by a garage door exposing the copper replaced and gave up leaving it bound up with insulation tape along with instructions to the customer to try and get it replaced. Bear in mind had it been the live phase there would have probably been a body on the floor.


    If I couldn’t get a damaged tail replaced I don’t stand a cat in hells chance of getting 16 mm tails upgraded to 25 mm on the grounds that they are dangerously undersized.


    Pick your battles, and this is not one worth fighting.


    Andy Betteridge
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