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meter tails max length...

K

Ken C

pfm Member
do we have any qualified electricians here who can tell me what the maximum length of meter tails is? i want to locate the CU for my hifi in the listening room itself -- and this entails long meter tails.

grateful for answer from someone who is qualified and knows about IEEE rules.

many thanks

enjoy

ken
 
I've quizzed the electrician who is currently wiring the new workshops and although this is the first time he's been asked this question, he gives the following advice:

He has, in the past installed consumer units some 12ft from the meter with no problems. He's seen meter tails over 20ft long where the CU is that distance from the meter.

His advice is that the cable should be of sufficient cross section to cope with any voltage drop and should be double sheathed. It should be run in a correct and safe manner and properly secured to walls etc...

Finally, the regulations say that the meter tails should be as short as possible and by that, we may interpret that they should run as directly as possible between meter and CU.

Hope that helps,
 
madhippy over on Zerogain is a qualified Electrician and helped me out when i fitted my Hi-Fi spur.

Just for info:
I just divided my incoming tails into two using a 'Henley' adaptor and sited the new 'Hi-Fi' CU next to the existing one, connected up with the same dia Tails as the originals (16mm). i know that my installation is still well within its safe limits as at the same time i had Full Gas CH fitted and removed 4 x Large Electrical storgage heaters and 7 x Convector/fan heaters from the house. All supplied through the same meter and incoming tails.
My entire Hi-Fi systen pulls much less than 3A when playing at max chat.

Both of my CU's are on the other side of the wall to the meter and so are less than 6 feet away in wiring length terms.

HTH.
 
Given your 'current' requirements in a domestic situation [ presuming you don't live in Buckingham Palace or simular] I think the tails could be as long as is needed for convenience. The regs are for normal domestic setups which don't tend to allow for 'odd' situations ie: yours. You are, in effect, bypassing the main CU and running the tails to a mini CU solely for the powering of a low- power demand load But if you look at the regs yourself, which I did prior to rewiring my house, it is common sense.

I am not a qualified electrician but it is obvious from the regs that they are just ensuring safety. The fact that someone might like to optimise sound quality by running their Walkman straight off the national grid would not, quite reasonably, occur to them. Need a step-down transformer mind !!
 
The problem with long tails is that if someone nails, drills, screws or cuts them accidentally at a later date they have very little protection (Just the 60 / 80 / 100 amp service fuse)
 
thanks a lot guys. high quality replies through-out.

i think i will keep the tails short as normal and just run long "fat" radial(s) to my hifi, which is in my office -- an extension to the house.


enjoy

ken
 
a related question:

is there any SAFE way of connecting meter tails to a consumer unit, other than calling an electrician, who will charge for this service. i plan to wire the circuits for the hifi from the consumer unit myself. as far as i can see the tails are always LIVE, unless there is another place one can switch them off. i seem to recally some discission about this here sometime ago.

grateful any info...


regards

ken
 
The only way to kill the power is pull the service fuse,which only your elecricity company should do.
Ask an electrician for a quote,it' a simple job if you don't mind messing about with live meter tails;)
Don't do it yourself though.

Paul.
 
Pulling the service fuse will only disconect the live. The neutral is just as lethal. Dont play with tails unless you know EXACTLY what you are doing (and then still dont)
 
many thanks guys. i guess there is no safe way. i still want to post here(!!) so i wont mess about with meter tails.

enjoy

ken
 
Ken,
Here is my effort and might give you a few idea's. Wouldn't wish to encourage anybody to risk hurting themselves or others, however it is not too difficult as long as you take plenty of common sense precautions. Having an independant light source ( i used a 12vdc flourescent inspection lamp on a long lead and a car batt), as well as a decent Multi meter are essential. I also always used proper electrically insulated tools whilst doing any work , even though I new that for the most part, the circuits i was working where unpowered. Basically i worked the system backwards from the Hi-Fi wall sockets. After testing the whole circuit out the very last things i did was reconnect the meter tails and then re-fit the main fuse. I also tested from the Hi-Fi spur meter tails by connecting the whole Hi-Fi spur via an RCD, flying lead and cable connector, connected to an existing house wall socket , this way the spur could be checked out before it was connected directly to the incoming tails and Henley adaptor.
sids spur
 
thanks sid and coke.

another question for you qualified electricians out there.

whats the regulatory position on improving the "earth" to your domestic supply by connecting it to a seperate earth spike, sunk deep and moisture maintained. is this OK with regulations?

seems to me better to connect this earth to the earth spike rather than anywhere else -- since all earths are eventually connected to it.

many thanks

enjoy

ken
 
another question: how does one know (from looking at the point at which mains enters house?) whether your electricity supply is PMC (protective multiple earth) or TT?

enjoy

ken
 
Originally posted by Ken C
another question: how does one know (from looking at the point at which mains enters house?) whether your electricity supply is PMC (protective multiple earth) or TT?
Click to expand...

TN-C-S (or PME) has the earth & neutral commoned at the inlet to the premises whereas TN-S has the earth going thru the screen on your armoured cable at the inlet to the premises. TT has an earth terminal and electrode in the ground by the premises(commonly used in rural areas where supply is overhead).

Hope this helps.

Mark
 
Originally posted by MarkS
TN-C-S (or PME) has the earth & neutral commoned at the inlet to the premises whereas TN-S has the earth going thru the screen on your armoured cable at the inlet to the premises. TT has an earth terminal and electrode in the ground by the premises(commonly used in rural areas where supply is overhead).

Hope this helps.

Mark
Click to expand...

mark, many thanks. i have determined that mine is TN-S. i presume this armoured screen is connected to sub-station neutral and that this is quite a low impedance path to earth (around 0.2-0.5ohms??)

i was thinking of installing a local earth spike. i need to read around a bit to figure out (a) if this will improve my hifi (a) if its safe

many thanks again...

enjoy

ken
 
Originally posted by Ken C
mark, many thanks. i have determined that mine is TN-S. i presume this armoured screen is connected to sub-station neutral and that this is quite a low impedance path to earth (around 0.2-0.5ohms??)

i was thinking of installing a local earth spike. i need to read around a bit to figure out (a) if this will improve my hifi (a) if its safe
Click to expand...

The full definition for your setup is:

T - at least one point of the supply is directly earthed.
N - all exposed conductive metalwork is connected to an earth provided by the supply company.
S - earth and neutral conductors separate.

I would suggest you stick to the supply earth else you may end up with a potential difference on your earths.

You may, however, wish to consider running your earth with a cable >=10mm^2 from your consumer unit earth bus bar to your hifi spur outlet.

Mark
 
Originally posted by MarkS
The full definition for your setup is:

T - at least one point of the supply is directly earthed.
N - all exposed conductive metalwork is connected to an earth provided by the supply company.
S - earth and neutral conductors separate.

I would suggest you stick to the supply earth else you may end up with a potential difference on your earths.

You may, however, wish to consider running your earth with a cable >=10mm^2 from your consumer unit earth bus bar to your hifi spur outlet.

Mark
Click to expand...

many thanks mark for the info. i always wondered what the acronyms mean. (what about the C in TNC-S?).

i agree stick with supply earth. i have two 10mm^2 radials from the consumer unit to the hifi, presumably this means i have to run 2 THICK cable earths from CU to each radial outlet. since my radials are wired with 45 amp rated T&E, i would assume (perhaps wroingly) that the earth of this cable is rated quite close to 45amps (do you know the actual rating? -- its a bit thinner than the L/N wires)

while we are talking about outlets, do you know where i can get an unfused/unswitched triple socket? the plugs will be fused, so we are still safe.

enjoy

ken
 
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