length of ring main circuit

[davidjones89]

what is the max length these circuits can go to in 2.5mm t & e ? 32a mcb with an installation method of clipped direct, just curious

 

[High Tower]

100Msq floor area

 

[DurhamSparky]

100Msq or to keep it easier 1x 100m Drum of cable!!

 

[High Tower]

When was the last time that you had a 100m drum???? i can garentee never!!

Next time you buy a fres roll of what ever size, use ur MFT to measure end to end resistance while on the roll and divide by the given value in the regs or osg, i can assure you it will come out to around 96-98 which means they are diddling us by a couple of meters a time!

What can i say, sad i kno

 

[davidjones89]

ok but what about volt drop

 

[Bigboy247]

OSG 100msq. Very true some cable companies got in trouble some years ago by trading standards short a roll or two and see how much there profits jump.

 

[DurhamSparky]

hahaha! might actually unroll the one on my van and get the meter stick out and count it!!! lol

 

[DaveyD]

Table 7.1 Pg 44 OSG

 

[High Tower]

hahaha! might actually unroll the one on my van and get the meter stick out and count it!!! lol

Do it with a brand new roll, you can get to both ends, no need to paye it off the roll

 

[High Tower]

ok but what about volt drop

(mv/a/m) x Ib x l /1000 if my memory serves me correctly

Tab value from the regs x design current x length / 1000

 

[tony mc]

(mV/A/m)xIbxL / 1000

Time to get your calculator out.

 

[davidjones89]

Table 7.1 Pg 44 OSG

my problem is if you use any length near to the maximum you do not comply with the volt drop ! am i missing something ?

 

[High Tower]

Its a ring main so 2x2.5mm conductors, you will be in on Vd by a country mile!

 

[DurhamSparky]

i fancy paying it off the roll and then when its short i will get wholesaler to coil it back up and grovel to me for selling me less than i asked for!! if it is 100m then i donald ducked and will have a snotty pile of cable!!

 

[Sintra]

To find max cable length on ring allowing for volt drop use formula

4 x max vd x 1000 / ib x mV/A/M