loop readings

[carlhenry01]

Hi, Part P newcomer here. When taking for example a loop impedence reading on say a ring main, linking live/neutral together you divide the result by 2 to give a reading for each cable because they are the same csa2 but how do you caculate for a live/earth reading when the cpc is a different size? Also information on how to do an insulation test on SELVs or flourescent lighting circuit without linking evey fiitting out?

 

[ian.settle1]

Are you sure you know what you are talking about as to take a loop impedence reading you need to have the mains switched on for the loop impedence meter to work

 

[carlhenry01]

Yes sorry I meant a continuity test when cpc is different size to live conductor but the lighting circuit question remains the same.
Carl.

 

[pope]

Stop being lazy and take out the flourecent fittings, i dont think there is any other way.

 

[slrichardson]

If too many fittings to practically link out then join line and neutral together and test to earth

 

[Shakey]

Hi, Part P newcomer here. When taking for example a loop impedence reading on say a ring main, linking live/neutral together you divide the result by 2 to give a reading for each cable because they are the same csa2 but how do you caculate for a live/earth reading when the cpc is a different size? Also information on how to do an insulation test on SELVs or flourescent lighting circuit without linking evey fiitting out?

for the ring

like Ian said, its continuity you are looking for

do end to ends

r1 (line)
rn (neutral)
r2 (cpc)

link incoming line to outgoing neutral and vice versa

reading between line and neutral at sockets is r1+rn divided by 4

link incoming line to outgoing cpc and vice versa

assuming 2.5/1,5 tw&E,

2.5 divided by 1.5 = 1.66, so r2 value should be 1.66 times higher than r1 and rn value

you should read r1 + r2 divided by 4 at the sockets, highest reading is your (R1+R2) for the ring (normally at a spur)

your readings should be +/- 50 milliohms for each socket

 

[wayne]

carl ,on the test results sheet are you trying to fill both the r1+r2 box and the r2 box ?they are optional

 

[carlhenry01]

Hi Thanks Wayne,slrichardson and shakey..........very useful and helpful.
thanks again.
Carl.