High Zs value with 2 sockets

[TheCodboy]

Hi all, Doing some pre board change testing and ive found 2 sockets with high Zs readings. Everything else is fine, done all my end to ends and the Zs's are what should be expected. A couple of the sockets have Zs lower than expected but 2 are higher. They should be about 0.8 ohms but ive got one at 1.20 and one at 1.40. Taken the highest value socket off, re terminated, still high. Tested at the terminals of the socket just in case the socket was duff, but still high. Its a PME system with a good low ZE (0.15). Any thoughts people??

 

[Pete999]

Hi all, Doing some pre board change testing and ive found 2 sockets with high Zs readings. Everything else is fine, done all my end to ends and the Zs's are what should be expected. A couple of the sockets have Zs lower than expected but 2 are higher. They should be about 0.8 ohms but ive got one at 1.20 and one at 1.40. Taken the highest value socket off, re terminated, still high. Tested at the terminals of the socket just in case the socket was duff, but still high. Its a PME system with a good low ZE (0.15). Any thoughts people??

Are the sockets in question spurs?

 

[Octopus]

spurs off spurs?

 

[westward10]

Did you test between line and neutral as well. Have you confirmed they are not spurred.

 

[TheCodboy]

The property is a bungalow with the cable drops coming in from the loft. The socket with the highest value has the ring coming in from above, and the cable looks to be original.

 

[westward10]

Have you actually confirmed they are part of the ring final.

 

[TheCodboy]

Have you actually confirmed they are part of the ring final.

Apart from Zs at the sockets,end to ends at the board and an IR test thats all i've done up to now.

 

[Midwest]

I had a job this week, where I removed some diy work on what I thought was an RFC in an existing extension. Well I thought it was an RFC, but in fact it was fed via a spur from another RFC.

 

[westward10]

Apart from Zs at the sockets,end to ends at the board and an IR test thats all i've done up to now.

You need to go back to square one and confirm how they are connected.

 

[Toneyz]

Are the sockets in question spurs?

how many cables was at this socket ? you posted you had done end to end at consumer unit (assumed) what about r1 + r2

 

[Midwest]

how many cables was at this socket ? you posted you had done end to end at consumer unit (assumed) what about r1 + r2

OP's having a little think, and I'm sure he'll realise he's made an assumption that's incorrect.

PS like I did this week

 

[TheCodboy]

how many cables was at this socket ? you posted you had done end to end at consumer unit (assumed) what about r1 + r2

The socket with the highest reading had 2 x 2.5 T&E. Took L-L, N-N, E-E reading at the consumer unit. r1 + r2/4 + Ze = 0.82 Ze was measured at 0.14. The calculated Zs of 0.82 was very near what i was getting all around the ring. 2 sockets were a bit lower (0.45 & 0.55) and apart from the 2 that were high, the rest were virtually spot on. ( My end to end values were L=0.92 N=0.92 E=1.83)

 

[TheCodboy]

OP's having a little think, and I'm sure he'll realise he's made an assumption that's incorrect.

PS like I did this week

Just getting my note pad with all my readings on!

 

[Octopus]

You need to do the end to ends at these sockets...

 

[westward10]

Delete.

 

[Pete999]

how many cables was at this socket ? you posted you had done end to end at consumer unit (assumed) what about r1 + r2

You mean R1+R2? and OP what was r1, r2,and rn?

 

[TheCodboy]

Delete.

You mean R1+R2? and OP what was r1, r2,and rn?

L=0.92 N=0.92 E=1.83
Measured Ze 0.14

 

[Midwest]

Do you see the point about doing r1, rn, r2 at the sockets with higher Zs result?

 

[TheCodboy]

Do you see the point about doing r1, rn, r2 at the sockets with higher Zs result?

If i take it at the sockets, they should obviously be the same as at the board,hence confirming a ring. So if they are different, interconnection maybe?

 

[westward10]

From your readings it will not be the same as at the board, they may well be open circuit.