Zs

[Lyngarth]

Hi,
Just a quick question, have just tested two circuits, one lighting and one ring. I got the following, 1.32 for lights and 0.89 for the ring.

Its a tnc-s mcb's 6amp & 32amp B type and both first floor so not a long cable run on both. The chap I'm helping has said both the readings are too high, but I think they are fine, but I don't have any books with me to check or show him.

Can anyone please tell me the max for both circuits.

Many thanks

Lyngarth

 

[DurhamSparky]

sounds ok....! what were the Ze readings and R1 R2 stuff???

 

[andyb]

No need to look anything up with those readings, they are both well within max Zs, even @ 80%.

 

[Lyngarth]

Ze = 0.34 ( tested by me )

R1 + R2 was 0.59 for lights & 0.40 for ring ( not tested by me ) info from the other chap.

So lights do sound a little high but I'm sure they will be OK ???

Cheers

Lyngarth

 

[pevvers]

They're not high at all, that's the common kind of reading that you'll come across.

For a B6 you've got 7.67 ohms to play with, and a B32 you have 1.44 ohms at 100%.

So even with the corrected values as mentioned above, you've still got 6.13 and 1.15 ohms...

Is this an experienced spark that's told you they're too high?

P.S. For a PME system, that Ze measurement is close to the maximum so it may be woth taking again in case there was an error in measurement.

 

[DurhamSparky]

well your allowed .35 so dont worry to much if it dont drop!


i have had it in one property that ze changed through out the day!! on morning i got 0.21 then after rain i got 0.16 and when i went back next day i got 0.23

 

[pevvers]

well your allowed .35 so dont worry to much if it dont drop!

I completely agree, but it's not very often I've found a PME system on the border line like that, so I would have rechecked it just in case....

 

[Lyngarth]

Hi
Sorry for the delay, back home now. I did check the Ze again and got 0.32 so a little lower.

Yes this was a sparky who said the readings were high, but he did phone me up (20 minutes ago ) to say sorry, he was having a blond moment and all was ok with what I got.

I just put it down to his age !!! (64 tomorrow) (good job hes not on here)

Many thanks for taking the time to reply and put my mind at rest.

Lyngarth