High TNS readingssssss

[Bradley6969]

TNS system
60947-2 main switch
60898 double pole 63amp MCBs that feed some caravan boxes now some circuits I can get below the disconnection times of 0.56 ohms but some are 1.22 ohms now I’ve tried changing glands anything else I can do apart from TT the hook up unit? Or do you need upfront RCD

If not change the distribution unit feeding boxes with RCD and Rod it

 

[Bradley6969]

You're contradicting yourself.



What do you mean by this then?

Sorry meant to put I’ve not tried changing any glands yet

Well calculates the max current flow between L+N same as earth loop between L+E in the event of a fault?

 

[Bobster]

Sorry meant to put I’ve not tried changing any glands yet

Well calculates the max current flow between L+N same as earth loop between L+E in the event of a fault?

Ok, but what has that got to do with Zs requirements?

 

[Baddegg]

So you’ve taken pscc at the origin and your testers also give you a Ze reading but that would include any parallel paths as well? I’m so confused.....did you take Ze with main earth disconnected?
I’d go with Petes post a while back and get some R1-R2 readings from the swa....

 

[Bradley6969]

Ok, but what has that got to do with Zs requirements?

Well you do a Zs at a panel/consumer so PSCC and PFC and record highest what’s difference but just another sub circuit? As if you measure either of these on my tester you get impedance value and kA so breaking capacity?

 

[Bobster]

Again, what has PSCC and PFC got to do with the Zs requirements?

Either I am misunderstanding the point you are trying to make, or you don't fully understand the difference in tests and what to do with the results.

 

[buzzlightyear]

In order to get the values write in the being at the incoming what was the ohms and the ka.
Ovasly you have sub circuits to diffrant pitches ,the sub circuits are on bs60898 and you are testing each circuit ,but some how you are getting well beyond the max range .
Are the glands in good order or they
Are not earthed correctly.some how we are going round the caravan pictches if you know what i mean.

 

[Bradley6969]

In order to get the values write in the being at the incoming what was the ohms and the ka.
Ovasly you have sub circuits to diffrant pitches ,the sub circuits are on bs60898 and you are testing each circuit ,but some how you are getting well beyond the max range .
Are the glands in good order or they
Are not earthed correctly.some how we are going round the caravan pictches if you know what i mean.

Well the panel feeding the sub circuits has Zs of 3.15 and KA of 3.0 but some of the circuits are ok and some are not but there are endless joints underneath the ground so can’t help and glands are ok

 

[Bobster]

So the Zs of the sub circuit is 1.22 ohm, the Zs at the panel feeding these is 3.15 ohm?

 

[Bradley6969]

So the Zs of the sub circuit is 1.22 ohm, the Zs at the panel feeding these is 3.15 ohm?

Yes, at a guess paralel paths

 

[Bobster]

Yes, at a guess paralel paths

From where though?

 

[Bradley6969]

From where though?

Supply goes in and out of gland plates?

 

[Charlie_]

you need to make proper arrangements with the client so you can turn the power off and then carry out all the necessary tests correctly.
You need to isolate each circuit, disconnect them from the MET and then test accordingly

 

[Bobster]

I'm out.

 

[buzzlightyear]

FFS ,hit your client over the head with the BBB and tell him either turn the power off for the pitches that dont comply with the reg or some body get else in.simples .
Me i would quote the elec act .

 

[davesparks]

Well the panel feeding the sub circuits has Zs of 3.15 and KA of 3.0 but some of the circuits are ok and some are not but there are endless joints underneath the ground so can’t help and glands are ok

Then you've got a serious problem because a Zs of 3.15ohm should give a pfc around 76A at 240V, or a pfc of 3kA would come from a Zs of 0.8ohm.
I'll ask again, what test are you using, high current or anti trip?