Ze testing using a MFT 1553

[JamesBrownLive]

Am I correct in thinking that when doing a Ze test using a 1553, the dial needs to be set on the 'Hi' setting in the green loop section of the dial settings?

Cheers

 

[pevvers]

If you want to conduct a high current test due to there being no RCD's upstream, then yes!

 

[telectrix]

as above. correct

 

[JamesBrownLive]

If you want to conduct a high current test due to there being no RCD's upstream, then yes!

Ok, a really stupid question here...

By Upstream do you mean the side that is heading back to the DNO? In my mind, Up is heading back where it came, down is heading into the cct and onto the accessories etc?

 

[pevvers]

Yes, upstream is towards the source. Just think of a river, with wherever the flow is coming from being upstream. Exactly the same in electric terminology, wherever the power is coming from is upstream,

 

[JamesBrownLive]

Ok, next stupid question...

I thought a Ze test was carried out at the installation's main switch, under what circumstances am I likely to find a RCD between the main switch and the service head?

 

[GStueyXR]

A Ze test is Live/dead test, ie you are working live, but all circuits in the installation are isolated due to the fact that you have the main protective conductor disconnected.

For this reason RCDs are not a consideration, and a high resolution test is performed.

 

[JamesBrownLive]

A Ze test is Live/dead test, ie you are working live, but all circuits in the installation are isolated due to the fact that you have the main protective conductor disconnected.

For this reason RCDs are not a consideration, and a high resolution test is performed.

Well that is what I thought, but when an upstream RCD was mentioned earlier in the thread, I was wondering if I had overlooked something.

Cheers

 

[Amp David]

Ok, next stupid question...

I thought a Ze test was carried out at the installation's main switch, under what circumstances am I likely to find a RCD between the main switch and the service head?

You may have an RCD protecting the tails depending on how they have been installed.

 

[JamesBrownLive]

You may have an RCD protecting the tails depending on how they have been installed.

Nuisance tripping in that scenario would be putting it mildly

So I presume discrimination would need to be spot on.

 

[Amp David]

Nuisance tripping in that scenario would be putting it mildly

So I presume discrimination would need to be spot on.

Whys that then? Time delayed RCD

 

[JamesBrownLive]

Whys that then? Time delayed RCD

I have always assumed that specifying a Time Delayed RCD (when necessary), was part of the discrimination process anyway? Or am I way off

Cheers

 

[Amp David]

Not at all, thats why they're used

 

[pevvers]

I merely mentioned the upstream RCD due to the fact that the "HI" loop setting should be used whenever possible, due to the higher current being able to show any latent faults in the connections, and also the fact that the accuracy of a high current test is much better.

If there is an RCD upstream of whatever you're testing, be it a submain or a final circuit, then a low current loop test should be applied, but in all other instances go for the high, you know it makes sense!

 

[Amp David]

I merely mentioned the upstream RCD due to the fact that the "HI" loop setting should be used whenever possible, due to the higher current being able to show any latent faults in the connections, and also the fact that the accuracy of a high current test is much better.

If there is an RCD upstream of whatever you're testing, be it a submain or a final circuit, then a low current loop test should be applied, but in all other instances go for the high, you know it makes sense!

It sure does!