Zs using Fluke 1653b

[Gringoking88]

Hi all,

This maybe a silly question and if it is please go easy lol!!!!

I have a fluke 1653b MFT and am having trouble doing a Zs test on a radial lighting circuit using low current (non Trip). For some reason I just cant get the thing to take a reading and it just buzzys at me.

The same test using the socket adapter on a ring circuit or a spur off a ring is absolutely fine and gives expected readings.

Also am I correct in saying a Zs low current test should in theory give the same result as a Ze test + (R1+R2), basically that is what I am trying to do on a lighting circuit but without doing the two tests.

Do any of you more experienced guys or girls have any idea why this is???

Thanks in advance

And any help would be great!

 

[davesparks]

What do you mean by that is what you are trying to do without doing the two tests? You cannot substitute a calculation for an R1+R2

Is there a dimmer or other control device in the circuit that you are trying to test?
What is the reason for doing a low current test?

 

[Gringoking88]

Dave,

E.g. when using the plug adapter you can do a low current test that does not trip the rcd this as I understand it gives you Zs. E.g. by doing one test as opposed to testing R1 + R2 then adding this to the external earth fault Ze, Zs = Ze + (R1+R2).

There are no dimmers etc on the circuit.

Thanks,

Martin

What do you mean by that is what you are trying to do without doing the two tests? You cannot substitute a calculation for an R1+R2

Is there a dimmer or other control device in the circuit that you are trying to test?
What is the reason for doing a low current test?

 

[rich.250]

Doing a low current test will not give you an accurate Zs at all.
Does it show an error code?


Sent from my iPhone using Tapatalk

 

[davesparks]

Dave,

E.g. when using the plug adapter you can do a low current test that does not trip the rcd this as I understand it gives you Zs. E.g. by doing one test as opposed to testing R1 + R2 then adding this to the external earth fault Ze, Zs = Ze + (R1+R2).

There are no dimmers etc on the circuit.

Thanks,

Martin

[emoji4]

But you need to do the R1+R2 before you can energise a new installation so you cannot replace it with a Zs test. Also a Zs test result is not equal to Ze + R1+R2 in all but the most simple of installations because parallel earth paths affect the result. Also low current Zs tests are very prone to giving inaccurate results.

I'll ask again, why are you using a low current test on this lighting circuit? Are you able to get a result using a high current test? Obviously use the alternative test method if necessary.

 

[tomspark93]

Not trying to be patronising but have you done an R1+R2? I.e do you have a continuous cpc at the point you want to test? Also, is polarity confirmed to be good at said fitting?

in reply to your two test situation Dave has given a good reason why not to rely on the Zs test to then subtract an R1+R2 reading from. However you can calculate a Zs using the equation stated but Personally I'd only do that if it was completely unpractical or unsafe to do so which isn't very often.

 

[not clever]

Reverse polarity L and N leads?

 

[Gringoking88]

Thanks gents, it wasnt that I was not or not going to do an R1+R2 reading or that I wasnt going to measure Ze, it was really just a question around my Fluke and why it would do it on a socket but not on a lighting circuit that was all.

 

[Simonslimline]

Your profile says trainee. Get access to the trainee section, lots of helpful advice. Do you have a mentor?

 

[Simonslimline]

Thanks gents, it wasnt that I was not or not going to do an R1+R2 reading or that I wasnt going to measure Ze, it was really just a question around my Fluke and why it would do it on a socket but not on a lighting circuit that was all.

Did you use an adaptor lead with a plug on for the sockets Zs?

How many leads did you use when attempting Zs on the lighting circuit?

 

[Deleted member 26818]

How many leads were you using?

 

[Gringoking88]

Hi,

i was using the plug adapter for the socket test so 3 leads in affect and 3 single leads when at the ceiling rose. Simon no I dont have a mentor????

 

[Simonslimline]

Hi,

i was using the plug adapter for the socket test so 3 leads in affect and 3 single leads when at the ceiling rose. Simon no I dont have a mentor????

I would start with dead testing the lighting circuit and go from there.

Are the leads ok?

I would still recommend the trainee section on here as well. How can you be a trainee and not have a mentor to show you these important things?

 

[markadams]

There are a few reasons for this.

1. No power on the circuit being tested (do you see the lightning symbol?)
2. Line and neutral reversed (you will get an indicator above the leads symbols)
3. No continuality on the CPC.