ZS testing without a No Trip function

[EFLImpudence]

I would be interested to know what the difference between the 3 lead L-PE test is compared to the later models No Trip test.

Not sure what you mean.

There have always been (relatively) high current EFLI testers but with the coming of RCDs something was devised to test it without tripping the RCD.

That's just Fluke's way of doing it with the 1650 range - I don't know about others.
As above, I believe it does it really quickly - possibly a few times - rather than use such a low current which would not trip an RCD.

With the appropriate meter settings -

The two wire test is so-called high current (and considered more accurate but Fluke's no-trip is quite accurate compared to other makes?), which will trip the RCD, but as I said, if there is no RCD it can be used for EFLI by placing the Neutral lead on the circuit CPC.

The three wire test is automatically non-trip and, conversely, to test L-N loop where there is an RCD place the Neutral lead and Earth lead on the circuit Neutral.

 

[muffking]

Thanks
What I'm trying to get my head around is if the Fluke's non trip test function is a totally different function to what my meter has, or if it's just another way of performing a 3 lead low current test as what I don't want to happen is me going round tripping peoples RCD's while trying to get a Zs.

 

[JohnW2]

I always understood that these particular MFTs made use of the old robin D-LOK method, where DC is injected to disable the RCD while the loop test is done

... I don't think so. ... Not sure where I read it, but I think it just does the test so quickly that it doesn't give the RCD time to react - but presumably lower current than the high current test.

I don't know about Flukes, but I was certainly under the impression that at least some used the method that Adam mentioned - and talk about that has recently re-appeared in some of the discussions about Type A vs. Type AC RCDs.

Kind Regards, John

 

[EFLImpudence]

What I'm trying to get my head around is if the Fluke's non trip test function is a totally different function to what my meter has,

I'm confused. You have a Fluke.

 

[EFLImpudence]

I don't know about Flukes, but I was certainly under the impression that at least some used the method that Adam mentioned - and talk about that has recently re-appeared in some of the discussions about Type A vs. Type AC RCDs.

I suppose some do. I am sure our 1650s do not.

 

[EFLImpudence]

Having said that, the 1650s have settings for various RCDs.

 

[JohnW2]

I suppose some do. I am sure our 1650s do not.

Although not through lack of looking, I've never found any real explanation of how ours do it - have you?

Having said that, the 1650s have settings for various RCDs.. ....

Indeed so.

Kind Regards, John

 

[muffking]

I'm confused. You have a Fluke.

Yes it's a 1653, I've only just got it. The later B models have a no trip test function for getting a Zs.
I'm just wondering how it differs to what I can do on mine so that I don't go round inadvertently tripping customers RCD while I go round getting a Zs.

 

[flameport]

The only test devices with D-LOK were the Robin separate loop impedance tester and possibly the last Robin multifunction, all of which were designed long before the Fluke takeover.

By the time the Fluke 1650 series was launched, D-LOK was old and obsolete, and wasn't included in any Fluke designed product. Even when D-LOK was popular, it wasn't guaranteed to never trip RCDs, just work most of the time on the typical RCDs that were in use during the 1980s and 1990s.

I'm just wondering how it differs to what I can do on mine so that I don't go round inadvertently tripping customers RCD while I go round getting a Zs.

Nothing. All 'no trip' testers can trip RCDs in certain circumstances. Testing using a low current will only work if the RCD is working within specifications, and there is a very low level of leakage on the circuits connected to it.

 

[muffking]

Nothing. All 'no trip' testers can trip RCDs in certain circumstances. Testing using a low current will only work if the RCD is working within specifications, and there is a very low level of leakage on the circuits connected to it.

So I can stop panicking after tripping the RCD when using the Fluke for the first time and not look at replacing it then?

 

[EFLImpudence]

Although not through lack of looking, I've never found any real explanation of how ours do it - have you?

No, I can't even remember where I learned what I think I know.

 

[JohnW2]

The only test devices with D-LOK were the Robin separate loop impedance tester and possibly the last Robin multifunction, all of which were designed long before the Fluke takeover. ... By the time the Fluke 1650 series was launched, D-LOK was old and obsolete, and wasn't included in any Fluke designed product. Even when D-LOK was popular, it wasn't guaranteed to never trip RCDs, just work most of the time on the typical RCDs that were in use during the 1980s and 1990s.

Thanks for clarifying. If D-LOK is not what they are using, what do they do - just literally use a very low test current (i.e. <15mA, given the ubiquity of 30mA RCDs), even though that is, I suspect, detrimental to accuracy?

I have to say that the suggestion that @EFLImpudence says he recalls reading ("... I think it just does the test so quickly that it doesn't give the RCD time to react - but presumably lower current than the high current test.") sounds pretty unlikely to me, for a number of reasons

Kind Regards, John