ze but no zs

hi, problem that i encountered today tt system Ze of 78 ohms but a zs on sockets came up at >2000ohms tester is a fluke 1652b tested ze high current and zs no trip as front end rcd. Any ideas? please note all dead tests were fine.

thanx

I tested a TT installation this week and luckily that had a good Ze 13.3 ohms. Check the connections on the rod to ensure they are clean and tight. I assume your R1+R2 values were good as you state dead tests were fine. I would tend to calculate your Zs values in anycase as on a no trip test they can be on the high side. What size was the earthing conductor going to the rod? What was your trip times for the rcd?

is the earthing conductor connected?

Not possible, without missing something.

If dead tests ok - and Ra reading from rod ok - Check ZsDb; for any bonding which may lower the reading. Then check you`ve re-connected everything, `cos it sounds like you`ve forgotten an earth connection somewhere.

KME

Not possible, without missing something.If dead tests ok - and Ra reading from rod ok - Check ZsDb; for any bonding which may lower the reading. Then check you`ve re-connected everything, `cos it sounds like you`ve forgotten an earth connection somewhere.

KME

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As KME says, cant see how its possible, may be worth checking everything again.

ian

Yes rod was definately connected and tested ze 5 times but could not get a zs rcd trip times fine redone all dead tests but still no zs. Did have a similar situation 3 months ago rod was 168ohms no zs loose connection to rod. Connection is fine. The only thing I can think of is the tester. Been to a friends house tt and done a couple of tests this evening. Tester is fine.

Could it be that you have an earth leakage greater than 50V which prevents the tester from doing the ZS?

OK Soulman,

you are going to have to go through this methodically,

and, this is the crux,

you HAVE a broken EARTH path somewhere between your EARTH CONDUCTOR and your CPC ,

its that simple.

Ze = good,

connect EARTHING CONDUCTOR to MET,

check Zdb = is this OK.?

OK so far,

NOW, and this is an important test,

IR across L-N, and also L-E N-E

then R1 R2 on cct, is this OK?

good,

then do an R2 just to double check.

now, ensure you have reconnected all cables to their relevant positions, then check them again.

next step, fire her up and you should have Zs, otherwise you havent connected the cpc to the MET.

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Could it be that you have an earth leakage greater than 50V which prevents the tester from doing the ZS

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a fluke 1652 will simply refuse the test IIRC, and a little indicator comes on.

Im fairly certain it doesnt show >2000 , that rings a bell to me as being a bad earth, plain and simple,

EDIT :- my R's / r's are wrong, live with it.

Hi Soulman,

could it have been possible that your earth test lead wasnt plugged into your tester properly?

I had a situation recently when after changing a consumer unit and finally putting my socket adaptor lead set into my tester I didnt notice I had put the blue lead into the earth connection on the mft and vice versa with the green lead.

When I tried to check Zs at downstairs sockets it tripped the rcd every time. I got really frustrated when I checked sockets on the upstairs ring and the other rcd tripped the same.

sometimes the problems are so simple and right in front of you, but when something happens unexpectedly it can get you all in a fluster!!!!

This is the time to take a step back and a breather and look at the situation starting with all of the basics.

PS have you checked Zs on any other circuits to ensure integrity of the earthing system?

Could it be that you have a front-end 100mA RCD but you are testing with your meter set at 30mA?

Could it be that you have a front-end 100mA RCD but you are testing with your meter set at 30mA?

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Soulman is trying to test Zs and not RCD trip times Springcrocus

a fluke 1652 will show that up when it trips out,

plus, it only has one 3 wire setting,

soulman,

just a thought, when you test Ze are you doing it on 2 wire or 3? also, on your Zs how are you doing that?

on the fluke 1652 the 2 wire test is across L-N but the 3 wire test is across L-E, are you using the correct probes at each part of the test?

Soulman is trying to test Zs and not RCD trip times Springcrocus

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If I do a no-trip Zs on my Megger 1552, and the RCD dial is on the wrong setting, it will throw a wobbly. ?:|

hi i done the two wire test for ze (l-pe) and and three wire test with socket adaptor for zs. i have been told by another electrician tonight to try the three wire no trip test for ze and see what i get. he has had trouble with a fluke during non trip testing.

cos meggers are a bit rubbish and only designed to do basic testing, flukes can be configured to do many different tests than are usually required, and that is why they are so much more proficient for fault finding.

Thanks for that, Steps. I know you got "bitten" by one sometime in the past.

right Soulman,

you are adding another variable by changing leads, can you do both tests with the same set of leads please,

have you done R1 R2 yet? what is that result?

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not just that spring, but they really are not very good for fault finding, you can only do the tests that are basic for filling in forms with,

they really arent very adaptable for finding faults etc.

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hi i done the two wire test for ze (l-pe) and and three wire test with socket adaptor for zs. i have been told by another electrician tonight to try the three wire no trip test for ze and see what i get. he has had trouble with a fluke during non trip testing.

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Im almost dead certain (99%) a 2 wire test on the 1652 is across L-N so you are using the wrong leads.

high current two lead test for ze or pfc on the 1652 can be toggled between line & pe to line & neutral. zs no trip for rcd's requires 3 wire test.

OK Soulman, so that only leaves the issue of you have a broken connection somewhere, you need to do an earth continuity test then with a fly lead, then an R1 R2, then if thats all OK then a Zs.

Im almost dead certain (99%) a 2 wire test on the 1652 is across L-N so you are using the wrong leads.

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Steptoe,

You've had me chuckling through most of this thread - and you've also come up with some good suggestions...........

But PLEASE, How the hell do you test Zs (which is Earth Fault Loop Impedance), between 'Line' and 'Neutral'?........without EARTH??............The clue is in the name of the test!!