High Zs

[Andy™]

I've read in other threads how questions people ask can lead to put downs.

only happens when people appear to be working as an 'electrician' and getting paid to go into a customers property to do a job, then ask basic questions on here that they should know the answer to

 

[Sidewinder]

Well, have you answered the questions that have been put to you in the thread?

Can you not see that the questions you are asking could be seen to be too basic for someone who is working alone and charging for their services?

If these above two questions are correct, can you see why others may feel that you "may" not be competent to do this work?

In which case, can you then extrapolate this to see why posters feel the way they do and give the answers they do?

I "may" be wrong, however, this is the way I see the thread.

It is easy to misunderstand things written in forums like this.

The solution you seek can only be found on site.

"YOU" need to go back and do more testing and identify "why" you have such a discrepancy, however, "you" need to be happy and understand the test results that you take, we are not there with you, none of us see the meter readings you see, none of us see the connections you make, none of us see the CU & the sockets & the wiring.

"WE" can only make suggestions.

However, when fully qualified and experienced guys are struggling for work and being undercut to the extent where they cannot cover their business overheads, let alone make a wage to pay their personal bills by incompetent persons, is it surprising that some are a little sensitive to posts from persons where they "may" "seem" to not be capable of undertaking the work the are, and are looking for help on the forum so that they can make money from the advice whilst undercutting those who did or do not need the help.

I am NOT saying that you are in this bracket, however, I can see why other members think you may be.

 

[Manator]

[quote name='Andy

 

[MSH1601]

Okay, fair shout Andy, I guess with all the short courses out there and plenty of people looking for a career change thinking "ooh, this is easy" and charging for their lack of competence. Be assured, I don't fit into that category. I am "selfemployed", but only work as an electricians mate. But for personal reasons didn't want to bother him over the weekend as I worked on my own house.

 

[Manator]

There can be many reasons for a high Zs reading, some testers are the principle fault for this, other reasons can be connections not properly terminated and an old favourite twisted but not connected. Proper testing socket to socket will identify any problem connection, so that when the Zs is tested it will be a true reflection of that. I see so many people neglect basic testing procedures and then wonder why the results are not what would be expected.

Go back to your original testing procedures and test continuity at each socket, then do your Zs. I think you will find that if it is not the fault of the equipment, it will be identified by your testing at each socket outlet.

 

[Sidewinder]

One of the reasons that the minimum testing under 7671 can be felt to be inadequate really to totally ensure safety.

I added a radial on Sat pm, 2 twin s.o, on an RCD & b16, pvc trunking, run <2m.

I checked Zs & rcd tripping at all 4 outlets, not just the minimum 7671 tests.

 

[MSH1601]

Thanks for your help guys, I'll let you know how I get on.

 

[Nicky Tesla]

Kitchen ring; you may have picked up extra resistance from the actual socket. Try pushing the plug in and out a few times and also flick the switch on and off a few times also. This does often reduce the reading a tad.

Also try your meter on a non rcd socket on high and low current Zs readings and compare.

As said earlier, your RCD itself can add resistance so check before and after + try high current reading also for before the rcd reading and compare.

 

[springcrocus]

1. RCD's in the OFF position

2. All MCB's in the OFF position

3. Place a shorting link from line to earth at the point you want to test.

4. Turn the MCB for that circuit to the ON position.

5. Green test lead on the outgoing line terminal of the relevant RCD

6. Red test lead on the incoming line terminal of the same RCD

7. There's your reading.

8. Turn OFF the MCB and remove the shorting link

 

[sellers]

I would seriously try zs testing at various points starting at the board! I don't know about anyone else but this is the most common for me and it usually is the rcd. Don't bother messing about by passing, test before and after, if that's where your big difference in zs is open and close it a few times. See if it lessens? If not it's just the internals of the rcd. Ive had a few contactums like this! Either replace or accept it is under 1667 ohms.

 

[steptoe]

Kitchen ring; you may have picked up extra resistance from the actual socket. Try pushing the plug in and out a few times and also flick the switch on and off a few times also. This does often reduce the reading a tad.Also try your meter on a non rcd socket on high and low current Zs readings and compare.

As said earlier, your RCD itself can add resistance so check before and after + try high current reading also for before the rcd reading and compare.

...

---------- Post Auto-Merged at 23:52 ---------- Previous post was made at 23:51 ----------

I would seriously try zs testing at various points starting at the board! I don't know about anyone else but this is the most common for me and it usually is the rcd. Don't bother messing about by passing, test before and after, if that's where your big difference in zs is open and close it a few times. See if it lessens? If not it's just the internals of the rcd. Ive had a few contactums like this! Either replace or accept it is under 1667 ohms.

.....

OK folks, how many times do I need to say this,?

if you dont get a satisfactory reading on the first attempt dont keep trying until you do,

the poor sole that gets hit with the actual shock/fault wont get a 2nd or 3rd chance to try and get the reading down to an acceptable level.

people that doi that are incompetent,

people that recommend that are not only incompetent, but obviously idiots that have no idea of the dangers or repercussions of what they are stating,

they are ****ing numpties.!

---------- Post Auto-Merged at 23:59 ---------- Previous post was made at 23:52 ----------

1. RCD's in the OFF position2. All MCB's in the OFF position

3. Place a shorting link from line to earth at the point you want to test.

4. Turn the MCB for that circuit to the ON position.

5. Green test lead on the outgoing line terminal of the relevant RCD

6. Red test lead on the incoming line terminal of the same RCD

7. There's your reading.

8. Turn OFF the MCB and remove the shorting link

do you want to read that again?

even without the obvious shortcomings of using colours for the leads, it just wouldnt work the way you have described it, and it may well possibly cause a massive bang.!

 

[springcrocus]

The way in which a meter does a no-trip RCD test to is, effectively, fool the RCD by saturating the balance coil with a DC-induced magnetic field or by using a test current of less than 30mA. Different meters will produce different results because of this and it appears that Megger instruments do not lead the field in this department! Bypassing the RCD in the manner that I posted above takes the RCD out of the equation entirely and will give you a TRUE (live-measured) Zs.

I am a Megger user myself and very seldom use the no-trip facility because of its unreliability.

Steps, have you had a play with that Robin tester you mentioned earlier? Is it better than your Fluke?

 

[steptoe]

no, I havent springcrocus, but I would deffo consider it on pedigree alone,

Robin/amprobe/fluke are among others the same in a multinational group, just different names,

easy way to do a full Zs is to simply link out the Line side of the RCD, bit of 1.5 is more than enough.

I really could do with a new meter, unfortunately money is not permitting just now, but if it was, then that would be one of my serious contenders,

unless I could find a reason not to I think that would be the one I would chose.

EDIT,

currently Im using an HT Italia, good meter, but its getting hammered on batteries, :| dont they all ?

I just dont like having onje meter do it all and being totally reliant on it all the time.

MM will be having it for cal shortly, but its never wavered on me once, 2weekly check on a cal-card and every so often against a couple of other meters I know the history of.

 

[springcrocus]

do you want to read that again?

even without the obvious shortcomings of using colours for the leads, it just wouldnt work the way you have described it, and it may well possibly cause a massive bang.!

Sorry, have I miss-typed something? This procedure has always worked for me. It doesn't matter WHERE in the circuit one tests for Zs, the meter is just making the line to earth link (high current test, obviously).

---------- Post Auto-Merged at 00:16 ---------- Previous post was made at 00:12 ----------

no, I havent springcrocus, but I would deffo consider it on pedigree alone,Robin/amprobe/fluke are among others the same in a multinational group, just different names,

easy way to do a full Zs is to simply link out the Line side of the RCD, bit of 1.5 is more than enough.

I really could do with a new meter, unfortunately money is not permitting just now, but if it was, then that would be one of my serious contenders,

unless I could find a reason not to I think that would be the one I would chose.

My Megger 1552 is getting a bit battered now, so I might see if I can get one to play with for a day or so. Be interesting to see how accurate the no-trip readings are. If I do, I'll let you know. Does Megger Mark sell them?

 

[steptoe]

Sorry, have I miss-typed something? This procedure has always worked for me. It doesn't matter WHERE in the circuit one tests for Zs, the meter is just making the line to earth link (high current test, obviously).---------- Post Auto-Merged at 00:16 ---------- Previous post was made at 00:12 ----------

My Megger 1552 is getting a bit battered now, so I might see if I can get one to play with for a day or so. Be interesting to see how accurate the no-trip readings are. If I do, I'll let you know. Does Megger Mark sell them?

that was the link I had, to MMs site,

as I see it all meters have a bad Zs with RCDs in situ, I only use it as a justification to my true readings.

Im a bit confused as to your procedure, but on reading it again I think I understand it now, its you use of colours rather than actual names that confused me I think, , and its late, and Im starting to sober up,!

 

[sellers]

Steptoe, my method is a perfectly normal way to find the point of high resistance, testing zs at various points.

 

[Andy™]

do you want to read that again?

even without the obvious shortcomings of using colours for the leads, it just wouldnt work the way you have described it, and it may well possibly cause a massive bang.!

that would actually work and get you a Zs reading on a high current test without tripping the RCD

 

[Steve3948]

[quote name='Andy

 

[MSH1601]

I kinda don't feel like I've asked a basic question now

 

[Nicky Tesla]

Jeez...........i wish i had a