Zs test

[Mark2spark]

Hi Guys,

I've got a Kewtech KT61 multi tester;

http://www.kewtechcorp.com/products/multifunction/KT61.htm

(and I can't work out how to do the link in my own words... lol)

and every Zs test i do on sockets, i get the reading of '1'.

This can't be right?

Ze doesn't appear to be a problem, so it appears that I'm not such a duffer that i can't press the right test button! ?:| Blushing Pray

I've got so fed up with it that I just add the Ze & (R1 + R2) together now for the test sheet, but with my ElecSa assessment coming up in 13 days time I thought i'd better figure it out.

Any ideas?

Cheers... Guiness Drink

 

[Andy™]

what range do you have the tester set to? on the old robin testers (that look exactly the same), 1 used to mean out of range

 

[Mark2spark]

I set it to both ranges, 20 or 2000 gets same reading.

I'm gonna have to do it at home later to refresh my memory on whether the rcd trips or not ?:|

I noticed that they (in the manual) refer to the 2000 range as 'Meg'... surely that should be K?

 

[Andy™]

I noticed that they (in the manual) refer to the 2000 range as 'Meg'... surely that should be K?

not always, that range could be for insulation, which would be meg

 

[Mark2spark]

Nah, think it's reasonably clear Andy, when it's set to test IR a big capital M appears in front of the ohm sign.

I've just read the manual again and it appears that theres a thermometer symbol that can come up when doing loop, maybe it's that instead of a '1' lol

Hope ElecSa bloke doesn't ask for a calibration certificate for my eyes!

 

[Robojin]

I set it to both ranges, 20 or 2000 gets same reading.I'm gonna have to do it at home later to refresh my memory on whether the rcd trips or not ?:|

I noticed that they (in the manual) refer to the 2000 range as 'Meg'... surely that should be K?

I have a KT64 so a little different as it's auto just turn the dial and press test

I've just had a look at the manual online for your KT61, and it seems not to be aimed at the novice, however your 61 does not support ATT which prevents any RCD on the circuit tripping with the test, and advises you to temporally replace any RCD with an MCB (nice idea but impracticable on new boards), so is there RCD protection on this circuit?, I've not used a 61 but I'd imagine set the sine to 0 phase, and test at 20ohm since your looking for a low ohms reading

 

[Robojin]

Nah, think it's reasonably clear Andy, when it's set to test IR a big capital M appears in front of the ohm sign.I've just read the manual again and it appears that theres a thermometer symbol that can come up when doing loop, maybe it's that instead of a '1' lol

Hope ElecSa bloke doesn't ask for a calibration certificate for my eyes!

Because the tester is chucking 6kW down the fault path, so the tester can become a toaster if you did rapid tests one after the other

 

[Mark2spark]

I'm following you Robo, but testing on the 2000 range tests at 15mA, so rcd shouldn't trip?

Your one tests at that as well according to the manual.

Hmmm.

 

[Robojin]

I'm following you Robo, but testing on the 2000 range tests at 15mA, so rcd shouldn't trip?Your one tests at that as well according to the manual.

Hmmm.

Yes one of the methods to avoid tripping is to use 15mA, the other is to saturate the RCD coil with DC moments before the test current

As to which my KT64 uses, never bothered to check as it's turn the dial and push the button, all you assessor will be interested in is that you are familiar with your test meter, might be worth giving Kewtech a call as the KT61 manual is a bit basic

 

[SPECIAL LOCATION]

I've got so fed up with it that I just add the Ze & (R1 + R2) together now for the test sheet, but with my ElecSa assessment coming up in 13 days time I thought i'd better figure it out.

Any ideas?

Cheers... Guiness Drink

Hello Mark,

Don't break into a sweat thinking you have got to be able to take ZS readings with an anti-trip meter!

Wiring regulations make it quite clear that determining ZS by calculations is perfectly acceptable.

Regulation 616.9 page 160... the big red book

10.3.6 Earth loop impedance page 87 On site guide.

*12 page 95 Guidance note3 Inspection & testing.

some meters without anti-trip don't trip some makes of RCD.. and some meter with anti-trip still do trip certain makes.

But you are under no obligation to have an anti-trip meter.. it would be more convenient. but not essential.

If your meter trips the RCD... advise you assessor you would do it by calculation...

and you are proving your knowledge of BS7671 and how to take required test readings.

I don't think your assessor would or could object.

 

[loucas74]

Hi

I got the same problem with an HT Italia (now being sold as a martindale multifunction tester) but looking in the manual it says that on the 15ma =no trip rcd setting its accuracy resolution is 1 ohm - so any reading less than 1 ohm will just show as 1 ohm and it works out a rubbish Pfc value based on this. I also have my Elecsa assessment next week and am not sure that if i should put < 1 ohm in the Zs column for each circuit on an Installation certificate or work it out from (R1 +R2) + Ze. Help! What about Zs phase to neutral test for a tn-c-s which doesnt trip the RCD or am i barking up the wrong tree

 

[batty]

Hi I got the same problem with an HT Italia (now being sold as a martindale multifunction tester) but looking in the manual it says that on the 15ma =no trip rcd setting its accuracy resolution is 1 ohm - so any reading less than 1 ohm will just show as 1 ohm and it works out a rubbish Pfc value based on this. I also have my Elecsa assessment next week and am not sure that if i should put < 1 ohm in the Zs column for each circuit on an Installation certificate or work it out from (R1 +R2) + Ze. Help! What about Zs phase to neutral test for a tn-c-s which doesnt trip the RCD or am i barking up the wrong tree

On my fluke 1652 if you do a phase to neutral test it will test very quickly and will not trip Rcbo's but there again it does not trip Rcbo's on phase to earth.

Batty

And welcome to the forum. (Paddy this is deffo a new member)

 

[Apache]

You're right Batty - Welcome Loucas74

 

[steptoe]

On my fluke 1652 if you do a phase to neutral test it will test very quickly and will not trip Rcbo's but there again it does not trip Rcbo's on phase to earth.Batty

And welcome to the forum. (Paddy this is deffo a new member)

L - N will generally be lower than L E tho due to difference in cable size, ie, 2.5 T&E 1.5cpc, unless com/ind using singles.

just use calc.

 

[Blue Fox]

LOUCAS74

Hi I got the same problem with an HT Italia (now being sold as a martindale multifunction tester) but looking in the manual it says that on the 15ma =no trip rcd setting its accuracy resolution is 1 ohm - so any reading less than 1 ohm will just show as 1 ohm and it works out a rubbish Pfc value based on this. I also have my Elecsa assessment next week and am not sure that if i should put < 1 ohm in the Zs column for each circuit on an Installation certificate or work it out from (R1 +R2) + Ze. Help! What about Zs phase to neutral test for a tn-c-s which doesnt trip the RCD or am i barking up the wrong tree

I had my ELECSA assesment the other day and I had filled my cert in with readings like 0.59 ohms and the guy said just put 1 down if it says that as the meter probably won't be accurate enough on non trip to give a reading like that with any degree of accuracy. No gauruntees for you though but thats what he told me.

 

[Andy™]

i dont think a EFLI tester that cant read lower than 1 will be of any use. how are you supposed to check Ze with it? or Zs?

 

[Robojin]

LOUCAS74I had my ELECSA assesment the other day and I had filled my cert in with readings like 0.59 ohms and the guy said just put 1 down if it says that as the meter probably won't be accurate enough on non trip to give a reading like that with any degree of accuracy. No gauruntees for you though but thats what he told me.

Hmm so with a cooker circuit on a 40A CB requiring 0.93ohms for disconnection would putting <1ohms on the SoTR meet the regs, or have I missed the point, aside that you can arrive at Zs by calculation therefore not need to do a live Zs test