Zs test with isolator

[pauly007]

Hi. could a Zs test be done at an isolator terminals instead of at the end of a circuit or equipment in any circumstances? I'm sure that i read this was OK but was always taught it was at the end of the circuit.

Thanks

 

[Sintra]

It can be done anywhere on the circuit but it's pointless unless it's done at the last connection. Why where you thinking about doing it at an isolator?

 

[kingeri]

It depends what is after the isolator IMHO. If the isolator is the final connection to a piece of fixed equipment then that is where you would take the Zs reading (if it is the last point on the circuit). If the isolator is inserted within the fixed wiring, e.g. feeding a socket for a built in appliance in a kitchen, then no you can't take the reading at the isolator.

 

[Engineer54]

It can be done anywhere on the circuit but it's pointless unless it's done at the last connection. Why where you thinking about doing it at an isolator?

Totally pointless!! It also makes you wonder what's going on out there??

 

[ArseyDee]

Quote........."The measurement should be made at the point or accessory electrically furthest from the supply of the circuit"

 

[Traineenoob]

Well tbh Ive been wiring a few Mitsubishi Ecodan Air Source Heat Pumps and always take my Zs reading at the rotary isolator. The cost of the ecodan unit is £4500 and dont really want to damage the unit! Testing Zs at low current also.

 

[Engineer54]

Well tbh Ive been wiring a few Mitsubishi Ecodan Air Source Heat Pumps and always take my Zs reading at the rotary isolator. The cost of the ecodan unit is £4500 and dont really want to damage the unit! Testing Zs at low current also.

If that is the end of the primary fixed circuit, that is where you would make the Zs test from. I'm taking it, that the isolators you refer too, is adjacent or fixed to the equipment it is supplying??

 

[Traineenoob]

Yes isolator positioned next to unit. Then from isolator in Sy bradded flex to unit. Always testing at isolator failing that then a calculated Zs test.

 

[Engineer54]

Yes isolator positioned next to unit. Then from isolator in Sy bradded flex to unit. Always testing at isolator failing that then a calculated Zs test.

I hope your not using the steel braid as your CPC intp the equipment??

 

[MDJ]

a calculated Zs test.

:banghead: I find these college lecturers really annoying these days, Calculated ZS tests, why? Bloody trade is going backwards IMO

 

[GMES]

:banghead: I find these college lecturers really annoying these days, Calculated ZS tests, why? Bloody trade is going backwards IMO

This is what they are being taught now on the course mate, I had a Electrical Trainee with me for a week's experience while I was on a 3 phase install small industrial unit, we did the install then obviously started testing, he tested while I stood at his side and was gobsmacked when the only test he didn't do was a zs when I asked why he felt it was ok to leave it it out is answer was the guy who ran the course said as long as you get your R1 + R2 then there is no need for zs and they only charged him 2500.00 for that little lesson. When I tried to explain it was probably the easiest test in the sequence to do he just gave me a blank expression. The times they are a changing my friend.

 

[MDJ]

Your right they are changing, we had a good debate about this very topic a while back regarding verification and Sintra came up with a valid reason which should be told to these college lecturer's, I can't find the thread at the moment but will do I'm sure and I may even post a link to it in my sig so these college lads can see real reasons for testing rather than calculation, as you rightly pointed out it is a very simple test to carry out, it amazes me that trainees are taught to calculate and avoid this test.

 

[GMES]

I would be interested in seeing that debate if you can resurrect it mate. My biggest gripe is with the muppets teaching these courses, they can't have any hands on experience to be offering some of the advice that they do! . But the biggest concern for me is to the pupils on these courses, because like my example above if had not sat the lad down and gave him some valid reasons , then I know for a fact he would have gone away still thinking that it is ok to omit a very important part of the test sequence. I will be back on later as I'm off to earn a few bob now so hopefully you will be able to find the debate you mentioned.

 

[Simonslimline]

I think the reason was that testing Zs would highlight a high resistance through an MCB etc, which a calculation obviously would not. IMO whats the point in owning a multifunction tester and then calculating results!

 

[Engineer54]

No harm in being taught how to calculate Zs etc, but testing is the only way to be sure that a circuit is complying in the field!!

Having said that what do you guy's really expect from someone that has been through a 17 day/5 week course at a training centre??