Initial verification questions

[gazdkw82]

I have my initial verification practical assessment in a few weeks.

I'm pretty sure I have covered all aspects however I have a few things I'm unsure about and was hoping someone could clarify.

Firstly, is zs of the installation performed directly after ze? And zs on a installation is the same test as a ze but the main earthing conductor reinstated into the board?

Secondly, insualtion resistance, I've watched many videos and all have slightly different methods. Should I just follow the instructions in the OSG? For each circuit, line to neutral, line to earth and neutral to earth?

Thirdly, to do the calculation on a calculator for r1+r2/4 and r1+rn/4 should an equals be pressed after r1+r2 before dividing by 4? So 0.19+0.19 = then that answer decided by 4?

 

[telectrix]

1.Ze can be measured directlyt before or after dead tests. Zs readings are taken after energising circuits following dead tests.
2.Zs testing is carried out on the individual circuits with earthing and bonding reinstated.
3. for single phase, L-N, L-E, N-E. for 3 phase no of tests is 10. can't be arsed to list, beer time.
the (r1 + r2)/4 is only an approx guide to estimate what you should get for R1 + R2.

 

[gazdkw82]

So there is no z's test for the entire installation?

I know you can calculate it.

As for the calculation on the RFC, I m aware it's only purpose is to provide a guide to the results that should be obtained at each socket outlet (within 0.05). I was just unsure on how the actual calculation is inputted because different figures will be shown when done in a different way.

The cculation for r1+rn and r1+r2 along with the cross connections respectively are steps 2 and 3 and we've been told to write the steps down on the right hand side of the test results sheet

 

[Richard Burns]

Zs of the installation is the test you perform to determine the prospective earth fault current so better to think of it as a PEFC test, even though it is the same procedure as for Ze, but with the earth reconnected. It can be performed subsequently to the Ze.

IR just follow the OSG then you cannot go wrong, remember to swap the switches for 2 way lights and link out any items that will cause problems. I would tend to go for circuit by circuit testing, easier to get right and know where a fault might be, although global testing is allowed.

r1+r2 =, then do divide by 4 (the brackets give it away)
r1
rn
r2
(r1+rn)/4
(r1+r2)/4

 

[MDJ]

I have my initial verification practical assessment in a few weeks.

I'm pretty sure I have covered all aspects however I have a few things I'm unsure about and was hoping someone could clarify.

Firstly, is zs of the installation performed directly after ze? And zs on a installation is the same test as a ze but the main earthing conductor reinstated into the board?

Secondly, insualtion resistance, I've watched many videos and all have slightly different methods. Should I just follow the instructions in the OSG? For each circuit, line to neutral, line to earth and neutral to earth?

Thirdly, to do the calculation on a calculator for r1+r2/4 and r1+rn/4 should an equals be pressed after r1+r2 before dividing by 4? So 0.19+0.19 = then that answer decided by 4?

What did you learn during your apprenticeship?

 

[gazdkw82]

What did you learn during your apprenticeship?

rhetorical question?

 

[MDJ]

rhetorical question?

No serious question, although you are still training I assume and perhaps wrongly you have been taught these things, if not I apologise, I am not trying to bust your chops honest, just wondering what you think really before we chip in?

 

[gazdkw82]

Well at work I'm not learning alot to be honest. We are maintenance based and pretty much just do simple fault finding, fixture changing and helping contractors find rooms. It's abit boring and I'm not learning. We hardly do any installation work or testing.

As for college, it's going pretty well. I'm one of the most dedicated and knowledgeable in the class. It helps that I research and study alot. I'm into it though so it's not hard work or ever feels taxing.

For the upcoming practical assessment on initial verification I am pretty sure I am on it so to speak but I just had those couple of queries. I think I knew the answers I just wanted to check here with all you knowledgeable folk ;-)

Another thing I have been doing when practicing but not sure if it's a recognised method is, when testing continuity of r1 on the dol motor, is it acceptable to operate the contactor within the motor to confirm polarity?

Thanks

 

[gazdkw82]

I should add, at college the tutor is really struggling to find time to help us all. At the minute half the class is doing dead treating whilst the others are with him doing live testing.

It's a problem the college are aware off but don't seem to be dealing with, hence why I'm also asking on here