Zs live Testing - does everyone do it?

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Zs live Testing - does everyone do it?
Or do you use a calculated Zs instead
 
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What if you've just done an R1+R2 test and not retightened the cables properly? Testing the live loop will eliminate possible errors, as well as measuring Zs for you.
 
Well, on a new install YOU MUST NOT CARRY OUT live tests until you have verified the earth continuity and other dead tests (polarity etc).

To do these, the R1+ R2 test is done.

As you have done and recorded this test, when you energise and measure the Ze, what is the point of doing the Zs? Just calculate.

For the ring, open circuit resistance of both the L and E loop added together and devided by 4 gives you the circuits R1 + R2. Again, you will have done this when dead before energising.

For periodic inspections you already have the system live so you can measure the Zs if you like.

I personally dont bother measuring the Zs on a new install, it's calced from the Ze and the R1+R2 which is the correct method ;)
 
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Measure Zs as it's easier to take R2 readings of an installation you didn't construct during the PIR you would carry out before changing the consumer unit.
 
I measure Ze and Zs as well as obviously doing R1+R2.

I just like to be sure, it's the mathematician in me, calculations are great, but nothing is good until proven!!!
 
What about the presence of parallell paths on a lighting circuit from a water pipe which is main protective bonded at the intake position, and linked to the lighting circuit in the bathroom as part of the supplementary bonding, or two circuits which have their CPCs linked somewhere along the line, such as in a dual box?

You could end up with a much lower measured Zs than the calculated value.
 
Good point RF!!!

I enjoy testing!!!!

I still do the calcs when I am checking my test data.

I suppose I could drop out all the earths on other circuits when doing each of the Zs's and isolate each of these circuits, bit long winded thou
 
For the ring, open circuit resistance of both the L and E loop added together and devided by 4 gives you the circuits R1 + R2. Again, you will have done this when dead before energising.
Not forgetting the measured R1 + R2 may be higher a spur. ;)
 
Yep, but if you have a spur on a new install you should rightly be shot :LOL:
 
Well, on a new install YOU MUST NOT CARRY OUT live tests until you have verified the earth continuity and other dead tests (polarity etc).

To do these, the R1+ R2 test is done.

As you have done and recorded this test, when you energise and measure the Ze, what is the point of doing the Zs? Just calculate.

For the ring, open circuit resistance of both the L and E loop added together and devided by 4 gives you the circuits R1 + R2. Again, you will have done this when dead before energising.

For periodic inspections you already have the system live so you can measure the Zs if you like.

I personally dont bother measuring the Zs on a new install, it's calced from the Ze and the R1+R2 which is the correct method ;)

Interesting - can you tell me which regulation calls for an R1 + R2 test. If you use it as a polarity test - can you also tell me when would you do it - i.e what is your sequence of testing.
 
Think R1+R2 comes under 612.2
Usually completed as the first dead test on an initial verification, flick the switches etc and also does as the polarity check.
 
Continuity of protective conductors
Ring final circuit continuity
Insulation resistance
Polarity (dead)
Polarity (live - confirm after energising.
'Lectrode (if applicable and if using a loop tester))
Earth eault loop impedance
Devices - incluidng RCD and functional switching

R1+R2 is the very first test you should do. (Or R2 if using the long lead method)
 
Now why does testing have to be done in a particular sequence?

BTW you will not find any requirement for an R1 + R2 test in BS 7671.
 

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