R1 plus R2 ??

[gpz900jim]

I was just reading on An Electrical Safety Council FAQs the following; "Does a R1 plus R2 test on its own confirm correct polarity of a radial circuit?" The answer was; "Not on its own." Could someone explain to me why an R1 plus R2 reading on its own is not sufficient to confirm polarity in this situation ? and what additional test would be needed to comply ? cheers !

 

[darren100]

R1 and R2 is checking continunity of the phase conductor and cpc. By carrying out R1 and R2 you are not checking where in the actual socket they are connected! this is generally tested when you carry out live testing when you are doing your earth fault loop impedance test, as your tester will show incorrect polarity and will not enable you to carry out the test! that is of course if you do not pick this up on a visual inspection first!!!

 

[Sparky Ninja]

If you do your R1&R2 properly then you will measure at each socket confirmIng polarity at sockets. What you can't confirm is single pole switching of the neutral conductor, among other things.

 

[Deleted member 9648]

You also need to confirm the supply polarity at the intake/DB.......if that is incorrect so will be the polarity of all the circuits supplied from it.

 

[pushrod]

All of the above, but very simply you would still get an R1+R2 reading if there was a reverse.

 

[IQ Electrical]

Yes, all of the above and a very good point from wirepuller regarding supply polarity!

 

[gpz900jim]

if you do an R1 plus R2 at each socket, wouldnt a reverse show up as an open circuit? and if so, isnt that adequate as a polarity check?

 

[pushrod]

and what additional test would be needed to comply ? cheers !

just noticed this - so as wire puller said... and if you do R1+Rn and you get a reading every time along with a reading for R1+R2 then you have confirmed polarity. (doing R1+R2 doesn't rule out a reverse but coupled with an R1+Rn you have confirmed R1 was correct)

 

[IQ Electrical]

if you do an R1 plus R2 at each socket, wouldnt a reverse show up as an open circuit? and if so, isnt that adequate as a polarity check?

How would a reverse be open circuit?

You could still have a complete R1+R2 loop but in the opposite terminals of an outlet.

 

[pushrod]

if you do an R1 plus R2 at each socket, wouldnt a reverse show up as an open circuit? and if so, isnt that adequate as a polarity check?

No you still get a reading they are just the wrong way around.

 

[gpz900jim]

How would a reverse be open circuit?

You could still have a complete R1+R2 loop but in the opposite terminals of an outlet.

if you tested between the socket terminal at the front that should be live, and the earth terminal, wouldnt it be open circuit if those 2 terminals were reversed in the back of the socket?

 

[pushrod]

if you tested between the socket terminal at the front that should be live, and the earth terminal, wouldnt it be open circuit if those 2 terminals were reversed in the back of the socket?

Think you might be getting a bit confused or i am not understanding your post - if you are doing R1+R2 you have isolated the circuit and have linked line and cpc at the CU. You are then low resistance testing between the earth and line at each socket. If the cpc had been put in the live and vice versa you would still get a reading and would only know it was reversed if you took the socket front off for a visual (unless you did what i suggested earlier and also check between R1+Rn - similar to ring final circuit testing)

 

[gpz900jim]

ok, yes i see what you mean, i didnt consider that it may happen that live and cpc may be reversed, was really thinking of reversed polarity. Thanks for all the input from everyone. jim

 

[nickblake]

oh as for the other question asked what other test would you do to confirm polarity and that would be the Ze at the supply , and a Zs within the installation

 

[malcolmsanford]

Ze is a novel way to confirm polarity but if you think about it, it does do it lol. Zs by measurement will confirm polarity and as our NICEIC people don't like us doing this by measurement, then their way wouldn't confirm it, but your quite right it is confirmed on testing.

 

[pushrod]

Ze is a novel way to confirm polarity but if you think about it, it does do it lol. Zs by measurement will confirm polarity and as our NICEIC people don't like us doing this by measurement, then their way wouldn't confirm it, but your quite right it is confirmed on testing.

We were taught to have confirmed polarity of supply with approved voltage tester not other instruments and to have confirmed installation polarity before doing a Zs. College world vs real world ??

 

[malcolmsanford]

No real world is on an intial verification if you installed you would be fairly confident you had not made a mistake. R1 + R2 would be your dead polarity test. If a ring main then the r1 rn and r2 would do this and confirm polarity even more.

PIR then Zs by measurement would confirm polarity for me. I don't think I do R1 + R2 on a PIR. I would do R2 with a wander lead and put R2 in rather than R1+R2. It depends on circuit access. Most likely domestic I would do a full R1+R2.

No I just thought Ze was a novel way to prove polarity becasue it does. Try get a Ze N/E or N/L

 

[pushrod]

No I just thought Ze was a novel way to prove polarity becasue it does. Try get a Ze N/E or N/L

Pretty sure my meter would give a reading on N/L.

 

[malcolmsanford]

I'm sure it will as Fluke I know will give you a reading on Loop impedance on L/N in ohms so I suppose yes you would get a reading L/N at Ze

 

[nickblake]

I was how i was taught and im sure you guys have come across a supply with incorrect polarity ,so it was always test your Ze then if you get reversed polarity doing a Zs test then you can be sure that the wiring is at fault ,this is part of the reason i do a Zs test at each point on a circuit whilst doing a PIR as you never know , its the same with PAT testing i always test the socket im plugging in the pat tester in as there would be no point testing appliance is the supply is dodgy

 

[IQ Electrical]

I'm sure it will as Fluke I know will give you a reading on Loop impedance on L/N in ohms so I suppose yes you would get a reading L/N at Ze

Yes, that's true, it's also a good way of helping to confirm the supply type if any doubt exists-on a TN-C-S your L-E loop test will be identical to your L-N loop test at the origin whereas on a TN-S the L-E loop reading is normally higher than the L-N.

 

[malcolmsanford]

I always confirm the TNC-S on the PSCC/ PEFC test as well