Question regarding dead polarity test. Please Help.

[nazoom]

Hi

I am bit unsure when carrying out dead polarity test on a one way switch and two way switch. Where do the test probes go and on what?

Do we make contact at the switch line and the cpc of a ceiling rose? or do we contact at the line and cpc at ceiling rose?

What happens in two way switch?

Many Thanks.

 

[JUD]

Connect probes to switch line and cpc at ceiling rose.

With the switch on you should get a reading and with the switch off it should be open circuit.

(Line an cpc connected at DB obviously)

 

[telectrix]

and if the reading doesn't go open circuit when the switch is operated, either the switch is wired incorrectly or you are switching neutral. (rare, but not unknown)

 

[SirKit Breaker]

Just to add to Jud's post, if you try to do it at the switch, you will not prove polarity, you will just prove the switch works. If for some strange reason you connected the switches in the neutral, you would get the same readings as if it were in the line, so as Jud states do it that way. If you are just venturing into the testing world, then get hold of Guidance Note 3, this explains in great detail, and with good illustrations all the testing procedures.

Cheers............Howard

 

[nazoom]

Many thanks to all.

 

[Farmelectrics]

Another way of doing it is link l e at board go to your last light fitting on circuit and test across l e this gives you your r1 r2 test and also proves polarity your switching arrangement could be done by function testing

 

[JUD]

Another way of doing it is link l e at board go to your last light fitting on circuit and test across l e this gives you your r1 r2 test and also proves polarity your switching arrangement could be done by function testing

This should also be done across switch line and earth. The switch drop should be included in your R1+R2. Operating the switch then proves polarity. Two birds with one stone and all that.

 

[nazoom]

Sorry what is the switch drop? Do you mean operating two way switch one at time?

 

[nazoom]

Sorry what is the switch drop? Do you mean closing light switch for 1 way and 2 way (switch one at time) at continuity and open the switch at polarity?

 

[JUD]

The switch drop is the wire/cable between the ceiling rose and the switch. It is part of the circuit and needs to be included in the R1+R2 test.

Connecting your probe to the switch line will include the conductors feeding and returning from the switch. Turning off the switch will break the line conductor, hence proving polarity.

 

[Farmelectrics]

If all your switches are in the on state the test will include your switch drops anyway

 

[JUD]

If all your switches are in the on state the test will include your switch drops anyway

Only if you connect your probe to the switch line at the ceiling rose. Connecting it directly to the loop doesn't include the switch drop.

 

[nazoom]

Thanks for clearing things to me.

 

[sedgy34]

Hi

I am bit unsure when carrying out dead polarity test on a one way switch and two way switch. Where do the test probes go and on what?

Do we make contact at the switch line and the cpc of a ceiling rose? or do we contact at the line and cpc at ceiling rose?

What happens in two way switch?

Many Thanks.

nazoom to your phone and call an electrician in

 

[Farmelectrics]

if your swiches are on then you can test at loop your swich wire becomes a continuation of your loop hence the light comes on just saves a bit of time with your testing you can do it the other way but why not put all switches on and do the test once

 

[JUD]

farm I don't think you're getting what I mean.

On the ceiling rose, as you know there is 3 terminal blocks, L, Loop and Neutral. Connecting your probe to the loop (center terminal) won't include your switch drop in the test as this is the permanent live.

Connecting the probe to the L (switch line) includes the switch drop as it takes a path down to the switch and returns back to the loop and then on around the rest of the circuit. Therefore turning off the switch breaks the continuity of the line conductor and proves polarity.

 

[morph]

if your swiches are on then you can test at loop your swich wire becomes a continuation of your loop hence the light comes on just saves a bit of time with your testing you can do it the other way but why not put all switches on and do the test once

because you are not
1)including switch drop
2) you are not proving cpc continuity at the switch

 

[Farmelectrics]

Am I missing something here if you test at the loop on ceiling rose that is your feed to the switch if the switch is on surely it's testing the switch wire

 

[JUD]

Because the tester is measuring continuity from one probe to the other in a "continuous" loop. When you test on the loop at the ceiling rose the feed to the switch and the return to the L terminal (switch line) on the ceiling rose are not part of the loop.

Here is the path with the probes connected to the switch line and cpc...

...and here is the path with probes connected to the loop and cpc...

 

[nazoom]

Nice diagram. Thanks.

 

[Farmelectrics]

Never mind

 

[Farmelectrics]

Just one last throw of the dice jud I still think your wrong now I'll be the first to put my hands up if it's me but can you understand we're I'm coming from live and earth linked at board all switches on you go to the last ceiling rose and test between live and earth no this takes in the switch drops because if you put your continuity testers across live to earth you get a reading if you put your testers across switch wire to earth you also get a reading even tried it today

 

[JUD]

Of course you get a reading on both, it's all part of the same circuit.

The only difference will be the resistance when you test on the switch line will be slightly higher than the resistance when you test on the loop as the circuit is longer.

Try connecting your probe to the loop and then have someone turn the switch off. You will find that you still have continuity because you are not testing the switch wire.

Now do the same test with your probe on the switch line and see what happens.

 

[Farmelectrics]

Let's leave it there both readings are acceptable anyway long day goodnight

 

[JUD]

Both readings aren't acceptable. An R1+R2 test is done to determine that the resistance of the line and cpc conductors at the furthest point in a circuit is sufficiently low enough for the OCPD to operate in the required time and should include all conductors in that circuit.

Like it or not a switch wire is part of the circuit and needs to be included in the test.

 

[Farmelectrics]

I'm well aware of that and all switch wires have and all ways have been included in my testing twenty years of testing experience backs that up

 

[Deleted member 26818]

Sorry farm, but if you don't conduct the test as JUD describes, then you will not be testing any of the switch wires.