lighting circuits on PIR's

[Murdy]

Evening all,

Coulds anyone advise of the best way to do R1+R2 for test a lighting circuit on clicker boxes that are swiched by PIR's .

Would you make up a test rig to clip straight into furthest clicker box and just link out the switched and feed live at PIR (to close switch) and link out live and earth at the board then measure R1 R2 at the test rig in clicker ?????

Cheers

 

[stretchyboy]

This reply will probably set a few fire works off but here goes ........

If it's speed you are after, why dont you get an R1R2 reading from the neutral to earth as this isn't switched and therefore easy to get without linking etc....
..... and before barrage of abuse arrives,
1/ if you are using PIR's to switch with the difference in reading will be nil as there is no switchlines to add length.
2/ The reading is being used to verify the earth only,really, as you are allowed to do an R2 reading on it's own.
3/ You are also allowed to use calculation, of which this could be deamed your method of calculating the correct value.


light blue touch paper and stand well back.........

 

[Deleted member 9648]

I'll take some of that flak as well as I've used the neutral on occasion under these circumstances.....sometimes the amount of faffing involved in doing it the 'correct' way isnt justified when experience tells you a simpler way will achieve the same result.
On the same note when faced with the usual ancient DB designed to be impossible to get at the wiring and ID neutrals etc ,I've done ring continuity tests at a convenient socket rather than at the DB......a lot less hassle.

 

[oldtimer]

Only problem is that if you measure earth and neutral you mis out the resistance of the feed and switchwire or did I miss something here ?

 

[Deleted member 9648]

Only problem is that if you measure earth and neutral you mis out the resistance of the feed and switchwire or did I miss something here ?

See stretchyboys post,the method would only be used where the continuous neutral was the same length as the lives ,which are switched by a device which needs to be energised.

 

[Tester Steve]

If it's speed you are after, why dont you get an R1R2 reading from the neutral to earth as this isn't switched and therefore easy to get without linking etc....

Hey, thats my idea!!
Use this method all the time in situations just like this!!

Steve.

 

[RexT]

Hi all,

Sounds an interesting idea and I can see why it is attractive time wise. I suppose its down to you what you write it up as, because you are actually measuring Rn + R2 and are producing data which is considered not part of the earth fault loop for the part of the circuit. On testing we do seem to ignore the neutrals a bit.

It obviously has its attractions and as had been said previously in this forum in one way or another is really down to the inspectors judgement.

Best wishes,

Rex

 

[chris gray]

as we use to 2plate at my last place, the nic man let us do it that way.
saved us messing about with the switches.

 

[stretchyboy]

you must remember that the test is designed to verify the R2 only, ie that the circuit is earthed to the end point and therefore safe to energise. When you test Zs you are verifying the earth fault path and how this will cause the protective device to react.

 

[Risteard]

That would be Rn + R2 (not R1 + R2) for stretchyboy's remarks.

Also, how then would you prove polarity without testing the line conductor?

 

[Deleted member 9648]

As long as the live and neutral are the same legnth then using the N will give an identical reading to R1R2.....regarding polarity if you have verified the N and E then you have proved polarity.....the other one must be the live.

This method is the exception rather than the rule.....but is useful when using the live for the reasons already stated would be a pain.

 

[Guest123]

Why not just carry out an R2 test then????

An NIC test form asks for one or the other, for this one R2 would appear easier.

 

[sean123]

if they are on click roses, i just make up a click rose plug top to link out the pir, just put a link between A and L terminals. saves dismantling the click roses to link out permanent live and switch live. i use this method because i come across pirs on every job im on.

 

[Risteard]

As long as the live and neutral are the same legnth then using the N will give an identical reading to R1R2.....regarding polarity if you have verified the N and E then you have proved polarity.....the other one must be the live.

This method is the exception rather than the rule.....but is useful when using the live for the reasons already stated would be a pain.

I know what you're saying but for polarity you are supposed to confirm that single-pole devices etc. are connected in the line conductor only. Therefore you need to operate the switches etc. and also the centre pin of bayonet cap lampholders.

 

[m25maintenance]

if u installed the circuit then u know u have correct polarity, unless ur a dumb nut