very confused

[james king]

hello all
today me and the boss went to a PIR on a 4 bed house.

there are a couple of things i am a lil confuselzed about...

1) we carried out a Zs test on the lighting cct. although when testing the bulb was flickering on and off even though the switch was turned off?

2) on that same light we cheacked polarity at the switch. tested between L and E at the lighting point and switched the switch on and off the reading stayed the same and fluctuated???

3) the house is full of lv down light so we use IR test 2 (connecting L&N to E) my boss said he has never come across the reading of 0.00 while doing that test is they any expinations why? usally this means a short but why is it not tripping the rcd?

all help will be great thanks very much

 

[DurhamSparky]

lots of things!!

Neons + Lamps to name a few!

 

[james king]

but when testing mephod 2 you by pass the bulbs and neons????

 

[mart8235]

1) dodgy switch? needs replacing?
2) same as 1
3) sounds daft but have you disconnected all the transformers? or have I misunderstood you?

 

[james king]

how can it be a doggy switch if the switch works? it turns the light on and off hense switchs on and off the light but when testing, the switch readings show the switch always has continuity. my boss have told me that mephod 2 you do not need to dissconnect any trannys or lv equipment???? is this correct??

 

[mart8235]

if the switch is off and the light flickers then my first thought is the switch. if not then the light fitting. no way of saying for sure without being there.
in my experience i've never been able to IR test lighting without removing/linking out lamps, neons, transformers and all other vulnerable equipment before testing. sometimes this is not possible on a pir so you are forced to use a Limitation for that circuit IR test, L-N and L-E but you can usually do N-E.
not sure what you mean by IR test 2? am i missing a trick?

 

[james king]

no it did not flicker on its own only when carryout out a Zs test?? GN3 has a mephod 2 of the IR test! you connect the L&N to gether and then test between E!

 

[Amp David]

Removing all your lamps is a good idea when measuring your Zs.

Sounds like your boss is a littlelacking of testing know how IMO

 

[i=p/u]

0.00 short circuit= line loving netural

 

[mart8235]

I'll have a look at GN3 on Monday, mines in work. (every days a school day, thanks for the education). does it say in there you don't need to disconnect the equipment?
as for the switch, I'm a bit lost, I'm still inclined to check the switch.
where are you taking you Zs from? you need the switch on for that test so why are you doing it off? am i missing something again?
Anyone else?

 

[james king]

sorry the switch was turned on during the test with light bulb on.... while carrying out a Zs test the bulb kept turning on and off? my boss has over 40 yrs experince and tbh he cant bebotherd any more and is retiering in june. what i am asking is why would the Zs test make the bulb turn on and off im sure if i asked him he could tell me but befor i had the chance he had moved on and i for got. it just crossed my mind??

 

[andekoch]

Some light switches have neons in them, mainly outside waterproof ones. In these cases there is seldom a neutral so the neon is connected between line and cpc; hence the zero reading. The rcd will not trip since the neon draws so little current. Usually a bugger to find these unless you looking for them specifically.

 

[mart8235]

You'll want to get confirmation on this, but I think that when doing a Zs the test itself can 'interfere' with the supply a little, or something like that.......
So it could explain a flickering lamp when then test is being taken.

as I say I'm not sure if this is right or not
anyone else confirm this? or shoot it down!!!!!!!

 

[andekoch]

Sounds about right. If you think about it doing the test involves passing a test current down the line so there must be something happening also the "non rcd/ no trip" tests use a higher test current so very likely things will light up. See for yourself by connecting a neon across the leads and doing an it test, neon will light up.

 

[james king]

ok so that explains that!! i would like conformation on the mephod 2 of the IR test and how this works and if it exectable as i am aware it is? and if so why would u get a dead short??? i am aware of the neon in the light switch but these are all standard 2way light swicthes.