tester/ ELI woes...

[the doctor]

hi all,

some say that as a doctor and electrical guru i am pretty much indestructible but.....

something happened this evening that has me stumped so i need some help from the forum.

the new part p doctor manual is based upon my buddy's house where i have put in one circuit, modified all the others and fitted two new consumer units.

i need to put in a minor works project in the new book so went round tonight to fit a snazzy fitting up in the main bedroom to replace the pendant hanging there.

i wanted to photograph a preview situation pretending it was not my work so put my megger on its no trip setting to take a loop impedance reading at the rose(rcd fitted).

i got >99.9k ohms:coat this was not good in view of the fact i wired and tested a few months ago!

doubting the meter i took a no trip loop at a bedroom socket and got 0.65 ohms so the meter was ok.....

checked at the light again and got no earth:_|

soooo i took the dimmer out of circuit wondering if this was the problem. wait for it.... still no earth.

it was 8 pm so i fitted the light anyway and told my friend that i would be back to fix it, though i was convinced it was ok as i had tested it....

i went downstairs for a beer and then had a re-think. i went upstairs with my buddy and measured good low readings from

1 a landing socket to the bed dimmer

2 from the bedroom dimmer to a bedroom wall light

3 from the same wall light to the newly fitted ceiling fitting

i then went back to the landing socket and no trip looped it and got 0.63 ohms

so in english, i have proved that the ceiling light is well earthed though the meter says not and the meter works ok on the sockets so the meter is ok!

PLEASE HELP ME SOMEONE!!!!!

 

[green-hornet]

This could all be down to the connection made to earth at test point, not being a good sound connection.

Or sinister tester gremlins we sometimes get.

 

[the doctor]

hi green hornet,

i installed the light by putting the fitting bracket behind the bare rose.

i slackened the large earth terminal to pop in the fitting earth, it was tight.

maybe you are right, or could it be other lights on the circuit that are selv electronically messing with the tester. this is my latest idea...

 

[wozz]

maybe you are right, or could it be other lights on the circuit that are selv electronically messing with the tester. this is my latest idea...

ive had certain dimmers in the past make the tester give false extremely high readings. for some reason...

 

[green-hornet]

Just a note for all interested, I always take out all dimmers for any testing as results are always a little on the erratic side.

You should never do an IR test for instance anyway, so I take them off for the other tests as well.

 

[msb2003]

Just a thought, why not disconnect the circuit at the CCU and short out R1 + R2 and go to the light and prove continuity there. That should at least set your mind at rtest as to the cpc continuity.

 

[M107]

Just a note for all interested, I always take out all dimmers for any testing as results are always a little on the erratic side.You should never do an IR test for instance anyway, so I take them off for the other tests as well.

It's dimmers out of circuit for me aswel when testing.

Doc the earth terminal on the fitting isnt laqured is it? did you connect directly to the cpc?

Tried using a wander lead between the cpc at rose & another point (sure you have).

Dodgy tester lead when hanging.......had the same on my fluke I hadn't tightened up the crock & lead fuse didn't make contact when hanging from earth terminal of fitting.

& thats as much use as I can be :coat

 

[the doctor]

hi

i put the lead with crock clip on the plain brass terminal of the rose, again and again. also i did take the dimmer out and short the line to switch wire....

as i said i have proved the earth in a daisy chain fashion from the landing socket so i am satisfied it is earthed, still dont get it though-one of my stranger evenings

 

[batty]

I have found if you try a continuity test with dimmers you don't get a reading but my fluke always gives a reading on loop even with a dimmer in circuit. I would use a voltage tester to see what voltage is present betweeen live and cpc.

Batty

 

[the doctor]

hi

i checked the voltages between the conductors and all was well.

i even did the fiddle test with my fluke 600 on its ohms setting between earth and neutral and got a nice low reading.

i was convinced it could not be wrong but said i would pop back over the week end. i had then intended to fully investigate with an r1+r2 test as mentioned previously.

however during a post jobbie beer i came up with the idea of looping the landing socket and doing a continuity test from the socket to the wall switch to the wall light to the new ceiling light....all was confirmed- real weird but good enough for me nonetheless:coat

alan