BAZ

Hello, i have just bought a Fluke 1652 and was testing lighting circuits, i bridged out the phase and nautral and tested between the phase and earth with 500 volts, the results that keep coming up is less than 500 M ohms is this right or am i doing something wrong. What would your results normal be.

thanks

baz

danzor

>2000

EasyFox

What reading are you getting.

The minimum is 0.5 Megohm
But anything less than 2 Megohm needs further investigation due to possible faults.

So I'd want to be seeing above 2 Megohm (>2)
You'll rarely get 500 Megohm (>500) unless a new installation.

Shakey

like the lads said, what are you getting?

i always get my students to measure a circuit with about 50Mohms on it, we use meggers, and they get so used to seeing >299Mohms, that the first time they get something else they think the sky has fallen in on them, even tough they are 100 times greater than the minimum reading!

BAZ

im getting >500 megoham, my test voltage is 500 volts, i might be doing the test wrong, i link the phase and nautral in the distribution board and then test between the phase and earth bar in the distribution board, im not getting any other reading >500 megohm. It is a new installation, there all lighting circuits wired is 1.5 pvc in conduits.

thanks

Baz

EasyFox

On the Fluke you will not get any better than >500 meg.

You are doing it right testing at 500volt (so long as not elv circuit) but if it was a new installation you will need to test between
line - neutral
line - cpc
neutral - cpc
after removing lamps / dimmers / neons / trannys etc

For PIR's it is acceptable to link neutral & line then test to cpc, lazy but acceptable

BAZ

Thanks Easyfox, i just got the fluke and was worried i was doing some thing and i need to fill out some test sheets.

jibspark

LOL that happened to me at college! all my work is new circuits, so at college when it came up at a reading <200MOhms i didn't have a clue why! i just couldn't get my head around the fact that ANY reading less than infinity would be acceptable!

EasyFox

Just saw this again & remembered that on Thursday (yesterday) this happened to me.
At 16:00 on my way home I take a call on the mobile from a bathroom fitter asking if I'd mind dropping by to give him a hand, as he was getting funny results (as in a fail 0.33Meg) on a ringmain doing IR test "I'll pay you for your time, cant work it out all I've done is extend the ring to power a shower"

Why did he call me, because I changed the cu a month ago & left one of my contact labels on the cu. I had no problems with any of the circuits when I tested it.

Anyway turned up as it was on my way home, found him upstairs poking 500v round the ring showing me the 0.33meg result " there see, are you sure you tested it because i've checked your cert & you got >200Meg"

So pointed out that in my oppinion it was a neon some where, told him to do a walkround & unplug the trailing lead with neon & retest..................... >200Meg yeeeeha
(it feels sooooooooo good when your right dont it)

His response " well thats the sort of thing that they should teach on the part P course, I didnt know what to do as its the first failed IR reading I've had"
I felt sorry for him he was at the crying stage when he called me, so told him to call if unsure in the future............that I may live to regret but heyho goodwill to all.

DonaldJ

Surely not!