Insulation Resistance of floodlights

[Davetherave]

I keep getting short circuit between live and earth. I can't work out wether this is normal or a genuine fault. Unfortunately I can't lower the floodlight to inspect further. Can only test at the bottom of the base. Can any one help?

 

[Pete999]

I keep getting short circuit between live and earth. I can't work out wether this is normal or a genuine fault. Unfortunately I can't lower the floodlight to inspect further. Can only test at the bottom of the base. Can any one help?

Hi Dave
Why can't you get to the top of the floodlight? In the mean time try gaining access to the trainee section, as a trainee you will get more help and less agro from the members, the trainee section has mentors to help you with problems. PM PaulM he will help you with access I'm sure

 

[Davetherave]

As the light is fixed and can't be lowered

 

[Pete999]

As the light is fixed and can't be lowered

Scaffold, ladder, cherry picker?

 

[Lucien Nunes]

short circuit between live and earth

By definition, this cannot be normal. It will eat the fuse or MCB at switch-on. Do you genuinely mean a short-circuit? That is not the same as a low reading on an insulation tester.

 

[Davetherave]

By definition, this cannot be normal. It will eat the fuse or MCB at switch-on. Do you genuinely mean a short-circuit? That is not the same as a low reading on an insulation tester.

The reading I got was 0.14

 

[Pete999]

Sorry Dave 0.14 what you need to be a bit more specific

 

[TJ Anderson]

If you have 0.14 ohms on low ohm continuity scale, then you have a short L-E. Like already said above you would blow OCPD immediately. You need to gain access to investigate further.

 

[VoltzElectrical]

cable drop could have chaffed through, or SON ballast could have gone down. See both regularly but latter more than former. You'll have to get up there dude.

 

[Davetherave]

Surely if that was the case, the floodlight wouldn't be working. At the bottom of the column is two 6A fuses and the floodlight is supplied from TT installation with 300mA RCD on the supply. Wouldn't these have operated or blown if there was a fault. Was thinking N and E may be linked within the floodlight

 

[VoltzElectrical]

Surely if that was the case, the floodlight wouldn't be working. At the bottom of the column are two 6A fuses and the floodlight is supplied from TT installation with 300mA RCD on the supply. Wouldn't these have operated or blown if there was a fault. Was thinking N and E may be linked within the floodlight

It might have been pertinent to mention that it was still working in your OP!

If it's working then there is no fault??? or have I missed something?

 

[Davetherave]

Nope no fault, just the first time i've tested a floodlight

 

[Davetherave]

Was just baffled by the short circuit between live and earth

 

[stevethesparks]

Surely if that was the case, the floodlight wouldn't be working.

DOH
It would certainly been worth mentioning that at the beginning.

 

[Darren Elliott]

0.14 Mohms?

ie 140000 ohms

 

[Marvo]

.....Was thinking N and E may be linked within the floodlight

And live and earth as well via an MOV perhaps? What test voltage was your IR tester set at?

 

[VoltzElectrical]

Only test I do at a column is Ze. Switch on, lights? Yep! Lock it up then and ride off into the sunset.

 

[Davetherave]

Sorry whats MOV stand for? I'm fairly new to this forum. Tested at 250V

 

[Marvo]

Sorry whats MOV stand for?.....

Google surge arrestor or lightning protection, metal oxide varistor.

 

[VoltzElectrical]

Google surge arrestor or lightning protection, metal oxide varistor.

Fairplay Marvo, I've never come across that.

 

[Marvo]

If the IR test was at 250v and no higher it's fairly unlikely it's an MOV, the clamping voltages are usually higher than that unless they're the type sometimes used in telecommunications and RS232 and other comms systems.

 

[SPARTYKUS]

Yep never heard of a MOV

 

[VoltzElectrical]

Yep never heard of a MOV

not just me then Solo.

 

[guest119]

0.14 what, bannanas,ohms, megohms, pineapples?
There is no such thing as a dead short. Its a fault of negligible impedance that exists.

 

[Marvo]

Yep never heard of a MOV

not just me then Solo.

MOV's are used as lightning and surge protection all the way through the network from transmission lines to being internally installed in control panels and appliances. They come in a multitude of guises.
All these are MOV based protectors and they'll all give low IR reading with a megger tester set on a high test voltage.



Many appliances have an internal filter circuit PCB which has MOV's on it amongst other things.

 

[Lucien Nunes]

This is daft. We're 26 posts into a thread called "Insulation resistance of floodlights" and the OP still hasn't told us what the insulation resistance of his floodlight is. It could be anywhere between 0.14 ohms and 0.14 megohms, which is the same ratio as that between a pint of beer and 24 articulated tanker lorries of it.

 

[micknew]

Perhaps he's not a qualified sparks.

 

[Davetherave]

0.14 ohms

 

[HandySparks]

0.14 ohms

OK, how are you measuring this 0.14 ohms?
Is the floodlight connected to the supply cable while you're measuring?
Is it connected in parallel with several other lights?
Where exactly are you connecting your test leads to?
What's the Zs of the supply at the base of the lamp column?
What type of lamp is it?

 

[SparkyJoe]

I Might have had too much beer (Slow week) but should that not be 0.14 Meg ohms? 0.14 ohms is rather low lol

 

[Marvo]

......ested at 250V

0.14 ohms

Doesn't sound right, unless you paid a fortune for it I doubt your tester is capable of distinguishing such a low resistance on the 250v test range.

 

[HandySparks]

I Might have had too much beer (Slow week) but should that not be 0.14 Meg ohms? 0.14 ohms is rather low lol

Exactly. Hence asking for clarification from the OP. He says 0.14 ohms, which then raises a whole lot of additional questions to enable us to try and work out what's happening.

 

[Lucien Nunes]

0.14 ohms

Well if it's really 0.14 ohms L-E and the light works, the CPC must be O/C somewhere and there is a risk of exposed bits being live. If this is not obvious to you, I suggest studying a bit more about testing before undertaking this kind of work.

 

[PEG]

...I think he's gone to purchase a non-conductive ladder...:conehead:

 

[VoltzElectrical]

Not sure why he is testing IR on the cable drop. The light
works, leave it alone!

 

[dazza1981]

OK so you walked over to a random floodlight that was WORKING and thought hummmm im going to do an insulation resistance test on this working light????
WHY MATE ???
Alternatively if you are part of the electrical trainee Nerd Herd then leave the flood well alone and let it continue working normally as it is before you do F it up !!