Lighting in the loft

[SUNRAY]

Thanks - that will be interesting.

On the face of it, any measurable resistance between the chuck and live parts from which it is meant to be separated by "double or reinforced insulation" is rather a worry. Even at 1000V, one would not expect to be able to measure a resistance between two parts even if separated only by a single layer of very thin/flimsy (hence certainly not 'reinforced') insulation.

For what it's worth, I've just measured 4 Class II power tools picked at random (2 drills, one biscuit jointer and one mitre saw), all well-used and relatively filthy, and in all cases got ">1000 MΩ" at 1000V from the metal chuck (or other metal 'working parts') to both N and L (with and without the tool switched 'on'). I'll therefore be interested to hear what you find.

Kind Regards, John

You have to switch the machine on, This is one area which is often missed by many PATers.

 

[JohnW2]

You have to switch the machine on, This is one area which is often missed by many PATers.

Indeed so - that's why ...

.... in all cases got ">1000 MΩ" at 1000V from the metal chuck (or other metal 'working parts') to both N and L (with and without the tool switched 'on').

Kind Regards, John

 

[SUNRAY]

This drill was taken on site where they insisted on PATing anything electrical taken in. It passed, however first pull of thebutton tripped their RCD. It has been on the shelf in the shed for 2 or 3 years since awaiting repair. IIRC the reading with a megger was significantly rower resistance than this. In case it's not obvious the reading is 4.74KΩ

 

[JohnW2]

This drill was taken on site where they insisted on PATing anything electrical taken in. It passed, however first pull of thebutton tripped their RCD. It has been on the shelf in the shed for 2 or 3 years since awaiting repair. IIRC the reading with a megger was significantly rower resistance than this. In case it's not obvious the reading is 4.74KΩ

That's surely just "plain faulty".

I don't know about your "megger", but nothing I have for IR measurement will even attempt to measure a resistance remotely as low as that. My Fluke MFT would indicate what voltage it had had to reduce to (to limit current), and that would almost certainly have been (displayed as) "0V" with your drill !

Kind Regards, John

 

[SUNRAY]

That's surely just "plain faulty".

I don't know about your "megger", but nothing I have for IR measurement will even attempt to measure a resistance remotely as low as that. My Fluke MFT would indicate what voltage it had had to reduce to (to limit current), and that would almost certainly have been (displayed as) "0V" with your drill !

Kind Regards, John

Oh yes absolutely it's faulty but I do find powertools, and particularly jigsaws, do seem to have this issue with age, however it's certainly very unusual to drop that low. The irony is I'd changed the cable not long before this and therefore would have tested it, so the failure was fairly abrupt.

 

[JohnW2]

Oh yes absolutely it's faulty but I do find powertools, and particularly jigsaws, do seem to have this issue with age, however it's certainly very unusual to drop that low.

I don't know about you, but I find it quite difficult to think of many ways in which such a fault could arise - and I wouldn't have thought that any of the things I can think of would be even remotely common.

Kind Regards, John

 

[SUNRAY]

I don't know about you, but I find it quite difficult to think of many ways in which such a fault could arise - and I wouldn't have thought that any of the things I can think of would be even remotely common.

Kind Regards, John

They fill up with crap.

 

[JohnW2]

They fill up with crap.

Sure but, at least in my experience, little of that crap is in the vicinity of any uninsulated live parts, and the path from any which existed to an (allegedly 'isolated') metal chuck would be pretty lengthy and tortuous - at least, in a drill. Also, the 'crap' would frequently (not always) be pretty non-conductive.

Kind Regards, John

 

[SUNRAY]

Sure but, at least in my experience, little of that crap is in the vicinity of any uninsulated live parts, and the path from any which existed to an (allegedly 'isolated') metal chuck would be pretty lengthy and tortuous - at least, in a drill. Also, the 'crap' would frequently (not always) be pretty non-conductive.

Kind Regards, John

In my experience the cooling fan blows or sucks the crap directly on the motor and gearbox, ie; the two main sources of heat.

That crap also contains, amongst other things, the carbon brush and copper commutator filings.

Additionally the gearbox is usually packed with grease and suspends any filings which, if conductive, can provide an electrical path between input and output shafts.

Ultimately any form of insulation can fail and having not opened that particular drill I've not attempted to establish the reason.

 

[BrettRogersUK]

Hi Everyone,

Quick update on lighting in the loft. I've installed the light but it is strobing when the switch is switched on.

I've the source from the bathroom light but I think I've used the bathroom light switch wire for the power source. When the bathroom light is switched on, the loft light won't switch on. When the bathroom light is off, the light in the loft comes on when switched but is strobing. It's not a steady light.

What I plan to do is take the light down and wire a plug into it and plug it into a socket to see if it lights properly. If not then I know there's a problem with the light itself.

There are about 4 grey T&E wires going to the light fitting. What may be the problem I've encountered.

Regards,

Brett

 

[RF Lighting]

It sounds like you have wired your loft light to the live and switched live cable for the bathroom light switch so your light is effectively in series with the bathroom light when it is switched on and the bathroom light is off like so.

You need to locate one of the feed cables and attach you new wiring to there instead.