Bad IR on kitchen ring final

[DomSparky]

Hello guys I just wanted to know if anyone has had the problem I had today while testing...

Firstly I went around the whole kitchen unplugging everything and switching of sfcu's and removing fuse carriers from fcu's before doing testing when testing between L&N I had a reading of 0.00Megaohms so guessed I had left something plugged in which I didn't so I started fault finding removing sockets etc anyway it turns out when I removed the fcu feeding the boiler my IR reading was perfect so I can only assume the fcu must have something weird going on with it I can only guess maybe when removing the fuse it isolates the Line conductor but the Neutral conductor remains connected through to the boilers circuitry giving the bad IR reading?

 

[Murdoch]

To isolate properly you need to switch live and neutral, so pulling the fuse from a fused spur isn’t good enough - as your readings show 

never fit single pole switches or sockets on socket circuits is my advice - you can buy them but don’t 

 

[kerching]

Was it a switched fuse connection was it just fused unit?

 

[DomSparky]

Thanks Murdoch that's what I was thinking you learn something everyday in this job never had this problem in the past I guess all sfcu's etc in the past must have been double poled.

I would never install single pole I don't see the point if your going to isolate it has to be done properly through both conductors 

 

[DomSparky]

Hi Kerching it was just a fused unit so guessing it only isolates the line when fuse is removed. The boilers circuitry must have affected the IR reading through the Neutral. In the past this has never been a problem but then it's all down to individual boilers different makes etc affect IR reading differently.

 

[Sharpend]

What voltage did you use for this test? 

 

[Murdoch]

Thanks Murdoch that's what I was thinking you learn something everyday in this job never had this problem in the past I guess all sfcu's etc in the past must have been double poled.

I would never install single pole I don't see the point if your going to isolate it has to be done properly through both conductors 

The most common SP isolator is the one for the house alarm .......... if you can find it

 

[Bruspark]

IMHO Best to avoid higher voltage (500+) L to N insulation testing on a ‘populated’ circuit .

At best the results may be confusing and you risk blame for the cunningly unfused spur-ed Chinese garden floodlight not working later...

 

[Murdoch]

IMHO Best to avoid higher voltage (500+) L to N insulation testing on a ‘populated’ circuit .

At best the results may be confusing and you risk blame for the cunningly unfused spur-ed Chinese garden floodlight not working later...

Always test at 250 first!

 

[SPECIAL LOCATION]

Always test at 250 first!

100% before doing anything @ 500v  :Salute

Personally I always test with continuity a check first.....

To double check for any bleedin' obvious appliances still plugged in & switched on!

(or lights or extractor fans etc on lighting circuits)

Not uncommon to find a reading of <1k which normally means an appliance still connected..

(TV amp in the loft, etc..)

Then IR @ 250v..  where readings around 2.5Meg to 2.7Meg are common values though neon indicators..

Both of which can give you a hint of what to look for on a quick walk around the circuit to isolate any bits still connected.

Guinness