Distro PAT test |
Post Reply |
Author | |
doober
Young Croc Joined: 03 January 2006 Location: Cornwall UK Status: Offline Points: 1118 |
Post Options
Thanks(0)
Posted: 20 June 2019 at 3:00pm |
I've got some amp rack distro's, 32a in and loop out, powercon and IEC outputs.
I tried testing them as class 1 appliance and as mains lead. Both of these fail on insulation resistance due to the neon indicators for incoming mains. These are wired L-N (green for live present), L-E (green for earth present), and N-E (red for bad/wrong dangerness). This is of course failing due to the neons linking live and neutral to earth and lowering the measured resistance. Earth bond and continuity are well within limits, as is leakage. What do I do? Thanks |
|
Blahblahblah
|
|
imageoven
Old Croc Joined: 28 March 2007 Location: Scotland Status: Offline Points: 2186 |
Post Options
Thanks(0)
|
Disconnect neon for test, then reconnect. You may find there is a bullet connector on the cable for this reason, or a fuse.
|
|
Keep pushing on, things are gonna get better.
|
|
kedwardsleisure
Old Croc Joined: 20 January 2009 Location: Staffordshire Status: Offline Points: 4938 |
Post Options
Thanks(0)
|
if it fails a pat test until you disconnect something, then you really just connect back the thing that's making it fail, is it really a pass?
I'd ditch those neons. Even with a lost earth they'll probably glow in use due to natural earth leak paths through whatever the rack's supplying. |
|
Kevin
North Staffordshire |
|
imageoven
Old Croc Joined: 28 March 2007 Location: Scotland Status: Offline Points: 2186 |
Post Options
Thanks(0)
|
Thats a fair point, but the distro is designed with the neons in place so you could argue that the test limit should whatever leakage they allow. Obviously this is then a fairly pointless measurement. Removing them from the circuit gives a useful measurement to determin if the insulation is breaking down or not.
|
|
Keep pushing on, things are gonna get better.
|
|
godathunder
Old Croc Joined: 19 July 2004 Location: wicklow Status: Offline Points: 1833 |
Post Options
Thanks(0)
|
Ive often seen the warning neons in distros fitted with a switch to remove them from circuit so they can be used to give a quick visual indication of the supply when first connected then removed from circuit when the distro is actually in use.
the obvious problem with this setup, however, being that the warning system has to be physically turned on by the user and doesnt automatically show any problems
|
|
LOUDER THAN LOUD
|
|
doober
Young Croc Joined: 03 January 2006 Location: Cornwall UK Status: Offline Points: 1118 |
Post Options
Thanks(0)
|
Some very good points there chaps. I've decided to fit a momentary push switch to the earth side of the neons. This means I will always have the L-N neon showing 'power on', and can push the button to check neutral and earth when connecting the racks. The slight drawback here is that I won't know if there are some horrific problems like live and earth swapped in the supply until I've touched the (possibly live) rack... I've never found a venue that dodgy though. Yet...
|
|
Blahblahblah
|
|
imageoven
Old Croc Joined: 28 March 2007 Location: Scotland Status: Offline Points: 2186 |
Post Options
Thanks(0)
|
"meter your mains" A martindale EZ150 type tester will tell you if your supply is correctly wired and if your earth loop resistance is reasonably low. Plug it into the wall supply when you arrive and into your final circuit sockets when you've finished constructing your temporary distribution.
|
|
Keep pushing on, things are gonna get better.
|
|
kedwardsleisure
Old Croc Joined: 20 January 2009 Location: Staffordshire Status: Offline Points: 4938 |
Post Options
Thanks(0)
|
Years ago I had to do a job for the local council who had condemned a batch of a school's lab equipment: power supplies which had an 'earth check' neon between live and earth. I had to remove the neons before they would allow them back into the school.
One of the problems with permanently connected neons is that there's the possibility of the resistor overheating and carbonising, causing a short. It's rare, but I have seen it several times in my career. |
|
Kevin
North Staffordshire |
|
snowflake
Old Croc Joined: 29 December 2004 Location: Bristol Status: Offline Points: 3118 |
Post Options
Thanks(0)
|
noticed the green neon on my distro wasn't lit the other day. coincidentally we had just had some work done on our electrics so I checked everything was earthed properly and began to suspect that the green indicator had failed. Removed it today and that is indeed the problem.
Looking for a replacement I noticed on one manufacturer's spec sheet that they are rated for 20,000 hours except the green which is rated for only 5,000 hours. Not sure why this is - I always assumed the colour came from the plastic lens and the insides were identical. As I have the lid off thought I might as well replace all three at once and to avoid the green I'm going to use yellow, orange, and flashing red. |
|
snowflake
Old Croc Joined: 29 December 2004 Location: Bristol Status: Offline Points: 3118 |
Post Options
Thanks(0)
|
going back to the OP - PAT test insulation resistance is minimum 240kohms which means max lamp current of 1mA. Camdenboss do a lamp which is only 800uA so that alone shouldn't fail the test. But couldn't you just add a resistor/diode in series - lamp will still glow just not as brightly.
|
|
Boxes-R-Blue
Registered User Joined: 11 December 2018 Status: Offline Points: 147 |
Post Options
Thanks(0)
|
I'd probably use a proper MFT not a PAT device....
testing a distro isn't tricky, bang PSC/PFC on all lines, if they are good it won't catch fire... Insulation wise, who really cares, @ 32A it MUST be fed off a 30/30 RCD so if it is truly hosed it will trip the RCD and TBH if you can't interpret the readings of a device testing a neon in circuit, should you really be testing anything? |
|
Kinda Been there, Kinda done that, YOU COULDN'T handle my bar bill!
|
|
Post Reply | |
Tweet |
Forum Jump | Forum Permissions You cannot post new topics in this forum You cannot reply to topics in this forum You cannot delete your posts in this forum You cannot edit your posts in this forum You cannot create polls in this forum You cannot vote in polls in this forum |