IET logo
 
IET
Decrease font size
Increase font size
Topic Title: Insulation Resistance
Topic Summary: 500V fail and 250V pass
Created On: 21 June 2013 10:21 AM
Status: Post and Reply
Linear : Threading : Single : Branch
Search Topic Search Topic
Topic Tools Topic Tools
View similar topics View similar topics
View topic in raw text format. Print this topic.
 21 June 2013 10:21 AM
User is offline View Users Profile Print this message



tattyinengland

Posts: 782
Joined: 23 November 2006

Very basic question -

at 500V the UNIVERSAL IR test on a 6 way 3 phase DB fails at 0.35M Ohms.
at 250V the UNIVERSAL IR test is 55 Meg Ohms.

I have recommended a code 3 and am very reluctant to put unsatisfactory on the PIR for this small glitch..........some other code 3s but minor IMO. I think this is a satisfactory install, but for this small hook.......

Would you put unsatisfactory?

(I could ask the NIC, but the forum opens up so much more by way of opinion)
 21 June 2013 10:58 AM
User is offline View Users Profile Print this message



intrinsic4225B

Posts: 1623
Joined: 30 September 2004

Are you absolutely certain that you have disconnected all neon indicators or any equipment that might have 'surge protection'?
 21 June 2013 11:01 AM
User is offline View Users Profile Print this message



jcm256

Posts: 1858
Joined: 01 April 2006

Aggree. Could be you have some were in the circuits under test, there be a clamping device either a transient voltage suppression device (TVS) or VDR.

Are you not going to identify the circuit that causing the problem or is it an all in test. The worst thing about testing (if you are nor fixing the defects yourself) is the smart electrician coming behind you fixing faults. He will try catch you out, belittling your report

I could be wrong of course, but only trying to give you one possible cause..

Here is description of varistor

http://www.frankshospitalworks...g_course_varistor.html
 21 June 2013 11:46 AM
User is offline View Users Profile Print this message


Avatar for sparkiemike.
sparkiemike

Posts: 1537
Joined: 24 January 2008

Don't forget to look out for RCD socket outlets and RCD fused connection units.
 21 June 2013 05:26 PM
User is offline View Users Profile Print this message


Avatar for davezawadi.
davezawadi

Posts: 2640
Joined: 26 June 2002

This effect can be caused by discharge between live connections with inadequate spacing, indeed this is why testing is normally at a higher peak voltage than the supply. Can you easily isolate the problem to one circuit? It may be caused by faulty cables etc and needs to be investigated as this kind of fault can cause fires.

-------------------------
David
CEng etc, don't ask, its a result not a question!
 21 June 2013 06:28 PM
User is offline View Users Profile Print this message



peteTLM

Posts: 3141
Joined: 31 March 2005

ive had this before, it was fine at 250, zero at 500v. At the higher voltage, it was arching across from neutral to earth against a galv back box.

-------------------------
----------------------------------------
Lack of planning on your part doesn't make it an emergency on mine....

Every man has to know his limitations- Dirty Harry
 21 June 2013 06:51 PM
User is offline View Users Profile Print this message



Thripster

Posts: 639
Joined: 22 August 2006

Or break down of insulation?
 22 June 2013 10:33 AM
User is offline View Users Profile Print this message



tattyinengland

Posts: 782
Joined: 23 November 2006

Thank you for the replies; had I been less tired, I probably would not have posted the question. Glad I did though.

The EICR was carried out on a project that we did in Leamington Spa, where the open plan office area was halved and the remaining side (Served by it's own DB) was a dilapidations job. The part returned to the Landord was EICRd.
Statistics

See Also:



FuseTalk Standard Edition v3.2 - © 1999-2014 FuseTalk Inc. All rights reserved.