Discuss Zs and IR pitfalls in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net

Welcome to ElectriciansForums.net - The American Electrical Advice Forum
Head straight to the main forums to chat by click here:   American Electrical Advice Forum

Reaction score
2
Hi folks,

I'm still fairly new to testing having just passed my 2391 and just looking for a bit of advice if poss..

Quick bit of background - I'm carrying out EICRs on a wide range of single and 3 phase boards, inc. motors, lighting, power, micc, singles, swa etc. Any general pointers/tips would be greatly appreciated!

Regarding IR testing, other than delicate electronics, fluorescent ballasts etc. is there anything else you would be testing at 250V or LN-E? Or any pieces of kit you might ordinarily get a strange reading for? For example I came across a strange 30M Ohm reading for a mechanical thermostat the other day - is this normal?

Also regarding Zs measurements, I'll be testing lighting circuits where it's not practicable to be removing all lamps - this hasn't been an issue for fluorescent lighting circuits, but testing circuits with LED lamps in situ and energised has caused the Megger to trip, even on the no trip setting. Can anyone shed any light (no pun intended) on this?

Many thanks in advance!

Tom
 
with the LED luminaires, maybe wander lead and get a R2. then in conjunction with a calc. value for R1 (same as R2 if same size conductors), use Zs = Ze + ( R1+R2).
 
Just a thought ...
With traditional pendant lampholders etc, it's easy to remove (or not fit initially) the lamps and be able to do L-N, L-E, and N-E IR tests. Now there's so many lamp types where this isn't the case, I wonder how many people either IR test the reels of cable beforehand, or IR test each individual cable before connecting the luminaires ?
 
Regarding IR testing, other than delicate electronics, fluorescent ballasts etc. is there anything else you would be testing at 250V or LN-E?
For periodic inspection and testing I would only ever suggest testing between live conductors connected together to Earth. I would never test between live conductors unless specifically agreed to do so. I certainly wouldn't be recommending it.
 
Steady and consistent IR readings of around 0.03MΩ or 0.04MΩ (testing between L+N tied together, and earth) might well be an RCD spur or RCD socket.
 
A really useful thread. Gotta be more mis-conceptions about IR's than RCD and continuity combined. USB sockets and dimmers just adding to the confusion.
My query is:
Before a board change and with all RCD's & MCB's "off" I'll I.R. test the Live from the dead side of the breaker to Earth and Neutral having removed both from their respective bars.

Something I've always done but was suggested I'm wasting time removing both N and E. Personally speaking, I want a fault-free system before I remove the old board and inherit all the hidden issues.

What's yer thoughts guys?
 
A really useful thread. Gotta be more mis-conceptions about IR's than RCD and continuity combined. USB sockets and dimmers just adding to the confusion.
My query is:
Before a board change and with all RCD's & MCB's "off" I'll I.R. test the Live from the dead side of the breaker to Earth and Neutral having removed both from their respective bars.

Something I've always done but was suggested I'm wasting time removing both N and E. Personally speaking, I want a fault-free system before I remove the old board and inherit all the hidden issues.

What's yer thoughts guys?
Disconnecting the cpcs from the Earthing arrangements for the installation is a non-compliance with BS7671.
 
I remove N but leave E in the E bar - a circuit can have a fault to earth that isn't to it's own CPC. I find a L-N test of limited use for an installation that's already in use and doesn't have a known fault. More useful is linking L+N of a circuit, and testing between that and all other circuits in turn, looking for interconnections. Testing at 250v, with equipment in place and switched to on position, can help find borrowed neutrals etc.
 

Reply to Zs and IR pitfalls in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net

OFFICIAL SPONSORS

Electrical Goods - Electrical Tools - Brand Names Electrician Courses Green Electrical Goods PCB Way Electrical Goods - Electrical Tools - Brand Names Pushfit Wire Connectors Electric Underfloor Heating Electrician Courses
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc
This website was designed, optimised and is hosted by Untold Media. Operating under the name Untold Media since 2001.
Back
Top
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock