Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Locked Locked
  • Replies 33 replies
  • Subscribers 31 subscribers
  • Views 7484 views
  • Users 0 members are here
Options
You may also be interested in
This discussion is locked.
You cannot post a reply to this discussion. If you have a question start a new discussion

EICR and IR Testing

Former Community Member
Former Community Member
Oh the bane of IR testing on EICRs

Now its just impracticle to disconnect all loads to carry out IR testing, I think everyone can agree on that. And that Phase and Neutral are connected then tested to earth.


This is what I do, and then test @250V as to avoid damaging any equipment in the installation. And unless the IR value was <.5 Meg, would not bother me. What BS7671 states, but BS7671 is maybe somewhat unclear in that if that voltage (250V) was used then .5meg value should used, but that value should only be used on SELV, and PELV. Now experience also tells me that even if you had a return 0.0, and then did Kohms by using the ohms setting, even values of 100Kohms are fine. (Actually can be much lower than this) and we are pretty clear that its not the cable reurning these values.


So question is when doing an EICR @ 250V, at what point would you recommend an FI? For me the value would have to be <.5Meg
Parents
  • 0
    I suggest you are saying (and  I agree) a single figure is always a compromise, and rather depends what issues we are trying to detect.

    A small flat wired in PVC  where we can be sure no wiring goes outdoors should pass a higher limit.

    Large rambling installations in 'pyro' wire such as are often found in churches and other old public buildings, may well read low on the megohms test, and yet have no real fault - it is just a feature of mineral insulated cables. Indeed if enthusiastic one can test the circuit in sections and find nothing.

    Arguably looming problems with failing equipment or the wrong kind of load, that may  soon give tripping issues with RCDs are better found with a clamp meter with the system energised.


    What is of interest is the sort of fault that if it were all in one place would be hot enough to cause a fire - and that is probably a dissipation of a watt or two - so even the 100k figure (2.3mA on 230v,  about half a watt dissipation) is no more heat than a small torch bulb of the kind not used in modern torches, and worse could be tolerated.


    Your approach may not be the official technique, I suspect it is just fine in reality, and a lot better than a row of 'lim' or ''n/a"

Reply
  • 0
    I suggest you are saying (and  I agree) a single figure is always a compromise, and rather depends what issues we are trying to detect.

    A small flat wired in PVC  where we can be sure no wiring goes outdoors should pass a higher limit.

    Large rambling installations in 'pyro' wire such as are often found in churches and other old public buildings, may well read low on the megohms test, and yet have no real fault - it is just a feature of mineral insulated cables. Indeed if enthusiastic one can test the circuit in sections and find nothing.

    Arguably looming problems with failing equipment or the wrong kind of load, that may  soon give tripping issues with RCDs are better found with a clamp meter with the system energised.


    What is of interest is the sort of fault that if it were all in one place would be hot enough to cause a fire - and that is probably a dissipation of a watt or two - so even the 100k figure (2.3mA on 230v,  about half a watt dissipation) is no more heat than a small torch bulb of the kind not used in modern torches, and worse could be tolerated.


    Your approach may not be the official technique, I suspect it is just fine in reality, and a lot better than a row of 'lim' or ''n/a"

Children
No Data

Join us to get the best from IET EngX.

Joining EngX lets you personalise your experience so you stay up to date on the topics that interest you, plus you’ll be able to make connections who are looking to collaborate, exchange ideas and more.

Join us Not now

Community Rules & Guidelines