IR test whats the point?

[nick611]

what is the point of an IR test? yes i know its to show low risistance on cable insullation [its in the name] and that can lead to short circuit and fire risk, but with the protection we use now wont this show its self eventually. what do you tell a customer in a nursing home ? that his IR is a bit low and some time in the future he may get a problem. HE says when,and you say,i dont know,he says,what,and you say,i dont know. AM i the only one who thinks while IR testing with all the ******* hassle that goes with it. WHATS THE POINT

 

[malcolmsanford]

Is this a wind up?

 

[nick611]

Is this a wind up?

no its not, i am asking for your views,this is a forum. how many problems have you identified in advance through IR testing? and how did you overcome them.would you for instance replace a submain because of a low IR before it had caused any real problem.and how would you justify this to the person you wanted to pay for it?

 

[gamblor6]

i sometimes find low ir on lighting circuits n to e that some sparks had just put on a 60898, we.re putting 61009s on and without the ir test i would have no way of knowing if the rcbo would hold.

 

[malcolmsanford]

Sorry Nick but i'm suprised.

Ok IR a circuit on a CU change as many faults that hold in on a fuse/mcb will trip on RCD/RCBO

On a PIR it will give you an indication on an older installation that there can be a problems developing. So you will alter the time frame of the next PIR to say 5 tears or even less.

On an initial verication it will tell you if your circuit as been damaged. You may have first fixed the before someone put a nail through your cable, it will stop you energising the circuit.

Again On fault finding it will help.

 

[nick611]

yes i see but on a domestic 17 edition board the rcd will find any l-e and n-e faults and the mcb any l-n faults so on a piriodic why IR test given the time and hassle [disconecting this and that] it takes. just a thought

 

[telectrix]

why not just power it up and see if it goes bang.

 

[tony mc]

You are trying to identify any future problems with the wireing in the instalation and if the insulation is starting to deteriorate the customer needs to know. Like Malcolm has said the inspection time can be reduced to see if the problem is getting worse.

Low IR readings don't just indicate that the cable insulation is failing as it could be other issues like dampness getting into joint boxes under the floor etc.

If the IR reading on the whole instalation was low then I would be testing each cct to find out if one particular cct was bringing the readings down and try and locate the cause.

I am sure if you did locate a joint box full of condensation because it was lying on the ground and the readings were now more healthy the customer would be alot happier.

In a Nurseing home I am sure that the insurance company will have there say re the report and they won't be happy to rely on 17th edition boards they will be looking at your report making sure that the home is safe and what needs to be done to keep it that way IMO.

 

[ezzzekiel]

not many other ways to locate a fault either

 

[telectrix]

not many other ways to locate a fault either

i find an uninsulated screwdriver is best for finding insulation faults. or a couple of horses........

 

[oldtimer]

Look at it this way years ago people said you should rewire every 30 years yes some would say but we have new type pvc covered copper cables and depending on its condition it could last years longer so just like a car on a mot test the garage tests the emissions and as they gradually get worse you get a warning to either repair or replace the engine. A PIR as far as I am concerned is a MOT for a buildings electrics and the IR test is telling you keep an eye on this you may have to repair/replace in the future and as for "why not let the RCD board tell you when there is a aproblem" the whole reason of IR testing is to prevent this from happening if you really want to question testing then point it in the direction of PAT testing.

Mind you our new primeminister says he is going to make it easier for small business by doing away with "crazy regulations" so heres hoping he might even get I&T sorted out ie 2 hours for a PIR but somehow me does not think so.

 

[mayfair]

You been reading the new amendments to the 17th, bet thats there advice

why not just power it up and see if it goes bang.

 

[mayfair]

sorry m8 but your wrong thats the test for rcds

i find an uninsulated screwdriver is best for finding insulation faults. or a couple of horses........

 

[telectrix]

sorry m8 but your wrong thats the test for rcds

what, the driver or the horses?

 

[mayfair]

Horses you see how many ms it takes for them to shout naaaaaaaaaaa thats for 1x ie 1 horse its different for half a horse and 5x ie 5 horses

what, the driver or the horses?

 

[telectrix]

5 horse. thats the bhp of my van.

 

[Deleted member 9648]

If you cant be bothered to IR test how many other tests cant you be bothered to do?

 

[telectrix]

he's just been offered a job at newbury.

 

[mayfair]

stuff it let em fry lol

If you cant be bothered to IR test how many other tests cant you be bothered to do?

 

[nickblake]

Old timer ,Malcome ,and tony MC's comments are spot on , Ask the same question to a family who's house has just burnt down , ill give you a couple of examples of why we do it , Recent fault ,on a post i put up RCD tripping at 10.30 every friday in a pub , switch it back on fine not problems , testing the circuit indicated a low IR between L and N , the fault turned out to be a rat chewed cable getting damp due to condensation could easily have smoldered and caused a fire , 2nd example MCB tripping Reset all ok, every so often it tripped ,testing the circuit showed a low insulation reading between all conductors disconnected all lights and just ended up with open cables still low IR, fault was located to a covered joint in a plaster board ceiling ,it had been plastered over , this had caught fire but due to the wood being chip board it extiguished its self if it was wood then there would have been a major fire , this is why we do IR tests as well as has been mentioned to monitor the condition of the installation befor it causes major problems , that could risk lives . below are some picks of the fault mentioned above where the wood caught fire look at the picture with the square hole cut out you can see the burnt wood ,That is why we do IR tests simple as !

 

[malcolmsanford]

Top class post Nick .................you and the pictures say it all mate.

 

[simpson93]

what is the point of an IR test? yes i know its to show low risistance on cable insullation [its in the name] and that can lead to short circuit and fire risk, but with the protection we use now wont this show its self eventually. what do you tell a customer in a nursing home ? that his IR is a bit low and some time in the future he may get a problem. HE says when,and you say,i dont know,he says,what,and you say,i dont know. AM i the only one who thinks while IR testing with all the ******* hassle that goes with it. WHATS THE POINT

with the protection we have now why test at all?
what your basicly saying mate is why dont you just bang test it?

 

[telectrix]

nice pics, nick.hope you stripped it back well and used wagos before platering it back in.

 

[nickblake]

nice pics, nick.hope you stripped it back well and used wagos before platering it back in.

The joint in the picture was twisted to gether with selotape over it , it now has a ashly J501 on it got a 2 gang blanl plate and glued and scred it to the ceiling with some intermesant sealant ,here's a pic of the other light twisted together , what we found whilst trying to locate the fault

 

[SirKit Breaker]

There are several reasons for IR testing, aside form all the previous answers including Telectrix

When the IR starts to get low it will induce voltage/current into the CPC. Once it gets down to about 1meg it can start to have an effect on the circuit protection to the point that enough current and voltage will be induced for the RCD to see it and start tripping off, and the safe touch voltage can be reached. Hence 1 meg is deemed to be the minimum IR value for domestic 230v circuits, and investigation is advised under 2 meg.

Widdler teaches 2391, he can probably explain it better than me.

Cheers..........Howard

 

[mart1711]

Surprised a contractor asked the initial question to be honest. When RCD's first became widely available, i think (by the manufacturers propoganda somewhat) they were heralded as the easy fit life saviving must have electrical item, and surpassed any other measures of protection and quality installation. All the tests are important and for a reason. I went to look at a fault on a lighting circuit in a local corner shop just the other week. The owners had added bits a pieces of their own over time with choc blocks and pvc tape etc. A fault had arrisen on the circuit (protected by rewireable fuse) and caused the cables to overheat and smoulder, then after creating a short pop the fuse. I showed the problem to the owner and how it was caused, to which i got this EXACT response "Can we just stick an RCD on it??"

 

[oldtimer]

(by the manufacturers propoganda somewhat) actually Mart RCDs were introduced to get us in line with Europe (yep that old chestnut) so the only thing left is the ring main, the 13 amp socket and to get the light switch to work when up not down.

Mind you the more I am reading this thread the more I am amazed why the question was asked in the first place

 

[bugsy]

Yea lets stop doing I/R oh sod it why bother with continuity - i will either work or not , thinking about it anybody wanna a buy fluke MFT ,Im gonna get a socket and see a nice neon and volt stick - what a saving

 

[nickblake]

RCD's are not the be all and end all they fail and regularly too , i may be a bit old school , but i do like to sleep at night , when i carried out my 2391 the routing of testing was drummed into you , i will always do my ring continuitys R1 & R2 tests and IR followed by the Zs , then if applicable the RCD tests , i will test the R1 & R2 tests at several points , just to confirm the polarity is contiuose ,What is the point of testing if you skip half the tests , Testing is probably the most important part of electrical work as it identifies errors and deterioration of wiring and accessories , i know it can be as boring as hell some times but its the job , where has the passion gone ,i supose im lucky and self employed so i take as long as i like and if it takes all day or all week then thats what it takes

 

[lloyd1980]

had a nightmare of fault today and couldnt have sorted it it without the IR tests

domestic house
old Wylex 3 phase disboard / obsolete (spelling?) cant get parts.
(3 phase board, single phase supply, phases linked out under main switch - its a big house)
guy wanted work in bathroom wiring more spots and a fan and a new whirlpool bath so wanted supply for the motor.
had to provide RCBO protection as bathroom on lighting and then up ring as motor supply is spurred of it via S/F spur.

Split the tails and fed new square d 2 way dis board , RCBO 10a for lighting and 32a for ring.
Ring held, lighting sadly did not so left in on the old MCB untill i could get back...................

came back 3 days leter...... the day from hell insued
removed every light/pendant /switch and spread all the conductors/ cpc's, went to each light and IR'ed each cable to find the culprit, found it after an hour or so. then had the pleasure of crawling face first through the loft fibreglass in a 2ft gap tracing the duf cable.
after countless coughing fits , itchy gritty eyeballs and a couple of hissy fits I found the cable was infact the main that came from the board and was plastered into the wall - bad times
they had 2 lighting ccts upstairs so in end I tested the other to make sure clear for an RCBO, I then tapped into it making 1 complete cct for upstairs lighting
re-introduced the rooms 1 by 1 and ok untill last room when RCBO started going bananas again. then found what can only be described as a 'nest' of JB's like ive never seen before - I spent all afternoon IR'ing all the cables and making them all off properly in new JB's this corrected the fault and the RCBO has now held and the readings are good.

So could I have got away without the IR test? .....no chance. it saved my --- and the customers window as by the end of the day I was about ready to put my head through it