R1+R2 your thoughts please

[leep82]

Hi all, First time poster here so go easy,

Firstly, i am currently working on a hospital refurb for my company. The job is nearing the end and is currently at the testing stage. Having passed my 2391 over 12 months ago and not having much site experience i put myself forward to test the job. I felt confident in what i was doing and as its my name going on the cert i was being as thorough as possible. This got me into a disscussion with a colleague who had tested the ward opposite. When doing my R1+R2 test i was told to do it at every point on the circuit, and so proceeded to do so at all switches aswell as lighting points, to which my colleague replied " i didnt bother ". I argued to him that what if the c.p.c's had been twisted together at the switch and come free from the terminal? I would still get a reading at my lighting point and proceed to think that everything was ok, when in effect i could have an exposed conductive part that is not bonded. I was just wondering what peoples thouhgts are on this.

Secondly and again whilst carrying out a R1+R2 test at a switch which had two supplys present i noticed only one c.p.c. My test results were fine as i wasnt removing my c.p.c at the MET, instead linking the MET and each individual MCB. This though got me thinking that surely it would be better to have two seperate c.p.c's at the switch one from each circuit. If not only for testing purposes but for any future additions or alterations. I did not install the job myself so dont know if this was done delibrately or sombody has just made a mistake when wiring. Again just wondering what your thoughts are on this.

Thanks

 

[sparks1973]

its an INITIAL VEREFICATION yes?....if so then a value of R1+R2 should be taken at EVERY POINT on the circuit.....furthest point for EICR testing....the same goes for sequence of tests...on an initial verefication the sequence of tests should be followed...not the case for EICR testing....

 

[johnboy6083]

On initial verifications, i also test R1+Rn at all points, even though itas not recorded. Is it just me who tests IR between all other lines and the line of the circuit under test?

 

[johnboy6083]

As for the CPC at the switch, its perfectly fine to use one CPC from one circuit to bond the switch. In fact it would be within regs to use that one CPC throughout all circuits, provided it met the requirements of the worst case.

 

[SYKRAPS]

Why are you testing some one elses install? Surely it is much easier and more cost effective for the guy who carried out the install to test his/her own work?

 

[sparks1973]

On initial verifications, i also test R1+Rn at all points, even though itas not recorded. Is it just me who tests IR between all other lines and the line of the circuit under test?

well its about polarity John...

 

[Jimmy Boy]

What if the CPC's are twisted together in a plastic back box or PB box ? You never mentioned this ..isn't it about sampling on a EICR or PIR ? Or a full verification on a new install ?...Use a wander lead I'd you want to prove an E at point I do !

J

 

[johnboy6083]

well its about polarity John...

the amount of people who i see just testing R1+R2 is mad. The neutral could be disconnected/ high resistance anywhere along the circuit. I try to be thourough when testing, as its my name on the ticket, and if anyone gets hurt,or property damage, ill be the one who gets the awkward questions.

 

[Brightspark2]

Why are you testing some one elses install? Surely it is much easier and more cost effective for the guy who carried out the install to test his/her own work?

Its a hospital refurbishment so medium to large job, not just one person would of done the install. One circuit could of had different people working on it.

Its how it's done on medium/large installs. Some companies have a dedicated test and inspection person/team.

Sent from my Xperia S using next doors WIFI

 

[the oracle]

I have to say that I find it very heartening to hear another guy saying that he tests R1+Rn on a radial circuit (e.g. lighting, radial socket outlets etc ). It is an all too common problem with radials that a neutral connection somewhere in the circuit is not carried out properly, and hence when the circuit is energised half of it does not work. This is a common scenario that I 'manifest' when I deliver Inspection and Testing training courses, and I instruct students to carry out an R1 + Rn test on all radial circuits, it only takes a few seconds after all, and can save hours of head-scratching later! Also, I ought to mention that the policy of carrying out R1 + R2 tests at ALL points on a lighting circuit has other benefits, i.e. the testing of functional switches, and of course, Polarity. One final word, if you have a radial socket outlet you absolutely MUST do both tests, R1+R2 plus R1+Rn otherwise you cannot ensure polarity, the line and cpc could be crossed over, stranger things can happen! (You could of course verify polarity visually, if you want to drop every socket outlet!).

 

[Billythekid]

Why are you testing some one elses install? Surely it is much easier and more cost effective for the guy who carried out the install to test his/her own work?

This is common practice for larger installs, would you let any Tom, Dick, and Harry loose with a test kit?
Larger projects often have a high turnover of labour, so it's quite likely that the person who has done the install isn't there by the time it comes to testing (probably a good thing tbh, or we'd lose a few good sparks to Her Majesty's B&B :banghead. Also when filling out test sheets you'd need a signature for every cct, this is why it's best to have few 'trusted' testers. Some guys refuse to test other individuals work, my defence is "If you've tested it properly, then there should be no reason to doubt the install". Sadly time/cost constraints have made this very difficult, and for that i sympathise!

 

[leep82]

Thats exactly how it is Brightspark. I'm happy enough with only having the one c.p.c at the switch containing two circuits. I was more leaning towards the idea that surely its better two have a c.p.c from each circuit at the switch, good practice maybe, but surely better for testing purposes and any future alterations/additions.

 

[the oracle]

Just a note about the cpc issue. I would recommend providing a separate cpc for each circuit, and I know this means taking two lots of cpc down to the switch, but I have a good reason for doing this. Should the customer, at a future time, wish to have one of the lighting circuits extended, and in this case, the one with the cpc at the switches. It is not unrealistic to suspect that, having isolated the circuit being worked on, the electrician may then remove the cpc from the MET at the board to complete an R1+R2, continuity of protective conductor test, while filling out the Minor Works form. This would now leave the switch plate, and possibly other parts of the second circuit without a cpc, whilst still being live. Also, if additions are carried out within the circuit, the existing cpc could be 'broken' while additional cabling is connected. Again this would leave a live circuit without a cpc. You hint at this in your question, and as with all things electrical, this is one of those 'interpretation' issues. In these cases I normally discard the 'Regs' and refer back to the EAWR 1989, it is down to us to ensure safety AT ALL TIMES, hence I would install a cpc for every individual circuit.

 

[vjsmarwick]

Mmmm let me see you say a separate earth for each circuit they are common at the board and common at the switch so your going to mark them either end ? Or test them to know which one your disconnecting ? Say you have a 12 grid plate four circuits three switches on each 4 earths ? Making an awful lot of extra work and I am not on big jobs anymore but we uses to run an earth strip on the trunking and all earths connected to that or does that not happen any more ?

 

[baazab]

sorry to say this ,takeing work like this and cant even do r1 & r2 ,and you said its hospital ,have fun, takeing jobs like this its not a joke