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

 

[leep82]

baazab are you a moron? Who said I can't do a R1+R2, certainly not me. I was asking for people opinions rather than there advice, and low and behold there seems to be a mixed bag, fancy that! I also suggest you start using proper grammar sometime soon.

 

[trev]

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

Be very careful who or what you criticise, I have a long memory.
Tell you what Baazab, erase that post and say sorry to the nice man and you might find that my memory isn't so long after all

 

[the oracle]

I did not notice any mention of installation method, steel conduit/trunking or plastic? so I did not consider relying on earthing from the containment system, which in itself is a method less used these days. A more common method is individual cpc's, and yes I do identify individual cables with cable markers, a little extra work to keep safe has never been a problem. But I would be interested to know how many firms/installers do still install steel containment systems and utilise them as a 'common cpc' for all circuits. It is still an approved method (trunking and conduit factors are given in BS7671), though not one commonly taught at colleges nowadays. When I first started out this method was 'the norm', but sometime over the years we started introducing individual cpc's for each circuit, hence the steel containment system was reduced to a 'parallel path'. I would welcome any feedback from guys that are still installing steel conduit and trunking without running separate cpc's through the system. If it is more common and popular than I thought, I might consider bringing it back into the practical syllabus at college.

 

[trev]

I used the method in the plant room of a school not so long ago Oracle. Steel containment all over the place which was wired in singles, installed and tested, everything was fine. Idiot architect came in for an inspection and told me to run CPCs, I wasn't too fussed as it was another day's pay for me.
There's a lot that don't want to understand.

 

[johnboy6083]

At work we install seperate CPC's but on my own work, I have no probs using containment as CPC. I don't often get the oppurtunity to install steel containment on private work though.
I often work on panels where the switchgear itself is used to distribute the CPC though

 

[leep82]

sorry should of said steel trunking /conduit installation although the vast majority of the containment is existing. As some of the containment is not accessible, it's hard to say what sort of state it was installed in however many years ago. So i tend to rule out any reliance on that as an effective earth.

 

[vjsmarwick]

Sorry it was me that brought up the trunking but I did say I have not been on major jobs like that for a long time now so I was just curious as to the script now sorry for digressing.

 

[the oracle]

That was, as far as I am aware, one of the main catalysts behind the use of additional cpc's, the fact that not all conduit joints were nice and tight and trunking fittings were less than competently fitted. So now the containment is mainly a system of mechanical protection for cables, albeit one that can provide a parallel earth path of some degree, depending on how good the installer was. Years ago we were instructed to really tighten conduit boxes onto conduit, if the box was not 'flat' on the wall you put a bit more thread on and got it perfect, or you got your backside kicked!. Many of the guys I talk to now say they just slacken them off a touch now to get the box flat to the wall ! (Check out Reg. 543.3.6!). Of course, Reg. 543.2.1 allows for the use of solid metal conduit or trunking as a protective conductor, and Reg 543.2.7 states that the earth terminal of each accessory must be connected by a separate protective conductor to an earth terminal incorporated in the enclosure. I think the overriding factor has got to be is it adequate, is it safe, and does it comply! If we can answer yes, in all circumstances, then OK.

 

[trev]

Many of the guys I talk to now say they just slacken them off a touch now to get the box flat to the wall

I'd have gotten my arse kicked so bad if I'd even suggested that as an apprentice, yeah it's a quick fix but it's not the right fix.
The words "electrically and mechanically sound" are not that hard to attain.
Oracle, is pyro still taught these days?

 

[the oracle]

WE do 'try' to cover the installation of 'pyro', or MICC cable, but it seems that it is being skipped over by many lecturers (maybe because they are not confident with it?). When I have enquired from students over the last few years, it seems that only a few get to try MICC termination in their practicals in the workshop. It is no longer in the AM2, the cable types covered there are PVC/PVC twin & cpc, PVC singles in trunking/conduit, SWA, FP200, and SY cable. I have not taught the practical installation sessions on the 2330 for the last four years, as they are part of the Level 2 course, and I have only been teaching at Level 3 and above. However at my own training centre, I do offer a 'cable termination' workshop, and one of the types of cable I demonstrate and train students on is MICC. I still believe it has a place in electrical installations, not just because of its superior performance under extreme thermal conditions, but also for use in 'architecturally sensitive' properties, i.e. what better to use if you need to run a cable up some stone-work etc in a church or stately home??

 

[vjsmarwick]

Awww I think there is a misunderstanding what we used to do was install the trunking all the way through the building then pop rivet a solid copper tape along the full length of the trunking and run an earth wire in the actual conduit from the fitting to the copper tape so even if the trunking became loose there was no loss of connection the copper tape ran all the way back to the main board saved miles of earth wire when wiring schools lighthouses etc etc

 

[sparks1973]

WE do 'try' to cover the installation of 'pyro', or MICC cable, but it seems that it is being skipped over by many lecturers (maybe because they are not confident with it?). When I have enquired from students over the last few years, it seems that only a few get to try MICC termination in their practicals in the workshop. It is no longer in the AM2, the cable types covered there are PVC/PVC twin & cpc, PVC singles in trunking/conduit, SWA, FP200, and SY cable. I have not taught the practical installation sessions on the 2330 for the last four years, as they are part of the Level 2 course, and I have only been teaching at Level 3 and above. However at my own training centre, I do offer a 'cable termination' workshop, and one of the types of cable I demonstrate and train students on is MICC. I still believe it has a place in electrical installations, not just because of its superior performance under extreme thermal conditions, but also for use in 'architecturally sensitive' properties, i.e. what better to use if you need to run a cable up some stone-work etc in a church or stately home??

well we were showed the virtues n benefits of pyro at college...i liked making it off....glandin n all that...good stuff....

 

[the oracle]

It's amazing how many variations there are of suitable good practice. I am making copious notes for my students, keep the ideas coming guys, thankyou.

 

[the oracle]

Some of my most satisfying work was done using 'pyro', it makes for a great looking instal when done properly..... those were the days,
I had hair then as well !!

 

[vjsmarwick]

Pyro happy memories a rewire in local distillery and cheap whiskey and a party at the end of the job one and only time I have tried 50 year old highlandpark and it was lovely but we must have done about 1000 pyro glands