Computer RFC Testing???

[Guest55]

4mm falls out?

eh ? what the hell you on about ?
why would a loose connection be a reason not to include the 4mm in the tests ??
its just as likely a 1.5mm could pop out in which case you'd be relying on the 4mm to help clear any fault current as well as the remaining 1.5.
totally lost me there.

 

[Paul.M]

CPC & earth ? i'd say CPC & CPC.
if the 4mm isnt performing the function of a cpc whats it doing ?
if it is considered as a cpc why not include it in the R2 / Zs measurement ?

When is a CPC not a CPC?

A. When it is an Earth.


CPC protects the cable and provides an Earth return path.

An Earth is the return Earth path for the appliance/s.


Now the repeated question:- Which one do I write down on the cert? Both doing the same job, but both are are doing a different function.

I pretty much know the answer but I'm asking for your opinions and some where that I've got it in the regs (thanks Jim).

What would you write on a cert???

 

[Guest55]

is that directed at me paul or just in general ? lol.

 

[D Skelton]

eh ? what the hell you on about ?
why would a loose connection be a reason not to include the 4mm in the tests ??
its just as likely a 1.5mm could pop out in which case you'd be relying on the 4mm to help clear any fault current as well as the remaining 1.5.
totally lost me there.

Why else would the regs specifically ask for the conductors to be terminated seperately? My guess is higher than average earthing conductor currents means expansion and contraction of terminations (even a miniscule amount) that have to be taken into account. As it is an earthing conductor extra precautions are there to ensure fail safes.

To be honest, I'm not sure, and I may be barking completely up the wrong tree but I was taught to install and test the way I said, but why? I've never really given it a thought until now. It would seem that none of us so far are 100% sure

 

[Paul.M]

You actually don't need it on a ring just in and out on diff terminals of each socket1.5mm is enough

hope this helps wee man.

Yes I know that IPU but the pr**k from the council clerk of works wants everything extra, extra, extra safe for the school.


And yes I have been helpful to you in the past but when you first joined you were a rounded door handle and you got on my ---- on a few occasions. After about your 1000 post you became an Electrician and posted better posts. You've become a sparky and you have the correct attitude now. You've become a valuable member of this forum over the years and well done to you.

Paul M

 

[Silly Sausage]

Hi Paul,

You seem to have become a very serious individual recently.
Where's all the good old banter gone? I hope you're not having some serious grief elsewhere.

 

[i=p/u]

I'm laughing.. Ty 10mArcd and ram it up clerks .,.,

 

[i=p/u]

And as the 4mm would be providing additional mechanical protection, just record your normal R1R2..

 

[Chr!s]

I'm scratching my on this because I've never done it before. I'm on a new build school wire with quite a few computer RFC's using 2.5 T&E + a 4mm single Earth that we are just pulling in now. When it comes to us testing these circuits, how do I/we record the results?

You dont nee the 4 mm, though it wont do any harm, are you expecting greater than 10 mA per circuit?

Both the 1.5mm CPC and the 4mm Earth will be in the same terminal at each socket therefore creating a parallel path with a higher resistance if only one of them is tested, but these are going to always be like this, so do I record the combine findings or test for continuity on each of the R2's then record the R2 of each on one cert or make another page for one of the findings?

The idea is to duplicate the CPC so best to put in seperate terminals.

I've got it in my head that we need to do 3 lots of R2 tests and put them all on paper:-

1.5mm CPC
4mm Earth
Combined CPC + separate Earth.

Well if the 4mm is ran as a Radial then at the last outlet in effect you have three CPC's back to the MET, so R2 is the paralell resistance of the three cables.

Or is it just me + the QS + another very qualified spark that is having a blond moment???

May be worth speaking to the Designer.

 

[Nic Norwood]

I may be very very new at the game, but as I've come to understand it the reason the c.p.c's are termintated seperately at the socket outlet and at the consumer unit is to reduce the high earth leakage current down each leg of the ring during the start-up or banks of computer's psu's? therefore reducing liklyhood of nuisance tripping? =/

 

[kingeri]

The extra CPC is nothing to do with 'safety', it provides an additional 'fail-safe' route for any additional earth leakage from the numerous switching PSUs used in PCs.

You need to test with the 4mm in place, as it is just as much a part of the circuit as the CPC in the T&E. I don't see any logic in the idea of testing without it in place. You can't cherry pick what you want to test because it's what you're used to, you test what is there and what will be in service long after you've gone.

 

[Chr!s]

I may be very very new at the game, but as I've come to understand it the reason the c.p.c's are termintated seperately at the socket outlet and at the consumer unit is to reduce the high earth leakage current down each leg of the ring during the start-up or banks of computer's psu's? therefore reducing liklyhood of nuisance tripping? =/

Are the cpc's at each socket not eletrically connected? Its just for strength and to improve the integrity of the cpc.

The RCD will just see all the leakage, not that its been split down several legs.

 

[Paul.M]

Hi Paul,

You seem to have become a very serious individual recently. Other people call that professionalism lol

Where's all the good old banter gone? It will be back shortly.

I hope you're not having some serious grief elsewhere. Nope, life is good and I'm building a better future

Thanks Archy for your kind questions but I'm fine mate. Just needed a bit of a break from the forum for a few months. Think I've turned into one of those old members that has seen everything (almost) on here and just sits back and watches. Thank God I'm not a Mod because there would be 50+ members banned straight away lol.

I'll post up some funny stuff soon. The Elex show is 3 weeks away and I have'nt thought of a funny name badge yet :rofl:

 

[Elmer BeFuddled]

At the end of the day a HI circuit doesn't need a second cpc to follow the first. The continuation of the cpc from outlet to outlet needs to have a separate termination, as it does in the CU.

 

[Silly Sausage]

Paul, glad to hear all is well!
I (generally) treat these forums as chatting down the pub, occasionally a serious topic comes up to to be discussed.
I'll keep any professionalism to the work I occasionally do!

Please don't turn into another Tony, one is more than enough!