Evening guys. Just got my extension ring final into the db and have some test figures as follows, the length of the ring is what some 30 mtrs (but that is approximate) End to End Ring Earth to Earth 0.59 ohms L to L 0.34 ohms N to N 0.34 ohms Loop Test 0.47 ohms Trip Tests @ 0 degrees x1 = 13ms x5 (fast trip) = 10ms @ 180 degrees x1 = 19ms x5 (fast trip) 16ms I am happy with the results excepting maybe the e to e at 0.59 might be a tad high? Guys what do you think? Thanks lads.
They look fine.. 0.59 is about right as the CPC is usally around 65% higher then Live & Neutral. But what is your R1 + R2 for the ring? Given your end to end readings your R1 + R2 should be around 0.23 Ohms.. but I know your dying to measure it rather then calculate it..
Thanks Caddy appreciated m8. I've got all the cables in now so how do you get the R1 + R2 by calculation. Thanks.
On a 2.5/1.5 ring circuit r1 x 1.67 =r2. And R1 + R2 = (r1 + r2)/4. 0.34 x 1.67 = 0.57 ohms. That is spot on mate. Also, your Ze (based on your Zs reading) would be around 0.47-(0.34/4+0.59/4)=0.24 ohms. And, R1+R2=0.23 ohms. Nice work JP.
Shouldn't that highlighted 0.47 be 0.59.. in which case ZE is roughly 0.24 ohms... I know its not going to make a difference in reality but the calculation is wrong unless i'm missing something. JP.. You should still measure R1+R2 for the ring to ensure you have wired it correctly. You should measure around 0.23 at all socket points (unless spurs) if you plug in a tester rather then probes on the terminals then the reading is lightly to be slightly higher but all sockets should still be the same reading.
Un and Caddy you have been extremely helpful and I am very grateful for your inputs - maybe I might try and learn a bit more about the testing side of things as I can see by your inputs that I am lacking in this field. Just one question - what test range do I use for R1 and R2? Thanks guys.
Also I forgot to do an IR which I will do even though they are all new cables. I don't really want to start disconnecting stuff in the db (but I will if I have to) so is it ok to just connect the tails L + N together and go from this to met? I presume if I can do this then I can leave all rcd's, rcbo's in line without damaging them? Thanks.
Cheers Fats. So ok to link L + N tails together and use one croc on this and one on the met? and leave rcd's in (no link out) and just do the whole lot at once. When pulling cables etc I know none of them were damaged, so would be quicker just to whammy the whole system with an ir test.
hi mate, sorry, what i meant by whole installation was test L-N, L-CPC, N-CPC at the tails/main switch of the new board.
Insulation testing has to be done with a certain amount of caution. 500V can damage components, particularly RCDs and RCBOs, which specifically should not be insulation tested. Unless you can be certain that there are no neons, RCDs, stuff plugged in to sockets, it owuld be unwise to do it. Traditionally where there is doubt L-N are shorted together and tested against E so that there is no PD between L+N.
Many thanks Un and Fats - all points noted. I should have tested the legs prior to connecting stuff up but have done a few which are all measured infinity. Appreciated lads.
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