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I know how to carry out the test, but i am not sure i understand the reason for carrying it out... some ideas of mine are ... R1+RN could be used to calculate PSCC ? A high R1+RN would signify spurs/alterations to the circuit ? "rn ring continuity" doesnt actually confirm there is a...

If i have an installation with no water, gas services ... then there are no equipotential bonds in place .... would this still count as EEBADS as the method of protection again indirect contact ? If EEBADS is not correct, then what would be ? :oops: EADS - earthing and automatic...

NIC told us that you dont need to do that, as the ones in regs are closer to real maximums ... dunno if thats right or not thats probably just because we do domestic and temps dont change that drastically

Or you can do following, as is shown in table 41B2, BS7671 16th edition Type B MCBs BSEN 60898 and RCBOs BSEN 61009 48 / Current rating of MCB Type C MCBs BSEN 60898 and RCBOs BSEN 61009 24 / Current rating of MCB Type D MCBs BSEN 60898 and RCBOs BSEN 61009 12 / Current...

over current due to shorts rather than load .... but you got what i meant :P

Say if its not possible to meet the disconnection for the overcurrent , are there ways around it, like ... installing double insulated cables to prevent short circuit or earth fault ?

hehe, ive done it for a Ze of around 0.35 and that allows ~35mm cable, i think im going there tomorrow so will get the true earth loops and see if all is OK again, thanks for the help guys

oh right, lmao thats a bit more sensible :oops:

yep im sure it is less than 0.8 ohms, but im using that as the maximum for TN-S for my learning you guys have been a great help, thanks

300 amp fault on 125amp BS88 take 300 seconds to blow :shock: if i understand the graph right then ... IxI = 300amps x 300 = 90000 xt = 300secs = 27,000,000 divide by K of 47 for steel trunking = 574468 Square root = 757mm + cable :oops: either ive done it completely...

oh yeah thats not really allowed is it ? :oops: can i ask where the 600 amps came from in ricicle's post 415/0.8 = 518amps

hehe i realised that after i posted the formula says that 25mm can take 600 amps for 23 secs, and the fuse will blow in less than half that time , right >?

thanks, t = k²S²/I² thats in the regs ?

the busbar is 3 phase but each phase will feed a different Switch fuse (single phase switch fuses) would this mean i use phase to phase PSCC ? because it is possible for a phase to touch to another phase if insulation broke down enough and they were touching is it not best to use just...

Ok thanks for the definitions Our tester has PSCC on the earth loop If im feeding switchfuse with just one phase, i wouldnt need to do PSCC phase to phase would i ? i would just do the phase-neutral as the fuse is single phase or would i need to do phase-phase because there is a...

PEFC is Voltage / Earth loop ... right ? or is it just the restance of the earth path alone ? and PSCC would just be phase to neutral short ? ... so at the incoming mains, with no Main bonds in place, the PEFC would be higher than PSCC, so if the PEFC blows the fuse, the PSCC will too ...

Know of better current time graphs than in the regs ? not too easy to read them very accurately K cable 115 K steel 47 do i add them together for earth fault or use the lowest of the two ?

hmm true ... i suppose its sort of the same thing as putting a spur off a ring final circuit .... 32amp breaker for ring, but a single 2.5 for the spur cant take 32 amps, so isnt protected against a fault current unless the current blows the 32amp breaker, same as the cable feeding the S/F isnt...

Cant get it atm, so says its maximum for TN-S of 0.8ohms, would 25mm be allowed then or ? what is the adiabatic equation for cable sizing? thx

If i have... 3 phases 70mm cables 120 Amps BS88s ....feeding a busbar chamber and then coming off the busbar in 25mm, single phase, to feed a switch fuse of 60/80/100 amp rating ... all run in steel trunking, all singles cables, all cable entries protect cables with paxelin(spelling?)...