max Zs, Which Value

[lennyallover]

hi quick question, i was debating with a colleague today about measuring R1 + R2 on a pre existing RMSO. My colleague insisted that it be measured from every point served whilst I said it should be measured from the furthest point only and as long as the other points served all checked for correct connection taking a resistance measurement from all points was not needed. Anyone clarify this?

 

[brucelee]

most of the martial arts films where and are very far fetched
this is why i liked bruce lee as he was trying to bring real martial arts to the film industry but since his death it reverted back to the tongue in cheek stuff

i will watch if i ever get the chance mate for a laugh

 

[brucelee]

hi quick question, i was debating with a colleague today about measuring R1 + R2 on a pre existing RMSO. My colleague insisted that it be measured from every point served whilst I said it should be measured from the furthest point only and as long as the other points served all checked for correct connection taking a resistance measurement from all points was not needed. Anyone clarify this?

mate what is RMSO do you mean ring final circuit if so then they should be measured at every outlet if you are referring to a lighting circuit then the furthest point is the R1+R2

 

[lennyallover]

ring final circuit mate , rmso-ring main socket outlets. thanks for the reply i'll go eat humble pie in the morning ... damn he'll be insufferable all day.lol.

 

[telectrix]

by measuring R1+R2 at every point, you verify that each point is correctly connected and you should get a slight variation from point to point. the highest reading is the mid point. if you get a reading which is at odds with all the others, then you know there is a problem at or close to it. it may just be a high resistance in a socket face. the way i do it, right or wrong is to short L/E on my break-out box, meter across at CU then move short from one point to another. then repeat with N/E shorted. on a radial, of course, the highest reading is the "end of line".

 

[lennyallover]

ty telectrix, very concise..i do however know all that know all that and have done the same. My point was , if the polarity of the ring final was being checked using continuity methods and the correct sixth and quarter values measured, is R1+R2 from every point really needed

 

[telectrix]

yes. supposing a cpc was continuous, but had come out of the socket terminal. only that particular socket would show it up when doing R1+R2 test., simply because the tester could not see the cpc when plugged in that socket

 

[lennyallover]

Yup!!! thats a solid enough answer for me, nice . Another one. if a person is in a stainless steel bath ,and the bath itself has all 4 of its feet attached attached directly to the man earth block in 16mm cable. the water in the bath is highly salted and in the most conductive state possible when an unfused live cable is placed into the water (er.. this is theoretical im not planning sod all)would the person in the bath be electrocuted? would the current pass harmlessly through the water taking the path of least resistance through the steel bath and on to earth leaving the person unscathed . or some other path?

 

[malcolmsanford]

Everyone in contact with a fault will be "electrocuted" but you limit that shock to a touch voltage of 50v and limit the duration of the fault/shock by making sure the protection device acitvates in the prescribed time.

On your post concerning the ring final circuit what "sixth" value are you refering to?

 

[lennyallover]

there is no protective device....imagine the fuses have been replaced with nails big chunky steel nails...given that the resistance of the bath water is .05ohm for each cubic ltr the current has to pass through and the resistance of the person is around 150Kohm(THESE FIGURES ARE NOT ACCURATE JUST A WHAT IF SCENARIO) would the water and bath act as a faraday cage protecting/ channeling current away from th person...my own thgoughts on this is that the person would survive though could suffer flash burns across the skin surface. disregard sixth....shouldnt post after drinkin on an empty head..was meaning th (R1 + R2)/4

 

[telectrix]

the only answer to that is try it with a monkey first

 

[TPES]

1.15 would go on my cert, or is that 1667. cus of that thingy with a test button. (Here we go again)

Seen many certs with 1667 as max permitted by bs7671, With 30ma on circuits, I get mixed opinions off sparks as to what they put down.

I do what Elecsa want to keep them happy, it's them I'm paying my money to.

 

[telectrix]

so, 3 possible answers, 3 different replies. opinion divided between 1.44, 1.15, or 1667. looks like a blindfold and stick a pin job. personally, as the column is labelled max. permissable value , i will continue to use 1.44
( for 32A).