Do You.. CALCULATE or TAKE ACTUAL READINGS ??

[WayneL]

WayneL... You can calculate R1+R2.. if not this can take up alot of time..

As long as you dont use the formula R1+R2 = Zs-Ze, ........

You would need to know the exact circuit length and allow for ambient temp to calculate it approximately.

Just not the done thing.....I'll stick my neck on the line and say R1+R2 should always be measured.

I Agree!

Not making a lot of sense, Sid

 

[TPES]

Why not..... ??

You can calculate R1+R2, which you never mentioned, but I agree with lenny you should take actual readings and not calculate.

 

[Risteard]

Not sure I see the point

The only one you can really calculate is Zs, which is pointless as, if you've had the fittings off to measure you R1 + R2, you might as well leave them like that and measure your Zs

But you would, of course, have replaced all covers prior to conducting an insulation resistance test - after measuring (R1+R2) and prior to measuring Zs...

 

[WayneL]

Why not..... ??

You can calculate R1+R2, which you never mentioned, but I agree with lenny you should take actual readings and not calculate.

Continuity of protective conductors..................no

R1 + R2.................................................not really, unless you know circuit length

Continuity of ring final circuit conductors............no

Insulation resistance...................................no

Polarity ..................................................no (although could be confirmed visually)

Ze ........................................................no (could enquire - probably be longer on the phone)

PFC........................................... yes (but whats the point if you're there measuring Ze anyway)

Zs............................................. yes (but you would need to have measured R1 + R2)

RCD/Functional .............................no

Volt drop.................................... yes

I think I did mention it

 

[SirKit Breaker]

Not being one for maths, and having spent a fortune on buying the appropriate piece of very expensive apparatus to do the calculations for me, i chose to stick in my probes and let the machine do the work, therefore i measure.

I leave my calculating until it is my turn at the bar, i can work out which beer is the cheapest and how much i can save on my round in a flash but doing Zs etc etc etc doesnt do it for me.

 

[WayneL]

But you would, of course, have replaced all covers prior to conducting an insulation resistance test - after measuring (R1+R2) and prior to measuring Zs...

Why??

Assuming you're not talking safety - eg people having access to the unfixed covers etc. That, of course, would be different.

What would you do -

plate everything back up after continuity,

then IR test,

then energise,

then safe isolate again to remove ceiling rose,

then re-energise to test ZS,

then re-plate again.......I don't think so.

If it is, then no wonder it's taking people two days to test a house

If you are in complete control of the installation, there's nothing wrong with leaving a rose or similar undone - and thats straight from our NIC Inspector/2391 instructor.

 

[TPES]

Must be just a missunderstanding of terms, looks like you put "R1+R2 .... Not really.

And also by circuit length you meant ZS.

I think I must be getting confussed with what your saying.. My mistake

 

[WayneL]

And also by circuit length you meant ZS.

NO, no, no - can't calculate it that way.

By circuit length I meant the length of the circuit - eg. 20m then multiplying that by the resistance/metre of the conductor/s to get the R1 + R2 measurement

 

[Davey101]

Before carrying out an R1+R2 test, does everyone remove ALL faceplates, sockets, spurs, and dissconnect and choccy block all cpc's in lighting circuits, disconnect all earths from flex's, etc,etc?

If not, then surely the parrallel earth/Zs argument doesnt apply?

Also pretty surprised that people are happy calculating Zs?

Personnaly, in the past I have been happy to measure Zs, and occasionaly calculate R1+R2, less so now though

No offence to anyone, but I cant see how one man could PROPERLY and completly test 40 circuits a day, would be happy to be proved wrong though

 

[YTSOxford]

I just measure the Zs at the sockets. For the rest of the Zs i calcualted with the R1+ R2

After all its against the 'Elecicity at work' to worklive!

 

[Deleted member 9648]

The big time waster is sorting out whats on a circuit on an installation not familiar to you,if all the circuits are correctly labelled,and points marked with circuit numbers i'ts a doddle. Most of the time you have no idea what is on the circuit you are testing...it takes time to find out....... Less than a day to test/inspect a typical 3 bed property including paperwork....wish I could get paid to hang one out for two days.

 

[sparky692]

correct me if am am wrong, guys, but R1+R2 can be calculated by measuring or knowing Ze and Zs. ie Zs - Ze = R1+R2 ... ??

 

[Risteard]

correct me if am am wrong, guys, but R1+R2 can be calculated by measuring or knowing Ze and Zs. ie Zs - Ze = R1+R2 ... ??

No. Zs can be calculated as Zs = Ze + (R1 + R2) however this calculation cannot be reverse engineered.

 

[TPES]

No. Zs can be calculated as Zs = Ze + (R1 + R2) however this calculation cannot be reverse engineered.

Do you all agree the same then ?

That.. ZS - ZE does NOT = R1+R2 ????

I know it may not be as accurate as taking a reading but its still a valid calculation isnt it ???

I cant belive im even questioning all collage tutors/ lecturers and assessors..

 

[Davey101]

TBH, I dont know why you can do it the one way, but not the other. Refering to my previous post, unless you are going to disconnect ALL parallel paths when doing your R1+R2, then there is no difference. I would argue that a loop test MUST be carried out, as this provides a real test, actually putting a current on the CPC.