Discuss Testing with a CU change in the Electrical Forum area at ElectriciansForums.net

Welcome to ElectriciansForums.net - The American Electrical Advice Forum
Head straight to the main forums to chat by click here:   American Electrical Advice Forum

Reaction score
51
Working with a spark, now when we change a CU no new circuits just old for new, We do all end to ends on rings, IR tests and Zs making sure all the new protective devices that disconnection times are met, would you do R1+R2?

If we do a CU change and add new circuits we do R1+R2 on the new circuits what do you guys do?
 
no i dont really think its required for existing circuits i just do zs testing and calculate r1r2

Maybe for lighting if my meter sometimes trips 6a mcbs on zs

Obviously test rings for continuity

For a new install i would dead test r1r2 first
 
no i dont really think its required for existing circuits i just do zs testing and calculate r1r2

Maybe for lighting if my meter sometimes trips 6a mcbs on zs

Obviously test rings for continuity

For a new install i would dead test r1r2 first
How do you calculate your R1+R2 as that should only be done by measurement only other than at the design stage?
 
Working with a spark, now when we change a CU no new circuits just old for new, We do all end to ends on rings, IR tests and Zs making sure all the new protective devices that disconnection times are met, would you do R1+R2?

If we do a CU change and add new circuits we do R1+R2 on the new circuits what do you guys do?
R1+R2 is for initial verification so if they are new circuits then this must be done, existing then not necessarily required tho not precluded.
Existing then I just make sure all exposed conductive parts are connected to earth with the R2 method and then just measure the Zs but it’s whatever makes you happy
 
How do you calculate your R1+R2 as that should only be done by measurement only other than at the design stage?
Measure Z E and ZS and take it from there ZE = ZS +(R1+R2) Transpose the formulae Bob's yer Uncle simples as Sergei would say.
 
Measure Z E and ZS and take it from there ZE = ZS +(R1+R2) Transpose the formulae Bob's yer Uncle simples as Sergei would say.
I was always taught this was incorrect and not permitted due to connected potential parallel paths when taking a live Zs reading giving a falsely low reading. R1+R2 measured dead and in isolation of other parts of the installation then worked with Ze into Zs always gives a highest and worst case value so can be trusted, but not the other way round.
 
Measure Z E and ZS and take it from there ZE = ZS +(R1+R2) Transpose the formulae Bob's yer Uncle simples as Sergei would say.
For a board change, I agree with you, Pete.....but with rcd involvement, how can it be guaranteed you have a true Zs reading.
The extent of testing should be agreed with the client, really, and allowed for accordingly.
 
I thought zs=Ze+ (R1+R2)...but Ze does not = Zs-(R1+R2) or something like that possibly maybe......I’m feeling really uncomfortable with the new look.....the only other time I’ve felt like this was when they spruced up my local! Took me ages to get over that....
 
I thought zs=Ze+ (R1+R2)...but Ze does not = Zs-(R1+R2) or something like that possibly maybe......I’m feeling really uncomfortable with the new look.....the only other time I’ve felt like this was when they spruced up my local! Took me ages to get over that....
You can not do R1 +R2 = Zs -Ze as for the parallel paths
 

Reply to Testing with a CU change in the Electrical Forum area at ElectriciansForums.net

OFFICIAL SPONSORS

Electrical Goods - Electrical Tools - Brand Names Electrician Courses Green Electrical Goods PCB Way Electrical Goods - Electrical Tools - Brand Names Pushfit Wire Connectors Electric Underfloor Heating Electrician Courses
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc

Electrical Forum

Welcome to the Electrical Forum at ElectriciansForums.net. The friendliest electrical forum online. General electrical questions and answers can be found in the electrical forum.
This website was designed, optimised and is hosted by Untold Media. Operating under the name Untold Media since 2001.
Back
Top
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock