Re: Ir Continuity And Elecsa

[jaysparks79]

Hi guys, new here and just starting out. Have got my Elecsa assessment coming up Wednesday and just wanted to run a few things by you all as it seems a great forum to help. I have changed a CU as my job and whilst I believe all to be ok I just wanted to query a couple of things. Namely the cooker continuity reading on a 32A type B MCB is 0.95 ohms which when added to R1+R2 for calculated Zs comes in just under the tabulated maximum in table B6 in OSG. is this figure acceptable or should I measure Zs and enter this reading on test results as this would be the actual resistance of the fault path? secondly I carried out a Line connected to Neutral and earth insulation resistance test at the consumer unit as couldn't be sure I could disconnect all neons and sensitive equipment. my meter came back with 17.85 mega ohms. now it is greater than the 2 mega ohms required but just really wanted to check that this figure is within normal readings. it is in a 2 bed flat with 2 lighting circuits (new) two ring final circuits, an immersion heater, cooker and electric shower. I will be totally honest that I have done very little actual testing to date but want to change this by getting Part P registered and doing about four years worth of domestic installs before going on to take my 2394 testing C & G. any help would really be appreciated and if anyone has any tips on making sure I don't balls up my assessment I would be grateful as really nervous! many thanks in advance guys.

jay

 

[kerching]

First question

Why are you "adding the cooker continuity...?" to R1+R2 to get Zs

Zs used to be Ze + (R1+R2)

Just curious......

Others will be along shortly to correct me as I am not a Proper Electrician

 

[jaysparks79]

apologies, should have put 0.95 is the R1+R2 and have added that to Zs which measured at 0.15 ohms.  thanks for spotting my mistake Proper Electrician! first post, bit nervous and am worried this might prove simple and I should already know it!

jay

 

[kerching]

What have you wired the cooker in?

Either it is

A). A fecking small cable

B). A fecking long run

C). A fairl dodgey connection somewhere

D). And I suspect this is the reason............test leads not zeroed prior to test

Work out length of cable and multiply it by the resistance in the BYB....that will give you an idea of the expected values

 

[Murdoch]

Does the cooker outlet point have a socket? If so do a Zs on this and see what the reading is!

 

[jaysparks79]

Proper sparks, I didn't wire the cooker in I just changed the CU, everything in is existing.  the cable size is 4mm and is approx. 6m from CU, I had it drummed into me to always zero the leads so do this before every test. may take a look at loose connections as I think the home owner had the plate changed.  Murdoch thanks yes it does have a socket so will do that and see what the difference is. am I right in thinking with parallel paths it will give me a lower reading the my calculated figure?

many thanks again

 

[Murdoch]

Proper sparks, I didn't wire the cooker in I just changed the CU, everything in is existing.  the cable size is 4mm and is approx. 6m from CU, I had it drummed into me to always zero the leads so do this before every test. may take a look at loose connections as I think the home owner had the plate changed.  Murdoch thanks yes it does have a socket so will do that and see what the difference is. am I right in thinking with parallel paths it will give me a lower reading the my calculated figure?

many thanks again

If the socket is worn and/or little used the readings can often be higher - if you get "odd" readings take the plug in and out a few times to see if the reading changes.

 

[apprentice87]

Make sure you know the difference between Ze and Zs... I do not think you do....

john...

 

[Andy™]

6mtr of 4mm with a R1R2 of 0.95... just because its within limits of the MCB does not mean its safe. there is a problem, most likely 1 (or more) of what kerch said

 

[jaysparks79]

will further investigate all aspects of this tomorrow. I do know the difference between Ze external earth path from distributor to Cu and Zs installations earth path.  thanks for all the advice

 

[Murdoch]

And out of interest, which forums responses have you found the most useful?

 

[jaysparks79]

Murdoch, im on 3 at the moment but I feel like im getting good advice from all of them.  don't think you can get too much advice can you? all helps to get a better understanding. appreciate your advice and thankfully ive got a bit more knowledge to work from than I did before I came on here.

 

[Murdoch]

Murdoch, im on 3 at the moment but I feel like im getting good advice from all of them.  don't think you can get too much advice can you? all helps to get a better understanding. appreciate your advice and thankfully ive got a bit more knowledge to work from than I did before I came on here.

Good man - just remember on Forums answer questions as best you can, and thank people for their input.

Nobody knows everything and courtesy costs nothing.

 

[jaysparks79]

will do. and thanks again for all the help so far.  I do appreciate people taking time out to answer my questions and it really is giving me a better understanding of things I haven't had much experience with yet.

 

[ProDave]

Firstly check you really have zero'd your probes.

Try measuring at the input to the cooker switch. Dodgy cooker switch is highly likely if it's not a measurement problem.

 

[binky]

Just as guidance I would expext R1+R2 to be less than 0.3 ohm for that circuit, make sure you are getting good contact with test probe, sometimes oxidised layer on cable / terminals can cause higher readings.

 

[jaysparks79]

Prodave, I did the test from input at the cooker switch, and binky that is what I am going to do. clean off the cables if they look dirty and check all connections are tight then test again. and also make sure the probes are making good contact.  thanks for all the advice. 

 

[jaysparks79]

Hi all. So had my first elesca assessment and over the moon I got an A! Found no problems with any of my stuff so im chuffed to bits. He was really friendly and knew his stuff and i was put straight as ease. Really pleased and thanks to everyone for advice and encouragement. The cooker issue hot sorted as i retightened all connections and got a much better reading, after also cleaning up the cable ends in the switch.

thanks again guys

jay