Confused!


Postby Tiesto » Thu Nov 26, 2009 8:02 pm

Just started a new electrical course and with that i have a Scenario Cd which is a vitual house on my pc and i have jobs to do, im stuck on the Finding the R1 + R2 section, i cant find out how to do live tests, says i need to take out devices but cant find what. If anyone has this cd and shed some light on what i have to do and maybe explain it abit better for me please lol! Been trying for ages but cant get my head round it. Thanks for your time, take care Jamie
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Postby ericmark » Fri Nov 27, 2009 6:50 pm

Not seen CD but R1 + R2 is not a live test. You can find the ELI (live test) and from that calculate R1 + R2 but since often the line and earth are different size cables not really something one would want to do. Normally other way around we calculate the ELI from R1 + R2 plus Ze to find Zs.

As to removal there is in the old book 3 a method shown where the cables are removed from the consumer unit and either linked or a long wire is used or it is linked output of fuse to earth to measure.

The latter would require removal of the fuse is that the "device" you need to remove?

But with reference to R1 + R2 and live test I wonder it bin is best place for CD as whole idea of R1 + R2 test is to ensure all is correct before switching on.
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Postby moggy1968 » Fri Nov 27, 2009 9:19 pm

The onsite guide has a good section on testing. this book is a must for any electrician. I would be alarmed if you didn't have one on your book list for the course. Are you sure about the credentials of this course. given the limited info in your post it sounds a bit suspect!
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Postby sparx » Fri Nov 27, 2009 10:40 pm

hi, not sure how far you are into the course so sorry if too basic, but I am surprised they are asking about live tests already.
I don't know the cd you have but when I was teaching 2330 at local tech we had sets of cd's for students but I did not find them very easy to use!
So quick run through circuit for finding R1+R2,
Mathematically Zs - Ze = (R1+R2).
so are they suggesting measuring Zs at end of circuit, measuring Ze at intake and calculating from that?
Not sure about 'taking out devices' except Ze should be measured with main earth disconnected from system for duration of the test, but would not expect this to come up so early in the course as great care needed when doing it 'for real'.
sorry not much to go on maybe someone else has the cd,
good luck with the course, which one btw?
regards Sparx
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