continuity clarification

[gazdkw82]

I am having a problem understanding a question in mylearning book.

It gives the scenario:

The following 6 line to earth values were recorded in aninstallation. What would be the expected values at the origin and what actionsshould be taken, if any.

Circuit 1 = 25 Ω
Circuit 2 = 2 Ω
Circuit 3 = 10 Ω
Circuit 4 = 20 Ω
Circuit 5 = 25 Ω
Circuit 6 = 15 Ω

So I’m assuming this is a continuity reading as it doesn’t state.

What would be the steps to figure this out. I’m not askingfor the answers because I need to understand and work it out myself, however I can’tunderstand where I’d start. Add them all up and divided by 6 to get andaverage?

Any help would be appreciated

 

[shanky887614]

I am having a problem understanding a question in mylearning book.

It gives the scenario:

The following 6 line to earth values were recorded in aninstallation. What would be the expected values at the origin and what actionsshould be taken, if any.

Circuit 1 = 25 Ω
Circuit 2 = 2 Ω
Circuit 3 = 10 Ω
Circuit 4 = 20 Ω
Circuit 5 = 25 Ω
Circuit 6 = 15 Ω

So I’m assuming this is a continuity reading as it doesn’t state.

What would be the steps to figure this out. I’m not askingfor the answers because I need to understand and work it out myself, however I can’tunderstand where I’d start. Add them all up and divided by 6 to get andaverage?

Any help would be appreciated

misread it.

have a look in your onsite guide and check if the values comply,

remember that zs= ze+(r1+r2)

what do you think?

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[gazdkw82]

misread it

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?? what do you mean?

 

[shanky887614]

?? what do you mean?

what reading can you only take at the origin.

there is only one

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[gazdkw82]

what reading can you only take at the origin.

there is only one

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a ze test?

 

[shanky887614]

a ze test?

what are the expected values at the origin?

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[gazdkw82]

what are the expected values at the origin?

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The values are in the onsite guide?

The values will depend on what type of earthing system is providedright? TT, TTCS, TTS??

 

[Andy78]

This question would make a lot more sense if the values were in MOhms, and the question was relating to being able to perform a resistance in parallel calculation, and illustrating the difference between single circuit and global IR testing.

It is very poorly worded though.

 

[gazdkw82]

This question would make a lot more sense if the values were in MOhms, and the question was relating to being able to perform a resistance in parallel calculation, and illustrating the difference between single circuit and global IR testing.

It is very poorly worded though.

I agree. Hence why im confused. At the top of the page it says im on the section of "insulation resistance" but that confuses me even more

 

[Andy78]

I agree. Hence why im confused. At the top of the page it says im on the section of "insulation resistance" but that confuses me even more

Then it's a question about insulation resistance. Are you sure that the values are not expressed as MOhms ?

 

[telectrix]

i would imagine that it should be an IR question and the figures should be in Megohms. then you would work out the resistance of the circuits in parallel to give a global value at the origin. ( using 1/Rt = 1/R1+1/R2+1/R3.......)

 

[gazdkw82]

i would imagine that it should be an IR question and the figures should be in Megohms. then you would work out the resistance of the circuits in parallel to give a global value at the origin. ( using 1/Rt = 1/R1+1/R2+1/R3.......)

:-/ sorry yes it does

my mistake. Note to self, read carefully!

 

[gazdkw82]

Doing some research on the calculations because it's new to me.

would this be correct with the values I have.

1/R1+1/R2+1/R3+1/R4+1/R5+1/R6

=

1/25+1/5+1/10+1/20+1/25+1/15

=

0.04+0.2+0.1+0.5+0.04+0.066

=

1/0.496 = 2.016 overall value

 

[Andy78]

Doing some research on the calculations because it's new to me.

would this be correct with the values I have.

1/R1+1/R2+1/R3+1/R4+1/R5+1/R6

=

1/25+1/5+1/10+1/20+1/25+1/15

=

0.04+0.2+0.1+0.5+0.04+0.066

=

1/0.496 = 2.016 overall value

I get 2.014 (reciprocals not rounded) so you are correct. The only thing I noticed was that in your initial post circuit 2 is listed as a value of 2, and in your final calc it is 5.

You say you have not performed this calc before ? why are you been given questions on subject matter you have not yet covered ?

 

[Simonslimline]

I get 2.014 (reciprocals not rounded) so you are correct. The only thing I noticed was that in your initial post circuit 2 is listed as a value of 2, and in your final calc it is 5.

You say you have not performed this calc before ? why are you been given questions on subject matter you have not yet covered ?

They will surely have covered resistors in parallel previously to this i would of thought.

 

[telectrix]

andy, i don't think it's a question of him not having done the calcs., but more that he needed to know what the question wanted.

 

[gazdkw82]

Well I covered insulation resistance testing in one of books but I don't remember having to use that formula. I'll have to recap

Andy, well spotted. It should have been a 5 in my original post

 

[hightower]

Just a reminder that the final figure will always be lower than your lowest original value when doing parallel calcs like this - just a quick way to check and make sure you haven't gone obviously wrong somewhere.

 

[gazdkw82]

thanks everyone for the help

So, I’m supposed to say what action should be taken if any.

Apart from the obvious safety precautions and use of correcttester and correct voltage I cant think of anything else to add.

The reading seem ok?? they are quite varied but I think that’snormal within different circuits

They are all above 1megaohm

 

[hightower]

thanks everyone for the help

So, I’m supposed to say what action should be taken if any.

Apart from the obvious safety precautions and use of correcttester and correct voltage I cant think of anything else to add.

The reading seem ok?? they are quite varied but I think that’snormal within different circuits

They are all above 1megaohm

I think personally, although the guidance states anything less than 2ohms should be investigated, I'd probably investigate a reading as low as this.

 

[gazdkw82]

I think personally, although the guidance states anything less than 2ohms should be investigated, I'd probably investigate a reading as low as this.

Well then all seems ok as the lowest reading is 5

 

[telectrix]

I think personally, although the guidance states anything less than 2ohms should be investigated, I'd probably investigate a reading as low as this.

TUT TUT, HT, you left the Meg out. :tank:

 

[hightower]

TUT TUT, HT, you left the Meg out. :tank:

Blast! And now it's too late to edit. Please don't let this little mark blemish what was a perfectly average record. :75: