2391 question

[huwtownsend]

Hi its not clear to me about testing Selv and pelv, i understand the 250v @ 0.5 M ohm , when tested on its own , has someone got a diagram for testing Selv , pelv with other circuits, so as i can picture what the NOT plain english GN3 means, also I have an old question paper for calculating two conductors in paralle, I supose this means something like a standbye genarator , to calculate this would i be right to assume that
R1xR2
------- = would be right for this Question
R1+R2
thanks
Huwy

 

[mattmoo1974]

Join L@N and test to CPC or do you mean like a shaver socket? where you join L@N from 1 side to L@N of the other to prove electrical speration?(mini transformer).Also test to CPC
I "THINK" its the same with Pelv. I remember this Que from my 2391 course, Hope this was helpfull altho badly worded.

 

[huwtownsend]

Thanks that makes sense, head full of lists and stuff ready for 2391 exam in march

 

[daveyzadams]

Can anybody help out here just studying for my resit and come accross Ra x In less than 50 its to do with earth electrode resistance,Where does the 50 come into the equation,I've got the last three test papers if anybody wants them {not februarys}

 

[Deleted member 26818]

That will be 50V, supposedly the maximum a healthy human can withstand before serious injury occurs.

 

[mattmoo1974]

"Touch Voltage"

 

[daveyzadams]

Cheers,if any body wants them past papers e mail me at [email protected]

 

[daveyzadams]

Alreet lads,
Just doin more revision and cant seem to find the formula for the ring final test when adding R1 + R2 /4 in stage three how to bring in the 1.67 when its twin and earth,did everybody i sent them papers to get them,anyone else need them e mail above

 

[mattmoo1974]

2.5mm line and netural. cpc is 1.5mm= 1.5mm x 1.67= 2.5mm same for your reading. if CPc reading is 0.8 omhs x 1.67=1.33, your line and netural should be close to this figure

 

[daveyzadams]

Cheers,so if for example you line reading was 0.6 ohms you would add 0.6 + 1.33/4
R1 + R2/4

 

[mattmoo1974]

0.6x1.67=1.002 ohms 0.6+1.0= 1.6/4=0.4
Your there davey

 

[tony mc]

2.5mm line and netural. cpc is 1.5mm= 1.5mm x 1.67= 2.5mm same for your reading. if CPc reading is 0.8 omhs x 1.67=1.33, your line and netural should be close to this figure

If the CPC is 0.8 ohms and is 1.5 mm then the Line reading should be less if 2.5mm

2.5/1.5 = 1.67

If your CPC is 0.8 you line & neutral should be around 0.48 ohms.

0.48 x 1.67 = 0.80


CPC 0.8 ohms 0.8/1.67 = 0.48

Hope this helps..

 

[daveyzadams]

Cheers for the reply Tony,
So the question in the paper is that if line is 0.35 and cpc is 0.56,what is the reading at the socket between line and cpc,is it 0.35 + 0.56/4
Also can you tell me how to write the calculation when adding the three electrode resistances and the dividing by three is it something like Ra + R + R /3 =
I am off shore at the moment does anybody know of any training centres in the north east where i could do a day or two refresher before the 10th of March I will be getting back on land on the eigth.I still have all of them past papers if anybody still need them my e mail is in an earlier post,thanks for everybodys help

 

[tony mc]

17th Edition IEE Wiring Regulations:..

Have a look at this book is is a good help if studying for 2391.

Re your test 3 on the ring final cct its right 0.35+0.56/4 =0.23 between L & cpc at each socket.

Earth electrode test. Obtain your 3 readings .

181+185+179/3 =181.67 ohms

Maximum diviation = 185(highest reading) minus 181.67 = 3.33

Express as percentage 3.33x100/181.67 = 1.83%

Measurment accuracy = 1.83% x1.2 = 2.2 %

Provided the value does not exceed a figure of 5% the accuracy of measurement is considered acceptable.

Hope this is some help.


Tony

 

[senor_fabulous]

Cheers,if any body wants them past papers e mail me at [email protected]

Cheers for the past papers nice one.