2391 exam question help

[sarni31]

Here goes ....

The ring circuit supplying general purpose socket outlets in a shop is being tested to confirm ring final circuit continuity. All the socket outlets are connected to the same circuit.

State

a) whether the values obtained are as expected in each case. (7 marks)

B) for any value which is not as expected, one reason for the reading obtained. (8 marks)

(Total marks 15)

Test 1

P-P = 0.60. N-N = 0.62. CPC-CPC = 1.00

Test 2

Socket B ........ r1 + rn = 0.29................. r1 + r2 = 0.6

so r1+rn/4 = 0.3ohm

and r1+r2/4 = 0.4ohm

why would Socket B give these results any ideas ?

Thanks

 

[kingsway47]

One reason for the higher reading is a loose cpc connection given that the

r1-rn test is as expected the line conductor is excluded

 

[sarni31]

yeah sounds good

if been loose for a while and tarnished .Guiness Drink

 

[kingsway47]

glad you think its good, this question comes in various guises, for example there could be no reading between cpc and R1 at socket B and c, d,e etc are fine

1 Reason x polarity between line and neutral

2 cpcs not in terminal at socket B but are twisted so this does not affect other sockets

3 Another reason for high resistance in the first case is if testing at the tubes , wear and tear.

 

[sarni31]

thanks for that...

though with the crossed over L/N you would get o/c result for r1+r2 test

Guiness Drink