waecE-LEARNING
Elect Installation & Maintenance Work Paper 2, May/June 2014  
Questions: 1 2 3 4 5   Main
General Comments
Weakness/Remedies
Strength













































QuestioN 5

           

                                                                                                                                    

5(a)    (i)       With the aid of a well labelled diagram, sketch a domestic ring circuit with 9 No.  13A socket outlets showing the recommended number of spurs.   
         (ii)       What is the fuse rating for the circuit?
        (iii)        Give the standard cable size required for this installation.
        (iv)       What is the procedure for determining the number of spurs?    
 (b)    (i)        Define domestic ring circuit as specified in the IEE regulations.     
        (ii)        State three requirements of the IEE regulations on domestic ring circuits.  

(c)    Copy and complete the table below.
        Faults in fluorescent lamp circuits

S/NO.

SYMPTOM

POSSIBLE CAUSE

(i)

Fuse blows when lamp is switched on

 

(ii)

Lamp appears dead when switched on

 

(iii)

Lamp makes repeated effort to start

 

(iv)

Lamp does not light but electrodes glow continously

 

        
(d) (i)   Give one reason why a capacitor is connected between fluorescent lamp terminals.
     (ii)   State two reasons why sodium lamps are used for street lighting.

 

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Observation

 

This question test the candidates’ knowledge on practical.  Majority of the candidates that attempted this question did not do well in the areas of ring circuits and sockets.  However, some candidates performed very well in questions involving systems and causes of lamp defects.

 

 

 

 

The expected answers include:
           
   5 (a) (i)

 

 

 

 

 

 

 

 

            (ii)        30A
            (iii)       3 x 2.5mm2  accept 2.5mm2
(iv)       Total sockets divided by three
                        OR      Total sockets    OR   1  of the total number of sockets
                                         3                           3
                                                                                                                               
  (b) (i)             Domestic ring circuit is defined in the IEE regulations as
                        a final sub-circuit in which the current – carrying and earth-
continuity conductors are connected in a form of a loop, both ends
of which are connected to a single way in a distribution fuse board
or its equivalent.     

     (ii)               -           Minimum cross-sectional area of 2.5mm2 for P.V.C or T.R.S. cable.

  •       Unlimited number of socket outlets allowed  for floor area under        100m2.

-           Spurs should not be more than half the number of socket outlets
on the ring circuit.

  •       Fixed appliances must be protected by a local fuse
  •       Fused 13A plug should be used at sockets outlets supplying

portable appliances

  •       30A fuse should be used to protect the ring circuit.

                                               
(c)                    Faults in fluorescent lamp circuit


S/N

SYMPTOM

POSSIBLE CAUSE

(i)

Fused blows when lamp is switched on

Short circuit  in the wiring

(ii)

Lamp appears dead when switched on

No power supply/broken tube
electrode/faulty starter/dead tube/dead choke

(iii)

Lamp makes repeated effort to start

Aging lamp/low voltage/faulty starter 

(iv)

Lamp does not light but electrodes glow continuously

Faulty starter/faulty (R.I.S.)
capacitor/aging tube/low voltage

                                   
                                                                                                                                   
(d)(i)    To improve power factor (output) of the lamp
                                    To suppress radio frequency interference         
                                                                                                                   
                            (ii)    It strikes immediately it is switched on
                                     It has warning effect
                   It is very bright         

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