The following points highlight the seven major faults that occur in wiring system with remedies to fix the same. The faults are: 1. Lamp does not Light Up 2. When Light up Lamps are Over Bright or Under Bright 3. Wiring System is Excessively Heated 4. Leakage in the Wiring System 5. Defects in Fluorescent Lamp Circuits and Corresponding Remedies 6. Defects in Fluorescent Lamps 7. Defects in Starter or Glow-Switch.
Fault # 1. Lamp does not Light Up:
Symptom 1:
Lamp does not light up in a circuit.
Cause:
ADVERTISEMENTS:
The fuse of this circuit in the fuse board has melted.
Remedy:
Replace the fuse. Sometimes the fuse-wire becomes narrower on ageing and therefore melts. Then replacement of fuse-wire sets things right. If, however, it melts again immediately after replacement, it is to be understood that there is a short-circuit somewhere in the circuit.
Put off the main switch then and take out the fuse of the circuit. Next, take out the lamps of the circuit from their respective holders and also put off their switches. Now connect a bell and a battery in series and touch the two terminals of the circuit under test with the two ends of this series combination.
ADVERTISEMENTS:
If the bell rings, it indicates that there is short-circuit between live terminal of the circuit and the switch (see fig. 260). If the bell does not ring, put the switch on. Now, if the bell rings, the conclusion is that the short-circuit lies between the switch and the lamp. But if the bell does not still ring, there is short-circuit in the lamp itself which was fitted into the holder. Connect a new lamp with the holder and test the circuit again.
In many cases, while fixing with the screw of a holder a strand of the flexible cord. Instead of entering into the porcelain block, develops a short-circuit with the other flexible cord due to carelessness or by touching the brass cap of the holder which may be touched by a strand of another cord also. As very little space is usually left within a lamp holder, care must be taken when fixing flexible cord with it.
Symptom 2:
ADVERTISEMENTS:
The lamp is perfect, but it does not light up when fitted into a holder.
Cause (i):
Due to slackness of the clamping ring of the bayonet holder, the porcelain block turns a bit at the time of fitting the lamp; as a result the plunger does not get a touch with the contacts of the lamp.
Remedy (i):
ADVERTISEMENTS:
On the body of the porcelain block of a bayonet holder there are two grooves on the opposite sides, and on the inner surface of the brass cylinder of the holder there are two high ‘dots’. At the time of the fixing the holder, the dots remain inside the grooves.
If somehow the brass cylinder is turned a bit from this position, the two contacts of the lamp do not get a touch of the plunger of the holder when a lamp is fitted into it. As a result the lamp does not light up when switched on. Under this circumstance the holder is to be replaced.
Fuse-wire will not melt on account of this fault.
Cause & Symptom (ii):
ADVERTISEMENTS:
If the cap of the lamp is loose, it is turned into a holder only to develop a short-circuit.
Remedy (ii):
Replace the lamp.
Cause (iii):
Contacts of the switch are too far apart or the flexible cord is broken or one piece of wire is open.
Remedy (iii):
Switch off the main switch or stand on a wooden stool. Now press the switch contacts to bring them close together. Examine and test the flexible cord.
Symptom 3:
Not a single lamp lights up when switched on.
Cause:
The main fuse is melted. There may be several reasons behind it.
To avoid the trouble of replacement, very often fuse-wires of larger cross-sections are used in sub-circuits. Although it is a very bad practice, it happens in many cases. If there be many such sub-circuits and all of them draw excess currents at a time (or a single sub-circuit draws very heavy excess current), the main fuse-wire may melt while the sub-circuit fuses remain intact.
Remedy:
In fact, prevention is better than cure. But if this practice cannot be avoided, the only remedial measure is to connect fuse wires of proper sizes in all sub-circuits.
Symptom 4:
The cables in all sub-circuits are excessively heated. (If wiring is excessively heated, the insulation of cables is deteriorated quickly).
Cause (i):
Each sub-circuit is heavily loaded (to draw current into a circuit is to load it).
Remedy (i):
Discard the existing wiring and re-wire the whole installation properly.
Cause (ii):
Copper wire is used for main fuse, while lead wires or wires made of lead-tin alloy are used for branch fuses.
Remedy (ii):
For the same fusing current size of copper fuse wire is less than that of lead wire or wire made of lead-tin alloy resulting in less dissipation of heat by radiation from copper wire. As a result copper fuse melts too soon on short-circuit. If in any wiring system this kind of different metal fuse-wires are used, these should be replaced by fuses of same metal for main and branch circuits.
Symptom 5:
Fuses are all intact, but many lamps do not light up.
Cause:
Somewhere In the wiring system the cable is broken or contacts are loose.
Remedy:
Adopt a new wiring system or tight up all the terminals.
Fault # 2. When Light up Lamps are Over Bright or Under Bright:
Symptom 1:
The lamp glows over bright.
Cause:
Lamp rated for less voltage has been connected in the circuit. The rated voltage of the lamp is less than that obtained by measuring the pressure at the terminals of the lamp holder. (Voltage at the holder should be measured by a voltmeter connected to an adopter fitted to the lamp holder, and lamp suitable for that voltage should be fitted to that holder. But in actual practice nobody seems to bother for this).
The life of a lamp shortens quickly when it is used in a line where supply voltage is higher than the rated voltage of the lamp. Of course the lamp glows over bright for a few days before expiry, but this is no justification for such use. Lamps which are rated for voltage suitable for supply line should be used. This will ensure a longer span of life. If, however, brighter illumination is necessary, lamps rated for higher wattage should be used.
Symptom 2:
Occasionally the light from the lamp throbs.
Cause:
Contact in the switch is loose.
Remedy:
If the switch is not a very old one, open the main switch first. Then stand on a wooden stool and bring the switch contacts nearer to each other by means of a screw driver or a pair of pliers. The switch may have to be replaced in case it is very old.
Symptom 3:
In case there is wind, light from the lamp throbs.
Cause:
The wire of the flexible cord at the entry point of the chord grip has worn out or the connection of the flexible cord with the holder is slack.
Remedy:
Either dismantle the holder and strengthen the spring of the plunger by pulling it out a little or replace the holder. Cut off and discard the- worn out portion of the flexible cord and reconnect the cord properly with the holder, or tighten the screw of the holder a bit. If, however, the threads of the screw have slackened, the holder must be replaced.
Symptom 4:
Light from all the lamps throbs for a time.
Cause:
There is loose connection at the main switch or at the terminals of the main board or at elsewhere.
Remedy:
Tighten up all the terminals. Checkup if the blades of the main switch are tightly fixed into the contact clips. If not, keep the clips pressed.
Fault # 3. Wiring System is Excessively Heated:
Symptom 1:
The flexible cord above the lamp is too much heated.
Cause:
The flexible cord above a high wattage lamp becomes heated.
Remedy:
In case the cord becomes too much heated, the rubber insulation of the cord becomes hardened and very soon deteriorated. (Cord should not be so much heated as to become hazardous). In most cases it is found that there is a mica disc above the filament of a lamp the wattage of which is 150 watts or more. Sometimes this disc moves away from position” making way for heating the holder and the flexible cord. In that case there is no other alternative but to replace the lamp. (It is to be remembered that P.V.C. flexible cord shall not be used with pendant lamps).
Symptom 2:
Fuse box is too hot.
Cause (i):
Current passing exceeds the rated value, i.e. the circuit is over loaded.
Remedy (i):
To understand whether the fuses have become too hot, at first stand on a wooden stool (i.e. insulate your body from the earth) and touch the fuses one by one with your hand. At this time you must be careful not to touch the wall by mistake. If you can keep touching the fuse, it is not too hot.
In case the load is increased, checkup if the current is in excess of this ampere rating of the fuse-wire. It is always a good practice to connect a larger size of fuse-wire maintaining all aspects of the wiring system. If, however, this remedy is not feasible, nor can the load be reduced, the fuse-box has to be replaced by a larger one.
Cause (ii):
The terminal of the fuse-block is unclean or loose.
Remedy (ii):
Tighten up every terminal-screw if there is any slackness. If found unclean, it must be properly cleaned.
Note:
Whenever any object is found to be too hot, checkup if the heat is locally evolved or transmitted from another spot. Touch this thing, that thing and other objects nearby and find the hottest spot which is obviously the source of generation and transmission of heat. Then diagnose the trouble leading to undue generation of heat and remove the trouble.
Fault # 4. Leakage in the Wiring System:
System 1:
On touching a wall a person gets electric shock near a switch (especially when the wall is damp or during monsoon).
Cause:
There is leakage in the wiring system (in all probabilities, near the switch). Often this defect is found in old lead-covered wiring system.
Remedy:
Switch off the main and take out the fuses of the distribution board. Connect the earth terminal of an insulation testing megger with earth (with a cold water pipe nearby or otherwise), make connections as shown in fig. 260 and test each branch circuit. Only the bell and the battery shown in fig. 260 should be replaced by an insulation testing megger.
One of the two terminals of the circuit should be connected to the line terminal (marked ‘L’) of the megger, while its other terminal should remain open. With both lamp and the switch taken out of the circuit and the neutral wire connected to the L-terminal of the megger, the handle is turned.
If the pointer of the megger shows very small resistance on the scale, there is leakage somewhere in the neutral wire up to the lamp. If, however, the megger shows sufficient insulation resistance, the L-terminal of the megger should be connected to the live wire of the circuit with switch taken out and the handle is turned again.
In case there is any leakage in the live wire up to the switch, the resistance indicated in the megger scale will be very small. With no fault indicated this time also, put the switch on and turn the handle. If there is fault in the circuit, the megger will indicate very small resistance. The leak then exists somewhere between the switch and the lamp.
In this way when the sub-circuits are tested one after another (in case of large buildings circuits from one D.B. to another D.B. are tested one after another), the defective circuit will certainly be found out. Then the defective cable is to be replaced. (The minimum insulation resistance of each circuit should not be less than 0.5 megohm.)
Symptom 2:
One gets electric shock when touches wiring conduit.
Cause:
At some point or points current-carrying conductor and the conduit are in touch with each other and the conduit is not properly connected to earth wire.
Remedy:
Locate the leak by testing as described under symptom 1. Perform continuity tests for joints in the conduit and checkup if more resistance is developing on account of a bad contact at any joint. If so, open the Joint, clean the conduit ends thoroughly and fit the two pieces of conduit again. Checkup whether earth electrode has been disconnected from earth wire or conduit by measuring the combined resistance of the conduit and earth electrode with the help of an earth testing megger.
This resistance should not exceed 1 ohm. If anywhere the earth connection is not maintained, this resistance will be considerably high. After locating the trouble spot, the earth connection should be re-set.
Symptom 3:
On testing, insulation resistance is found to be less than 1 megohm.
Cause:
Earth fault or leakage at a spot in a cable or a fitting.
Remedy:
Complete all the tests for earthing and remove the fault.
Symptom 4:
Meter disc rotates inspite of no load current flowing through the circuit.
Cause:
Leakage current in the circuit is considerably high. This symptom is practically absent in circuits having leakage within permissible limit.
Remedy:
Since the leakage is very high, only switching off the main may not always be sufficient. In such a case, after switching off the main, the main fuse should be taken out and the supply main to D.B. should be disconnected from D.B. Then test the circuits at D.B. one after another by means of an insulation testing megger and locate the faulty circuit or circuits. Replace the cable or fitting whichever is found to be faulty.
Symptom 5:
Meter disc rotates even when the consumer’s main switch is off.
Cause:
The defect is in the meter.
Remedy:
Inform the supplier about this defect. But before doing so, test the insulation resistance of the wiring system and be sure that there is no defect in the wiring itself. If possible, it is better to measure the insulation resistance of the main cable from supplier’s meter up to consumer’s main switch also.
Fault # 5. Defects in Fluorescent Lamp Circuits and Corresponding Remedies:
No illumination is obtained from a defective filament lamp, but the thing is otherwise with a defective fluorescent tube. The tube then throbs or may develop other symptom, but does not stop emitting light. It is better to replace the tube at this stage. But before that it should be put to proper tests to make sure that its life has really expired. If the symptom persists even after replacement, it is needless to say that there is other defect in the circuit.
Whenever there is any fault in the circuit, at first it should be switched off. If a number of fluorescent lamps are controlled by a single switch, remove the defective tube and observe how the other lamps are performing. Even a good tube becomes no good when connected in a defective circuit. A doubtful tube shall be tested in a healthy circuit, but a good tube shall never be connected in a defective circuit.
To check up whether there is anything wrong with the switch, at the very outset take out the switch from a defective circuit and connect it in a healthy circuit. When the switch is checked up, test the tube also in the same manner.
Next examine the choking coil. Choking coil should always remain connected in the live line or phase wire. If it is connected elsewhere, the defect in the earthing system is not clearly indicated. Checkup whether the accessories are getting supply at their rated voltage from the supply line. If the choking coil is provided with tappings, checkup whether proper tapping is being used.
Trouble may arise due to fault in the starting switch or, starter. Hence, checkup whether the starter is working properly. Once the fluorescent tube lights up, no current flows through the starter. So it may be taken out for testing after the lamp is switched on.
Fault # 6. Defects in Fluorescent Lamps:
Symptom 1:
Very often the lamp throbs.
Cause:
(i) Life of the lamp is coming to an end.
(ii) There is defect in glow-switch, i.e. starter. Sometimes flow of current through it stops, sometimes current continues to flow through it. Close observation reveals that the lamp appears to be brighter when lights up.
(iii) There is defect in the lamp tube,
(iv) Circuit voltage is less than the rated value,
(v) Due to cold during winter season or due to sudden gust of cold Wind, the lamp throbs.
Remedy:
Replace the tube for the defects mentioned in (i) & (iii). Replace the glow-switch or starter for the defect mentioned in (ii). Steps must be taken to obtain rated voltage in the circuit in order to rectify the defect mentioned in (iv).
Symptom 2:
Light from the tube seems to be rotating.
Cause:
Such a defect is likely to happen sometimes with a new tube. After use for a while, this is set right.
Remedy:
Switch off the lamp, and after a while switch on it again. Very often the defect is found to be rectified when such a measure is adopted. If, however, the defect is not rectified after switching off and on a few times, the tube has to be replaced.
Symptom 3:
The frequency of variation of light from the tube appears to be less than the frequency of supply.
Cause:
Probably the life of the tube has come to an end.
Remedy:
Replace the tube.
Symptom 4:
When the lamp is switched on, the filaments glow up as expected, but the tube does not light up.
Cause:
Contacts of the starter close up as soon as the lamp is switched on, but these do not open out even after the gas is ionised.
Remedy:
Very often a gentle tap at the starter removes this trouble. If not, replace the starter.
Symptom 5:
Only the filament at one side glows up when the lamp is switched on, but the tube does not light up.
Cause:
There may be ‘earth’ in the starter or in the radio-suppressor circuit. Perhaps there is a short-circuit in the latter or there is an ‘earth’ in the wiring.
Remedy:
Replace the radio-suppressor. Test the insulation resistance of the Wiring system and rectify the earth fault.
Symptom 6:
The lamp is switched on, but nothing tangible happens.
Cause:
(i) The filament of the tube is fused.
(ii) Contacts of the starter do not close up.
(iii) The circuit is trimmed or damaged somewhere.
Remedy:
Test for each individual cause and rectify the defect.
Fault # 7. Defects in Starter or Glow-Switch:
Symptom 1:
Contacts get stuck up when the switch is still on.
Cause:
Probably a short-circuit has developed in the resistance of the radio-suppressor unit.
Remedy:
Replace the radio-suppressor.
Symptom 2:
Glow-switch remains bright even after the tube lights up.
Cause:
Voltage for excitation is not sufficient.
Remedy:
Replace the glow-switch. If there is no change in symptom even after this replacement, the trouble may lie in the tube itself. In that case the tube is to be replaced.
Symptom 3:
The electrode inside the bulb of a glow-switch is slack.
Cause:
If there be earth’ in the connecting wire of the switch, such a defect is possible.
Remedy:
Locate the ‘earth’ in the wiring. Replace the switch.
Symptom 4:
Filament does not get enough time to heat up in-spite of frequent on and off operations of the glow switch. As a result the tube does not light up.
Cause:
The switch is defective.
Remedy:
Replace the switch.