Building
Electrical Installation Maintenance Guide 2019 | The
article is all about how to do the building electrical installation maintenance
and operation. For the lighting installation electricians commonly used the electrical conduit pipes to make cable ways in the buildings. Electrical cable trays not
usually installed in the building construction. In domestic lines, Cable glands
usage is unnecessary for the electrical cables. The guide is completely covered
about the topic. so, read carefully without skip any paragraph.
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| Building Electrical Installation Maintenance Guide 2019 |
Building Electrical Installation - Points To Be Inspected for Maintenance
Every part
of the installation should be checked by a responsible official and preferably
recorded
in a
register or entered in a tabulated form.
In brief,
this consists of the following inspections:
1. Service
connection.
2. Main
switchboard.
3.
Internal wiring and its insulation.
4. Earth
tests and bonding.
5.
Switches and fuses.
6.
Portable apparatus.
7. Fire
precautions.
If the
annual inspections are carried out conscientiously, most of the defects come to
light and
could be
corrected before they result in a serious breakdown or accident. Some of these
defects
would
perhaps be installation defects and a few even due to faulty design. Both these
aspects will,
therefore,
have to be borne in mind, when carrying out inspections.
Insulation
Resistance Measurement Procedure
Megger
value for insulation test of the electrical wiring is a 500V and comprises
mainly two parts, viz., line to earth test and line to line test. Before
starting the tests, switch off the supply, remove the main fuses and disconnect
the neutral link. Then proceed as follows:
Line
To Earth Test
- First, insert all fuses at the fuse board and insert all the fluorescent lamps and also close all the single pole tumbler switches. where fans are provided, close the fan switches and put the regulators in the ‘on’ position.
- Now just short the phase and neutral terminals on the dead side of the main switch and connect them to one terminal of the megger. The other terminal is connected to the earth, or the conduit in which the wiring is run, or if the wiring is in lead covered cables, to the lead sheathing.
- Note and record the megger reading.
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Line To
Line Test | Building Electrical Installation
|
Note :
where 2-way staircase type switches are provided, reading should be taken in
both
positions
of the switch
This gives
the total combined insulation resistance to earth of both the phase and the
neutral
conductors
(I.E.E Wiring Regulation - 1103), The minimum permissible resistance should be not less
than 50/ no. of outlets.
Read IEE Full Form - Electrical Abbreviations and Full Forms
If there
are 30 wiring points, the insulation resistance should not be less than 50/30
i.e. 2 ½ megohms. If the megger show the value below than that, it cannot be
considered as satisfactory. The insulation resistance of each sub-circuit
should than be taken individually and the faulty section located and attended
to each final sub-circuit should have a resistance of at least .5 megohms,
under the worst conditions, i.e. during the rainy season when wiring is damp.
Line To Line Insulation Test on Building Electrical Installation Maintenance
- Disconnect all the consuming devices such as lamps, fans, or portable apparatus plugged on to 2 or 3 pin sockets,etc.
- Keep all single pole tumbler switches in the ‘on’ position.
- Remove all fuses in the fuse boards, and open the neutral link.
- Take the insulation resistance between the phase and neutral lines of each final sub-circuit for simplicity, a single circuit alone is shown. The insulation resistance between lines of each final sub-circuit should be not less than 5 megohms for 10 wiring points. If the readings are lower, the cause must be located and rectified.
I.E rule
No.48 states that the maximum permissible leakage on the consumers’ premises is
1/5000th part of the maximum current supplied to the consumer. Thus, if the
maximum load on the premises is say, 5 amps. On a 230 volts system (1150
watts), the maximum permissible leakage is 5/5000=1 milliampere. On a 230 volts
circuit, the minimum insulation resistance should, therefore, be 2,30,000 ohms
or .23 megohms. The above tests would reveal nearly all insulation defects in a
wiring installation. Insulation resistance of all portable apparatus such as
electric irons, heaters, etc. should, however, is taken separately.
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Continuity
Test
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Points To Be Checked in Switches and Fuses – Building Electrical Installation Maintenance
The
following points should be checked:
1. Every
fuse should be of the correct size. The correct size should be indicated on the
fuse board or the main board as the case may be. Examine the fuse wire; if it
shows any signs of overheating or sulphation, renew it.
2. The
main contact jaws of all switches should be cleaned and lightly vase lined.
3. The
inlet and outlet holes in iron clad switchgear, fuse boards, etc. should be
properly protected by means of suitable insulated bushes. The leads themselves
should be taped up, protected with insulating varnish and sealed with compound
to prevent moisture or water from getting into the equipment.
4. All
switches, fuses, etc. should be properly numbered to facilitate identification
of circuits. The main switch should also be prominently marked to facilitate
quick identification and to comply with the I.E rules.
5. The
V.I.R. connection inside wooden distribution boards should be rearranged and
taped up. Renew them if necessary.
6. Every
single pole tumbler switch should be tested for its being correctly connected
in the phase line. It shall under no circumstances be connected in the neutral
line. This can be checked by a test lamp, connected between the earth and the
switch terminal, with the switch in the closed position. If the lamp burns, it
proves that the switch is in the phase line. It is, however, very important to
remember, when conducting this test that the tumbler switch should be kept
closed. If this precaution is not taken, the results will be misleading. The switch
connected in the neutral line is incorrect.
Yet the
test the test lamp will light up since the test lamp and the main lamp are in
series across the supply. Both of them will light up but they will be dim.
Since the test lamp lights up one is likely to conclude erroneously that the
switch is in the phase line even though it is not.
The
correct method of conducting this test is to keep the switch closed the test
lamp will then not light up unless the switch is in the phase line.
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| Single Switch |
Points
to be Inspected in Portable Electrical Equipments
1. The
insulation resistance of the conductors should be checked by a megger. If the
reading is low, the cause must be investigated and rectified. Frequently the
cause is perished lead-in connections due to chafing of the leads.
2.On
effective cable grip should invariably be provide on every portable apparatus
and also at the plug end, where flexible cable connections are made the
effectiveness of the cable grip should be checked periodically, the internal
connections should not get disturbed when the cable is pulled, jerked or
twisted, But the grip pressure itself should not pinch the insulation unduly.
It is a good practice to redo the connections periodically after cutting off
the exposed ends of the cable. in the absence of a cable grip of good design ,
the cable may be looped and bound to the handle by whipcord as a temporary
expedient.
3. Where
interlocked switch plugs are provided, check if the interlocking action is
effective, i.e. it should not be possible to close the switch without the plug
in position, nor to withdraw the plug when the switch is in the closed
position.
4. In the
case of heavy equipment like a refrigerator, heater or boiler which remains
more or less in a fixed position, an independent permanent earth connection
should be made to the metal casing of the equipment by a copper wire of
sufficient section (8S.W.G), in addition to the usual earth connection derived
from the plug socket through the connecting cable, as a further measure of
safety.
5. When
making cable connections take care to see that the wire ends are twisted and
bend into a neat eyelet, to take in the screw securing it. The wire end should
always be placed clockwise below the screw head so that the end may tend to
close inside inwards when the screw is tightened; if placed anticlockwise, it
will tend to open out and get loose. Use a washer immediately below the screw
head to ensure that the wire is firmly gripped.
6.
Whenever wiring is passed through a hole in a metal body, it should invariably
be protected and insulated by a bush.
7.
Flexible wire ends should be neatly twisted together and preferably soldered so
that there may be no loose strands; Such loose strands may come in contact with
the metal body of a lamp holder or adjacent terminals causing as accident or
short circuit.
8. The
outer insulation of wires should only be stripped to the minimum extent
necessary. If stripped too long, there is every possibility of a short circuit.
9. Lamp
holders: The screw securing the wire end should be of proper length. If too
long, it may touch the body of the lamp holder. If the porcelain
interior is wrongly assembled the locking nick in the outer brass. Ring may
touch the live terminals. For Hand Lamps, Porcelain or Bakelite lamp holder
should be used as far as possible as brass lamp holders are not so safe.
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| Double Switch |
Action
To Be Taken If Electrical Equipment Catches with Fire
The
following are the steps:
- Switch off the main supply.
- Use fire extinguishers recommended for the electrical fires.
- Water should not be used.
- Sand should not be used on electrical machines/equipment; this may be used for other purposes.
- There should be provision for fire extinguishers and buckets filled with sand on every large installation or industry.
Final
Word
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