Types of switches and protection MCB classification

Classification of MCBs

First a fall what is MCB 

Let see

Definition of MCB

(1)  Low‐voltage (less than 1,000 VAC) types are common in domestic, commercial and industrial application, and include: 

(2) MCB (Miniature Circuit Breaker) — rated current not more than 100 A. Trip characteristics normally not adjustable. Thermal or thermal‐magnetic operation. Breakers illustrated above are in this category. 

(3) MCCB (Molded Case Circuit Breaker)—rated current up to 2,500 A. Thermal or thermal‐ magnetic operation. Trip current may be adjustable in larger ratings. 

Components used  in  MCB

The design includes the following components: 

(1) Actuator lever ‐ used to manually trip and reset the circuit breaker. Also indicates the status of the circuit breaker (On or Off/tripped.

(2) Actuator mechanism ‐ forces the contacts together or apart. 

(3) Contacts ‐ Allow current when touching and break the current when moved apart. 

(4) Terminals 

(5) Bimetallic strip. 

(6) Calibration screw ‐ allows the manufacturer to precisely adjust the trip current of the device after assembly. 

(7) Solenoid 

(8) Arc divider/extinguisher 

 

Electrical Accessories & MCB or Wiring material

Termination ;

A wire termination means that end of the wire that allows to connect to the device socket ,connecter, terminals etc. Eg  like take the two wire and then end of wire to end in socket or any terminals it is called wire termination. 

Splicing or jointing 

Splicing is the process of combining 2 lengths of wires so they can carry a current. Before you splice your wires together, you need to prepare the wires by stripping them and turning off the power.

Switch :

There are mainly 3 types of switches:

1 One way switch 

2  two way switch 

3 intermediate switch 

1 one way switch : It is used  to control  single circuit and lamp. 

Eg on and off Normal switch 

2 Two way switch : It is used to divert the flow of current to either of two directions. The two switch can also be used to control one lamp from two different places as in case of staircase wiring. 

Eg :staircase wiring  two switch control one lamp 

3 Intermediate switch : It is used to control a lamp more than two locations. 

Electrical Accessories 

1 Termination 

2 splicing or jointing 

3 switch 

4 Holder

5 Junction box 

6 MCB

7 RCCB

8 Fuse

9 Lamp

10 Push Button 

Load Calculations

Load calculations 

Light load;  bulb, fan, 5A socket  these are  light load 

Power Load;  15A socket, Heater,AC ,gyser,  exhaust fan these are power load 

These 2 condition always friends you learn to do numarical  

Condition for circuits; 

Light load : 800w & 10 points

Power load : 3000w & 2 point 

First a fall we take a eg of 1 numarical  easily  understand friends 

Eg  Numarical 

1 The House has following Load :-

ROOM 1 :-  FAN              :-    1                                  Tube Light  :-   2

5A socket    :-    3 

     AC   1.5 ton :-    1

       Kitchen;               Tube Light   :-    2                                                    5A socket   :-   2 

                                                                          

                

ROOM 2 :-  FAN              :-    1         

               Tube Light   :-    2        

  AC   1 ton    :-    1

           Bathroom :-   Tube Light  :-  1 

                                                              Gyser (  15A socket ) :- 1

                     5A socket    :-    1

                   

Note :- ( Fan = 80 W , Tube light = 40 W , 1 ton AC = 1500 W , Gyser = 2200 W, 5A socket = 750 W )

Do step by step Numerical and write down all conditions for each type of load

Find out the Total Circuits in the house and Total no. of Mcb’s and Size of DB Box.Also find out size of wire

First a fall calculate total load of Room 1 and Room 2 

Room 1 

1 Fan  * 80 w =80

2 tubelight * 40w=80

3 5 A socket* 750w=2250

1 AC  1.5 ton*2250=2250

Total.                     4660w

Room 2 

1 Fan * 80

2 tube light  *40

1 5 A socket* 750

1 AC 1 ton* 1500

Total.         2310w

Kitchen 

2 tubelight * 40 

2 5 A socket * 750

   Total.          1500 w

Bathroom 

1 tube light * 40

1 15A socket * 2200

Total.             2240w

Calculate light load 

Light circuits;  7 

Power circuit;  3

There are 10 way to connect MCB in house

Size of Distribution Board is 10 way 

Same as MCB  size of DB

Total No. Of circuits : 10

Total No. Of MCB;  10

total No. Of Distribution board;  10- way 

I hope you understand step by step 

Conduit wiring

Conduit wiring 

Conduit wiring system is the best for domestic and commercial installation. 

It provides proper protection to the installation against fire hazards, shock, mechanical damage and dampness. 

The cabe used in this system is either V. I. R. OR P. V. C. Insulated and is run in mild steel or pvc pipes called as conduit wiring. 

Advantages 

1 Conduit provides prtection against mechanical injury and fire. 

2 The whole system is water proof.

3 Conductors are safely secure from moisture.

4 Conduit provide protection against chemicals. 

Disadvantages 

1 It is costly system of wiring. 

2 It requires more times for erection. 

3 It requires highly skilled labour. 

Application 

1 In workshop for lightning and motor winding.

2 Place where important documents are kept such as record room. 

3 Damp situation. 

Metal Sheathed Wiring

Metal sheated wiring 

This type of wiring is also adopted for low voltage installation. 

This system is more of less similar to CTS wiring except that the cable used is different in this wiring. 

In this system conductors used are insulated with V. I. R and the coverd with an outer sheath of lead aluminum alloy containing 95%  lead and 5% aluminum. 

Advantages 

1 Conductor are protected  against mechanical injury.

2 It has longer life. 

3 It is suitably employed under damp situation. 

4 Conductor are protected against chemical. 

Disadvantages 

1 Cables are costlier than CTS or TRS wires. 

2 In case of leakage there is eveey risk of shock.

3 Skilled labour and proper supervision is required. 

Application 

This wiring system is suitable for low voltage installation. 

It may be used in places exposed to sun and rain provided no joint is exposed. 

CTS or TRS wiring

CTS OR TRS WIRING 

This type of wiring is also used for house wiring and is quite cheap. 

Cab tyre sheathed wire or rubber sheathed wire is normally used as conductor for this wiring. 

The wires are run on the teak wooden battens which are fixed on the wall or the ceiling by means of screws and wooden pluge. 

Advantages 

1  It is easy to install and rewire. 

2 Its life is long

3 It is cheaper than the other types of wiring except cleat wiring. 

4 Conductor have strong insulation. 

Disadvantages 

1 The conductor are open and liable to mechanical injury therfore this type of wiring cannot be used workshop etc. 

2 Good workmanship is required to make a sound job in TRS wiring. 

Application 

1  This type of wiring is suitable for low voltage installation and is extensively used for lightning purpose. 

2 This type of  wiring is suitable where acids and alkalis are likely to be prescut. 

Wooden casing and caping wiring

Wooden casing capping wiring 

1 This is one of cheapest types of wiring and is commonly used for house wiring.

2 The cable used in this

    type of wiring is either 

    V.I.R or P.V.C or any

   other approved insulated   

   cables.

Advantages

1 Better appearance than cleat wiring. 

2 Cheap in cost.

3 Easy to install and rewire. 

Disadvantages 

1 Not suitable in damp places. 

2 Risk of fire 

3 This type of wiring can be used only on surface and cannot be concealed in plaster. 

4 Since it requires better workmanship labour cost is more. 

Application 

This type of wiring is suitable where acids and alkalis are likely to be prescut.