Calculate Size of Main ELCB & Brach MCB of Distribution Box
October 2, 2015 99 Comments
Design Distribution Box of one House and Calculation of Size of Main ELCB and branch Circuit MCB as following Load Detail. Power Supply is 430V (P-P), 230 (P-N), 50Hz. Consider Demand Factor 0.6 for Non Continuous Load & 1 for Continuous Load for Each Equipment.
- Branch Circuit-1: 4 No of 1Phase, 40W, Lamp of Non Continues Load + 2 No’s of 1Ph, 60W, Fan of Non Continues Load.
- Branch Circuit-2: 2 No of 1Ph, 200W, Computer of Non Continues Load.
- Branch Circuit-3: 1 No of 1Ph, 200W, Freeze of Continues Load.
- Branch Circuit-4: 8 No of 1Ph, 40W, Lamp of Non Continues Load + 2 No’s of 1Ph 60W, Fan of Non Continues Load.
- Branch Circuit-5: 4 No of 1Ph , 40W, Lamp of Non Continues Load + 1 No’s of 1Ph 60W, Fan of Non Continues Load.+ 1 No’s of 1Ph 150W, TV of Continues Load
- Branch Circuit-6: 1 No of 1P , 1.7KW, Geyser of Non Continues Load.
- Branch Circuit-7: 1 No of 1Ph, 3KW, A.C of Non Continues Load.
- Branch Circuit-8: 1 No of 3Ph, 1HP, Motor-Pump of Non Continues Load.
| Fault Current |
|
| Voltage | Fault Current |
| 230V | 6KA |
| 430V | 10KA |
| 11KV | 25KA |
| Class of MCB/ELCB/RCCB |
||
| Type of Load | Class | Sensitivity |
| Lighting | B Class | I∆n:30ma |
| Heater | B Class | I∆n:30ma |
| Drive | C Class | I∆n:100ma |
| A.C | C Class | I∆n:30ma |
| Motor | C Class | I∆n:100ma |
| Ballast | C Class | I∆n:30ma |
| Induction Load | C Class | I∆n:100ma |
| Transformer | D Class | I∆n:100ma |
| Size of MCB/ELCB |
||
| Current (Amp) | Lighting Load MCB/ELCB (Amp) | Heating/Cooling/Motor-Pump Load MCB/ELCB (Amp) |
| 1.0 to 4.0 | 6 | 16 |
| 6.0 | 10 | 16 |
| 10.0 | 16 | 16 |
| 16.0 | 20 | 20 |
| 20.0 | 25 | 25 |
| 25.0 | 32 | 32 |
| 32.0 | 40 | 40 |
| 40.0 | 45 | 45 |
| 45.0 | 50 | 50 |
| 50.0 | 63 | 63 |
| 63.0 | 80 | 80 |
| 80.0 | 100 | 100 |
| 100.0 | 125 | 125 |
| 125.0 | 225 | 225 |
| 225.0 | 600 | 600 |
| 600.0 | 800 | 800 |
| 800.0 | 1600 | 1600 |
| 1600.0 | 2000 | 2000 |
| 2000.0 | 3000 | 3000 |
| 3000.0 | 3200 | 3200 |
| 3200.0 | 4000 | 4000 |
| 4000.0 | 5000 | 5000 |
| 5000.0 | 6000 | 6000 |
| 6000.0 | 6000 | 6000 |
Calculation:
Size of MCB for Branch Circuit-1:
- Load Current of Lamp= (No X Watt X Demand Factor)/Volt =(4X40X0.6)/230=0.40Amp
- Load Current of Fan= (No X Watt X Demand Factor)/Volt =(2X60X0.6)/230=0.31Amp
- Branch Circuit-1 Current as per NEC = Non Continues Load+125% Continues Load
- Branch Circuit-1 Current as per NEC =(0.4+0.31)+125%(0) =0.73Amp
- Type of Load=Lighting Type
- Class of MCB=B Class
- Size of MCB=6 Amp
- No of Pole of MCB=Single Pole
Size of MCB for Branch Circuit-2:
- Load Current of Computer = (No X Watt X Demand Factor)/Volt =(2X200X0.6)/230=1.04Amp
- Branch Circuit-2 Current as per NEC = Non Continues Load+125% Continues Load
- Branch Circuit-2 Current as per NEC =(1.04)+125%(0) =1.04Amp
- Type of Load=Lighting Type
- Class of MCB=B Class
- Size of MCB=6 Amp
- Breaking Capacity: 6KA
- No of Pole of MCB=Single Pole
Size of MCB for Branch Circuit-3:
- Load Current of Freeze= (No X Watt X Demand Factor)/Volt =(1X200X0.6)/230=0.87Amp
- Branch Circuit-3 Current as per NEC = Non Continues Load+125% Continues Load
- Branch Circuit-3 Current as per NEC =(0.87)+125%(0) =0.87Amp
- Type of Load=Lighting Type
- Class of MCB=B Class
- Size of MCB=6 Amp
- Breaking Capacity: 6KA
- No of Pole of MCB=Single Pole
Size of MCB for Branch Circuit-4:
- Load Current of Lamp= (No X Watt X Demand Factor)/Volt =(8X40X0.6)/230=0.83Amp
- Load Current of Fan= (No X Watt X Demand Factor)/Volt =(2X60X0.6)/230=0.31Amp
- Branch Circuit-4 Current as per NEC = Non Continues Load+125% Continues Load
- Branch Circuit-4 Current as per NEC =(0.83+0.31)+125%(0) =1.15Amp
- Type of Load=Lighting Type
- Class of MCB=B Class
- Size of MCB=6 Amp
- Breaking Capacity: 6KA
- No of Pole of MCB=Single Pole
Size of MCB for Branch Circuit-5:
- Load Current of Lamp= (No X Watt X Demand Factor)/Volt =(4X40X0.6)/230=0.42Amp
- Load Current of Fan= (No X Watt X Demand Factor)/Volt =(1X60X0.6)/230=0.16Amp
- Load Current of TV = (No X Watt X Demand Factor)/Volt =(1X150X1)/230=0.65Amp
- Branch Circuit-5 Current as per NEC = Non Continues Load+125% Continues Load
- Branch Circuit-5 Current as per NEC =(0.42+0.16)+125%(0.65) =0.57+0.82=1.39Amp
- Type of Load=Lighting Type
- Class of MCB=B Class
- Size of MCB=6 Amp
- Breaking Capacity: 6KA
- No of Pole of MCB=Single Pole
Size of MCB for Branch Circuit-6:
- Load Current of Geyser= (No X Watt X Demand Factor)/Volt =(1X1700X0.6)/230=4.43Amp
- Branch Circuit-6 Current as per NEC = Non Continues Load+125% Continues Load
- Branch Circuit-6 Current as per NEC =(4.43)+125%(0) =4.43Amp
- Type of Load=Heating & Cooling Type
- Class of MCB=C Class
- Size of MCB=16 Amp
- Breaking Capacity: 6KA
- No of Pole of MCB=Single Pole
Size of MCB for Branch Circuit-7:
- Load Current of A.C= (No X Watt X Demand Factor)/Volt =(1X3000X0.6)/230=7.83Amp
- Branch Circuit-7 Current as per NEC = Non Continues Load+125% Continues Load
- Branch Circuit-7 Current as per NEC =(7.83)+125%(0) =7.83Amp
- Type of Load=Heating & Cooling Type
- Class of MCB=C Class
- Size of MCB=16 Amp
- Breaking Capacity: 6KA
- No of Pole of MCB=Single Pole
Size of MCB for Branch Circuit-8:
- Load Current of Motor-Pump = (No X Watt X Demand Factor)/(1.732XVolt ) =(1X746X0.6)/(1.732X430)=0.60Amp
- Branch Circuit-8 Current as per NEC =Non Continues Load+125% Continues Load
- Branch Circuit-8 Current as per NEC =(0.60)+125%(0) =0.60Amp
- Type of Load=Motor-Pump Type
- Class of MCB=C Class
- Size of MCB=16 Amp
- Breaking Capacity: 10KA
- No of Pole of MCB= Three Pole
Size of Main ELCB/RCCB:
- Total Brach Circuit Load & MCB Detail is
| Brach Circuit | Total
Current (Amp) |
Size of MCB (Amp) | Class of MCB | Breaking Capacity of MCB | Pole of MCB |
| circuit-1 | 0.73 | 6 Amp | B Class | 6KA | SP |
| circuit-2 | 1.04 | 6 Amp | B Class | 6KA | SP |
| circuit-3 | 0.87 | 6 Amp | B Class | 6KA | SP |
| circuit-4 | 1.15 | 6 Amp | B Class | 6KA | SP |
| circuit-5 | 1.39 | 6 Amp | B Class | 6KA | SP |
| circuit-6 | 4.43 | 16 Amp | C Class | 6KA | SP |
| circuit-7 | 7.83 | 16 Amp | C Class | 6KA | SP |
| circuit-8 | 0.63 | 16 Amp | C Class | 10KA | TP |
| Total | 18.04 |
- Total Load Current as per NEC= 18.04Amp——–(A)
- Max Size of Branch circuit MCB=16Amp
- Total Current of Panel as per Branch Circuit= 2X Max Size of Branch circuit MCB
- Total Load Current of Panel as per Branch Circuit =2X16=32Amp——(B)
- Total Load Current of Panel as per NEC = Maximum of (A) and (B)
- Total Load Current of Panel as per NEC=32Amp
- Min Size of ELCB/RCCB as per NEC=40Amp
- Class of ELCB/RCCB= B or C Class
- No of Pole of ELCB/RCCB=TP or FP
- Sensitivity( I∆n)=30ma
- Breaking Capacity=10KA
Size of Distribution Board:
- No of Single Pole Branch Circuit MCB (SP)= 7 No’s
- No of Three Pole Branch Circuit MCB (TP)= 1 No’s
- Main ELCB (TP)=1 No’s
- Total No of Way of D.B (SPN)= (SP)+3X(TP)=7+(3X2)=13Way SPN
- Total No of Way of D.B (TPN)= (SP)/3+ (TP)=(7/3)+(2)=4+2=6Way SPN
- Select Either 14Way SPN or 6 Way TPN
Load Balancing of Distribution Board:
- To Balance Load We need to try distribute Single Phase load on each Phase.
- Suppose We connect Branch Circuit load on following Phase
| Brach Circuit | Current (Amp) | Type of Load | Connection on |
| Branch circuit-1 | 0.73 | Single Phase | Y Phase |
| Branch circuit-2 | 1.04 | Single Phase | B Phase |
| Branch circuit-3 | 0.87 | Single Phase | Y Phase |
| Branch circuit-4 | 1.15 | Single Phase | B Phase |
| Branch circuit-5 | 1.39 | Single Phase | Y Phase |
| Branch circuit-6 | 4.43 | Single Phase | B Phase |
| Branch circuit-7 | 7.83 | Single Phase | R Phase |
| Branch circuit-8 | 0.63 | Three Phase | RYB Phase |
| Summary of Load | |||
| R Phase Load | 8.5 | Amp | |
| Y Phase Load | 3.5 | Amp | |
| B Phase Load | 7.23 | Amp | |
| Total Load | 18.04 | Amp | |
Summary of Distribution Box :
- Size of Distribution Box : 14Way SPN or 6 Way TPN
- Size of Main ELCB: 40A,B or C Class,30ma,10KA
- Size & No of Branch MCB: 5 No’s of 6A,SP, B Class,6KA
- Size & No of Branch MCB: 2 No’s of 16A,SP, C Class,6KA
- Size & No of Branch MCB: 1 No’s of 16A,TP, C Class,10KA
JIGNESH PARMAR
Dear Sir, Very Nice information on Electrical. Do you have such link for Instrumentation also if so please send link..? RegardsVilas Garde
Very elaborate, precise and complete information about the calculation of size of MCB, ELCB, RCCB has been given to the knowledge of users for various load options. Kindly can you give us what current rating or amparage and milliamps MCB, ELCB and RCCB to be used for residential wiring with heating and lighting circuits/ loads at main panel outside the house (electric pole to main panel), Main panel to Distribution Board or Box inside the house, from distribution board to heating load/ circuit and lighting load/ circuits.
So Useful tips for electrical power distribution design of residential and commercial Building
Thank you Sir,
Dear Jignesh sir,,,
I m selvam working in ISRO as an Electrical Engineer, It is very useful material for everyone who wants to select the ELMCB nd MCB, DB…i really enjoy reading ur all blogs nd it gives me a clear idea and all practical concepts..i wish to continue ur valuable nd wonderful efforts…thanking u sir…
That is a good example. How to design an Electrical panel board and do the wiring ? Also, what are the useful software available in the market to do that?
Thanks and regards,
SUPER SIR IT IS REALLY VERY HELP FULL TO ME SIR . BECAUSE I AM A FRESHER AND I STARTED MY WORKING WITH OUT PRACTICAL KNOWLEDGE……AND ONE MORE HON ABLE REQUEST IS PLEASE MAIL BUILDING CONSTRUCTION RELATED ELECTRICAL TOPICS MEAS CALCULATION……………………PLEASE SIR
Am very interested on article of sizing CB,
My request is, if possible let me have full topic of switchgear where I can help other on proper electrical installation and utilisation as well.
Thanks
Even a short course as right now am working in academic institution from Tanzania.
hello sir,
I am using a 2 pole,30ma sensitive rccb on the main line for the entire house.All the phase and neutral connections are done from the output of the rccb.I have one inverter/ups also which is getting the power supply from the output of the rccb.I want to connect a separate rccb on the output side of the inverter connection,but for this i am not able to find the proper way to connect the new rccb. if i am connecting the o/p from inverter and the same neutral,which is used for the power supply of the inverter as the i/p of new rccb and the single load wire(phase) at the output with leaving the neutral pole as it is then the new rccb trips.If i short both the i/p and o/p neutral of the new rccb and connecting the phase as above then also the new rccb trips .i guess there is some problem regarding neutral looping.please suggest me the proper way of connecting the rccb.
good info. Is it possible to conduct basic design induction in Mumbai? In case interested then it can be discussed
can you please tell me why you are not multiplying the calculated load current with 125% for branch Ckt calculation. as its non continuous load mentioned by you in the beginning.
This is very useful for those who are in construction field.
Where to fix the Z CT in HT Cable. i.e only three core or three core with earth. please explain with diagram sir.
sir send and update s of electrical calculations please
Sir for Current Calculation we use formula I =P/V x (Power factor )
Or I =P/V x (Power Factor) x(1.73)
But here You used I =P x (Power Factor)/V
Plz Sir explain
It is Demand Factor….Not Power Factor
Why calculation not include with power factor?
dear sir,
what size of wire should be used for Light Points,fan points,etc and how many runs [ 2 or 3 runs]
hello Sir,
Can we use a 400v main mcb double pole in a 240v supply.will it trip or work same as a 240v breaker?
Thnx fr
Deepak
Is there an article who to do this calculation as per IEC?
Overload calculation for MCCB in case using it on the primary side of small dry type transformer by IEC code.
Do you have calculation as per IEC standards?
Your notes r very useful for to study for any kind of installation of an electrical equipment. Thanking you
ur notes are awesum
Tanx for a very wonderful job. May Almighty Allah guide you right
good
sir, very nicely understand every things thanks for u
Thank you very much for your kindly Sir;
Thanks
Dear Sir,
Thanks for the useful informations. But the formula for calculating the load you used in all circuits the demand factor must be down not up! Am I correct? I= (no. * P)/(1.7*V*Factor)
Hi……..SIR…..
I WORK IN ONGC AS ELECTRICIAN.ON A FIRST DATY OF
MY JOB I FOUND THAT THERE IS TWO PHASE SHOWS IN 5A AND 15 A PLUG
SOCKET OF 110 VOLTS EACH . HOW CAN AMPLIENCES WORK ON TWO PHASE OF
110 VOLTS WITHOUT NEUTRAL.?? AND WHEN I ASK FOR THAT TO MY SENIOR HE
TOLD ME THAT THIS IS RULE IN ONGC THAT THEY CAN NOT USE NEUTRAL FOR
LIGHTING PURPOSE. BUT HE HAD NO REASONE FOR THAT. CAN YOU HELP ME TO
UNDERSTAND THIS
why multiplie 125 %
Dear Jignesh sir,,,
I m selvam working in ISRO as an Electrical Engineer, It is very useful material for everyone who wants to select the ELMCB nd MCB, DB…i really enjoy reading ur all blogs nd it gives me a clear idea and all practical concepts..i wish to continue ur valuable nd wonderful efforts…thanking u sir…
Dear sir please let me know for 20hp power what
size of elcb rccb is required
Asap
fault currents are given for 1second or more time plz add answer?
sir can u please suggest if i have 30 volt bulb then how to count watt and ampere for it
dear parmer,it is wondrful information given by u.i think crores of indian population need to read and learn about this house electricity information.i am 71yrs and i learn from u which i have been waiting to learn this basics.thanks
Dear Sir, Thanks alot for providing a clear article on this topic. I enjoyed reading.
Sir,
I think all the phases (R,Y,B) have to be equal load and balanced. but here r=8.5,Y=3.5,B=7.23 Watts. For a balanced connection phases should have equal loads.
Nice sir,
Sir i need how to calculate the cable sizing for the building from transformer centre .
can you tell me formula to calculate breaking capacity of MCB for load 200W 415V with 5% impedance n transformer ratings are 1500KV
Current rating of mcb
How much ELCB required for 48 AMP load extension
I’m working for many years but no one explain me like this, thank u so much sir.
Sir should you go for mcb board for Microwave oven
Good day Sir,
I am trying to size a MCB for a 3 phase 380Vac, 2.5kW motor. and based on what I ended up calculating was a MCB of the size 16A with a fault current of 10kA, will this work?
sorry ac is single phase load.
Dear Sir,
Could you explain the load balancing. Here load is not balanced, in a ckt the load current is 3.5 A which is more less than other two ckts.???
Hi how to determine demand factor ?
thank s
Thanks alot sir
Sir in your above calculation of selection of MCB i want to ask a question i.e. in your branch circuit no. 3 you have include the freeze in a non continuous load why? and what is the us
Its very useful article or information to choose proper mcb,rccb etc. I am a local electrician . Its increase my confidence more than before. Its very very helpful fo me. Thank you.
thanks sir
63A MCCB 25 KA- WHAT IS 25 KA ? How will i find out the ka rating of MCCB?
Branch Circuit-3: 1 No of 1Ph, 200W, Freeze of Continues Load.
but why did u calculate its load current as a non continuous load sir? can u explain?
sir
this is very helpful and nice
and can you give details of cable size and selection all like internal wiring and LT/HT cable.
please sir.
Laxman
how to choose the right mcb rating for drawing
Dear Jignesh ji, My requirement may be a very very small problem for you as I am not an Elect. Engineer but has ample curiosity to know about basic electricals. My question is about the Ceiling Fan connection with Capacitor. Generally there are 3 wires given from the Ceiling Fan coil I.e. Starting Coil / Running Coil and Combination of Running and Starting coil wires. While connecting with the capacitor and Connector ( on 3 points – 1. Phase 2. Neutral and third dummy ) please advice which are the wires connected with phase / neutrals of the fan connector – 3 holes ( after connecting with Capacitors ) Some electricians says Running and Common on Phase/Neutral and the remaining in dummy and some says Starting and Common in phase/neutral and other in dummy whole. Pls. explain. I am very much eager to hear from you about this. . If I am confusing, my requirement is in the 3 whole connector which are the two wires to be inserted in the phase / neutral and which in dummy whole ).
Our light switch is 10 amps and MCB is 20 Amps
My question is if current increase in the circuit due to blasting chock sort circuit in some turns than what happened, As per me switch suppose to be meet the MCB ampacity as as NEC same thing
Dear Jignesh Sir,
I require to know as per IE rules what should be the circuit distribution system for residential building?Is it mandatory to provide separate MCB for power ckt to different rooms in a flat?
What you mean by continuos load & non continuous load ? Can u explain selection of demand factor too
I am not clear that,
1 why incoming Circuit Breaker 40A and
2 Out going circuit breaker total 78A (6+6+6+6+6+16+16+16)
definitely out going ckt breaker will be in single phase.
Hi, can i check why total current is 18.04 amp instead if 18.07? Is it due to rounding off?
Sir,
Nice information on electrical power system and network of distribution. I look forward seeing more information on distribution network.
Please prepare and upload a form (online/offline) for calculating the requirement.
My Panel here has 2 nos of 250 A outgoings, 2 Nos of 100 A outgoins, 2 nos of 63 A outgoings and 1 no 200 Amps outgoing. How can I calculate Incomer rating.
The article is in detail and easy to understand.please tell me the NEC details taken as reference in the article.
Very nice infarmatio, keep on!
Beautifully explained
Found your post interesting to read. I cant wait to see your post soon. Good Luck for the upcoming update.This article is really very interesting and effective.
You sound so practical a teacher , parmar .
Can you explain about demand factor and nec
Great help sir
Thanks very much
Hi Jignesh ji,
I am working in a electrical project Company. Pls upload the NEC Codes with Brief Description.
Branch circuit-8
how to select 16A TP MCB as per current rating 0.60Amp.
In Branch circuit 8 how to select 16A TP MCB but given current value 0.60Amp.
I Want witch type of use mcb
please provide the coordination chart for replacement of fuses with MCBs
Thanks sir very informative article, but why are not taking power factor in calculation ?
dear sir i need to know ups operating please
how do we know we need 10A SPN MCB Type B for lighting?
Why spare MCB are not considered?
Should we take spare MCB load in the calculation.
Please clarify.
If one of the brach circuit rating is 40A, then what will be the main RCCB rating? please advise.
Any book where i can read this kind of stuff.
Dear sir
Thank you
Are u sure we can use 30mA rating for earth leakage sensitivity at the main incomer of this circuit, especially when you have 1 no. of 1 hp 3-phase motor? I think later will create frequent nuisance tripping. 30mA is ok for the individual circuit.
Nice one
for a current of 4.43 A in Circuit 6 , a 16A MCB is used please clarify. is there is constant to be multiplied.
Thank you much for this article..I WOULD LIKE TO KNOW HOW TO CALCULATE THE MAIN RCB SIZE IF THE TOTAL BRANCH CURRENT IS GREATER THAN TWICE THE MAXIMUM MCB
Sir,
why did you not considering Power factor in the calculation
Nice information
Suitable Mcb and Rccb for 3phase 30 kw
ummmm can I find the PDF yeah I learnt a lot here thanks to the author
Dear sir,
This material is very informative and useful me. Thank you for your service.
its really valuable info to us , keep update sir
thanks
Very good explanation,
This is a good stuff but there is a mistake in the calculation which is overseen.
Current as per NEC = Non Continues Load+125% Continues Load