1.25 is assential for Breaker

[Hameedulla-Ekhlas]

Greeting dear all, My question is regarding to circuit breaker size. I have the following calculation

TOTAL DEMAND LOAD
(KVA) 122.41

25% FUTURE LOAD
(KVA) 30.60


TOTAL LOAD DEMAND LOAD + 25% FUTURE LOAD

(KVA) 153.01

TOTAL CURRENT 231.83 Amp

CIRCUIT BREAKER RATING 231.83 * 1.25 289.79 Amp

STANDARD CIRCUIT BREAKER SIZE 290 Amp

My question is in the above information I have been already asked for 25% future load and I haved added it. So for determining the breaker size. Should I again Multiply the 231.83, which already contains 25% future , by 1.25.

Please advise me soon.

BR
Hameedullah Ekhlas

 

[ron]

Depending on the circuit breaker type, such as standard molded case CB's, you will need the additional 25% on top of your continuous load.
There are CB's that are breakers that are fully rated, but you need to specify that.

 

[John Paul]

TOTAL CURRENT 231.83 Amp

How did you calculate that?

153kVA / (.48 x 1.73) = 184.26A

153kVA / (.208 x 1.73) = 425A

 

[Hameedulla-Ekhlas]

Dear Sir,

TOTAL DEMAND LOAD
(KVA) 122.41

25% FUTURE LOAD
(KVA) 30.60


TOTAL LOAD DEMAND LOAD + 25% FUTURE LOAD

(KVA) 153.01


Line to line voltage in Afghanistan is 380 and line to neutral voltage is 220 volt.

Hope your question is solved

 

[augie47]

My opinion would be that if your "demand load" and "future load" is not continuous then you don't need the 1.25 on either. To me the number would be 153.01 if you wanted to add a "future load"

 

[bob]

TOTAL DEMAND LOAD
(KVA) 122.41
25% FUTURE LOAD
(KVA) 30.60
TOTAL LOAD DEMAND LOAD + 25% FUTURE LOAD
(KVA) 153.01

What method did you use to get the 122 kva demand load?

 

[Hameedulla-Ekhlas]

It is a residential load and contains receptacles lighting and etc. So, I applied the NEC demand factor, which is give for receptcles and lighting, and I got the total.


best regards,
Hameedullah Ekhlas

 

[John Paul]

Line to line voltage in Afghanistan is 380 and line to neutral voltage is 220 volt.

Thanks - Question solved, yes.

 

[bob]

It is a residential load and contains receptacles lighting and etc. So, I applied the NEC demand factor, which is give for receptcles and lighting, and I got the total.
best regards,
Hameedullah Ekhlas

If you used section 220 to calculate the load in the residence, you would not add 25%. In the US you would then take the largest motor, usually the A/C unit and add 25% to that load and then include it in the total. So you need to determine if your residence fits this situation. Usually the NEC calculations will allow for additional loads in the future. Let us know what you decide.

 

[Hameedulla-Ekhlas]

In this design's scope of work has asked me to add 25% for future load.
So, for motors I have already consider artical 430.47 and 430.32 and so on.