Data Logger Results

[john37]

Can anyone please tell me how to determine the actual panel amperage panel load based on data logger results. Someone in my office explained to me that you take the average amps of each line and times that by the line voltage. The system voltage is 480/277V, 3 phase, 4 wire.

Example: L1 Phase amp average is 31.3A so you would times 31.3A x 277V = 8670.1VA
L2 Phase amp average is 35.9A so you would times 35.9A x 277V = 9944.3VA
L3 Phase amp average is 32.7A so you would times 32.7A x 277V = 9057.9VA
Total = 27,672.3VA

Now you divide 27,672.3 VA by 480V x square root of 3 (831) and would get 33.3 amps that
would be the actual amperage load on the existing panel.

Is this the correct way to determine the actual amperage load of an existing panel based on data logger results? I am attaching one page out of the data logging results for each phase line.

Thank you for your help.

 

[jumper]

If this is for determining existing load per 220.87, the average is not what you use.

Maximum demand x 125%, see section 2 of the reference cited.

Make sure seasonal loads and such are factored in also.

 

[john37]

Thank you very much. I just read the article. Is the method that I am doing correct to determine the existing load if I use the maximum demand number x 125%?

 

[jumper]

Thank you very much. I just read the article. Is the method that I am doing correct to determine the existing load if I use the maximum demand number x 125%?

No, you were calculating average, maximum is peak at any one point. The largest of all the samples taken on any one phase.

Max sample point in amps x Voltage (L-L) x 1.732 = kVA, kVA x 125% + additional new loads is what you would need.

 

[john37]

Got it. Thank you very much!