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| Subject - Load Calcs | |
| gnu_mike |
Say you have a 120/208 Y 3ph service. Now when you have 120 volt circuits you list the VA for the panel schedule branch circuit based on the 120 volts, but when you total the panel VA you use 360 (208 x sqrt.3) as the divisor for the total VA to arrive at total amps? Say I have a 120 volt circuit that's listed as drawing 8 amps. Would you list the VA for the panel schedule as 8 x 120 for that circuit, provided no other loads? Then how does this square when you total the VA and divide by 360 for total amps? |
| gnu_mike | Right - 8 amps on one leg (L-N). Hypothetical example. Example nevertheless. So, one 120 volt 8 amp circuit equals 960 VA. So it's entered on the panel schedule for the 120/208 wye 3 Ph. service as 960 VA. So say we have other loads on there - the VA's get totalled and divided by 208 x (sqrt.3) for total amps to the panel. Now initially we multiplied volts x amps to get 960 VA. Now this 960 (as part of the total) gets divided by 360 for total panel amps.This is a reduction in total amps of 1/3 (2 x 1/(sqrt.3))Does this balance? |
| cs409 | VA/(208)(1.732)= Total Amps or, VA/360 = Total Amps what r you figuring? what all is planned for this 120/208Y 4wire service? u need to do a total load cal for the building/home r what ever this service is used for........ then total all your VA and then div by 360.... best to u casey |
| gnu_mike | Like I phrased it previously... If you have a 120 volt circuit with an 8 amp load on it, now you multiply 8 amps x 120 for the VA and enter it on the panel schedule as 960 VA. But now when you total the panel you divide each VA entry by 360 volts to arrive at your total amperage.No? How does that balance? |
| SteveMc | So if your panel had just three loads each 120v and 8 amps (120 x 8 = 960) That would be a total panel load of (960 x 3 = 2880) There for the total panel load for each phase of the panel is (2880 / 360 = 8). I think you may be missing the fact that the load is 8 amps per phase and not the entire panel. |