Single Phase Loads on a Three Phase Panel
- Thread starter KWH
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victor.cherkashi
Senior Member
- Location
- NYC, NY
Yes, VA/208V
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I understand to divide by 208 for branch circuit but for total load on panel would you add those in with everything else and divide by the 359.84 or do that branch separate and add to the rest of the loads for a total panel load.
ptonsparky
Tom
- Occupation
- EC - retired
victor.cherkashi
Senior Member
- Location
- NYC, NY
By dividing total load of panel by 360, you're assuming that all phases are balanced, but usually it's not. By dividing total load by 360, it's gives you estimated Amps on each phase.
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kwired
Electron manager
- Location
- NE Nebraska
Looks like it is the result of 208 x 1.73.
So VA / 359.84 is going to give you amps.
But is only good for balanced portion of load across all three phases.
Cow
Senior Member
- Location
- Eastern Oregon
- Occupation
- Electrician
The way I was shown and what makes the most sense to me to do load calcs in instances like this, is make a small spreadsheet.
4 columns, one for each phase plus the neutral too.
Then for your rows, you write down your loads. I prefer to show amps on my spreadsheets, but KW's work too. Of course 3 phase loads would show a load across all 3 phases. Single phase across two phases. Pretty straightforward. 25% for largest motor. 125% for continuous loads, lighting, etc.
Add the columns up when you're done and see where your at.
We also use a Fluke logger, it's a little more real world.
4 columns, one for each phase plus the neutral too.
Then for your rows, you write down your loads. I prefer to show amps on my spreadsheets, but KW's work too. Of course 3 phase loads would show a load across all 3 phases. Single phase across two phases. Pretty straightforward. 25% for largest motor. 125% for continuous loads, lighting, etc.
Add the columns up when you're done and see where your at.
We also use a Fluke logger, it's a little more real world.
ptonsparky
Tom
- Occupation
- EC - retired
Thank you. IDR that I’ve ever calculated just that step. Always the whole thing at the same time.
kwired
Electron manager
- Location
- NE Nebraska
Me neither, but got to thinking and wondering if it wasn't a combination of what most of learned to do in two steps and sure enough it is. I first figured out 208 x 1.732, which is the precision level I usually use and came up with 360.256, and thought where is he getting that, then I though about it and realized it is close enough he may just be using 1.73 level of precision - and then it came out right on.
dmsv10
Member
- Location
- Frisco Texas U.S.A.
You can calculate all you want, normally, I would allways do a before and after for total load in amps. Knowing that heaters are normally a PF of 1, and the remaining unbalanced loads will also increase your neutral current. Best to Amp Clamp Pre and Post install.
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