Panel Calculation

[onemarketplace]

I have calculated a panel but i am confused as how to calculate VA per circuit. All loads are continuous. My question is:

If I have 5 fluorescent fixtures in a circuit and they are 108W, the load per fixture would be 0.9Amps at 120V. right? 108W/120V= 0.9Amps


Now Total load for this circuit = 0.9 X 10 Fixtures = 9 Amps X 125% = 11.25 Amps


Everything is fine. But what number do I use to calculate VA on the panel?

The 9Amps value or 11.25Amps value? I am very confused about this. I think is 9Amps since the 125% is just for circuit and breaker calculation. Can someone explain if I am correct?

Thanks



My last question is. Once I have all this VA per circuits the process to find total Amps would be to devide total VA/240. In this case the service is 120/240 single phase? Explain please.

 

[LarryFine]

Welcome to the zoo! :smile:

If I have 5 fluorescent fixtures in a circuit and they are 108W, the load per fixture would be 0.9Amps at 120V. right? 108W/120V= 0.9Amps

As long as that number is coming from the ballast label and not tube wattage, that's correct.

Now Total load for this circuit = 0.9 X 10 Fixtures = 9 Amps X 125% = 11.25 Amps

For a continuous load, that tells you the minimum cicruit ampacity.

I think is 9Amps since the 125% is just for circuit and breaker calculation. Can someone explain if I am correct?

Correctamundo.

Once I have all this VA per circuits the process to find total Amps would be to devide total VA/240. In this case the service is 120/240 single phase? Explain please.

If you already know you have 9a per circuit, just divvy them up between the two lines.

If you have 10 of the circuits, place 5 on each phase: 45a at 240v.

 

[onemarketplace]

I forgot to tell.

I forgot to tell.

Thanks for your response, very clear but.

1 - I forgot to tell that I have on every circuit a 150W 120/12V transformer. My question is

Do I use the total wattage of transformer or Can I calculate low voltage lights separated and add them up for load? Thanks.

 

[LarryFine]

Thanks for your response, very clear but.

1 - I forgot to tell that I have on every circuit a 150W 120/12V transformer. My question is

Do I use the total wattage of transformer or Can I calculate low voltage lights separated and add them up for load? Thanks.

The conservative thing to do would be to use the full rating of each transformer, but at 1.25a, you could probably use 1a and be okay. Someone could add more loads to each one.

While we generally don't have to allow for "what-ifs," for lighting fixtures, we're supposed to use the fixture's maximum allowable rating, and not merely that of the bulb we install.

 

[A-F-E]

Well here there are some technicalities
Such as True power and apparent power

True power = watts used & real power consumed

Apparent power = VA or name plate and stands for volt ampere used to calculate an assumed load

 

[LarryFine]

Well here there are some technicalities
Such as True power and apparent power

True power = watts used & real power consumed

Apparent power = VA or name plate and stands for volt ampere used to calculate an assumed load

True enough, but if he already has the amperages, he can simply add those together. Poor PF doesn't change that.