Jcomeaux21
Member
- Location
- Lafayette la
From my understanding you dont take the lamps wattage into consideration. It's the ballast it self correct?
200 amp 3 phase 208 volt service
- Thread starter Jcomeaux21
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From my understanding you dont take the lamps wattage into consideration. It's the ballast it self correct?
I am going to point out that if we are really tying to do a calculation that that NEC requires we use the ballast info not the lamp wattage. PF and efficiency do not come into the required calculations.
We can start a new thread about the NEC requirements if we need to.
The ballast information contains the power factor and efficiency information. It is reflected in the ballast input amps at the given voltage.
If you have the actual ballast input amps from the nameplate or data sheet, then you don't need lamp watts.
- Location
- Massachusetts
I am a layman and I will tell you how I would do it. I am sure others will take issue with the details.
The basic calculation for your service is this
208 volts x 200 amps x 1.73 for three phase = 71,900 watts more or less
You can't just add up the load amps when dealing with three phase, you need to convert everything to watts (actually VA but I don't get to worried about it)
So figure out the existing load in watts / va, subtract that from the 71,900 and that will be how much more load you can put on the service.
- Location
- Massachusetts
Yes, so no need to bring it up here just to make things more difficult right?
kwired
Electron manager
- Location
- NE Nebraska
The ballast info will be based on the lamp wattage, PF and efficiency.I am going to point out that if we are really tying to do a calculation that that NEC requires we use the ballast info not the lamp wattage. PF and efficiency do not come into the required calculations.
We can start a new thread about the NEC requirements if we need to.
The red flag that came up right away was that the figure given to us was a value that would have to be 100% power factor and efficiency - which is pretty unlikely, so we sort of assumed there may be a mistake of reading the current associated with 240 volts instead of the 208 volt rating. Or maybe even that these do not have a 208 volt tap? I have mostly only seen quad tap or straight 120 or straight 277 volt ballasts, but that typically for 400 watt luminaires, maybe is more common to see 240 only in 1000 watt versions?
The ballast info will be based on the lamp wattage, PF and efficiency.
That's what I said (although I was chided for it).
- Location
- Massachusetts
The ballast info will be based on the lamp wattage, PF and efficiency.
Can you tell me about the sun, is it hot?
kwired
Electron manager
- Location
- NE Nebraska
never been there, not sure.Can you tell me about the sun, is it hot?
Jcomeaux21
Member
- Location
- Lafayette la
kwired
Electron manager
- Location
- NE Nebraska
My guess on the 50 amps in is that you are required a 50 amp supply circuit, the actual load is the 40 amps out.
You still need to figure that extra 25% though for continuous loading on your service/feeder supply conductors and overcurrent device selection though, unless you have 100% rated devices but that would be rare for this kind of application.
Jcomeaux21
Member
- Location
- Lafayette la
kwired
Electron manager
- Location
- NE Nebraska
That is likely power factor, you still need to factor in 125% for continuous load reasons on your conductor ampacity calculations and overcurrent device selection. So a 40 amp continuous load will require 50 amp conductor and 50 amp overcurrent device.
- Location
- Massachusetts
You do not know that.
Can you tell us what make and model?
- Location
- Massachusetts
AMJcomeaux21, if you want meaningful answers to your questions this basic info would be very helpful.
kwired
Electron manager
- Location
- NE Nebraska
What I don't know is if it is a continuous load, or if he has 100% rated breakers. The chances are pretty high he needs to factor in the additional 25% though.
JFletcher
Senior Member
- Location
- Williamsburg, VA
Missed this post. So you have 22 lights now + AC loads/fans and want to go to 40? You probably have room for that.
I and I think most everyone else figured you had 40 lights already looking to double that to 80.
Your loads are very well balanced tho the amp readings are lower than I'd expect; were all 22 lights + all equipment running when you took those readings?
My calculations for 40 1000W lights running simultaneously are not incorrect; that alone would pull north of 111A on a 3ph 208V service, which is much higher than your calculation of 64A, nearly double; the only thing I can think of that accounts for the difference is half the lights being on while half were off.
kwired
Electron manager
- Location
- NE Nebraska
I think he has 40 lights now but was only running 22 plus the HVAC loads when he took the measurement.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
It would be helpful if the op gives us a total understanding of what he is trying to do so we are not just throwing things out there. Is he looking for a feeder size? Is he looking to calculate the load of the 200 amp panel? We will need much more info but perhaps he has already gotten what he needs.
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