[closetking]

My point is, its the current draw from the ballast that determines its consumption. Not the wattage of the bulb since that voltage is not 120, it's stepped up way high to fire the sodium gas.
Look at your ballast, the current rating is on it. My 430 draws 5.2 amps 624 watts at 120v. My 1000 draws 1080 watts at 120v. Using your calculation I would be under stating the power used my lights at 120v and the true Kwatt consumption of the ballast. Thats why the current is printed on the label. they don't tell you the resistance, they tell you the current. The formula is below.
In order to know the power you need to know the current, in order to know the current you need to know the resistance. Heres ohms law. 35 years in electronics.

Again it's not the wattage from the bulb it's the wattage from the ballast you pay for in your bill.

P=EI P watts E volts I current
I=E/R R resistance

P.S now you understand why 1000W lights are more efficiant than smaller ones . More lumens per watt consumed.

[splif-magnet]

okok,, now we are getting into the nity grity... fair dues the amperage will be slightly diff for each balast,, BUT a 400 w ballist or a 1000w balist will figure CLOSE to the needed CKT rating,, given the math used,,,,

PS what other bulb would you use on a 1000w balist,, ???

1000w bulb or a 1000w balist.. whats the real diff??/ 1000w consumed....

[closetking]

Using your formula of divideing the wattage by the volts gives an erroneous current rating i.e. 430w /120=3.5 amps according to your way of calculation (which is wrong, it only works for the 1000 because of it's efficency.) That puts you 30% diff btwen the rated current on the label and your calculation method. And if you read the previous posts regarding safety margin, you're already off by your calculation. Same thing for flouro lites. 80 watts from the 2 bulbs is not the result of the current draw from the ballasts. Your calcs will show a fluoro fixture drawing .6 amps. Wrong, fluoro ballsts draw different current based on the length of bulb.
And watt is the difference in which watts you calculate?
As exampled above, if you are figuring power consumption and current draw for your ckt brkrs, you'd better use the rated current on your device for your calculations. Load transformers (ballasts) are different than light bulbs and other devices not using transformers and capacitors. The important thing is to use the rating on the device, that way you'll know the current draw for sure for saftey purposes.

Don't figure a large commercial installation by your calc method, you'll start a fire. Read up on the practical uses of Ohm's and Kirchoff's Laws, you'll be a valuable electrician.

[splif-magnet]

hmm ok to be more "exact"... you are correct.. i was just trying to show guide lines for general safty..

HELL NO,, would i NOT use rougth caculations for a large commercial job.. as i first said.. large HID lighting jobs are not my norm these days....

peace

[closetking]

No problem, I know you meant well, and actually your calc method is acceptable for rough estimation of AC incandecent circuits. But you need to go by the manufacturers listed rated amps when working with reactive AC devices, such as transformers, ac motors, etc.

Peace

[Slowmoe]

In April here in Mpls. police stormed what they thought was a pot grow site, but found only a family that uses a lot of electricity.
$300 a month. Safe growing to all Slowmoe

[Vapour]

1000 watt HID lamps are NOT the most efficient. You need to check with the manufacturers.

[babylon by bus]

600's are the most effiecient but I wouldn't really worry about power usage. Remember the 2k flower room you want to run will only be on 12 hours, so its only 1k of power a day.

If I was renting a house I would run AT LEAST a 4000w flower room. You won't have any trouble as long as you keep your mouth shut.

[closetking]

B by B in what way is a 600W light more effecient than a 1000w?
You get more lumens per watt with a 1000 than a 600. It is cheaper to run a 600 but more lumens/watt for a 1000 = higher efficency.

Running a 1000w light for 12 hours will be 13kw/per day. at 10 cents /kw will cost $1.30 per day

[Aquaman2112]

How could I add to my circut breaker box extra circits if I cannot get an electrician, I want to set up three 1000w on timers in a room but have no idea how to do it and cannot figure out a story that says I need three timers for one room! could have one setup for said outside lights Soo I would like to do it myself but never have done more than change an outlet!