Mh fixtures

[Derick]

I have 70W metal halide fixtures at 277v.Ballast line open circuit current 0.8Amps,PF 90%.
How do I get a total fixture current draw?.Since open circuit is the largest
current do I need to add fixture wattage to it as well or leave it alone?

Thank you

 

[benaround]

it is on the nameplate of the fixture.

 

[Derick]

it is on the nameplate of the fixture.

We haven't purchased the fixtures yet.All I got is the cut sheets.Seems by knowing bulb bulb wattage (70 w) and ballast pf 0.9 it comes around 78w
70w/0.9=77.7/277V=0.28A ~0.3A. (per fixture without applying feeder's loss).We have 67 of them to do and point to point feeders loss is different issue. Was wondering if this is correct way to do so.

 

[Mr. Bill]

The cutsheet should also state the watts. Like this one.
http://www.advancetransformer.com/eCatalog/out/10496641062.pdf
INPUT WATTS 85

It should also give amps at specific voltage
LINE CURRENT (Amps)
Operating: 0.32
Voltage 277
277V * 0.32A = 88.64VA

It states that the minimum power factor is 0.90 but if you compare the info above (85W / 88.64VA) you get an operating PF of about 0.96.

The ballast or cutsheet should plainly state the operating amps on it somewhere. Don't just use the largest amp value on the sheet. You don't want the open circuit current for what your doing. (Do you size your panels for the locked rotor amps of motors?) And you're not using the lamp wattage of 70W for anything when you try to determine the ballast amps. The ballast tells you the amps and wattage, not the lamp.

 

[Derick]

Ok thanks Mr.Bill cleared my mind