View Full Version : how many amps
spsrookie
02/02/2016, 10:20 PM
I have a ballast, with one plug, that runs two metal halide 400 watt lights. Roughly how many amps might this be>?
Johnic
02/02/2016, 11:49 PM
I have a ballast, with one plug, that runs two metal halide 400 watt lights. Roughly how many amps might this be>?
To get amps you take watts and divide by volts. So 400w/110v. But you usually don't get exactly 110 volts so divide by a loss factor of 99
spsrookie
02/03/2016, 01:43 AM
Why have people been telling me it's 8 amp? Trying to figure out if this plug could be used in apex
sfdan
02/03/2016, 03:04 AM
Your bulbs probably use ~450 watts each counting losses, so ~900 watts / 120v = ~7.5 amps
The 10A plugs on the apex could handle it properly, but it would probably be too much for the 5A plugs
Member No. 1
02/03/2016, 04:32 AM
Why have people been telling me it's 8 amp? Trying to figure out if this plug could be used in apex
Maybe because you have 2 400w lamps.
As Johnic stated "To get amps you take watts and divide by volts. So 400w/110v. But you usually don't get exactly 110 volts so divide by a loss factor of 99", that's for 1 lamp. Then you need to multiply that by 2.
alton
02/03/2016, 07:15 AM
400 x 2 = 800/.9= 888w / 120v = 7.4 amps
The only ballast I know of that are 99% are Fluorescent.
jamie1981
02/04/2016, 04:03 PM
If you know your watts amps are simple 1 amp = 125 watts..... that is @ 120v If your in doubt get a kill-a-watt meter and plug them into it will tell you the exact power usage.
Utwo229
02/04/2016, 07:46 PM
While all these calculations are all correct, the actual calculation is: amps = watts / power factor / volts.
The power factor is in essence the efficiency of e ballast. You may be able to find your power factor (pf) on the label of the ballast, however if it isn't listed a good rule of thumb for metal halide is around .90.
Typically we use 120 volts nowadays for electrical calculations.
So for two 400 watt lights it would be 2 x 400 watts / .90 power factor / 120 volts = 7.4 amps.
vBulletin® v3.8.4, Copyright ©2000-2024, Jelsoft Enterprises Ltd.