KVA of a fluorescent Lamp??

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chee_dee

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When I want to calculate the Loading of say an appartment block flats.. Is it safe to asume and use 60W per lamp. Say you have a 2x58W Double Fluorescent Lamp, what KVA should I use.

I mean doesn't the balast ant starting current also come into play.

I use 60W per lamp. Thus for a Double Fluorescent I use 120 W = 0.12kVA.
 
I was taught to add the wattages of the lamps and then add 10% for the ballast. Thus, in your example, I would get 132 W. To get kVA, you need the power factor which you should be able to get from the manufacturer's spec sheet. If the power factor were 90% (a.k.a. 0.9) you would divide it into the wattage: 132/0.9 = 147 kVA.
 
Sometimes the ballasts underdrive the lamps, and actually take less current (or power) than you would calculate by using the lamp wattage.

The best thing to do is to use the ballast spec for input current.

Here in the US, many times the NEC makes us use a number like 3.5 VA/sq ft, which tends to result in an inflated load. But that does help cover any lights that may be added at a later time.

Steve
 
drbond24 said:
I was taught to add the wattages of the lamps and then add 10% for the ballast. Thus, in your example, I would get 132 W. To get kVA, you need the power factor which you should be able to get from the manufacturer's spec sheet. If the power factor were 90% (a.k.a. 0.9) you would divide it into the wattage: 132/0.9 = 147 kVA.
Click to expand...

However...be careful with the "K"

132W / .9 doesnt actually equal 147000 VA

it does equal 147 watts
 
drbond24 said:
I was taught to add the wattages of the lamps and then add 10% for the ballast. Thus, in your example, I would get 132 W. To get kVA, you need the power factor which you should be able to get from the manufacturer's spec sheet. If the power factor were 90% (a.k.a. 0.9) you would divide it into the wattage: 132/0.9 = 147 kVA.
Click to expand...

The 10% add was a rule of thumb estimate for magnetic ballasts. I don't suggest anyone use this rule of thumb for electronic fluorescent ballast. There are a lot of subtle things that can affect current draw in a modern ballast. Input voltage, number of lamps, ballast factor, Ultra efficient. If you want the VA then look up the ballast that will be used. It will be listed with input current. Take that value and multiply it by the input voltage. This VA will differ from the listed Watts. This can be used to determine the power factor if your interested.
 
in 220.16(B)
For circuits supplying lighting units that have ballast, transformers or autotransformer, the calculated load shall be based on the total ampere ratings of such units and not on the total watts of the lamp.
 
Hello Cheedee,

What i suggest you do is connect a sample 2 X 58w fitting and measure two parameters.

a) Starting current.

b) Running current.

Calculate kva = V X A (running curent)

This will factor in the existing pf of your system, and I hope your fittings have pf improvement capacitor built-in.
 
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