240 or 120 volts???

[Olyver]

There is confusion or 120V or 240V. The amps is not cut in half. The amps is cut on half, and each of the 120V lines carries 5 amps for half a cycle, and it cycles 50/60 times a second. A 1000 watt ballast draws @ 10A over one 120V hot feed. For 240V @ 1000 watts, the 5 amps flows over both 120V hot feeds. You are still drawing 10 amps, it's only split in half over both 120V.

Olyver

 

[johnnyballbag]

Um...not sure what you're saying exactly, but doubling your voltage does in fact cut your amperage in half.

 

[Olyver]

From what my EE instructor told, the voltage is not in fact doubling, as each hot (120V) is drawing 5 amps for 1/2 the 50/60Hz cycle, the voltage increases, but only for half the cycle. If you look at the wiring for a ballast, it has 120V, 240V, 277V, and 347. Each of these is a hot and then you attach the "common/neutral" and you complete the circuit. The 50/60Hz is how many times per second that the voltage changes direction. So for half the cycle (25/30) times per second, L1 is powering the ballasts, then for the other 25/30 times per second, L2 is powering the ballast. All I remember is my instructor explaining this to the class. He said that it's the biggest misconception about 120V over 240V. The only savings come from the size of the wire you need. Since each L1 and L2 are drawing 5 amps, then you can use 14AWG even 16AWG.

Olyver

 

[johnnyballbag]

Yeah i know what you mean. For the average guy though, that can be confusing when trying to determine electrical issues. As far as ratings go at least.

 

[acubus]

Olyver, not sure what your trying to say. L1 and L2 are equal, but 180 degrees out of phase. Each line in a 2 pole single phase system does equal work at the same time(just out of phase). Take either L1 or L2 out the circuit and see if your load only works 1/2 the time.....or not all.

 

[johnnyballbag]

Try testing a 240V circuit with a multi-meter and see what it tells you.

 

[acubus]

Olyver the potential voltage has infact doubled from a 120 to a 240 volt system. -120 to +120 is in fact 240 volts. Compare to a potential on a 120 volt system of 120 volt from L to N.

 

[acubus]

Most mutlimeter measure RMS....an average kinda. Need a scope to really understand AC and see AC in perspective. Gotta love phasors.

 

[boxmunch9]

My house you would burnt to the ground if it was in fact not cutting the amps in half

 

[Olyver]

If you clamp both sides L1 and L2, both are the same, 5 amps for a 1000w ballast. The total of both is 10 amps.

Olyver

 

[Rural_GrowOp]

I love these conversations. To make it really easy ohms law says that A=W/V so if V increases than A will decrease. The idea that in a 240V system both L1 and L2 are both pulling 5A is deceptive. If you were to clamp them both that is what you would see but amps you are truly only pulling 5A combined.

 

[acubus]

Olyver the only thing you've said that truly makes sense is......higher voltage means smaller guage wire. Imho opinion your getting DC and AC single and polyphase principles confused and 240V and 120/240V split circuits mixed up some how.

 

[Olyver]

Olyver the only thing you've said that truly makes sense is......higher voltage means smaller guage wire. Imho opinion your getting DC and AC single and polyphase principles confused and 240V and 120/240V split circuits mixed up some how.

I'm just going by what my instructor told me. He's got a masters in EE, so I have no reason to doubt or question him. This was explained in front of the class, and specifics were mentioned about ballasts, how they have a common and the multi-tap voltages, 120V, 240V, 277, and 347. He was using some time of power factor meter and it was measuring both amps and voltage together. It looked like some sort of oscilliscope. If I'm wrong that's kewl, just going by what I was told.

Olyver