Watts vs Volt-Amps - huh ??

[shella]

I chuckled when I first read this post. This is pretty much a DIY forum and the posters looking for help have ZERO electrical knowledge and all this is is GREEK to them and will never understand one bit of it.

lol i was really really trying to understand........ but i got lost when 3+4 = 5

[Sunking]

lol i was really really trying to understand........ but i got lost when 3+4 = 5

3 + 4 does equal 5. Any carpenter or steel man will tell you that.

[Naptown]

Yes but 3 squared + 4 squared = 5 squared
The Pythagorean theorem

[Sunking]

Yes but 3 squared + 4 squared = 5 squared
The Pythagorean theorem

Correct to make a perfect right triangle is what any carpenter knows. Take 3 toothpicks. One 3-inch, 4-inch, and 5 inch. Lay them down with the ends touching to form a right triangle, and you will have a perfect 90 degree right triangle. Very simple basic trigonometry.

[Naptown]

Or any numbers for that matter
In a right triangle base squared + height squared = hypotenuse squared
Very useful when squaring up a rectangle by yourself.

[Sunking]

Or any numbers for that matter
In a right triangle base squared + height squared = hypotenuse squared
Very useful when squaring up a rectangle by yourself.

Correct any unit of measurement works. Like building a foundation for a building or laying out walls. It is the exact same formula used to find the relationship of AC impedance and resistance relationship.

[SunEagle]

Correct any unit of measurement works. Like building a foundation for a building or laying out walls. It is the exact same formula used to find the relationship of AC impedance and resistance relationship.

The formula is also used to calculate power factor where the based is kw the height is kvar and the hypotenuse is kva. The angle between the kw and kva is the % power factor.

[Sunking]

The formula is also used to calculate power factor where the based is kw the height is kvar and the hypotenuse is kva. The angle between the kw and kva is the % power factor.

True but much easier to just use the Power Factor where Watts = PF x VA.

Doesn't require a calculator, only a 5th grade education.

[SunEagle]

True but much easier to just use the Power Factor where Watts = PF x VA.

Doesn't require a calculator, only a 5th grade education.

Boy. There is always someone smarter that likes to give me a poke.

I do use the formula to determine how much kvar is needed to improve a poor power factor.

Like you said the math is easy and used in many applications.

[Robert1234]

Ok dudes. I thought I was starting to understand power factor with regards to magnetic flux, etc, but now I'm not so sure. Does this make sense to you guys?

Individually Measured...

(a) I have two small pumps running on my aquaponics.
34.3 Watts Total
97.5 VA (0.35 PF)

(b) I have flourescent grow lights (two ballasts I believe)
4x32 Watt T8 bulbs
108 Watts measured
177 VA (0.61 PF)

Put them together on the same circuit

(c) Combined (all units on) I measured
136 Watts
181 VA (0.75 PF)

WTF???? I might be off on (b) a little bit because I'm recording it here from memory, but I'm pretty sure I'm close. Measurements (a) and (c) have been repeated a couple times now on the AC side. It just hit me last night when I was keying the data in my spreadsheet that the power factor was higher on (c) than I expected. I pulled out my DC clamp meter this morning before work to see if the inverter power was balancing and on the DC side I got at the inverter input: 6.9 amp @ 26.5v (183 DC Watts) - pretty much what I'm measuring at (c). I'm gonna remeasure everything again tonight to make sure I'm right on what I'm remembering.

Does this make sense? Is it real? Can PF of the combined items be better than the PF of the individual components?

[SunEagle]

Ok dudes. I thought I was starting to understand power factor with regards to magnetic flux, etc, but now I'm not so sure. Does this make sense to you guys?

Individually Measured...

(a) I have two small pumps running on my aquaponics.
34.3 Watts Total
97.5 VA (0.35 PF)

(b) I have flourescent grow lights (two ballasts I believe)
4x32 Watt T8 bulbs
108 Watts measured
177 VA (0.61 PF)

Put them together on the same circuit

(c) Combined (all units on) I measured
136 Watts
181 VA (0.75 PF)

WTF???? I might be off on (b) a little bit because I'm recording it here from memory, but I'm pretty sure I'm close. Measurements (a) and (c) have been repeated a couple times now on the AC side. It just hit me last night when I was keying the data in my spreadsheet that the power factor was higher on (c) than I expected. I pulled out my DC clamp meter this morning before work to see if the inverter power was balancing and on the DC side I got at the inverter input: 6.9 amp @ 26.5v (183 DC Watts) - pretty much what I'm measuring at (c). I'm gonna remeasure everything again tonight to make sure I'm right on what I'm remembering.

Does this make sense? Is it real? Can PF of the combined items be better than the PF of the individual components?

In section B you have 4 x 32 watt lamps that you only measure 108 watts total. I think it would be closer to 4 x 32 = 128 watts plus ballast losses of ~ 10% so add another 12 watts for 140 watts total. with 177 VA that is closer to 0.79 PF. Considering the majority of your load (lighting) has the higher pf it is possible your overall pf is around 0.75.

I would check all of your measurements again to understand you true Wattage load and then measure the voltage and amps to get your VA.

[Sunking]

(a) I have two small pumps running on my aquaponics.
34.3 Watts Total
97.5 VA (0.35 PF)

(b) I have flourescent grow lights (two ballasts I believe)
4x32 Watt T8 bulbs
108 Watts measured Wrong 4 x 32 = 128 watts
177 VA (0.61 PF)

Put them together on the same circuit

(c) Combined (all units on) I measured
136 Watts
181 VA (0.75 PF)

Power = 34.3 + 128 = 162
VA = 97.5 + 177 = 274
PF = 162 / 274 = .59

[Robert1234]

Yep... 4x32 Watt T8 bulbs - 108 Watts measured... It measured lower than expected. Like I say, memory isn't what it used to be. Maybe it was 118, but it is in my head that it was lower than the 4x32 value. I'll get back with the rechecked values, but if I read your responses correctly, I think I should conclude that VA should have been additive as I originally expected?

Are those little Kill-A-Watt meters accurate with regards to VA and Watts? (Cause that's what I'm using for AC Watts and VA)

http://www.bing.com/shopping/kill-a-watt-ez-electric-usage/p/C8A4DD55A28484705001?q=kill+a+watt&lpq=kill%20a%20watt&FORM=HURE

[SunEagle]

Yep... 4x32 Watt T8 bulbs - 108 Watts measured... It measured lower than expected. Like I say, memory isn't what it used to be. Maybe it was 118, but it is in my head that it was lower than the 4x32 value. I'll get back with the rechecked values, but if I read your responses correctly, I think I should conclude that VA should have been additive as I originally expected?

Are those little Kill-A-Watt meters accurate with regards to VA and Watts? (Cause that's what I'm using for AC Watts and VA)
http://www.bing.com/shopping/kill-a-...watt&FORM=HURE

They are usually pretty accurate. Have you measured each of your loads individually as well as the total load on your inverter?

I'm trying to get an understanding of how you get both your wattage and VA measurements. If you are using multiple meters to measure (a watt meter, and amp meter and a volt meter) there may be some inaccuracies between them.

You mentioned calculating 183 watts DC based on a 6.9 amp and 26.5 volt measurements. How are you getting your AC wattage, amps and volts?

[Robert1234]

I'm trying to get an understanding of how you get both your wattage and VA measurements.

AC measurements come from the Kill-A-Watt meter - both Watts and VA. The pumps & lights are on a common line that I can feed through the meter. That way I can measure them individually and/or combined simply by turning them on/off. I can use the clamp meter to confirm amps back at the AC legs leaving the inverter (and have in the past), but have not as of yet on this paticular setup. Previously, it has lined up very well with Kill-A-Watt measurements (within 5% or so) but I'll note those measurements were on resistive loads (high PF).

DC Measurements are from a multimeter. The DC amps specifically were measure on the 3-0 positive lead to the inverter using the clamp meter. I elected not put put a shunt in this system.

Yes, loads were measured individually and the VA total didn't add up. That's what I am struggling with. Additionally, the Kill-A-Watt meter power factor is significantly higher on the combined load than either of the individual loads. Very strange and certainly unexpected (at least by me).

I'll get new measurements today or tomorrow and we'll go from there.