Power Factor for AC Pumps

[mrhasan]

Alright so I talked with my prof and he said you are billed for what you consume and its the amount of current that you are taking OUT from the power outlet, not the amount of power that the device is using. Because there is no way an utility meter can determine how much power each of the device is consuming separately. So in this case, since you motor is pulling out 1.8A through a 115V AC line, you meter is going to read 1.8A * 115V * number of operating hours. It cannot see the PF of the motor and the motor doesn't have any sort of feedback circuits that will tell the meter how much it is "actually" consuming. Meter will only note how much current you are sucking in the house for how long and at what voltage line.

So bottom line, your motor is "consuming" 207W from the grid but is using 82W for operation. Its how much you consume that gets billed on, not how much you actually use. Its like those phantom powers, you don't use it but you get billed for it.

I don't know about the calculation that someone did about less amp consumption but no impact on bill - its not theoretically viable. Less current = less consumption from the grid = less bill. Meter's don't look at the rating on the motors, it looks at how much "power" a.k.a V*I you are pulling in.

[sphelps]

That goes against everything I read online, I just don't buy it. My understanding is still that it's not actually using that much current, that just the apparent power and not the actual. That extra 60% of the current in the circuit can't just disappear. A power factor of 0.4 doesn't mean 40% efficient.

[Goatman]

Originally Posted by sphelps

OK so has anyone measured amps and watts on their AC pumps before? I've never looked too closely until today and I'm surprised at some of the numbers, take a look.

Voltage is 115V

Mag Pump - 0.3A , 22W (PF 0.64)
Red Dragon 6.5 - 1.85A , 82W (PF 0.39)
Red Dragon BK - 1.33A, 79W (PF 0.52)

Waveline DC10000 - 0.83A, 93W (PF 0.97)

I'm no electrical guy this makes no sense to me. Anyone care to educate me?

http://www.reefcentral.com/forums/sh....php?t=1989362

[sphelps]

Originally Posted by Goatman

http://www.reefcentral.com/forums/sh....php?t=1989362

I read that thread already, it really isn't what we're talking about here.

[Goatman]

Originally Posted by sphelps

I read that thread already, it really isn't what we're talking about here.

oops, sorry wrong paste...ignore

[mrhasan]

I am not reading online since I am getting infos from electrical engineers. I have, out of curiosity, confirmed with another colleague of mine just now and is also saying that you get billed for the amount of voltage and current you are drawing out from the outlet; NOT how much your device is consuming. There's no such utility meter that can determine which device is consuming what. With the difference in calculation, he came to some conclusion:

1. The motor is really horrible
2. The readings are not taken from the correct point

I am not with number 2 because the DC pump is right on target regarding the readings; so I stick with the motor is horrible

[sphelps]

I cannot find anything to suggest a residential meter measure kVA, only watts.

There are three terms you will encounter when dealing with alternating (AC) power (as opposed to DC or batteries). The first is the kilowatt, abbreviated kW, and it represents real power. Real power can perform work. Power company utility meters on the side of your house measure this quantity and charge you for it.

The second term is reactive power, and it is measured in KVAR which is short for kilo volt amp reactive. Unlike kW, it cannot perform work. Residential customers do not pay for KVAR, and utility meters on houses do not record it.

The third term is apparent power, referred to as KVA. If you hook up two multimeters to measure current and voltage and then multiply the readings together, you get apparent power in volt amps, or VA. To distinguish it from real power, VA is used instead of W.

[Madmak]

You've probably scared the crap out of her...

[sphelps]

Well I thought it was a legit question, we've been talking about it all morning.

[hillegom]

I like the fine print in a certain "other" thread