Power Factor for AC Pumps

[mrhasan]

Originally Posted by sphelps

While the pump is pulling 1.8A it's not using it all, essentially most of it is going back to the grid so to speak.

That's only applicable in some microgeneration programs. You are pulling out 1.8A through the pump and hence its yours. And more or less, the whole current is consumed by the motor other than some leakages.

[StirCrazy]

Originally Posted by sphelps

Ok now we're getting somewhere. My assumption is I'm getting billed in kWh which would include PFs so if my pump is using 82W I'm paying to 82W and not 212W. While the pump is pulling 1.8A it's not using it all, essentially most of it is going back to the grid so to speak. So it's not actually being used, hence the PF related to how effective not efficient. It would certainly be very valuable information for if you could confirm this.

nope this is not how it works
here is a simple explanation of PF I found

"Power factor is the percent of electrical power that does work. Resistive loads, such as lights and heater elements, always have unity (1.0) power factor; all power is used for work. Motors, because they are essentially large inductors, lag current and cause power factor issues. A motor with a .85 power factor uses 85 percent of the power for work. 15 percent is wasted.

For example, a 480VAC, 10HP motor with a 1.0 power factor uses 10.6 amps to run at 10HP. Lowering the power factor to .8 requires the motor to consume 13.2 amps to produce that same 10 HP."

I read up on this years and years ago and can talk about it all day (well maybe not all day) but it is hard to sit and type it out, hence the simple explanation I found. we used to be realy concerned with PF with lights to get the efficiency.


you if you have a pump that is rated at 120 watts but has a power factor of .6 in reality it will use 200 watts to do the work. the extra 80watts are lost through ineficient circuts, heat, ect... so when the power company bills you you are billed for the 200 watts. this is why the hydro companies have rebates for big business to upgrade to high PF equipment, it lowers the demand on the grid.

Steve

[Jeff000]

Where are you getting your power factor numbers from?

In any case put your watt meter to the pump, that will tell you the watts.

You're not billed kva in residential. And even if you were you need to look at what your whole system is drawing, not just one little part.

[sphelps]

Originally Posted by Jeff000

Where are you getting your power factor numbers from?

In any case put your watt meter to the pump, that will tell you the watts.

You're not billed kva in residential. And even if you were you need to look at what your whole system is drawing, not just one little part.

Watt meter on the pump reads 82W, same meter reads 1.8A & 115V

P = V * I * PF
So PF = P/(V*I) = 82W/(115V*1.8A) = 0.4

[wmcinnes]

I'm just restating what has been said but:

PF= True Watts/ Volts*Amperes
True Watts= 82w
Volts= 115v
Amps= 1.80a

PF= 82/207 = 0.396

You're pump output is only 40% of the power it is drawing. Not good, not efficient! haha

[mrhasan]

Originally Posted by wmcinnes

I'm just restating what has been said but:

PF= True Watts/ Volts*Amperes
True Watts= 82w
Volts= 115v
Amps= 1.80a

PF= 82/207 = 0.396

You're pump output is only 40% of the power it is drawing. Not good, not efficient! haha

There you go Steve. Another justification You better change the motor if you want the consumption to cut to half! DC motors FYI!

[lastlight]

Originally Posted by mrhasan

There you go Steve. Another justification You better change the motor if you want the consumption to cut to half! DC motors FYI!

The RD is a DC motor ?

[sphelps]

[wmcinnes]

Originally Posted by sphelps

Watt meter on the pump reads 82W, same meter reads 1.8A & 115V

P = V * I * PF
So PF = P/(V*I) = 82W/(115V*1.8A) = 0.4

Exactly.

[Jeff000]

Originally Posted by sphelps

I'm fairly confident at this point power factors really have nothing to do with a residential power bill, we're billed in kWh and our meters can't measure power factors, only real power in watts.

Some more talk about power factors and correction devices
http://michaelbluejay.com/electricity/powerfactor.html

If you live in Canada you are billed in kwh for a residential service, by law. Pf has no outcome on your bill.