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

oops, sorry wrong paste...ignore :)

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 ;)

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

Yap residential meters record KWh, not KVA.

Thus your meter only counts the real power.


I'm with Steve and his research.

Then my question is, how would each of the real power of individual components in the household be calculated by the utility meter?

They simply measure kW and not kVA.

They consist of a motor with the stator current being the current into the building and the rotor curreent being proportional to the voltage at the building input. The motor turns a disc (the disc you see rotating in the window) that passes through a magnetic field generating eddy currents in the disc and this regulates the speed at which the disc turns so that the meter can be adjusted to read correctly.

Because the utility meter measures the exact same thing as the energy monitor, it measures actual power in kWh. It doesn't measure apparent power or vars.

1. KW is not a direct unit so the meter actually does some conversions within itself

2. That is exactly how it is done. The rotor moves proportionally to the product of voltage and current to shows kWh consumption. No PF involved that's it. So when a outlet draws 1.85A @ 115V, that means the rotor is turning at a proportional rate directly to the product of those two.

The motor needs 82W to run and it is taking in 82W but due to its inefficient manner (age, water, etc.), the pump has to take in more power and hence 1.85*115V.

For this motor, you are bringing 1.85A "in" the house.

If the current and voltage are in phase, the motor speed is the product of voltage and current (PF=1). If they are not in phase the motor in the meter will run fast for part of a cycle and slower for the other part with the average speed being the product of the in-phase voltage and current. Thus measuring real power.

According the producers of the energy monitor:

Yes. So how would the meter know which device has what amount of PF? It must do an equivalent resistance scenario for all the loads in the house with one common PF for the whole house and thus multiplying the voltage * current going into house * common PF. The meters can't judge individual PF of the devices.

Yap that's right. Like I said in the very beginning, the utility companies either consider pf=1 or maybe they just do some calculations to find a relative pf for the houses to multiply the RMS volt and current. The meter's simply can't find the individual PF of each appliances. Alongside, households doesn't generally have heavy PF lowering stuffs and hence its more or less above 0.9. Two or three pumps may have low PF in your house but in the end, it won't effect much to the pf of your whole house.

I have sent an email to enmax regarding this. The theory and the claims are just not going through and would love to clear it up too. :razz:

Another thing, if possible, if to measure the resistance of the motor (disconnect it and then measure) and then putting in the current (1.85) and resistance into the formula:
I^2/R.

Well my understanding of AC power isn't great, not my specialty by a long shot. However it seems obvious to me that the term reactive power (the difference between apparent and real) when referred to "imaginary power" isn't something you're going to billed for. It's not being used despite the fact it goes through the circuit. While I might find it amusing to see a line on my power bill that said "Imaginary power usage = 958 kWh (this is the power you didn't use)" I just can't see it.

It's why everything online states a utility meter that measures in kW measures real power and not apparent power. It's clear power factors have virtually zero impact on your power bill which is why all those power factor compensation devices are a scam, also well documented.

I've also sent an inquiry to Enmax and GE (meter manufacturer) for conformation.

Alright Steve you don't have to break the motor. I came across an energystar article and they say that in NA grid system, if you have a low pf equipment in domestic facility, you draw in more current but you are only charged for the amount of power that you are consuming and the extra power due to the charge is actually put into the penalty of the industries who have to pay for pf corrections.

So I guess you are actually getting charged for 82W :P

Sorry for the confusions; sometimes theory and practical stuffs doesn't match :) I will still post the response I get from enmax.

Please do post what they say. It will help me get my theories straight too.

World should revert back to DC grids like Edison's time. AC stuffs are just too complicated :twised:

That's really not what my quote said by the way, but at this point we'll have to agree to disagree until we get conformation either way.

Good news so far, I'll wait for conformation from Enmax before celebrating though ;)

I am convinced that utilities charge households just for amount consumed so you are getting charged for 82W. Maybe that's why household businesses are becoming popular now a days? ;)

I am feeling bad for someone out there who is paying more because of your motor having low pf :lol:

I still don't think it works that way, the extra current isn't lost. The only losses are from heat resulting from the difference in current that feeds through the lines plus some very minor losses in the pump which you would experience with most devices. The extra current flows back to the source. Large industries are sometimes penalized for low power factors due to the provider having to supply higher currents and accept higher losses due to cable inefficiency. In residential the losses are minimal and probably absorbed in general as delivery charges.

The real advantage of high power factors is the ability to design lower powered circuits, it really has very little to do with efficiency.

And before you curse me, measure your own pumps :lol: many home appliances such as washing machines are known to have very low power factors. And while I'm still really surpirsed at the number for these expensive pumps at the end of the day at least they don't cost that much to run and I'd still rank then significantly higher in quality over the wavelines I have as well.

Funny story, I just got a phone call from some direct energy provider wanting me to switch to them for electricity. I asked if they'll charge me for reactive power and she said she didn't know. I then asked how can you expect me to switch if you can't even tell me if I'll be billed for the imaginary power my pumps use. She hung up..

Power Factor for AC Pumps
 

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

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

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

What you SHOULD do is find out why your pump is running at a power factor completely out of line with my numbers. How old is it?

About 4 years I think, in service for around 2.5. Everything seems good, runs like new and from my googling it seems a few users have discovered that RD pumps have low power factors. Also the bubble king 2000 is following a similar path. Doubtful I have two defective units.

You're asking some girl that has no technical training, only a script to read to sell you the service and answers to standard questions.
Had you said power factor and not reactive power you might have gotten an answer.

I'm a sparky myself, but not a power lineman. But I did call a buddy working for epcor, he's a meter tech for them, he said the meters only measure actual power use for residential and light commercial.

They aren't even allowed to have the smart meters monitor power factor for statistics.

Good stuff, thanks Jeff.

Lol. She must have been like..."huh, imaginary power"......she chose a great day to call you ;)

pretty much everything you guys are asking about is all 2nd year electrician apprenticeship. Residental meters measure power, not apparent or reactive power. the meters used on larger commercial and industrial buildings are called demand meters and only charge for true power used until the buildings peak apparent power goes beyond a cirtain point, then they are charged heavily for the extra demand. even if your pump has a pf of 0.5, and pulls 120 va or apparent power (120v*1a), its only using 60w of power, and your only charged for 60w of power. Power companies dont charge residential buildings for apparent power because most of the devices we use have power factor correction to 0.9.

Yeah, yeah. Where were you this morning? ;)

I was actually thinking that too! So many words, searches and (umm...) interrogations could have been saved!

sorry i just saw the thread tonight. just for credits sake, i am a 4th year electrician, so ive had 2 school terms of the trig calculations to back this up. last year was all 3 phase which is quite a bit harder =P

Three phase is "quite" a bit harder? :neutral: You must be a genius when it comes to power. Being an electrical major myself, I feel crap when it comes to stuffs regarding AC and three phase Y-Delta craps. I am more of a DC person and my undergrad is not from here so never knew about how the grid works over here.

Thanks for clearing the confusions up. Learned a lot today :)

Cheers to Steve for starting this thread in the first place and keeping it warm! I wish I saw your powerhead add before; I need a power head badly :P

Us Power Engineers know everything there is about power generation but when it comes to how a residential power meter works.. Me feel stupid haha:lol:

In my defense, I am from a 3rd world country where we have more blackouts than on the moon :lol: Our generation works in a totally different way ;)

Haha I can imagine it does!

3 phase is like single phase, which is what is at the wall outlet, only x3. the phases are each 120 degrees out of phase with each other. 3 phase motors are far more efficient, smoother and quieter than single phase motors. I cant wait until one of these manufacturers comes out with a 3 phase pump and variable frequency drive.

electrician isnt really that difficult. we only learn what pertains to our trade. I know almost nothing about power generation =)