Pentair VS Watts Mystery Not Equal to Volts x Amps Why?

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EnoughToBeDangerous

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Oct 4, 2018
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I have a pentair intelliflo pump running at 1900 rpm. The pump is wired at 240v on a double pole breaker. I have a current meter in the panel on one leg of the pump circuit. The current meter displays 2.63 Amps. So in theory 2.63*240 = 631 watts. However the watts measurement on the pump itself reads about 400 Watts.

I reduce the speed to 1300 RPM. The current meter in the panel displays 1.62 AMPS. 1.62*240= 389Watts, but the pump LCD readout displays 140Watts.

Now here's a video by swimming pool steve on youtube which shows this same effect, but he doesn't seem comment on it. The pump is pulling one amp at 240 volts, but his meter is showing only 137 watts.
I feel like I must be doing something wrong, but I can't figure out what. Anyone understand this?

Thanks!
 
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You need to be able to measure the power factor.

Volts x amps only equals the watts when the power factor is 1.00.

The voltage and the current both have sine waves.

When the waves are synchronized, the power factor is 1.0.

When they are shifted out of phase, the power factor drops below 1.0.

When the power factor is below 1.0, some of the amps are not doing any work.

You have to be able to measure real power and apparent power.

You need a "True RMS" wattmeter that can measure real power and power factor.
 
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So I have an emporia vue monitoring my panel. Emporia says they should be accurate if the power factor is not less than about .60. They do measure the phases and adjust for the reactive power. Do you think the pump has that much reactive power? They are going to consult their engineers about that and the voltage clipping. But if the current transducer can't catch the waverform clipping, how does the meter catch it? If I'm paying for twice as much power as the pump is reporting, that's the number that I want to use to configure my pump, not the theoretical energy usage. The number that matters is dollars per second, not joules/second(ie watts).
 
Residential power meters should only record real power. So, you should not be paying for reactive power.

To test the real power, I would recommend that you get a True RMS meter that can measure real power and power factor right at the pump like what is shown in the video.

The pump drive converts the single phase input power into 3 phase output power to the motor.

I don't know if the pump is measuring the power on the single phase input or the 3 phase output or if that makes a difference.
 
I have ordered a true RMS clamp meter, so when I get that I'll take some readings. If the meter can measure the power, we should be able to determine how much power is passing through a circuit in the panel without looking at the interior electronics 3 phase components of the motor. So it seems like we'd expect the true RMS clamp meter to show a lower amperage than the emporia vue is showing. Is that correct? If the waveform is being clipped down though, I wonder if I'd need a high sampling rate. The clamp meter I orders is only 3x per second. Still it should average out.
 
True RMS should account for a distorted waveform.

Make sure that the meter can do real power and power factor because most meters can't do that.

The amps should be the same either way.

If you are measuring amps on a distorted waveform, only a true RMS meter will be accurate.

An averaging meter will be inaccurate.



 
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EnoughToBeDangerous said:
I have an emporia vue monitoring my panel. Emporia says they should be accurate if the power factor is not less than about .60.
Click to expand...
If the meter measures the power factor, then it should be able to report real power, power factor and volt-amps.

It looks like it can only show volt amps.

Check to see if the meter is true RMS and if it can measure real power and power factor.
 
According to emporia and it's user forum, they do measure the power factor but do not currently make that data available to user. However their engineers should be able to see it, so hopefully they will be able to let me know if the real power matches the pump power more closely, they seem interested. I don't want to drop 300 bucks on an ammeter, but I ordered a true rms unit that was cheaper. If it reads closer to the pump value, that would suggest the waveform clipping is causing the problem. If it's closer to the VUE, then it's more likely the power factor.

Has anyone roughly tied out their watts with their meter readings? Is the bill in line within a reasonable range of what would be expected at those watts?

Also, have you or anyone else reading this ever measured the power factor on a variable speed pool pump? If so what did you get and at what rpm? The power factor would have to be .4 or so to explain the watts I'm seeing at 1300rpm.
 
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EnoughToBeDangerous said:
According to emporia and it's user forum, they do measure the power factor but do not currently make that data available to user.
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They are not reporting watts. They are reporting volts and amps.

I don't think that they measure power factor, but even if they do, it doesn't change the amp reading.

Ask them directly if their system is true RMS and if it really measures power factor.
EnoughToBeDangerous said:
Also, have you or anyone else reading this ever measured the power factor on a variable speed pool pump? If so what did you get and at what rpm?
Click to expand...
The video that you posted has the power factor displayed on the wattmeter.

I think that at low rpm, the power factor was 0.55.
 
Ok I found this quote on another forum from a pentair employee:

"The IntelliFlo uses Pulse Width Modulation to control the motor. Pulse width modulation is the expression of digital manipulation to the DC voltage whereby it is reconfigured to represent a sine wave instead of a flat DC pulse. In doing this we are able to control power factor to a staggering 1.0 at full speed and do not start to deteriorate until we fall to very low speeds and only give up about 3-5% all the way to 400 rpm. Pool two speeds and single speeds running 2 pole speeds are roughly 70-90% depending on model, however, 2 speeds on low use induction run and have a very low power factor of 50% or less. Residential properties do not pay for power factor, however, when you understand it what better can you do for the environment?"

So they are claiming that the intelliflo has a power factor of .95 to 1.0. He says that is good for the environment though, which is not really a correct understanding of power factor in my opinion as the same amount of energy is being used either way, but it would enable a larger load on the same circuit and perhaps reduce line losses.

At any rate if the power factor is .95 and emporia says they correctly account for power factors of .6 or greater, that strong suggests the waveform distortion is causing the discrepancy. I can't wait to get my new ammeter to test it out.

By the way, I think the emporia vue is going to be a really great tool for optimizing the variable speed pump and my variable speed aquacal heatpump once I figure this out. The vue allows a linear factor adjustment to a circuit ie x2 but not a curve so it may be a problem if the error is too non linear to get a good reading.
 
JamesW said:
They are not reporting watts. They are reporting volts and amps.

I don't think that they measure power factor, but even if they do, it doesn't change the amp reading.

Ask them directly if their system is true RMS and if it really measures power factor.

The video that you posted has the power factor displayed on the wattmeter.

I think that at low rpm, the power factor was 0.55.
Click to expand...

Ahh you are right! That is a superflo rather than intelliflo but the power factor is right there! Now emporia says they are measuring real power, I talked to them today, but I did not ask if it is measuring true rms. But the .55 factor on the superflo is telling me that power factor could account for most of the error. Interesting.
 
Steve's power meter seemed relatively close to the pump for watts.

Here are the power factor readings from the wattmeter in the video.

Rpm.....pf
1000....0.56
1500....0.79
2000....0.91
2500....0.95
3000....0.97
3450....0.98
 
EnoughToBeDangerous said:
The IntelliFlo uses Pulse Width Modulation to control the motor. Pulse width modulation is the expression of digital manipulation to the DC voltage whereby it is reconfigured to represent a sine wave instead of a flat DC pulse. In doing this we are able to control power factor to a staggering 1.0 at full speed and do not start to deteriorate until we fall to very low speeds and only give up about 3-5% all the way to 400 rpm.
Click to expand...
You have input power to the drive and output power to the motor.

The power factor going into the drive is going to be different from the power factor coming out of the drive going to the motor.

The motor is a three phase motor and they can adjust the voltage sine wave to maximize the power factor on the output, but the input will be different.
 
EnoughToBeDangerous said:
Now emporia says they are measuring real power, I talked to them today, but I did not ask if it is measuring true rms.
Click to expand...
If the power readings are always exactly the same as the volt-amps, they are not reporting real power.

Steve's video shows that his power meter tracked fairly well with the pump.

His power readings were slightly lower than the pump power readings.

If you want to know for sure, you need the right test equipment.

With a true RMS meter, you can at least check the voltage and amperage compared with the vue.

The variable frequency drive significantly distorts the waveform of the voltage. So, you really need true RMS.
 
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JamesW said:
If the power readings are always exactly the same as the volt-amps, they are not reporting real power.

Steve's video shows that his power meter tracked fairly well with the pump.

His power readings were slightly lower than the pump power readings.

If you want to know for sure, you need the right test equipment.

With a true RMS meter, you can at least check the voltage and amperage compared with the vue.

The variable frequency drive significantly distorts the waveform of the voltage. So, you really need true RMS.
Click to expand...
Here look at page 4 of this publication labeled "Tech talk for engineers":

They are claiming that the intelliflo has a power factor of 99%. Also the specs for the intelliflo claim "Robust on-board power factor correction." So if true, and I don't know if it is, then the power reading should be very close to the volts x amps, so that doesn't necessarily mean the vue is wrong(with respect to power factor). But if the true RMS meter, on reports fewer amps that may be a hint as to what's going on. The vue is reporting power as approximately 98.5% of volt*amps. They don't report the volts, but the tech I spoke to gave me a reading I was able to use.
 

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