Real vs Apparent vs Reactive Power & why things dont add up in the app

[natbesh]

Do some reading & learn about Real vs Apparent vs Reactive AC power – it’ll do your head in, but just make sure you get the basic gist of it.

The key thing is that reactive power isnt really doing anything, it comes into the load & then goes back out – so you dont pay for it (check your local rules etc etc), however its flowing & it gets measured.

Now – the Vue2 measures Apparent power on each of the 16 sensors – which includes that fake Reactive power. Things like an air conditioner have HUGE amounts of reactive power when in standby. My A/C unit shows 300W of power!!! but its all reactive.

The Vue2 measures Real power on the 3 main CT’s – so it removes the reactive power from its calculations and shows what you’re actually using & being charged for.

So…. Your main power readings from your incoming supply will be very accurate, however all the other circuits may be somewhat inaccurate depending on what is running on them. Thats why the things dont add up & there’s magical “free” feed-in power from somewhere. There’s likely a load with high reactive power somewhere on the smaller CT’s.

So if something looks like its consuming heaps of power – yet there’s nothing on the main power CT’s, trust the main power CT’s.
Culprits are switchmode power supplies, induction motors… anything that has a low “power factor”.

Hope that helps others!

[scrambler]

Do you know for a fact that the load CTS do not account for the power factor? If so from where/ whom?

Because I was told initially that they did measure power factor to measure real power.

[natbesh]

yes i’m 100% positive – i went & purchased the instrumentation to test it.

The test equipment is a few hundred $, it taps the voltage on each of the 3 phases and clamps each phase as required, and shows active/reactive power on each phase.
The circuits I was testing had 300W of pure reactive power. The emporia was measuring “300W” on the sub circuits, but “20W” on the mains side with a balance of “-280W”, this corresponded to the test equipment and also the meter on the grid.

Thinking of the internal hardware, it would be hard to detect & setup 16 ports and check the phase angles & check them all.

 

[scrambler]

That is disappointing to hear then

[djwakelee]

My experience is different.  I have all circuits monitored, and zero balance (or so).  At times there are plenty of inductive loads (AC compressor, pool pumps, forced air blower), which greatly exceed any 1.0 power factor devices.  The math always adds up with the individual circuits, balance, and mains – within that 2% tolerance.  If the circuits were only measuring apparent power (VA), things would be way off.

The original Vue 1 only measured VA (apparent power), and was horribly inaccurate for non-resistive loads.  The Vue2 is spec’d to measure true power, and I have no reason to believe this is only on the mains.  My observations do not support that conclusion at all.

Would like to hear from Emporia regarding this.

[scrambler]

Confused …

[djwakelee]

From Emporia chat…

“we measure apparent and real power, and use real power on all circuits”

The poster who theorized VA measurement on the 16 circuits did mention 3 phase – so maybe there is some bug there.  But with 120V/240V split phase in the US, I see accurate W (real power) for the 16 circuits and mains with mixed power factor loads – as confirmed by Emporia.

[scrambler]

@natbesh, may be time to dig deeper on this …

[natbesh]

yep – 3 phase power in my readings & results.

Not much more i can dig into or do – I look at the App & it says 300W (100W x 3), i check the equipment it says next to nothing.. the mains say next to nothing… My grid cancelling inverters that use CT’s (2 different models) both say next to nothing.

So thats test equipment, the equipment manufacturer (300W load), 2 different inverters, the view mains CT all giving the same results… then the Vue load CTs giving different results…

[djwakelee]

For 3 phase, understand the Vue2 is only compatible with Y (Wye) type configuration with neutral.  If your 3 phase is Delta type or without neutral, it wouldn’t work properly.  The majority of people use the Vue2 with residential split phase 240V/120V in the US (and 240V single phase in other countries), in which case it correctly measures real power on all circuits.  3 phase commercial setups are not as popular, but are supposed to be supported if up to 415Y/240VAC Y type with nuetral.  Perhaps some other folks with that setup can chime in and report if they see in discrepancies in operation with 3 phase setups (as well as what country).

You may want to verify your 3 phase hookup, and/or contact Emporia chat.  They don’t seem to monitor this forum as much as they used to.

• This reply was modified 7 months, 1 week ago by djwakelee.

[Scott9]

I can’t get a CT on my incoming mains but I measure the six 240v split phase circuits from the service entrance using two Vue2s. So far, I have three data points with daily power running from 41 KWH to 107 KWH and the total Vue2 power was always within 1 KWH of the Duke Power daily numbers. Plenty good enough IMO.

But I did wonder how the Vue2 correctly associated the A and B phase voltages with the phase/branch currents? I suppose the voltages should be close (except for sign) so maybe it doesn’t matter.

But three phase is a whole different deal; if voltages are not correctly associated with leg currents there could be really odd results for power at the mains.

[ArubaUser]

I experience the exact same thing as topic owner! I live on Aruba, we have 127/220V 3 phase here. All my AC’s show huge consumption in the app when in standby: I have several split units, varying from 80 to 300 watt according to the app, in standby. When I add up the shown usage of all my AC’s the total is much higher than what the main is showing (which indeed DOES seem to show real power). So that’s the first indication that topic starter is right.

Then I ran a test, I have a simple ‘killawatt’ wattmeter, which has a Watt/VA switch (real vs apparent). So I connected my dryer, it showed 600 in the app but 400 watt in my killawatt meter in ‘watt’ mode. Then I switched the meter to “VA mode” (= apparent power) and it showed 600!

So in conclusion, yes, topic starter seems right. The app (at least in my country) seems to measure apparent power on the 16 sensors and real power on the mains.

Hopefully somebody from Emporia can jump in and explain this

• This reply was modified 4 months, 3 weeks ago by ArubaUser.
• This reply was modified 4 months, 3 weeks ago by ArubaUser.
• This reply was modified 4 months, 3 weeks ago by ArubaUser.
• This reply was modified 4 months, 3 weeks ago by ArubaUser.

[ArubaUser]

I was wondering what 3 phase power you exactly have? Are there 3 phase users who do not have this problem? So to describe the problem again, on (some?) 3 phase installations the emporia seems to measure the apparent power. This makes a difference on devices that have huge reactive power flows, like airconditioners, tumble dryers, in general devices with a motor. For example my water heater (for tea) only has a heating element, no motor. It shows about 1600 watt, my killowatt meter shows VA=Watt and indeed, the emporia shows the same. But for devices where my killawatt shows a substantial difference between VA and Watt (mostly devices with a motor), the Emporia correlates wih the VA, not with the Watts…

As this is a problem on all locations that we’ve tested in my country (Aruba) I’m pretty sure this must be a bigger problem. For example big parts of Mexico and Brazil use the exact same 127/220 3 phase so I’m expecting people in these countries to have the same problems. But I was wondering if it happens on other 3 phase configurations  too?

• This reply was modified 2 months, 3 weeks ago by ArubaUser.

[ArubaUser]

I was wondering what 3 phase power you exactly have? Are there 3 phase users who do not have this problem? So to describe the problem again, on (some?) 3 phase installations the emporia seems to measure the apparent power. This makes a difference on devices that have huge reactive power flows, like airconditioners, tumble dryers, in general devices with a motor. For example my water heater (for tea) consumers about 1600 watt, my killowatt meter shows VA=Watt and indeed, the emporia shows the same. But for devices where my killawatt shows a substantial difference between VA and Watt, the Emporia correlates wih the VA, not with the Watts…

As this is a problem on all locations that we’ve tested in my country (Aruba) I’m pretty sure this must be a bigger problem. For example big parts of Mexico and Brazil use the exact same 127/220 3 phase so I’m expecting people in these countries to have the same problems. But I was wondering if it happens on other 3 phase configurations  too?

[John Polasek]

I am making some assumptions here, but it sounds like the confusion comes in when considering 3 phase equipment that uses 3 individual CTs for a large load.  The VUE does not recognize that they are part of a single device and simply adds the three individual current times voltage values together… which if the equipment is “Y” connected (all 3 phases tied to a common return wire) delivers the correct result.  However, because in 2 phase circuits, the phases are displaced 120 degrees from each other, in a “delta” wired motor with no tie to the neutral, a lot of current simply runs around in circles without actually being used for power, but the CTs don’t know that and so give inaccurate readings.  And the only way to “fix” it would be for Emporia to enable “grouping” the individual CTs in the app in order for them to employ the same calculations they do on the mains (which they DO know are out of phase with one another)… all of the single phase loads (plugs, lights and the like) that come off one phase and go back to a neutral will be completely accurate.

[ArubaUser]

Still no update on this? It’s so annoying, this is a wonderful device, we’d love to start selling it in our country but as long as it doesn’t work correctly we just can’t sell this  …

• This reply was modified 1 month ago by ArubaUser.

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