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 1 month, 3 weeks ago by djwakelee.

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