Whole home energy monitoring

[tarun]

In the US - I have 2 sources of electricity:

1. Mains coming in to a large panel
2. SolarEdge

While SolarEdge has an app and API, what do I use to track the mains side of things? I would like to measure the gap between solar and mains throughout the day and perhaps trigger more power hungry activities during times of high energy or at least know about them.

There are a lot different options:

• Sense - no API
• OpenEnergyMonitor
• Curb
• This guy
• and a bunch of others.

[Andrew B]

I use one of these:  https://www.brultech.com/greeneye/

Have had it running for about 4 years now, working great.  Have collected around 50GB of data thus far.

[John Verdicchio]

ARCELI 50A SCT-013-050 Non-invasive Sensor Split Core - find on Amazon or ebay. I have two of these ; one monitoring the incoming power and another after the solar injection and a 15A version to monitor the solar. Wired them directly into Loxone 10V analogue input. I'm using IObroker and Grafana to monitor usage. 

[TomM]

@John - very interesting idea.  Hadn't considered connecting a CT directly to the analogue inputs.  This is a very cost effective method of energy monitoring.

I assume it's as simple as chopping off the 3.5mm plug and connecting the resulting 2 wires - 1 to AI1 and the other to 0V common?

Then I think it's a 0-1V scale for 0-50A (or whatever model purchased).

Any thoughts on whether it's ok to extend the cable by up to 1 metre?  I assume the voltage won't drop over that length.

Any other advice for connecting these?

Thanks

[Duncan]

if you use it in voltage mode (with  a load resistor across the outputs) then the length of the cable wont matter at all

[Duncan]

https://datasheetspdf.com/pdf/1328320/YHDC/SCT-013-050/1

[Duncan]

https://learn.openenergymonitor.org/electricity-monitoring/ct-sensors/introduction?redirected=true

On Tuesday, 16 February 2021 at 12:36:44 UTC TomM wrote:

[tarun]

Okay - I love the idea of just directly feeding to the analogue inputs since it is very elegant and doesn't involve more controllers or hardware.

[Jonathan Dixon]

Does this technique give you any means to detect the direction of power transfer (e.g. for the main meter tails, to differentiate import vs PV export)? Assume not, but wanted to check.

For individual circuits that only consume (or generate) it's fine though

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[Deac99]

Not sure if this is helpful but I have 4 of these installed, been in service for over 5 years now with no problem at all.  Integrated right into Loxone via modbus.  They detect direction for PV setups as well. 

https://www.aliexpress.com/item/32409196221.html?spm=a2g0s.9042311.0.0.27424c4dVRahJp

In addition, I found these in the USA for monitoring multiple circuits.  I checked with the company and the software can accomodate 220V vs 102V for determining watts.  You can also install as many as you want (16 channels per unit) with no upper limit and they can be installed in sub panels as well as long as each unit has access to your wifi / router.  I have not found any of these in Europe (yet) for a reasonable price which surprises me as my observation is that Europe is a bit more advanced than the USA when it comes to energy efficiencies etc.   If anyone has info on something like this in Europe by all means let me know, otherwise I'll be bringing some of these with me when I get back next year.

The only thing I don't like about these is that each channel is displayed as a discreet channel and the software does not have an option to combine 3 channels for the few true 3ph appliances that I have - but I can live with that.

https://shop.emporiaenergy.com/collections/commercial-energy-devices/products/gen-2-3-phase-emporia-vue-with-16-sensors-bundle

[TomM]

@duncan - what size resistor would you use across the outputs? (i have researched a fair amount but still haven't been able to figure it out definitively)..

Thanks

[Duncan]

the voltage output type already have the built in resistor - see the pdf i linked to for details

https://datasheetspdf.com/pdf/1328320/YHDC/SCT-013-050/1

[Tim]

I wish I understood this more as it sounds like a really neat solution.

Does anyone fancy putting some more information together about this for those of us that don't fully understand? As TomM said earlier, it sounds like I just need to connect the CT to the analog inputs to start getting values. I've done this and seem to be getting values such as 0.16 for a 50A SCT-013-050 - I'm still a bit lost about how I calculate amps used from this as I don't quite understand the page Duncan pointed to. 

The CT I bought says "Output: current output or voltage output (burden resistor needed to add); ", so does this mean I'd need to add a Burden Resistor?

Also, I'd be interested how you setup the Loxone side? I went with <v.2> as the unit, 1 second Minimum time interval, does that sound sensible? 

[Duncan]

the model you have is the 0-1v output that has a built in resistor

1v = 50A, so use the correction settings for the analog input:

input value 1 = 0 target value 1 = 0

input value 2 = 1 target value 2 = 50

 1 second sounds fine

v.2 is 2 digits which again should be fine to start with

[TomM]

Thanks for your help Duncan, I too am having some issues getting a relevant reading.

Firstly, I'm comparing my readings to a 2nd(?) Gen energy monitor installed by EON about 4 weeks ago, it displays import and export values and appears to have a 5s averaging going on (confirmed by nothing more than my observations).

I have connected:

 - 50A 0-1V CT clamp on my 230V Live inbound tail (just after the meter)

 - 15A 0-1V CT clamp on 230V Live tail from the solar panels into the PV junction box

Connected both CTs to 0v DC and an Analogue Input each, with the following settings:

   - Input val 1 = 0, target val 1 = 0

   - Input val 2 = 1, target val 2 = 50 or 15 (based on which CT)

   - Minimal change = 0.05s

   - Minimal time interval = 0.5

   - Average over 5 secs

I've then got the AI input value plugged into a multiplier with 230 thus producing an instantaneous power reading at the output (averaged over 5s as per settings).

I am getting readings but they don't really get anywhere close to the EON monitor.

On the positive side, I get 0W from PVs at night (as you would expect) and 0V from inbound power when we're exporting to the grid.  Other than that, the values don't really make it anywhere near each other.

E.g. yesterday we charged the car so the EON monitor was showing about 5KW usage, the CT value was showing less than half that.

Am I missing something?

Also, how do we know when we're exporting? Is it the case that I can just use another CT in reverse on the inbound feed?  In my head, we get a 0 reading on the inbound CT when we're exporting so just flipping it round will produce a reading when the current flows in the opposite direction. (am I being too basic in this concept?!)

Thanks in advance for any help people can give.

[Duncan]

i can think of a couple of things;

power isnt just current x voltage when it comes to AC, there is also the phase angle/power factor where the peak current doesnt occur at the peak of the ac voltage, but lets ignore this for now...

the voltage generated will be AC as the secondary current induced in the transformer and burden resistor is AC - you would need therefore to rectify this and calculate an RMS value to multiply by the voltage to calculate power.

to do this accurately you will need some extra circuitry such as:

https://electronics.stackexchange.com/questions/276437/how-to-convert-current-obtained-from-ct-to-precise-voltage-applied-as-input-to-a

it will be easier and cheaper to just buy one of these and have the final power values pushed to a loxone virtual input:

shelly EM or shelly 3EM  https://shelly.cloud/products/shelly-3em-smart-home-automation-energy-meter/

[Techdoctor]

Just been on their website its quite a cheap solution, may require further investigation. Too many projects on at the moment apart from my bathroom lights misbehaving. 

[Jonathan Dixon]

Another contributor maybe the metering period

 I read elsewhere that electricity meters aren't a perfect integral of power over time, but use in essence a 1 Wh bucket, and only increment the import counter each time complete watt-hour is consumed. So if you have a PV redirect that is causing the meter to oscillate between import & export, then a perfect integral will measure some quantity of time importing but the supplier meter might measure 0 (if the import/export oscillation net to 0)

This maybe what appears to be 5 sec averaging, if you have a 720W base load then it will be cranking over 1Wh every 5s

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[Techdoctor]

@TomM Have you tried to connect your 50A clamp after the main breaker (the one you use to switch off the whole house). If I remember correctly from Uni  that the main cable going into the house normally has very thick insulation and sometimes its double insulated, this could be attenuating the signal to the clamp. Also try turning the averaging off. 

Daft question as I am sure you have checked this, is the clamp connected the right way round. 

And finally are the lower readings always about the same, so when charging the car is it always the same amount.