Positive or negative

Today is my first day with the emon base, vs and Tx with CTs to monitor Total house consumption P1, Solar Production P2 and Heat pump P3. It all worked great out of the box and the attached is the output feeds. I’m conscious I need to learn to walk before I run so I’m just checking that the CTs are the right way round. I did follow the online materials and the output shows P1 as a negative. Is this correct ? Also, the heat pump P3 had no demand until I created some which is why there is a blip at the end. I see the mains value blipped as well to virtually match. I hope this is all good as I don’t want to set off on the journey with a limp.
Thx in advance.

Welcome, Mark, to the OEM forum.

I’m not sure! I think you don’t mean what most of us understand by “house consumption”. To us, House Consumption means just that - the power/energy you use to run everything in the house - lights, TV, router, appliances, etc. From the look of that screenshot, I suspect P1 is actually the Grid power - CT1 is on the single-core meter tail right next to the meter? - and if so and bearing in mind today’s weather, it’s very likely it would be negative as you would have been exporting power, which by our convention is negative. So it’s probably right.

If P1 really is just the household appliances etc and doesn’t include your P.V. input, it’s definitely wrong (by our convention).

But it looks as if the heat pump (P3) is facing the wrong way - it should be positive when it’s consuming electrical energy.

In summary, our convention is:
Power into the house is positive, whether from the grid or from any other source (P.V, wind, hydro). Power exported back into the grid (or sold to a neighbour?!) is negative. Power consumed is always positive.

Hi Rob, thank you for the reply and the welcome.

Yes, I got the heat pump CT3 / P3 in the wrong direction. The attached is what it looks like now.

CT1 is 100A, is P1 and is on the positive grid feed to the fuse box with the L pointing to the load I.e. the breaker. CT2 is 20A, is P2 and is on the positive feed from the solar with the L pointing to the breaker. I haven’t found out how to rename P1,2,3 etc yet.

What does MSG mean ? I cannot find the explanation in the docs.

MSG is the serial number of the message from the emonTx - it allows you to see if/when one went missing in transit (which happens by design, the emonCMS database runs at (typically) 10 s intervals locked to Internet time, the emonTx runs independently and cannot be synchronised to Internet time so we typically run it at 9.7 or 9.8 s so that occasionally a value gets overwritten, which is less bad than having a gap in the data).

Look in Setup → Inputs and see which Node shows as active - it will have the time elapsed since the last message in green. (I think it’s) Node 17.
To the left of “P1”, tick the box and click the pencil icon at the top - change the name as you wish, and save.

Thx. Can I reset the device to delivery condition ? Can’t find instructions for that.

— update … I flashed a new std fine.

I twice followed the instructions to rename the feeds, but twice now, the act of renaming has stopped feed data from the input

For me, it appears to rename the Input OK, but then a new Input with the old name (as it is given in emonhub.conf) appears with the incoming data. The renamed input fails to receive the new data.

Is this what you see?

Yes, precisely that.


I consider this wrong.

This is the correct behaviour, inputs should not really be renamed as the names are set in e.g emonhub. The location to change the name and keep the data coming through is in emonhub. It would probably be less confusing if emoncms did not allow renaming of inputs…

This is certainly far less bad than allowing a change that promptly introduces unwanted and unexplained behaviour. I concur with removing the ability to change the name on the inputs page - if feasible a ‘help’ text there explaining where to change it would be a massive help.

I’ve removed the ability to change the name now. The field is disabled:

The intention behind changing the name was to improve the usability/ readability at the point the user sees it. Perhaps in a future release the concept of front end ‘labels’ can be associated with input names so that the UI can be changed without disrupting data structures / integrity in the backend.

You can still change the name - you do it in the emonhub configuration file emonhub.conf, rather than in the Inputs page of emonCMS. As Trystan wrote:

I know. Thx.

The description field can be used as a front end label. Should do what you are after.