Input value showing negative on 3 phase

Hi I have setup a emontx v3 and im running the default 3 phase sketch with ct4 used to also measure my solar.


I have my CT1 connected to my phase 1 and also solar wire and this all appears to be ok.  

However my phase 2 and 3 CT's show negative values of -564 and -15 respectively.  I tried to flip the clips around which of course gives me a positive value as it should read but then when i run my oven which is connected to my phase 2 line the increase in power usage shows a negative reading of about -2400 so i know that the CT clamp has to be the other way but at low usage it gives me -564.  When i keep the clamps connected so that i get a negative value at low usage ie -564 and then put on the oven it then goes into the positive. 

I have used a clamp meter and it shows that i have this amount of power going through but that it should be positive.  

Any suggestions of what i can do to fix this as i also have a emonglcd that reads the input values and with the negative values it causes it to be inaccurate.  thanks.

dBC's picture

Re: Input value showing negative on 3 phase

Somebody here: claims to have found a bug that causes the stored voltage array to not always be correctly loaded.  I'm not familiar with that code, but his patch seems simple enough to make it worth a try to see if it improves things for you.  Hopefully, someone more knowledgeable will review that patch soon.

nihonjin's picture

Re: Input value showing negative on 3 phase

I cant see anything in that thread that relates to my issue.  Mind you im pretty noob when it comes to this sort of stuff.

Why when i use my clamp meter on either phase 2 or 3 i get the same reading but positive yet the emontx shows it as negative. Also even if i turn off my solar in the fuse box these values remain negative so i know there is no possibility for the solar to be exporting on these phases (its not connected on them anyway but just to be sure).

How is it that its negative value is exactly what it should be but positive?  I know the ct clamps are correct as if i switch them around to get a plosive value and then turn on the oven it goes negative about -2400.

I purchased this device about a year ago and im still trying to get it set up.  Its certainly not as easy as i thought.  But im willing to learn and keep trying.


Anyone else have any ideas?

dBC's picture

Re: Input value showing negative on 3 phase

Jose's post in the thread referenced above is the one of interest.  If he's correct, and his analysis seems pretty thorough, then a mis-loaded storedV array could cause lots of weirdness, including negative power readings.

TimSmall's picture

Re: Input value showing negative on 3 phase

FWIW, I think I've also seen this behavior (negative values at low consumption on L2 / L3), but I've not tried to debug it.

christophe_meyers's picture

Re: Input value showing negative on 3 phase

Hello all,

See my comment at
Seems to require rethinking the voltage array procedure.
Please let me know if it works for you, as my code surely requires more testing and feedback.



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