Hello all. My EMONPI V3 has been working perfectly and all of a sudden my inputs are showing negative after a power failure. I rebooted the unit again but still the inputs are show negative. Has this been seen before? I’ve seen some previous posts about it but it’s only during 1st installs when you have the CT’s turned around. I can’t believe my solar panels for send power into the sky. 
Release: emonSD-07Nov16
Anyway, any help would be appreciated on this issue.
Glen
Well I just learned something new about this. It appears I had the AC voltage sensor plugged in differently and it reversed the sensing and caused the numbers to be negative. I turned it around and low and behold it was fine. Guess that serves me right to switch things around and not keep them the same.
Lesson learned.
Glen
Have you turned round your a.c. adapter? I assume that your version is reversible in the socket, and that will have exactly the same effect as reversing all the c.t’s.
[EDIT]
So it was not the power failure after all, but digitus erroneous. 
Thanks for the reply. I took a stab at it and just turned it around. New to this stuff so I’m still learning.
Thanks for posting it though.
Have a good one.
Glen
We have polarised plugs, so it’s never a problem in the UK. Which is probably why it’s not mentioned very often.
[I’ve now added that to the FAQ.]
We do too. In addition to the rounded contact, one slot is narrower than the other.
If the “wall-wart” manufacturers would use polarized contacts on their products,
either the third contact, or one blade wider than the other…
Unfortunately, very few of them actually do, so it remains a “gotcha.”
I’m currently experimenting the same problem.
I switched the CT clamp (blue donut click) and the values still appear negative. When you say “turning it around and low”, what do you exactly mean?
Thanks for any help and reply, even it is not directly my question, originally!
That is a misspelling. It should be “lo and behold” - an expression of surprise or astonishment.
The direction of power is determined by the relationship between the voltage wave and the current wave. It’s explained on the 'Docs" section ‘Determining the Direction of Power Flow’: An Introduction to AC Power — OpenEnergyMonitor 0.0.1 documentation
If you reverse either the a.c. input to the emonVs or the direction the c.t. points, the positive parts of the wave will become negative and vice-versa, and you will change the sign of the power. If your reverse both, both voltage and current waves will flip over together and then the sign of the power will not change - because the relative phase of the two waves has not changed.
Positive × positive = positive, and negative × negative = positive.
But I see you (@juan_andres) are using the old blue c.t. so you have the old emonTx V3 or earlier and an a.c. adapter - but the principle is the same. Your c.t. has “SCT 013 - 000” written on the side. Say the main cable is horizontal and the low voltage output lead is hanging down, and the clip is towards you. The “SCT 013 - 000” is on the right. Unclip it from the cable and rotate it 180° so that the clip is away from you, the writing “SCT 013 - 000” is now on the left but everything else is the same.
Thanks for clarifying so much things in your post, @Robert.Wall !
First of all the experssion, thanks! sometimes is hard to follow some discussions not just because of the topic (I’m not expert on anything regarding energy) but the language itself.
I did say I switched one of the CT’s but was the one that measures the solar power, and was in the night, so the difference was none. This time I did switch both CT’s and they are now behaving normally!
Also I’ve got the old blue ones, good point, and still working great!
Many many thanks, again!