I am trying to implement my openevse with emonpi to control charging of my Leaf.
I also have a PV/inverter that exports power.
I have a type 2 setup with the CTs (one CT on one leg of my solar inverter (220) and the other CT on line 1 of my breaker panel. Same line (NOT PHASE)).
My voltage is USA 110/220 and I have the emonpi configured for 110v.
I have created feeds in emoncms for solar/use/import following the instructions and the data is there BUT since I am using only one line, the powers are incorrect because they are being calculated for 110v NOT 220v.
I want to control my openevse charge controller’s output based on my net power so the powers must be correct.
Do I need to use 2 CTs on the incoming lines and 2CTs on the solar inverter’s output?
can I take the values from the inputs an apply a multiplication factor to them?
Or is the charger’s output based on the sites power vs. the solar output? The charger is 220 and uses L1 and L2 for power.
Am I asking the correct questions? Do my questions make sense?
I have been reading post after post and just getting more overwhelmed. Most of the posts are from users Not in the USA, so their setups are different from USA power setups.
I don’t know about EVSE, I shall have to leave any comment about that to someone who knows.
Regarding measuring your power etc:
If your load / inverter is only connected Line-Line, or there’s a neutral connection but it’s only for the control electronics, then you will measure the correct power with one c.t. on either L1 or L2, and a voltage connection from line-neutral and you multiply the result by two (to account for measuring 120 V instead of 240 V). We tried to spell this out on the “Use in North America” page in the ‘Learn’ section.
If you have any significant 120 V loads, then you need two c.t’s and you connect them together in one of the ways on that ‘Learn’ page, into the input you’re presently using to monitor L1.
It looks to me as if, in any case, you probably want to add another c.t., because that will then give you the correct power notwithstanding any imbalance of the 120 V loads.
I think that leaves this for someone else to answer:
Thank you Robert for your reply.
I read that also and it makes perfect sense. I guess first, I will have to find out IF the inverter uses the neutral for ONLY the control, or if any output is used for generation. I will do this by using a clamp on and see what kind of current the neutral is carrying when solar production is high. Just to be sure, I will also measure the L1 and L2 currents out of the inverter, although they SHOULD be the same, just 180 apart.
Then I can multiply the resulting power by 2 to “simulate” 220v.
As far as I can tell by reading the information available, because I want to use the PI for controlling my Openevse charge controller, I will use the second CT on the incoming L1 and make sure the polarity of the CT is correct (plus I for import and -I for export).
And yes I did read the “use in North America” page in the learn section. My problem was there wasn’t much mention on using the PI for charge control with the Openevse. This is where my confusion/stumbling block is coming from.
I know in EU, the power is 220 (L to N), so the problem of two lines doesn’t exist.
I know I will get there, it might just take alot of trial and error on my part, and more than likely more questions…
@Bill.Thomson: I read that as acknowledging that Bill McK knew that the US supply was one phase, and that we could have 3-phase.
That’s because OpenEVSE didn’t exist when that was written! If you let us know how you get on, we can probably add a piece to that page.
Actually, it’s 230 V ±10%, the UK used to be 240 V ± 6%, but to “harmonise”, our spec changed to be the same as the EU. The UK voltage is still centred on 240 V (because otherwise a huge number of expensive distribution transformers need to be replaced!).
So now that we know that my terminology/semantics is lacking, what kind of thoughts/answers/suggestions does anyone have about what I am trying to accomplish?
I live in the US, I have 120/240 with a neutral (giving me the 120).
My Openevse is 240 with L1 and L2 and NO neutral.
My solar inverter is 240 WITH a neutral (although I still need to find out if the neutral is used for power production or just control/sensing).
Would scaling the voltage (from 120 to 240 calculated), scaling the current from L1 on the inverter and the incoming power (only on line), or both or neither be what I need to do,
should I invest even MORE money on a EmonTX and CT’s and monitor BOTH L1 and L2 on the incoming line AND the inverter’s output?
Since a part of the monitored current is going to include the current used by the car for charging the battery, will this confuse the charger and make it change the charge current?
OR do I need to just go away with my stupid questions?
Thank You Bill for the reply.
Yes, the inverter is set for Auto, and there is a neutral connected, so it should be detecting 240 V.
I know when my voltage was extremely low last week, the inverter did shut down and the errors that were displayed were “AC voltage too low” and " Phase Balance Error". The voltage did dip down to about 103V (206V) during the hot days.
As I write this (5 a.m.), the inverter is displaying 243V (or 121.5V).
Yes, I remember those days of blackouts too. We still have them although rarely.
As far as the inverter shutting down, the grid voltage is lower than the cutoff points so, yes, it shuts itself down very similar to “the grids gone… halt production”.
Good to know about the neutral so now I can “simulate” the watt value by multiplying the voltage by two, and that should get me very close to what the inverter is producing.
I did something even simpler
Since I and simulating the PV inverter’s output for 240 V, I changed the emonpi’s calibration for 230 V.
I modified the 9V input with a fine adjust (a pot) and a 12 V transformer, since originally the indicated 120 V was low with the “stock” AC wall wart.
Seems to be working now and the power from the solar inverter is pretty close… just need to tweek the AC trimpot.