Got Iotawatt setup. Split phase system - added mains and monitoring most but not all circuits. After configuring an output to calculate the remaining power usage of my unmonitored circuits, I’m getting negative reading on remaining circuits. Not sure what I’ve done wrong. I checked the mains CTs to make sure no paper is left between connections. Only thing I saw was one CT has some discoloration on one of the contacts. Not sure if that’s related or not.
That doesn’t look right. Those CTs are shipped in a sealed pouch with a desiccant to avoid corrosion. I’m very surprised at that. Could be the cause of what you are recording. Is that main_2?
Yes, the one with discoloration is main_2.
Ok, I’ll send a replacement tomorrow.
From the screenshot it looks like you should have “misc” of 20 watts.
Did the replacement CT fix it?
Also, can you show a screenshot of your “misc” output formula?
Replacement should be here tomorrow. I’ll post updated results this weekend.
My formulas are:
total_power Watts = main_1 + main_2
misc Watts = main_1 + main_2 - (circuit_2 + circuit_4 + circuit_6 + circuit_8 + smart_box + washer + dryer + refrigerator + circuit_1 + oven + master_heatpump + lroom_heatpump)
So the formula looks good and I double checked my math on your screenshot. I get the same total you are seeing. (a negative value) I thought I double checked before I posted the first time but my calculator skills obviously failed me.
Will be interesting to see if it’s the CT once you get it swapped out.
Hmm… well, I swapped the main_2 CT with the replacement. At first it looked alright. I was getting positive values for the “misc” calculation, but I’ve been monitoring it for the last hour and it’s still not adding up right. Is it perhaps within the margin of error for these CTs? Or maybe one of the other smaller CTs isn’t reading right?
Still getting a negative value for “misc” most of the time. Every so often it’ll be positive.
Maybe I should troubleshoot each of the 50A CTs and see if they add up correctly to the mains? Thoughts?
The status display is damped averages over the last few seconds. Your variation is 1.2%. If you want to check accuracy and reconcile, I’d recommend looking at it over a longer timeframe.
You can reconcile your mains against the meter. Take a record your meter reading and the time, to the second, then again a couple of days later. Use Graph+ with those date/time as begin and end and look at the cumulative Wh.
Add you misc to that plot and compare the cumulative Wh to the meter and mains total. They should all be within 1% - probably better.
Can you post a Graph+ plot of misc and mains over an hour or more with the statistics tab showing the average?
Sorry for the delay… 4th of July and got busy with a bunch of other projects. Is this what you wanted to see? Unfortunately, I don’t have physical access to my meter. I live in a high rise and all the meters are located in a locked facilities room. I’m happy so far with the readings I’m getting. I’m just baffled by the misc difference.
The misc is remarkably stable in the graph given that main1 varies quite a bit and main2 does vary more than misc. that leads me to believe the problem is not with the CTs.
Taking a closer look at the picture that you posted of the panel, I count 4 240V circuits. I suspect those are the two heat pumps, the dryer, and oven. All of these are being monitored with a single CT, yet it looks like at least two of them may be three-wire circuits.
I’m assuming you have checked double for all of these. If one of these is three-wire and the side you happen to be monitoring is carrying more current than the other (difference is going to the white neutral), then you would be overstating the power used by that circuit, and it would drive misc down by the amount of the overstatement.
The docs talk about various ways to monitor three-wire circuits, and this will not fix it, but as a diagnostic step you could move those CTs to the other hot conductor and see if it swings misc the other way.
You are correct about the four 240v circuits. Dryer, oven and two heat pumps. All of which we don’t use very often. As in, maybe once or twice a week and it’s usually the dryer.
So they should be pulling next to nothing when not in use. And that’s what I’m not able to rationalize (that steady negative misc value).
I did check double on all four of these circuits. Maybe what I should do is remove the 240V CTs one by one, adjust the misc forumla, and monitor for a few hours or days to see if the misc power comes closer to the correct margin of error. Or perhaps there’s another three wire circuit I’m not aware of or seeing.
I’m away from home again for a week so I won’t be able to try again till next week but I’m interested in figuring this out.
Next time you engage, could you post the inputs setup display please?
I’m trying to make some sense out of this. I see that something has changed between the two posts of the status display. One has circuit_1 in channel 11 and the latest has something called rover_23. Is that just a name change or were there any other changes between the two?
More perplexing is the fact that in the picture from the first post, all of the branch CTs on the left are oriented one way, and those on the right are oriented the other way (with respect to the breaker). Best I can tell looking at the picture, all but three of the branch circuits are on one leg. Yet none of the inputs in the Inputs configuration show as having reversed checked, and none of them show the reverse arrow in the status display. Maybe its late or I’m losing my edge, but I don’t think that is possible.