OpenEnergyMonitor Community

Still Confused about alternate CT's

So let me know in what areas it isn’t helping, and maybe it can be improved. There seems to be a lot more interest now from that continent than when the page was created, therefore we’ll try to respond to that interest by filling in the gaps.

If it’s not connected to another c.t hardware-wise (i.e. it’s physically wired in parallel), then you don’t need daylight. You can put a minus sign in front of its scale factor in the “scales = …” line in emonHub. That’s equivalent to turning the c.t. round on its cable, or swapping the connections to the plug. (Be warned - don’t disconnect the c.t. from its burden while it’s on a current-carrying cable. Yes, I know there’s supposed to be protection inside most c.t’s, but don’t bank on it and don’t rely on it.)

the service panel I have is the type that most new homes in America might have. so maybe it would be a good example to work from. anything else should have smaller gauge cabling. Maybe I’m not doing this right but my setup for EmonPi is a little different because I read both hots coming in because it’s not uncommon, since outlets are 120v there there is a imbalance going on. using this tool I’m managed to balance equipment in the house, washer, fridge, microwave on to circuits that don’t put the load on just one leg or line. I so miss UK power… kettles take ages to boil here running on 120v.

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"If it’s not connected to another c.t hardware-wise (i.e. it’s physically wired in parallel), then you don’t need daylight. You can put a minus sign in front of its scale factor in the “scales = …”

I’m sorry, I don’t know what that means yet. Scale Factor? I’ve been going through the inputs and I don’t see where I would add this. is it a line in the process list?

I’ve managed to get this thing working using the steps but I feel very lucky so far in getting out the results that I do. I’m not as smart as you guys so bear with me.

Oh but you are doing it right. Even though you’ve tried to balance the loads, which in itself is the correct thing to do, you’ll never achieve perfect balance all of the time. There will inevitably be an imbalance most of the time. You must measure the current in both legs. If you -
and your neighbours who are supplied by the same transformer - could always guarantee a balance, your electricity company would be most grateful because they could do away with the neutral conductor and save money! [It won’t happen - ever.] And then you could guarantee both voltages would be the same too, so you wouldn’t have any error from assuming they’re the same when they aren’t. But experience shows there’s little error in that assumption.

There’s nothing technically against a 240 V kettle connected line-line, but I’m prepared to bet there’s a regulation forbidding it.

You have an emonPi? If you go in via your web browser, you’ll find listed under “Setup”, and entry for Emonhub, and there “Edit config”. That takes you into the configuration file for emonhub - emonhub.conf, which you’ll find mentioned very frequently here. It’s in sections, the one you want is


and your emonPi is Node 5

    nodename = emonpi
        names = power1,power2,power1pluspower2,vrms,t1,t2,t3,t4,t5,t6,pulsecount
        datacodes = h, h, h, h, h, h, h, h, h, h, L
        scales = 1,1,1,0.01,0.1,0.1,0.1,0.1,0.1,0.1,1
        units = W,W,W,V,C,C,C,C,C,C,p

Your scale multipliers are there.

If you want to do it in the process list, you can. Just add “x” with a value “-1” fairly early on in the list. But as I wrote here only minutes ago in another thread, there’s a danger of needing to do it more than once if you re-read the input to process it for another purpose.

I’m not that smart - I’ve just been doing it a long time.

i thought it was config file so I edited it. I looked for the lines related to power2 on the TX, which is the one my Solar lines are connected to. my emonpi only has two CTs and those read the service lines only.
anyway, I changed it from 1 to -1 for the 2nd digit on the line called “scales” under node 6. Saved, rebooted the emonPi and it didn’t change the input feeds readings, is that ok or should i see the reading flip the other way in the inputs page?

edit: whoops… Emontx3 is node 8… wrong place. see, I’m learning but only through my mistakes.

If you change the config file, you should see the input and the feed change. If you change the process list, only the feed will change.

You’ve only mentioned the emonPi, so though I realised the might be others, that’s why I wrote “Node 5”. But all follow the same pattern.

If you edit emonhub.conf, you don’t need to reboot the PI. In fact, I’m not sure that you even need to restart emonHub, but restarting it won’t hurt.

Welcome to the new world Duncan. I don’t know anyone, and I know a few electricians, who pay any attention at all to trying to balance 120V loads.:microscope: The way the panels are built, the phase alternates as you go down each side, so things kind of get scattered between the two naturally. But more to the point, all of the larger loads are 240, pretty much like the old country. With a 200 Amp panel, there is no advantage to trying to balance the 120 loads. Even in an extreme case where you and your neighbors overload one side, the utility company will not see it in their network. It looks to them exactly as it would if the load is balanced, because the source is still one high voltage primary. So as a practical matter, I’d say don’t bother.:v:

Unless you’re using a hotplate that plugs into a wall socket, electric ranges do use 240 when on high heat. But I agree, electric resistance is slow. If you really want to boil water in a hurry, I’ve got one word - induction. Unbelievably fast. Faster than commercial gas. Safe and clean too. We do some things right, and if you happen to touch one of those mains, you will appreciate the 120v zing vs a 240v whallop.:exploding_head:

Don’t beat yourself up about the config stuff, I don’t get it either. That’s why I built IoTaWatt - Power Monitoring for Dummies.

Some years ago a guy I knew told me, and I’ve never been able to verify this, that if you have say 20Kwh go through line1 and 5kwh go through line2 you get charged, on your electric bill the highest of the two, so I’d get a bill as though I’d used 20kwh on both lines… so ever since then I’ve used tools like TED monitor to make sure I don’t have all of my large energy hogs on 1 line. Fridge, Freezer, Washer, (Gas Dryer), Microwave, computers, TVs and I still have some rooms with electrical heaters on 120v.

I did have an imbalance going on so I just rearraged some circuits around in the panel and I had pretty much even numbers each month. the Fridge was on 1 and the freeze on a another, that kind of thing. But now my question is this… was my friend telling me a line of BS or was he right? did my meter just read the highest of the two lines and average them out by 2 or are the new meters smart enough to measure what I use no matter if one line has nothing and the other has 30 Kwh.

I do have a number of 240v appliances. Two electric cars, Stove and I’ll be adding an electric dryer soon as I have a 8kwh solar system helping me collect about 35-49kwh per day during the sunny days… though i had my lowest ever production yesterday at less than 2kwh in a day

I can’t say if he believed that or not, but if he was talking about a typical US service meter, I believe he was mistaken.

The simplest proof of that is the absence of commercial products to perform dynamic load-balancing. There are some switching devices available to better balance the load for a whole house generator where an imbalance could cause problems, but the market would be rife with “money saving” load balancing devices if that were true.

I measure both legs of my split-phase service independently and get exact correlation with the utility meter. Clearly that wouldn’t be the case if the meter were not recording the sum of the two individual legs. Looking at the graph,

I added a plot of the difference between the two legs called “imbalance”. You can see by the statistics on on the feed lists that each main averages a little over 1000watts, yet the average imbalance is 22.7 watts. The Mains pretty much track each other because the most significant components are 240v loads - heat-pump, dryer, oven, hot-water, range - all of the things you mentioned. That’s the nut. It’s pretty hard to balance loads like fridge, freezer, washer, microwave because you really have little control over when they are on. I suppose you could wait for the refrigerator to come on to run the washer…

Anyway, just wanted to dispel the notion that 120 load balancing was a priority. These tools can do a lot more useful things when it comes to managing energy. That’s a lot of energy from an 8kW system.

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2 posts were split to a new topic: Data analysis with IoTaWatt Outputs

In the USA for residential service there is no demand charge typically (there might be some exceptions for trials in some part of the country). But, for commercial service they very much have a demand charge. This is a charge for the maximum demand (power use) by the facility. This charge can cause the bill to increase dramatically, so there are lots of companies that have put into place systems to mange their demand to minimize the costs.

Standard residential meters in the USA measure the total power draw. They measure the current on each hot line and add the two power values together. It does not matter if the loads are equal or not. In my house many of the single phase loads are on phase A. I have not bothered to rearrange them, because it does not make any real difference.

Right, as opposed to trying to balance the load on various phases, there are incentives to looking at transient aggregate high demand, identifying the significant components, develop strategies to mitigate, and measure the results. It’s no surprise that there are plenty of high-end tools to manage commercial power - the incentives are in place.

thank you guys for letting me know… I’ve now dropped the idea that I can balance the kWh used each day to be close. What I was doing was making sure the fridge was on 1 side of the panel A or B and the Freezer was on the other and the kids rooms were on different sides too. That was a OCD thing I didn’t need.