Still Confused about alternate CT's

Robert.Wall · 2017-11-14T07:19:05.109Z

Hopefully, your CTs will obey the same convention as the USA, so look at the “Use in North America” page for details:
“For consistency with the standard YHDC CT supplied by the shop, connect the white wire to the plug tip and the black wire to the sleeve. There should be no connection to the ring.”
Elsewhere in ‘Learn’, you should find enough information to determine whether you need to change the burden resistor inside the emonPi, and calculate the calibration coefficient.

Duncan_Cunningham · 2017-11-15T02:11:26.817Z

did some pretty nasty soldering and got them connected with the white to the tip and black to the rim or sleeve.

I get outside, and by this time is cold and dark. I manage to open up the panel but the two copper wires that feed in from the meter side are too close together for the CT to slip around the lines and clip together. I’m going to come back to this when I have day light and less risk of blowing myself up. So the main issue I’m having is the lines are closer together than the thickness of the CTs that I got in from YHDC.

Wish me luck

Robert.Wall · 2017-11-15T12:56:39.166Z

Those of us who are engineers would have looked inside the panel first, before buying anything. (He says - too late!)

You might be able to split the cables apart with some gentle persuasion, but this is where experience is necessary to know when to stop - before you do damage. A photo might help.

Duncan_Cunningham · 2017-11-16T01:14:22.432Z

i am familar with my panel and I’m not an engineer. What I didn’t know was the size of the CTs they are very chunky and no dimensions were on the webpage and, anyway, I had no choice of what I was to get and I see others stating that they sometimes have to make changes to the hardware to allow them to fit. I’ll take a picture when it’s not dark and attach to this post. I was able to move, safely, the wires to allow the CT to wrap around the lines coming into the service panel.

I’m now trying to figure out how I set this up a few months ago and get it going again. US setups are not as straight forward as the UK and I do miss that simplicity but I don’t miss small homes and gardens and the lack of sunshine… a list of what I miss or don’t for another book.

I think I’ve got it going and I’ll post my findings.

Robert.Wall · 2017-11-16T16:55:27.365Z

Duncan_Cunningham:

and no dimensions were on the webpage

That would depend on which web page you looked at. On the “Use in North America” page of ours, there are dimensions for some and links to the manufacturers or distributors’ websites for the remainder. We can’t speak for c.t’s that we haven’t looked at and checked.
If we were to reproduce the manufacturer’s data, there might be copyright issues but more likely, there is a risk that we would not know when there was a change and we’d be offering out of date information.

Duncan_Cunningham · 2017-11-16T17:49:41.782Z

Robert, I’m not attacking or criticizing anyone, I’m stating that when I ordered from the company I didn’t look for dimensions because I’m not smart enough to realise that maybe the CT would be larger thickness from the inside to the outside and more difficult to fit into place. If I’ve offended anyone by asking questions and reporting back what I’m doing wrong then I apologise, this is not my intention. I’m just trying to use OEM in a different situation to most of you. I envy the UK typical power to a home, 240V or 220V or whatever it is now is much better than 2 lines of 120v and having different loads on them means that i have twice any many CTs to get accurate readings so the steps a little bit different and it takes me a long time to figure out and the page you keep referring to “use in North America” that I’ve look at many times isn’t helping me all the areas I’m dealing with. I’m not ready to start tearing apart my emonpi and putting on resistors to the CTs, i’m just not that confident at this kind of stuff yet but I’m not afraid to ask.

I think I have put one of my CTs on backwards over one of the legs coming in from the array inverters and I will not be able to fix than until I get home tonight, by which time I’ll have less than 40 mins of light to test.

I might be able to get a picture of the service panel then too.

Robert.Wall · 2017-11-16T20:16:38.227Z

Duncan_Cunningham:

“[The] use in North America” that I’ve look at many times isn’t helping me all the areas I’m dealing with.

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.

Duncan_Cunningham:

I think I have put one of my CTs on backwards over one of the legs coming in from the array inverters and I will not be able to fix than until I get home tonight, by which time I’ll have less than 40 mins of light to test.

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.)

Duncan_Cunningham · 2017-11-16T20:21:57.243Z

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.

Duncan_Cunningham · 2017-11-16T20:59:19.961Z

"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.

Robert.Wall · 2017-11-16T21:19:34.882Z

Duncan_Cunningham:

Maybe I’m not doing this right

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.

Duncan_Cunningham:

Scale Factor? I

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

[nodes]

and your emonPi is Node 5

[[5]]
    nodename = emonpi
    [[[rx]]]
        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.

Duncan_Cunningham:

I’m not as smart as you guys so bear with me.

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

Duncan_Cunningham · 2017-11-16T21:55:40.553Z

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.

Robert.Wall · 2017-11-16T22:31:21.307Z

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.

overeasy · 2017-11-17T02:10:05.698Z

Duncan_Cunningham:

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.

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. 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.

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.

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.

Duncan_Cunningham · 2017-11-17T21:21:23.469Z

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

overeasy · 2017-11-17T22:42:10.135Z

Duncan_Cunningham:

was my friend telling me a line of BS or was he right?

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,

image1175×857 157 KB

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.

overeasy · 2017-11-18T18:00:05.534Z

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

Frogmore42 · 2017-11-19T18:47:18.823Z

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.

Frogmore42 · 2017-11-19T18:51:01.329Z

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.

overeasy · 2017-11-19T19:02:44.823Z

Frogmore42:

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.

overeasy:

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.

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.

Duncan_Cunningham · 2017-12-03T19:27:48.959Z

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.