Basic question about monitoring 240V circuits and amperage

[sub3marathonman]

As an aside looking forward to new and more updates in your projects thread!

Oh boy, you had to mention that?

I have actually made excellent progress, with the hardware portion! By great fortune, Sears has once again made me an offer I couldn't refuse, and I've gotten another Gladiator component for the wall storage in the garage. And the connection to the GEM is that the wall piece will be used to cover up the wires running from the panel to the GEM. So at some point hopefully before the end of the month I'll have things completed.

The software has also had some progress, but it has been much slower and more difficult, which there really isn't any reason everybody has to reinvent the wheel with the emoncms, but help there is very limited. As an aside, for setting up the program, there is a step which has changed since the instructions were put on the Github, I and several others have needed to ask for help because of that, I pointed out that it would be great to update the instructions, and the instructions remain unchanged. But yes, I've just about got things finished up with the software too.

Finding out I can measure and record amperage with the GEM has been a great help. And of course, it did lead to the bit of initial confusion, but thanks to all who've helped, I and hopefully any future users do understand how it works.

It would be great to have the Power Factor available too, as wci68 is suggesting, because it will give people more insight into if motors are working efficiently. I just happened to quickly find this article: http://ecmweb.com/motors/motor-efficien ... r-and-load

In the GWN where Teken is, pools are probably rare, but down here they are everywhere, with the corresponding pool motor most likely working inefficiently. I have gotten to the point with the GEM that I can see when the filter is needing to be cleaned because you can see a greater electric usage from the pool motor.

And it really would be great to have the additional channels, but I don't know how much that would add to the cost of the GEM. It was pretty tough to justify the what I consider significant amount spent, although yes, it was definitely worth it,

[Teken]

As an aside looking forward to new and more updates in your projects thread!

Oh boy, you had to mention that?

I have actually made excellent progress, with the hardware portion! By great fortune, Sears has once again made me an offer I couldn't refuse, and I've gotten another Gladiator component for the wall storage in the garage. And the connection to the GEM is that the wall piece will be used to cover up the wires running from the panel to the GEM. So at some point hopefully before the end of the month I'll have things completed.

The software has also had some progress, but it has been much slower and more difficult, which there really isn't any reason everybody has to reinvent the wheel with the emoncms, but help there is very limited. As an aside, for setting up the program, there is a step which has changed since the instructions were put on the Github, I and several others have needed to ask for help because of that, I pointed out that it would be great to update the instructions, and the instructions remain unchanged. But yes, I've just about got things finished up with the software too.

Finding out I can measure and record amperage with the GEM has been a great help. And of course, it did lead to the bit of initial confusion, but thanks to all who've helped, I and hopefully any future users do understand how it works.

It would be great to have the Power Factor available too, as wci68 is suggesting, because it will give people more insight into if motors are working efficiently. In the GWN where Teken is, pools are probably rare, but down here they are everywhere, with the corresponding pool motor most likely working inefficiently. I have gotten to the point with the GEM that I can see when the filter is needing to be cleaned because you can see a greater electric usage from the pool motor.

And it really would be great to have the additional channels, but I don't know how much that would add to the cost of the GEM. It was pretty tough to justify the what I consider significant amount spent, and yes, it was definitely worth it,

I really look forward to some detailed pictures of those new cabinets then! Also interested in the detailed steps you had to take to get emon fully operational.

I won't lie having the Dash Box showing all of the things you are now looking for has been a Godsend for me. Many years ago I had asked Ben to show VA, PF, and Current. As you noted it has helped tremendously in confirming start up (inrush current) and efficiency.

Can't wait to see your journey progress!

[wci68]

Many years ago I had asked Ben to show VA, PF, and Current. As you noted it has helped tremendously in confirming start up (inrush current) and efficiency.

Perhaps I'm missing something.

If you have a motor start between the V & A samples taken for two consecutive records sent by the GEM, your V & A values would never reflect the event. However the reported energy (and power) values would reflect this. That would skew any PF calculation towards unity, even if only slightly. Similarly if that motor start occurred at the moment when the V & A samples were being taken for any particular record it would skew any PF calculation towards zero.

This is where reducing the interval between records comes into the picture as the amount of the skew would be similarly reduced, particularly since such transients are actually fairly common even if not to the same extent (magnitude) as a motor start.

Calculating PF is easy, but getting it accurate not always so. For a strictly sinusoidal waveform measuring the time between zero crossings would be all that is required to determine PF. Unfortunately with non-linear loads (see my other post) it isn't necessarily that simple but might be good enough.

Alternatively, measuring the RMS values for each full cycle (which is what I am guessing the GEM does and reports as the "instantaneous" values) and dividing by the accumulated power values for the same cycle would be the most accurate. Since we wouldn't be able to read 60 (or even 50) records per second for 32 channels this would need to be done by the GEM itself. That might be a bit too intensive and would be overkill.

Going one step further, the interval for calculating PF can be stretched out to a full second (50/60 cycles) or longer. In fact it wouldn't make sense to actually calculate PF any more frequently than the GEM send interval, but the RMS interval really needs to match the accumulated power/energy interval to maintain an accurate PF calculation.