Measuring electricity

[DavidL]

There are splitcore inductors that we have plugged into an analog WeederTech board to detect energy usage w/ MainLobby. If I can find the link, I'll post it.

I suspect this gives you a simple current reading, rather than a true energy reading. A simple current reading will give relative information over time, but doesn't give true information about motor/compressor usage and won't match your power company meter.

WayneW,
Can you expand on that? If we are monitoring both phases of a primary power panel over time, with a given constant voltage and databaseing those results, why would it not be a good measure of electricity usage? Of course we won't be making constant measurement (as the utility meter does), but it should give very good approximation if the data resolution time is kept relatively short like every second or so, maybe every minute. At least that is my thought.

My assumption is that most energy usage in a home isn't a one minute on / then off device that the energy "sniff" might miss consistently. At least in my home, the big energy grabbers are the HVAC (which by their design, won't short cycle and run for many minutes in a given cycle), the water heater (long cycles), lights left on (never just for a minute), the computers on the LAN (most 24x7), Wal warts (24x7 typically), security sytem (24x7), actually can't think of many hit and run consumers. And by the nature of hit and run, shouldn't amount to much energy usage anyway.

Am I missing something there?

 

[ckindt]

There are splitcore inductors that we have plugged into an analog WeederTech board to detect energy usage w/ MainLobby. If I can find the link, I'll post it.

I suspect this gives you a simple current reading, rather than a true energy reading. A simple current reading will give relative information over time, but doesn't give true information about motor/compressor usage and won't match your power company meter.

WayneW,
Can you expand on that? If we are monitoring both phases of a primary power panel over time, with a given constant voltage and databaseing those results, why would it not be a good measure of electricity usage? Of course we won't be making constant measurement (as the utility meter does), but it should give very good approximation if the data resolution time is kept relatively short like every second or so, maybe every minute. At least that is my thought.

My assumption is that most energy usage in a home isn't a one minute on / then off device that the energy "sniff" might miss consistently. At least in my home, the big energy grabbers are the HVAC (which by their design, won't short cycle and run for many minutes in a given cycle), the water heater (long cycles), lights left on (never just for a minute), the computers on the LAN (most 24x7), Wal warts (24x7 typically), security sytem (24x7), actually can't think of many hit and run consumers. And by the nature of hit and run, shouldn't amount to much energy usage anyway.

Am I missing something there?

Sorry to jump in here, but how are you calculating your power consumption? By your posts it sounds as if you are measuring current and are multiplying your "known" voltage. If so, this results in apparent power (S). This does relate to real power (P or kW), but is not what your electric company bills you for, fortunately, or your bill would be higher. The missing link here is the power factor which is a ratio between real and apparent power.
So comparing your electric company's bill in kWh to your calculations of VAh? is not equal.

This method is an approximation at best. How close depends on your PF, the closer to 100% the more accurate it is.

You mention HVAC. The motors and compressors are all inductive which will reduce the PF from 100%.

 

[mdiehl]

The Energy Detective is one product that will do it, and can be automated/monitored. http://www.theenergydetective.com/index.html

Otherwise search for submetering.

Does anyone know if this has split core sensors for installing on the power lines?

Also any word on an available protocal to use HS/CQQ/Girder plugins?

John

Yes, the T.E.D. uses current transformers that are spring loaded and "clip-on" to the main power leads to the breaker box.

 

[hult]

I have not done this, but one methodology would be to use WattNode devices at each 200 amp service entrance.

Another DIY approach is to purchase a Microchip's MCP3905 Energy Meter Reference Design for $54 shipped direct from Microchip ($45 from Mouser, Digikey etc) This stand-alone low-cost power (energy) meter is assembled, input protected (but not UL-lsted), and suitable for use with both electronic and old-timey mechanical counter* simultaneously.

Details with picture here. It accurately calculates P = V*I by measuring instantaneous voltage and current separately and calculating power from them. This provides accurate measurement for all power factors. The board also provides facilities for calibrating.

You would also need a current transducer (I have about 50 that are excess to my needs including Magnelab CT150 and CT-400 150-amp and 400-amp split core current transformers for about $25 + shipping each ) I'll post them to my Internet Porch Sale Home Automation and Electronics Sale.

Monitoring of the output pulses could be done with a Dallas/Maxim DS2423 1-wire counter and a backup mechanical pulse counter* like this one for $8 if desired.

I believe Michael McSharry may have some suitable software for measurement and monitoring using 1-wire counters.

So you could have very accurate AC power measurement and computer monitoring with mechanical display backup* for less than $100 per AC leg. The reference design and gerber PCB files are provided by Microchip. The IC's themselves are only about $2.50 each, so one could make the boards for a bit less than $45 (depending on quantity and assuming zero-value for the time expended) if one were so inclined.

(Of course , as always, you are completely on your own with respect to safety and code issues.)

* IME, a _simple_ data backup like a mechanical counter is very helpful. Folks tend to underestimate how difficult it is to achieve 100% up time with environmental monitoring equipment.

HTH ... Marc

Visit my personal Internet Porch Sale of Home Automation and Electronic gear at www.ECOntrol.org/porch_sale.htm

 

[Rupp]

Sorry to jump in here, but how are you calculating your power consumption? By your posts it sounds as if you are measuring current and are multiplying your "known" voltage. If so, this results in apparent power (S). This does relate to real power (P or kW), but is not what your electric company bills you for, fortunately, or your bill would be higher. The missing link here is the power factor which is a ratio between real and apparent power.
So comparing your electric company's bill in kWh to your calculations of VAh? is not equal.

This method is an approximation at best. How close depends on your PF, the closer to 100% the more accurate it is.

You mention HVAC. The motors and compressors are all inductive which will reduce the PF from 100%.

So if you can count the revs on the spining power meter this is accurate right?

 

[ckindt]

Sorry to jump in here, but how are you calculating your power consumption? By your posts it sounds as if you are measuring current and are multiplying your "known" voltage. If so, this results in apparent power (S). This does relate to real power (P or kW), but is not what your electric company bills you for, fortunately, or your bill would be higher. The missing link here is the power factor which is a ratio between real and apparent power.
So comparing your electric company's bill in kWh to your calculations of VAh? is not equal.

This method is an approximation at best. How close depends on your PF, the closer to 100% the more accurate it is.

You mention HVAC. The motors and compressors are all inductive which will reduce the PF from 100%.

So if you can count the revs on the spining power meter this is accurate right?

I'd say so if I understand correctly. If the meter you're counting revs on is the electric co's meter then you should be perfectly accurate provided your display/counter is calibrated correctly ( ? pulses = 1 kWh). This came up on another post about power measuring. It's a clever idea, but in my case Omaha PPD swapped out my old style with the wheel that goes round and round for a new digital one. It's actually nice for me because it only displays kWh on an LCD. I can easily see my power monitor is very very accurate with OPPD's meter. They're lucky.

 

[Rupp]

So if we could figure out how to interface with this device we would have a true cost measuring device.
http://www.mymeterstore.com/p3982/power_cost_monitor.php

 

[ckindt]

So if we could figure out how to interface with this device we would have a true cost measuring device.
http://www.mymeterstore.com/p3982/power_cost_monitor.php

I'm sure it's possible, but what are you trying to integrate it with?

 

[Ranger Digital]

rupp., thats cool. but it since it reads the meter, it will tell me the consumption of BOTH buildings, right? otherwise, its slick.

I like Hults idea, under $100 bucks, but his post is way over my head, LOL.

looks like the ezmeter davidge is easiest. The TED looks simple to but i like the idea of the meter being in or near the breaker box and hidden.

oh the choices.

 

[sda]

You could do it the old fashioned way ... get a watthour meter off ebay and stick it in front of the second building panel. I'm guessing you can cut off power to the second building somehow to install it. Used watthour meters are cheap, item #200194748981, standard I70, is 4 for $35 plus shipping. In fact, item #290201019149 the seller says "The wire that comes out of the back is for some sort of a remote sensor and does not affect the normal performance of the meter" so you might be able to get metering and a future interface for HA, if you can figure out how the sensor works.

 

[mdiehl]

As an addendum, my original model TED, the 1000 is at the factory undergoing an "upgrade" to PC logging compatibility. If there's interest, I'll let you know how the "upgrade" and new software work out. Serial port for the original model, the new one is USB.

 

[keepersg]

Here is the scenario. Two buildings. One meter. Each building has its own main 200 amp service box. The monthly bill of course only shows total for both buildings as there is only one meter. Is there a way to determine how much power ONE buildings uses? Maybe something I can add to one of the main power boxes that registers something? Doesnt have to be automated as I dont mind reading at the box. Later I may want to automated though because, well, you know, it feeds the addiction.

I am assuming YES as anything is possible these days. Especially with the help of cocooners, LOL.

Any ideas?

Sorry to come in late on this. I use products from Davidge Controls http://www.ezmeter.com/news.html to do this. I monitor the apartment in our house which is on a separate panel and generate a bill each month. They make a variety of metering and monitoring options. Everything from a mechanical pulse counter to a serial or powerline interface communication system which your computer can read and generate a bill--they provide the software for this. It was all reasonably priced when I bought it a year ago.

Apologies not necessary.
This doesn't look any different from the wattnode. I only saw pulse output meters on the website at similar prices as wattnode.

Please note I don't endorse either...I just endorse the facts.

The website is a little confusing. Here's the link that describes their remote monitoring setups. http://www.ezmeter.com/yosemite.php Scroll down to the bottom of the page and you'll see what I'm talking about.

 

[Ranger Digital]

Here is the scenario. Two buildings. One meter. Each building has its own main 200 amp service box. The monthly bill of course only shows total for both buildings as there is only one meter. Is there a way to determine how much power ONE buildings uses? Maybe something I can add to one of the main power boxes that registers something? Doesnt have to be automated as I dont mind reading at the box. Later I may want to automated though because, well, you know, it feeds the addiction.

I am assuming YES as anything is possible these days. Especially with the help of cocooners, LOL.

Any ideas?

How soon do you need it, Tuck? I´m working on a GUI for CL.

Ant, how did that GUI turn out?

 

[AnthonyZ]

Real time feedback, done. Piece of cake. Data logging, not done. Hell, not even started. I'm stupid broke and crazy busy right now. I'm hoping to hit it again by the end of this month.

Did you see Convergent Living on "Invention Nation" (Science Channel) over the weekend? It's replaying on the 25th. My new friend, Travis, had me down in AZ after they filmed that to monitor the water storage and flow. Built a custom GUI and A/D program to "watch" the H2O. He was actually back on site today adding a 15" TP on the same job and has a new GUI to drop on top of the "stock" GUI shown on the program. Pretty cool to see HA on national television and really cool to see a good buddy (and my friends at CL and HAI) get some attention. The only way it would have been better is if they filmed after my part of the contract was loaded and got my ugly mug (and more importantly, my business info) on national TV.

 

[Ranger Digital]

anthony, no I didnt see it. Will sure tune in or at least dvr on the 25th! Ya too bad they filmed just a bit early. Met my new rep Trent (CL) today as he came to Fort Worth for a short training/presentation. Its turning out its not at all as complicated as it looks. No piece of cake but not as intimidated.

Um, if your busy you shouldnt be broke, LOL.