Electrical wiring and measuring whole house electricity use
Measuring whole house energy use in the UK.
If its a house in the uk it will probably be a 240VAC 2-wire single phase system.
To measure energy use you need one current sensor and one voltage sensor, see the diagram here:
Here's a picture of the current sensor connected to the main live coming in to the house:
Measuring whole house energy use in the USA
If its a house in the us it will probably be a 120VAC 3-wire single phase system.
To measure energy use you need two current sensors one on each leg and one voltage sensor, see the diagram:
The combination of both legs is simply summed:
Total real power = real power leg 1 + real power leg 2
Wiring diagrams modified from hyperphysics.
3 fase system
Hi Trystan,
I was wondering how much effort it would be to use this system on a 3-fase house energy system. I don´t know about the UK, but on mainland europe, if you have a Heat Pump, you have a 400v system, consisting of a 3 fases of 230v and a 0, and earth. I have this drawn in the same fashion as the drawings above, and I´m sure there is enough intrest for a monitor in this configuration.
As far as I can tell, in this case you need 1 Voltage sensor and 3 Current sensors. But is this still possible on the standard Arduino board, and I guess you need to modify the software. In the ideal situation I´d like to monitor my total use of energy and what the HP uses. This askes for the need of 3 extra CT sensors, or as in my case, a pulsecounter for the pulses from the energymeter on the WP. Logging-wise I understand how to handle the info from the database and create a graph with the use of "normal" energy and on top of that the energy used by the HP.
If you´re intrested I gladly sent you the drawing.
Thanks,
Willem.
re: 3 fase system
Hey Willem
I think it certainly should be possible to monitor 3 phase, the sampling rate on the arduino would be a bit slower than for single phase due to need for extra analogRead()'s but Im sure it would be enough, I haven't done it myself yet and am not entirely sure of the theory or how the code would work out.
There's some info on 3 phase at allaboutcircuits here: http://www.allaboutcircuits.com/vol_2/chpt_10/5.html
Im very much interested in finding out how to do this so if you do work it out let me know
Thanks
Trystan
Power factor can be negative
Hi,
I noticed that when the polarity of the AC-AC adapter is changed, the sign changes... I understand why, but do you think we can find a way to make it irrelevant in the setup?
(like software correction or so?)
Re: Power factor can be negative
Yes shouldn't be too hard to do. We could add:
if ( realPower<0 ) realPower = realPower * -1;
just after the line that calculates realPower from the sum of the square of instP
that was my first thought,
that was my first thought, but I had some doubts... :)