monitoring PV output problems

Gary K · Jan 27, 2012

Hi all I have been attemping to monitor the output of my system using an energy monitor that was provided by one of the energy companys for the purpose of measuring used energy.
I also use the Sunny Beam but this has to be prompted to interrogate the inverter and therefore will not provide an instantaneous reading.

The problem I have is that I cannot get a reading from the cables above or below the generation meter(on left in photo) ,but strangly if I take the sensing clamp and place it between the import meter and whatever the tan coloured box is( on right) it will then pick up the exported energy.
I have also tried the cable between the inverter and the generation meter with the same results - no reading, so I am a bit bemused.

Has anyone come across this before or could someone come up with an explanation?

I have been considering buying a piece of kit so that I could dump energy into heating water but if we cannot measure generated energy obviously such an idea will be a non starter.

[ElectriciansForums.net] monitoring PV output problems

SolarCity · Jan 27, 2012

I think the problem you are having is that you are attempting to clamp around both the phase and neutral. The phase and neutral will effectively neutralise each other and give you a zero reading. You need to clamp the cable around the phase cable only - as you do when you clamp around one of the tail from in your income meter.

Earthstore · Jan 27, 2012

My knowledge on these is limited, but this type of monitor senses the electricity going along the cable, they are not 100% accurate though, and as inverters read in a similar way they are not 100% either.
The generation meter should be accurate though as the power runs though it.
If your pv system is producing, you should get a reading from the pv cables, unless the cables are shielded (just a thought).
These monitors can not determine which way the current is flowing, so where you have it clamped it may be reading import not export, to check this, watch the monitor, then turn your pv system off, wait for at least 5 seconds for the pv system to power down, then you should see the the monitor reading rise.
EG House using 3 kw, pv system producing 1kw,monitor would only show 2kw, turn off pv, monitor would then show 3kw.
Also as this type of monitor only senses the power going through the cable it can also pick up current from any cables close by, giving you false readings.

Sorry, but due to the nature of these monitors, they are only a rough guide, but there are better systems coming to the market place all the time now at reasonable prices.
I hope this helps

Ps Biggs has more knowledge than me..

Gary K · Jan 27, 2012

I am definately getting a reading of export where the meter is currently clamped as I can reduce the figure by turning on lights. Have been exporting 1.5-2.1 kw since 11am.

Biggs-
where would I need to clamp this or any other devise to get a reading as it is not possible to avoid the neutral?
Isn't everyone going to have the same problem?

SolarCity · Jan 27, 2012

One way you could do it is by rerouting your positive cable in pvc/pvc cable out of your isolator and then clamping on to that.

Gary K · Jan 27, 2012

BiggsSolar said:
One way you could do it is by rerouting your positive cable in pvc/pvc cable out of your isolator and then clamping on to that.

And this wouldn't pose any warranty/safety issues if I was to do this?

series530 · Jan 27, 2012

Anything using current clamp technology is rather inaccurate. These systems cannot deal with direction or the phase difference between the voltage and the current. This term "the power factor" can have a huge effect upon what you actually measure (assuming, of course, you can measure something in the first place).

I have found that the EnviR (CurrentCost) monitor is better than many once it is paired with an optismart pulse reader. The optismart counts the led pulses on most modern meters and, because consumer meters take power factor into account, they are, by definition, more accurate than a current clamp.
Even with these though, if the meter is solid red or solid green, the optismart cannot count pulses. So, you cannot measure power export.

I have a couple of EnviR's and a couple of Optismarts. One measures PV and the other measures incoming. It's accurate to within about 2% when pulsing. Not bad for a consumer monitor IMHO.