I have just been trying out the emontx I have built, it is version 2.0 (about 1 year since getting kit) the problem I have is that the measurement for  the solar output output appears quite accurate but the power being used by the house appears to track the solar output ie if I am generating 2Kw I will be using about 1 Kw but |f I turn the solar off the consumption drops to around 150w which is what i would expect with just fridge clocks etc on. Ie at night the consumption is correct but once I start generating my consumption also goes up.


Does anyone have any thoughts





Robert Wall's picture

Re: emontx

Stupid questions possibly:

1. How are you reading the values?

2. Have you assembled the kit correctly and there are no solder bridges etc on the pcb?

3. Presumably you have two current transformers. If you take each one off its mains cable in turn, does the other then read correctly?

4. Are you measuring the currents in the right places?

5. Do you have a voltage monitor installed?

6. Are you using the up to date sketches (which?) and library?

7. What happens if you swap inputs - what does the third c.t. input report with each c.t?

glyn.hudson's picture

Re: emontx

Hi Modbury,

It sounds like you have what we have termed a 'type 2' solar PV wiring. This is where the output from your PV inverter get's fed into the consumer unit to which other loads are connected. See: http://openenergymonitor.org/emon/applications/solarpv

The second CT is reading both your consumption and generation. You need to use an AC-AC voltage adapter connected to the emonTx to measure the voltage and give the emonTx a point of reference to enable it to determine the direction of current flow. The power reading from the second CT should then reverse it's polarity depending on the direction of current flow i.e importing or exporting. You will also need to run the emonTx_CT123_voltage sketch on the emonTx. 

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