Hardware needed


I want to install OpenEnergyMonitor in a house to monitor a photovoltaic 5.4 kW installation. This installation is connected to the power grid.

I have two energy meters, one for the produced PV energy and another for the energy consumed by the house.

I want to:

  1. Monitor all the energy (produced by the photovoltaic panels, consumed by the house)

  2. Control a 150l electric boiler with the surplus power using PV Diversion.

I’m not sure about the hardware I’ll need. I think I need:

  1. To monitor the energy: EmonPi with Optical utility Meter. I’m not sure about the necessity of one EmonTx. What about the temperature sensor?

  2. To control the bolier: One emonTx plus another hardware (psu, Ac/Ac adapter, CT, …)

About it, I have some questions:

a) Will I need another hardware?

b) Is it possible to avoid using wireless connections?

c) Is it possible to use a remote screen

d) Why will I need a temperature sensor?

Thanks a lot

Welcome, Poldom.

I see you are in Spain, is your electricity supply single phase or three-phase?
And the photovoltaic inverter - is that three-phase? (Of course, if your house is single phase, that must be single phase too.)

You only have a temperature sensor - or more than one - if you want to measure and record temperature.

Yes - you view the data on a normal web browser.

That is possible, but it is not our standard configuration.

Check what your electricity meter does. You can only rely on a meter to flash the LED when importing energy. Many give no indication when exporting. Some do pulse the LED when exporting, but then you cannot tell the difference between importing pulses and exporting pulses.
Normally, we recommend the optical pulse sensor only when you do not have the ability to generate electricity, but it can be useful to calibrate your current transformers.

Have you seen the section in ‘Learn’ about PV Diversion? Learn;→PV Diversion. For more information about Robin Emley’s Mk2 PV Diverter, see https://mk2pvrouter.co.uk

I cannot advise you about the need for an emonTx until I know what your electricity supply is.

Thanks for your answer Robert.

Yes, both my house and my photovoltaic inverter are single phase.

My energy meter pulse the LED in the same way when I am importing and when I am exporting, it’s impossible to differentiate the two options only with the Led.

Thanks a lot

Thank you for clarifying those points.

So, unless you want to accurately calibrate your emonTx/emonPi accurately against your meter, the optical pulse sensor will not be very helpful.
Only yesterday Chris Wilson Large discrepancy between pulse counter and CT - #3 by qris had exactly the same problem with his electricity meter.

I think you can do the monitoring with an emonPi (with 5 V DC power pack and cable, a.c. adapter and 2 c.t’s) - the Solar PV Bundle, and I think you can divert the surplus energy either with an emonTx to which you add a power switch (a triac), or you can buy Robin Emley’s Mk2 PV Router in kit form to build yourself. You can of course also buy a ready-made diverter, but you then must rely on the manufacturer for support. I recommend Robin Emley’s Mk2 PV Router - he developed it here and we know it well, and there are many units working successfully in many countries.

I do not see a need for a second emonTx, unless it is not possible to run or extend one or both of the c.t. cables. If your PV inverter connects near to your main (grid connection) meter, then there should be no problem. You put the emonPi near the meter and have an Ethernet cable to your LAN (the emonPi comes with Wi-Fi, you can use either Wi-Fi or Ethernet).

Thanks Robert.

Ok, I’ll buy the solar bundle without temperature sensor, and the MK2 PV Router for the PV Diversion.

My PV inverter connects near the main meter (4 meters). I understand that is possible to extend the c.t. cable without losing signal.

These are the main questions. I have some doubts, less important:

  1. Will be possible to connect the Mk2 router with the EmonPi, so that the emonPi log the Mk2 data? I will use this data on the Open-Hab server.
  2. I readed the MK2 can control more than one load. Will be possible to control a heat pump (on /off only) and the boiler, assigning differentiate logic to each one?
  3. I really will find useful to have an LCD screen with the energy data, inside my house, separated from the EmonPi. I found the EmonGLCD possibility, but I don’t find it in the shop. Where can I buy it?

Thanks a lot

Yes, that is correct. 4 m should be OK - the instructions are here: Learn→Electricity Monitoring→CT Sensors→Extending CT Sensor Cable→Extending the Current Transformer Cable

It should be possible - @calypso_rae will confirm that. A small change to the software might be necessary. [Robin: Boiler = immersion heater]

It might be worth emailing The Shop to confirm, but I think unfortunately, and sadly, the emonGLCD kit of parts is no longer available. The recommended solution is to use a discarded smartphone or tablet to display the data.
But if you have the skills, the information to manufacture and assemble an emonGLCD is available in “Resources”.

Thanks for all the information.

I think I have all the information I need, for now.