OpenEnergyMonitor Community

Confused Newbie

Hi All,
i admit i have done quite a lot of reading of forums and resources at this site and its left me fairly confused, all i really want is a list of items i am going to need to monitor my household electric and solar PV.

Apologies if this has been asked before, i have read a lot of newbie questions but with information overload i am struggling a bit.

What i want to monitor:
Household electricity (Incoming and outgoing)
Solar PV
(Later in the year i will be adding a battery system but ignore that for now)

The Solar is in the garage, i have 2 strings as i have one solar array on the roof of the main house and one on the garage, both plugged into a single inverter that can handle both strings. The battery will also be fitted into the garage in March.

I do have adequate WIFI available in the garage even when the up and over metal door is closed as i have reliable data from the inverter coming in over wifi.

I do have a spare PI3 kicking around including a case and power, so i dont want to buy another, but other than that i have nothing, though assume i can download images and get the PI3 working.

I assume i am going to need the following hardware:
Inside the consumer unit (Kitchen) mount the PI which will need me to purchase and fit an “RFM69Pi” in order to receive data.

As the Pi and its receiver cannot actually monitor anything directly i am also going to need to add an “emonTx V3” to the equipment to be purchased list.

As far as i can make out that leaves clamps, how many clamps am i going to need to measure electricity in and out of the property and solar produced, sounds like three to me but i am not certain.
and an AC-AC Power Supply Adapter - AC voltage sensor (UK Plug) to power the emonTx

So Bill of materials:
emonTx V3
100A max clip-on current sensor CT * 3?

anything obvious i am missing?
am i going to need one emonTX in the house for the grid electric and another in the garage for the Solar? The solar does have a small consumer unit next tot the house consumer unit.

Hi @Sprinter

What make/model is the solar inverter?

If its one of the supported types, it may be easier to “talk” to that over serial cable or bluetooth rather than trying to read its power output via emonTX.

You will need an emonTX unit to monitor the voltage + current (power) near to the fuse board/consumer unit - this sends its readings wirelessly to the RFM69PI.

Somewhere else in the building, you use your Raspberry Pi and the SDCard image from this site to run the emonCMS system and plug in the RFM69PI device to the PI.

Note you may need a second emonTX (or to re-position the first one) if your solar inverter is wired directly to the electric meter via a split feed (sometimes called a henley block).

The inverter is a Growatt 3600 mtl

Okay, thats not supported at the moment, but does have a serial output.

I’ve updated me comments above about the positioning and wiring of the emonTX.

Can you describe where the wires run in your house? To from the solar inverter for instance?

If you have good wifi coverage in the garage and can get away with using one emonTx (depending on where the meter is and the cabling between the meter, the inverter and the consumer unit in the kitchen) you could forget using the rfm69pi and connect the emonTx to the emonBase (Pi) via serial, this would remove any chance of “dropped rfm packets”, make the FW in the emonTx accessible for update without a programmer and potentially improve the accuracy slightly as the AC:AC would no longer need to power the emonTx (resulting in a better Vac waveform) as it would source it’s power from the Pi.

This would be cheaper, more reliable, more accurate and easier to maintain/update.

At some point in the future there may also be a FW revision available to make the then redundant RFM components in the emonTx work as a base station so you can add further devices eg an emonTH etc (see 4 CT emonBase using emonTx and Pi Zero W) effectively making your P13 and the new emonTx a 4ct emonPi (even if you are only using 2ct’s)

ok i will try to describe the system.

The consumer units pictured above are in the house, on the right hand side in red i have a cable coming into the cupboard from the inverter carrying the DC current to a trip switch with what looks like a fuse and an idolater, this cable running from the inverter in the garage comes in through the ceiling above the cupboard so does actually give me easy access to that for CT clamps etc if necessary.

On the left in Yellow i have the meter for the house

In this Pic from the garage you can see the inverter and the 2 strings from the Panel ST1 (Main house) & ST 2 (Garage)

To be honest i think it might be beneficial for me to break this down into three seperate projects:
1, monitor the house electricity
2, add solar monitoring at a later date
3, add battery monitoring after that.

I think you mean AC not DC current if it’s between the inverter and the meter/grid.

It looks like everything could be done in the kitchen, no need to go to the inverter as long as the cable between the house and the inverter isn’t used for any other services.

One emonTx with 2 CT’s would monitor the PV and the grid/use, both export and import.

Yes, sorry i did mean AC.

I can always look into adding another PI int the garage and serial connecting it at some point in the future.

But i am happy, and will start ordering the basic kit, many thanks for all of the assistance.

Wellas an update,
The kit arrived and i had a play with it, i like poking aroung on the RPI so i connected it all up and had a play.

There was a few things i struggled with, couldnt expand the SD card being the main one and i have not yet setup remote logging.

In the name of “playing” i will probably wipe the system a couple more times before i have finished playing with it.

I will get another sensor ordered for the solar and try to add that next.

Are you using the emonSDexpand function or trying to use Raspbian’s raspi-config utility? Raspi-config won’t work as there are 3 partititions and the OS is read-only.

I was using the pi method, but i was not waiting long enough, the RPI looked like it did the upgrade then shut down, at that point i made a schoolboy error and rebooted it (before the expansion had completed) thinking it was done.

After re-reading it this morning i kicked it off and just ignored it for half an hour, SD card now properly expanded.

Now to get another clamp so that i can start looking at capturing solar data as well.

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