Configuration suggestions please


I’ve just got a solar PV system installed and want to monitor it. Most off the shelf systems I’ve looked at won’t work for me as my solar is on my detached garage, I’ve just found this site and am a bit overwhelmed with the number of options!

I don’t think getting a wifi/powerline hub to extend my broadband to the garage will be a problem but I think the distance (about 25m between the domestic grid meter and the PV meter) is probably too great for a direct wireless connection.

What I’ve got is 2 separate solar arrays, one facing east (5.1kW), the other facing west (4.2kW), each via its own inverter with a single export meter. So I can monitor this via an LED sensor on the meter and/or CT sensors on the inverter outputs. It would be nice, but not essential, to see the relative performance of the individual arrays.

Then in the house I can access the incoming supply in the meter box which is on the outside wall with the main consumer unit on the adjacent inside wall. Next to this I also have a separate sub-consumer unit for my EV charger which it would be nice, but again non-essential, to monitor.

Advice please on what hardware I need.

Apart from 25 m of air, what else is there in the way - e.g. walls, how many and what construction, parked vehicles?

Beware, you’ll get different numbers if you use both! Not a real problem, but it’ll require very careful calibration to get agreement.

If you can give a satisfactory answer to the radio path question, it sounds as if an emonTx in the garage, using two c.t’s (of the 4), and the pulse input; with an emonPi in the house using two c.t’s (one on the main incomer for ‘Grid’ power, and one for the E.V.) is what you need. You’ll also need two a.c. adapters and one 5 V USB adapter and lead, and a temporary wired Ethernet connection just to set up your emonPi. If calibration is really critical to you, a programmer will be necessary.

If we think the radio won’t work (or you find it doesn’t), then you’re going to need another 5 V d.c. adapter for your emonTx, which will need an ESP 8266 Wi-fi module adding to it (not in the shop, but we know how to do it) - plus of course the Ethernet cable /Powerline. (I’m wary of Powerline - a friend had his blown up by spikes from a neighbour’s milking machine - this was rural Scotland.)

Hi Robert, many thanks for the reply,

There’s an up and over garage door, then 25m of air/driveway often with a car parked there, then the house consumer unit is is halfway along the side of the house behind a cavity wall/the back door.

[quote=“Robert.Wall, post:2, topic:4328”]
Beware, you’ll get different numbers if you use both! Not a real problem, but it’ll require very careful calibration to get agreement. [/quote]
Yes, aware I’ll get different readings. Absolute accuracy doesn’t matter, as I said, it would be nice to see the relative contribution of each array and it just seems a waste not to monitor the output of the generation meter.

Excellent, thank you. Probably worth me trying the emonTx and see how that goes - if it works it saves the hassle of sorting out the broadband in the garage.

I guess the benefit of using a CT on the grid connection versus the meter pulse sensor is that it will measure export as well?

That’s bad news if it’s metal. It would be worth trying to find a place inside the garage for the emonTx that has a clearer view towards the house. Also not good is the slant path through the cavity wall. (I get the impression that the garage is set well back from the road, with the house in between, with the back door at the side, opening onto the driveway.)
Both ends might be improved with an external aerial fed by a cable through the wall, but it’s well worth trying first, and be prepared to move things about a bit because at 433 MHz, a few inches can make a lot of difference.

And the c.t’s on the inverters will measure the overnight ‘keep alive’ power too!

OK, well my kit arrived today and seems to be working fine via the RF. It’s reporting a rssi of -67 with the garage doors closed and a car on the drive. No idea where that sits in the range of what’s acceptable but it seems happy enough. Both units are just temporarily propped up at the moment, I haven’t tried any kind of position/orientation adjustments to see if that improves things.

Now to suss out getting the feeds right and getting some data I understand :slight_smile:

That sounds entirely reasonable, I think you’ll be OK there. It would be worth noting what it goes down to if the wall get a good soaking.