New setup with Emonpi and 2 EmonTX

Hi All,

We have moved our consumer unit and is more practical to now purchase an emonpi.

Firstly, I’m not a programmer, I struggle to understand many of the terms or how to program a RPi. With that in mind, this is the setup I was thinking of. I would be grateful for any feedback, positive as well as negative or alternate ideas.

Emonpi as the hub(?) no CTs
EmonTX with 3 CT clamps (solar, grid & spare for battery bank later on).
EmonTX in our loft with 3 CTs for individual solar inverters (sounds odd I know but we have three. - this is to monitor each one individually.

The first EmonTX would be next to the Emonpi, my thinking is that I can have three CT clamps on one device?

Welcome to the OEM forum, Tristen.

If you buy an emonPi, you’re also buying two power channels. Are you ever going to use them? If there’s a possibility that you will, fair enough. If not, the emonBase is more economical, but it doesn’t come in the nice aluminium case. You use the same SD card as the emonPi, so not much do do there.

(Unfortunately, there just isn’t room on the emonPi’s box for a third c.t.)

Other than that, the two emonTx’s sounds entirely reasonable. You’re in the UK, so a single phase supply, so again nothing much needs doing with the emonTx’s. One will need an internal switch moving to give it a different identity (NodeID) so that you can tell them apart (and the shop might do that if you ask), other than that, it’s plug them in and it should all work. You’ll probably need to learn a bit about emonCMS so that you can display what you need how you like it, but that’s something you’ll pick up as you go along.

Thank you!
You already answered another question about the nodeID. If I did decide to get the Emonpi, would all three need different IDs?

CT Sensors, I’m not sure how long the leads are, but are they ok to extend?
Was a bit gutted that the Emonpi couldn’t take a third one, but you can’t have everything.

Is it worth having temp sensors?
The AC-AC sensor, where ideally should this be? On the Emonpi next to the Consumer units or in one of the socket circuits?

I’ve just read another post about the differences between the emonPi and emonBase. So now I understand you suggestion @Robert.Wall Thank you.

One question about connectivity between this, our house is quite large and WiFi is horrendous (to be addressed in one of the next projects). I’m also the worst fan of WiFi, so can the Base and Tx’s just be connected via my unmanaged network switch’s (LAN)?

So the emonTX and emonPi/ emonBase communicate via 433 MHz communication. This may be an issue between consumer unit and loft.

What I do suggest is if one TX is in the consumer unit and the other in the loft, put the emonPi/emonBase halfway between the 2. That can be hardwired to the Network and will possibly solve a number of problems.

@borpin Thank You. I have a switch in the loft, so I can probably experiment with placement.

Indeed they do, but the default for the emoni/emonBase is 5, for the emonTx’s the default is 15, with 16 available for the second one.

They are about 1 m, there’s an article in ‘Learn’ showing the best way to extend them.

Do you want to measure the temperature? I don’t know!

You need two, one for each emonTx (ideally). With the a.c. adapter, the emonTx can calculate real power (which is what your tariff meter reads). Without it, it has to guess the voltage, which inevitably leads to one approximation, and it can only give you apparent power anyway, which is a second approximation. That might not be too bad for the inverters, but the house power is likely to have a significant error. Besides all that, you need either a 5 V d.c. supply OR the a.c. adapter for the emonTx’s, so there’s no significant saving - but see below.
The voltage around your house should not vary too much except when you have a heavily loaded long circuit. The emonPi (if you have one) won’t need an a.c. adapter until you add c.t’s (for the same reasons) but it will in any case need a 5 V d.c. USB power supply.
(So at your consumer unit, you’ll need two sockets, possibly three, and one, possibly two, by the inverters.)

The 433 MHz ISM Band radio is a significantly lower frequency than Wi-Fi. So it should penetrate the house somewhat better. (Is it brick or stone?) The emonBase/emonPi has both Wi-Fi and Ethernet. If the emonTx is right next to the emonBase/emonPi, it might have a problem because the signal is too strong. The one in the loft can have the power turned up (you’ll need to add a programmer, and be able to take a laptop to it to do that), but unless you’ve not got wooden floors, the signal is less likely to be hampered coming down than it would be going around on the same floor.

If you’re adding more than a couple of temperature sensors, or you turn the transmitter power up, you’re likely to need a 5 V d.c supply to the emonTx as well as the a.c. adapter.