No, you can’t determine from the emonTx which RPi receives it - it’s just like a broadcast radio, once the message is broadcast, it’s out there for anyone to receive it.
Does RPi 120 see either or both the emonTx’s? If it doesn’t, it’s a radio problem - the signal isn’t being received.
Are all four (emonTx’s and RPi’s) all working on the standard frequency and Group No? (If you haven’t changed anything, they will be.)
The RPi 120 is not seeing either emontx. I’ve swapped the RFM69Pi between the two RPi. The 179 RPi still sees both emontx but 120 RPi still sees no input. The red light is on constantly on the RPi and the red light flashes on the RFM69P1 on both. I haven’t changed anything to do with frequency or group number.
This would seem to indicate that the RFM69Pi is receiving, so it sounds like a problem with the Pi itself. I’m not a Pi expert, so I’m hesitant to give any advice. Are both Pi’s new and running the same image? Is it possible to swap SD cards and see if the problem follow the card or stays with the Pi?
Ive swapped the SD card and the problem has followed the card. Both cards were bought at the same time pre loaded. I have 1 x RPi 3B and 1 x RPi 3B+ neither has been used for anything else.
I don’t know the difference between a 3B and a 3B+, nor importantly, whether it’s significant. There was a problem with a speed setting, I think it applied only to a Pi 2, and I thought that had been fixed - are the cards recently bought?
I’d suggest, if you have a computer with a card reader/writer, you could download a new image and write it to the ‘faulty’ card (using Balena Etcher is the easiest and safest - Using Etcher tool to flash emonSD image to SD card, or there’s this Alternative to Etcher to write images: USBImager).
If you don’t want to try that (or if it fails) then it could be a faulty card - email the shop with your order number and refer to this thread: [email protected]
Thanks for your help I will give it a try, big learning curve for me 
Can the RPi be programmed to switch a relay hat when the load exceeds 100A on a 230VAC supply. I’m looking at the situation where I need to do load shedding via a contactor but not sure if this is done through Emoncms programming or some other programming method and not being a programmer I’m a bit lost. There are priority devices that I can buy off the shelf but as I’m already looking at fitting the emontx to monitor the site energy I thought why not try and use that via the RPi.
There is this: WiFi MQTT Relay / Thermostat - Shop | OpenEnergyMonitor
I presume there’s something in the Resources/Wiki/Guide about setting it up, but as that’s not my area, I haven’t looked. Somebody else will need to help there - or with using the Pi Hat directly.
I’d suggest something like Home Assistant or Node-Red is a better solution in some, domestic, situations. EmonCMS can publish the data (current load for instance) on which a decision could be based. It partly depends on how quickly you need it to happen and the safety critical nature of the load shedding.
Hi Brian
Sorry is Home Assistant or Node-Red some sort of programming. This is actually for a pub/restaurant that has ordered external parasols with 9kW of electric heating so I need to limit maximum demand as the place only has a single phase 100A supply. Switching speed isn’t critical as short term overload can be accommodated but if over 5 -10 mins I could start to reduce some of the load by operating contactors.
Thanks for your input.
TBH, I don’t think that is a very clever setup for a public facing organisation so I’m not prepared to offer any advice - sorry.
I’m sorry Brian you are quite correct I should not be asking such basic questions for a commercial implementation, I shall use off the shelf load curtailment until I have a better understanding of setting up something by my own means. I apologise if I have caused you any distress.
No not at all.
Good plan 