I need to do something that really isn't all that technically complicated, but a little opaque to someone outside the biz.

I have 41 flats (owners and tenants). I need a device on each unit, at either the meter or on individual DBs, that will feed usage data. I then need to be able to apply simple logic to those feeds (if we're on battery power; is current draw greater than x; has total draw exceeded y since going on battery) and then be able to

a) send an alert. preferably text but other options possible
b) cut off an individual flat if need be

We have already integrated sonoff smart switches to shut off geysers etc. automatically when we're on battery power. So I know it's possible to have a system that takes inputs, applies logic, and sends outputs.

Bonus points if:

a) it allows remote meter reading
b) it costs <R2.5k monthly e.g. for the management platform. We can pay upfront for the hardware and setup.
c) it has an interface that will allow us to adjust parameters and logic

Please don't say "don't do a central system". We've cracked the finances, it's a good plan and doesn't depend entirely on solving this problem. But this would smooth the way significantly.

Thanks

Hi @jharber

Is totally doable and all with open source software so no costs apart from your time setting it up and paying school fees 🙂 

What is the maximum current draw per flat? 

What inverters are you using and would you be able to integrate into Home Assistant, would be useful to have total power consumption and what the grid frequency is so you can detect load shedding. 

If you need more than 20A per flat (am guessing that you would) and seeing as you have already got Sonoff switches, I would suggest that you use the 63A Sonoff compatible DIN rail switches  https://e-glow.co.za/products/wifi-smart-controller-63a-kwh-timer which will handle up to 63A although any of the smart switches with energy monitoring would be suitable. 

What I would then do is pair all the switches up to your primary Ewelink account, then create a secondary account for Home Assistant to use (or you could do it directly in Node Red if you preferred) and share all the switches with that account. Unfortunately only one device can access the API per account but you can get around this by just sharing the devices over multiple accounts. 

Install Home Assistant onto a Raspberry Pi/INtel NUc/Desktop computer and install the integration for Ewelink/Sonoff.

You would then be able to monitor the power draw through each circuit and switch them off individually either from your phone or from the Home Assistant  console. 

I think that you could create a Scene on the Ewelink which would allow you to manually set a limit on each of the switches and then implement it across all the switches with one button push

Once you have the Sonoff's installed/setup there are various ways you can add some intelligence to the setup. 

Simplest would probably be to use the Home Assistant integrations (which were recently upgraded.) These would allow for the automatic disconnection of the units when they exceed the permitted load during load shedding. 

I would also suggest put a smart globe into each of the units that switches on when there is load shedding so people know to conserve energy and that they will be cutoff if they exceed the permitted load.

 Software is all free so there would be no monthly cost for the software

I have a similar system set up at my house that monitors all loads in the house.

 

 

 

Sonoff have released some new switches themselves but they have a maximum current of 20A 

https://sonoff.tech/product/spm-main-spm-4relay/ 

If you have wifi in the apartments and 20a is sufficient, you could install the new Sonoff Power Elite Switches into each apartments DB Board, advantage would be that they would know exactly how much power they are drawing at that specific time as it has a display on it. 

https://sonoff.tech/product/diy-smart-switch/pow-elite/ 

Both Tuya and Sonoff have DIN-rail Mountable Smart "breakers" that will connect to their respective Apps,since you already apply logic via ewelink you should be familiar with the interface and process as it operates the same,it also allows for remote metering

Often these are flashable to communicate locally too instead of Cloud-based

Example:

1 minute ago, PsyWulf said:

Both Tuya and Sonoff have DIN-rail Mountable Smart "breakers" that will connect to their respective Apps,since you already apply logic via ewelink you should be familiar with the interface and process as it operates the same,it also allows for remote metering

Just be careful with tuya powered devices unless you are happy sharing your data with big corporate industries.

7 minutes ago, WannabeSolarSparky said:

Just be careful with tuya powered devices unless you are happy sharing your data with big corporate industries.

Given our phones and televisions are pretty much permanently spying as evidences by Youtube and Facebook ads suddenly targeting any subject spoken about the previous day,some Chinese company knowing my electricity use isn't particularly concerning🤣

(Do use LocalTuya to make them LAN-only if it's a big concern)

Edited September 28, 20223 yr by PsyWulf

Another alternative which may be worth investigating, especially if you want to have switches installed in each of the apartments  would be the use of a Zigbee network for the comms with the switches instead of wifi. You will need to install a Zigbee bridge to enable the devices to connect to the internet but functionality will be pretty much the same.   

Zigbee has the advantages that the signal travels much further than wifi and uses less poweron the devices so it is possible to have battery powered devices. It does have much lower bandwidth but this is generally not an issue with IOT devices.

https://en.wikipedia.org/wiki/Zigbee 

You do get them, just haven't seen any locally yet. 

These ones are on the Tuya platform, functionality ios very similar to the Sonoff/Ewelink devices, just uses a different app and integration into Home Assistant. 

https://www.aliexpress.com/item/1005004747066832.html 

 

 

 

This is brilliant information. Thank you! Am I right that this, at 100A, would also be compatible through eWelink: https://www.robofactory.co.za/smart-switches/371-100a-1p-smart-circuit-breaker-with-monitoring-ewelink.html

 

2 hours ago, jharber said:

This is brilliant information. Thank you! Am I right that this, at 100A, would also be compatible through eWelink: https://www.robofactory.co.za/smart-switches/371-100a-1p-smart-circuit-breaker-with-monitoring-ewelink.html

 

Yes, would be compatible.  

I woudln't size the switch larger than the size of the breakers supplying power to each apartment thogh

100A switches sound like they would be a bit of an overkill . 

Look again, it shows "C63".
That is a 63Amp breaker.
Below it show 10000A, so 10kA short circuit rating.