Hi
I’m new to this forum and am a bit confused as to how to proceed with this project.
I wish to monitor all the feeds in the electrical distribution system in my house. I’m UK based.
I have a single phase 230v AC mains supply incoming through a meter into a 4 way consumer unit, DB1.
That consumer unit then feeds an 8 way distribution board, DB2, 15m away, and a 4 way distribution board, DB3, 20m away. The consumer unit also feeds 2 circuits - a ring main circuit and a shed.
Distribution unit DB2 feeds 8 circuits - 2x lights, immersion heater, 2x showers, 2x ring mains and a kitchen hob.
Distribution unit DB3 feeds 4 circuits - EV charger, kiln, lights and a ring main.
DB1 and DB2 are within Wifi coverage but DB3 is not.
I have a diagram showing the set up but as a new user, I’m not sure how to attach it.
I’d like to monitor each of the 14 circuits individually if possible but I’m stuck on how to go about this using the Open Energy Monitor modules.
Any help would be very much appreciated.
Thanks
Dave
Welcome, Dave, to the OEM forum.
The easiest is drag and drop it into the post. If you couldn’t do that, you can now - I’ve promoted you by 1 level. Note we always prefer you attach things here rather than on 3rd party sites, if they live elsewhere, they’re prone to disappearing and then your post and much that follows becomes worthless.
It looks as if you’re going to need an emonPi at the centre of the system, and three emonTx’s monitoring the outlying CUs.
- DB1 (Main CU): emonPi: Ring Main & Shed.
- DB2: EmonTx 1: shower 1, shower 2, Immersion Heater, lights 1.
- DB2: EmonTx 2: ring main 1, ring main 2, hob, lights 2.
- DB3: EmonTx 3: EV charger, ring main, kiln, lights.
The point about putting the low-power circuits 4th is you won’t need to change the sensitivity of the emonTx’s 4th input.
By design, the emonTx sends its data to the emonPi by ISM band radio, not WiFi, so the primary consideration is, are DB2 and DB3 within range? and to answer that, what is the straight-line distance and what lies along that line - in terms of walls (thickness & material) and other obstacles?
Failing that, another method of getting the data back is required. For DB2, that would presumably mean equipping the emonTx’s with the ESP8266 WiFi adapter.
For DB3, is there a cable route back to your router, where you could lay in some CAT5 to take your LAN to DB3? Then, if you want WiFi coverage there, you can have a mini wireless access point with a serial input, otherwise, a serial to Ethernet adapter would do what’s needed.
Is it practical to monitor individual circuits from the distribution panel? I’m guessing if you can open up the panel and hook small CTs onto the individual cores in the outgoing cables then it should be possible, but “possible” and “practical” are not always the same thing 
I’d certainly love to be able to do that here if I could.
James
It’s not necessary to use split-core c.t’s on outgoing circuits, where it’s practical to disconnect to install the c.t., and of course you can use lower-rated (than 100 A) almost everywhere. RS components carry a useful range of smaller c.t’s, rated at 25 A / 40 A / 50 A: https://uk.rs-online.com/web/p/current-transformers/7754909 or /7754903 or /7754912 The secondary current of 50 mA means that only a calibration change in the sketch is required (except possibly for CT4 - an additional burden resistor might be needed). I have not had the opportunity to measure one, however.
The recommended RS-Pro alternatives for the 25 A & 50 A models also look to be suitable.
[Edit - January 2024]
The above range of c.t’s from RS components are only usable directly with the emonTx V2 & V3 and the original emonPi. You must either supply a burden resistor or use a c.t. with a 0.333 V output at rated current with the emonTx4 and emonPi2.
However, the comment about it not being necessary to have a split-core c.t. where it’s practical (and legal) to disconnect the circuit to install the c.t. remains valid, and a ring-core c.t. of the same rating will be both more compact and cheaper.
Now that could be rather handy. I will have to look into that and perhaps try it on one of our shed/workshop panels first.
Thanks for that,
James
Have a look at the Shelly, DIN rail kit. Probably needs a major rewiring, but if I ever manage to build another house this would be part of the spec (as would radial installation).
You can also get Wago type Busbars to make it easier still.
You can quite easily feed that data to emoncms.
Very tidy CT’s indeed, thanks for the link