Emonpi/EmonTX Queries Before Purchase

Good afternoon,
I am looking to get an EmonPi set-up for home electrical monitoring. The property is single phase (UK) but has a newer E7 meter.

There is no easy way to get a power supply out to the meter so I was thinking of using the EmonTx on battery power for monitoring within the meter cabinet (which will allow one CT and the pulse sensor). While I appreciate that it recommends the EmonTx is plugged in for VRMS monitoring can this be done by the EmonPi that the EmonTx is passing data along to?

I’ll likely be using OpenHAB and a z-stick to monitor specific circuits/sockets (e.g. my home office) until I can get a new distribution board set-up the way I would like, unfortunately reliant on a previous owner’s idea of “good” wiring (e.g. extension/office/workshop lights run off the upstairs lighting circuit)

Yes and no. You can have the voltage monitored by the emonPi, but you’ll only get apparent power by multiplying Irms × Vrms. If you give the emonTx - or the emonPi - both current and voltage feeds, then both can measure real power.

Is your consumer unit by the meter, or can you get to the meter tails at the consumer unit end?

Robert, thank you for the response.
Unfortunately the meter is outside and the consumer unit is in the living room at ceiling level. 1980s UK installation at its best!

The ceiling level consumer unit means that the meter tails are very hard to get to without removing either the whole consumer unit housing or sections of the ceiling/coving hence why I hoped this would be a neater solution if EmonPi could effectively work with both sets of results. So much for hoping for a neat/discreet installation.

Nearest plug socket to the consumer unit is around 3 metres as well thanks to the layout of the ring main. If there was a reliable way of extending the CT cable I could potentially come in via the BT duct but that would require extending the CT to around 3-4 metres. However that means an EmonTx or EmonPi could sit right next to the power supply. Not sure how much loss/interference would be introduced to the CT signal this way but it would avoid running an extended CT alongside the meter tails into the property.

I’ve extended my CT cable to about 5m without any problems - think others have pushed 10m +

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Extending by 3 - 4 metres should not be a problem. I’d be very careful with screening and earthing if it was 30 - 40 m.

Thank you both of you, if 3-4m extension isn’t a problem (I’ve now had a read of the knowledge base article and just need to think about earthing) then this becomes a lot more feasible off just the EmonPi set-up without involving an EmonTx.

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Gentlemen, thank you again both of you for your advice. I ordered last week and extended the CT using Cat 6 following the guide. This is all up and working and kW load is changing appropriately to the devices being turned on and off.

Next step is configuration and setting up OpenHAB/z-wave devices to monitor individual areas (including my office).

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