As the title suggests, I’ve had the level 3 heat pump monitor kit installed recently, now I’m getting into the OEM world a little bit more.
What additional kit do I need to augment the emonpi2 to get some monitoring of power? Do I replace the raspi power supply with the EmonVS-PSU to enable CT sensor capability?
Appreciate this is incredibly basic… Thanks I’m advance!
Welcome, James, to the OEM forum.
What power(s) do you want to measure? Obviously, not the heat pump itself because you already have this with the in-line meters. Where is your heat pump monitor physically in relation to what the other powers you want to know about are and where you can get c.t’s on the cables to measure their currents?
Strictly speaking - it doesn’t do that! I suggest a bit of background reading of the ‘Learn’ part of Docs for the fundamentals of electricity and especially power measurement, but in brief you need to know both voltage and current and the exact relationship between the waves to be able to calculate ‘real’ power (the quantity you pay for). Your emonPi can measure the current - just plug a c.t. in - but it can’t do anything with it until you feed it an accurate sample of the mains voltage, this is what the emonVs does (in addition to providing operating power for the emonPi). Note you can’t measure current in one emonPi and the voltage in another - both current and voltage need to get into the same emonPi or emonTx by a direct physical cable connection to be able to calculate real power.
If the place you can measure the powers is your consumer unit, and it’s not close to the heat pump monitor emonPi, then it might be easier and more acceptable (to ‘the management’ ? ) to have a second emonPi + emonVs dedicated to the purely electrical side. You’d send readings from one emonCMS to the other so that you correlate the data and present it all in one place.
One current transformer (abbreviated to ‘c.t.’ - they aren’t “clamps”) for each cable where you want to measure the power. Presumably one for the incoming mains (100 A) and then I’d be guessing - PV (20 A)? EV charger? Ring Main(s) (50 A)? and the emonVs. You could add emonTHs for the temperatures in various rooms, if you wish. And a handful of cables and at least one dedicated mains socket outlet!
What you can’t do is automatically distinguish individual appliances from a measurement of the whole-house power. It’s the Holy Grail of energy monitoring, many talented researchers have tried, nobody has yet succeeded in making a reliable and accurate system.
Do come back with any more questions.
Thanks, that makes sense!
I am basically trying to replicate a “local” equivalent to my octopus home mini, now that I’m switching to OVO heatpump plus.
Simple needs really, just need a CT for picking up the rest of the house’s demand. Sadly can’t have solar on the roof where we live, as our south facing roof pitch is street visible from the street… And no EV yet…
And how practical is it to install what where - thinking about future expansion etc? That’s probably the primary worry.
Should be pretty straightforward, all the heat pump equipment and house distribution board are in the same cupboard 
In that case, it looks like an emonVs and a single c.t. is all you need. I’ve never had a Heat Pump Monitor emonPi2 in my hands, so I don’t know what software is in the ‘emonTx’ front end, but as it’s a common PCB, I assume it’s the standard 6-channel sketch. As far as I know, it’s only the pulses from a heat meter that go through the front end, so it should be able to do its electrical energy stuff with ease, but it might be wise to check with The Shop before you part with cash.
Trystan says the default software in the Heat Pump Monitor emonPi2 is the emonLibCM version, which gives a current/apparent power estimate only, as it’s used to detect (and not measure accurately) the current.
Therefore, you’ll need to update to the emonLibDB version to get accurate real power measurements using both c.t. and the emonVs.
Good to know, thanks!