If I order your level-3 heatpump monitoring kit (Level 3 Heat Pump Monitoring Bundle (emonHP) - Shop | OpenEnergyMonitor) is there any reason why I need to use a modbus electric meter, rather than just a CT sensor?
It’s not entirely clear from that OEM Shop page whether the EmonPi it includes is just the standard one including the 6 CT inputs, or whether is is somehow different and specifically for heat pumps?
Ultimately, accuracy and perhaps more importantly, traceability.
Yes, but in a very minor way. If memory serves (and I can look this up later today and confirm, unless @Gwil can?), it has the ‘current-only’ sketch loaded, that’s used only for detecting a ‘running’ status. Of course, everything in the Ri is the same.
Yes, there is an important difference - the Level 3 kit does not support CT sensors; it is a different board to the emonPi2.
As for why CT sensors are not included - perhaps the primary reason is that CT sensors are not MID certified and the accuracy of the data is very important when comparing systems. There are other issues too regarding improper installation and cost.
That is as standard though, you can definitely go down the CT sensing route - we can put a quote together if you want to pop an email to us at [email protected].
What does “MID Certified” mean exactly? Why is it important?
I don’t have a heat pump yet but am looking into getting one. Having used OEM for a number of years with an original EmonTx and EMonGLCD, and later one of the original EmonPi models, I am thinking of updating this to current hardware. Power readings from my three existing CTs match pretty well with the figures from my PV and battery storage inverters – so they are ‘good enough’ for my purposes I believe.
I don’t really want to pay the necessary extra expense to install a DIN-rail inside another CU box for the modbus meter if a simple CT will do the trick well enough – there is not space in my CU for the modbus meter but there would be space for a new RCBO or MCB to feed the heat pump.
So – what extra does using a ‘proper’ electric meter really add beside better accuracy? I would only be monitoring this for my own edification, so it does not need to be spot-on, just good enough to give a reasonable picture of what’s going on and a reasonably trustworthy COP figure when combined with the data from a heat meter on the flow/return pipes.
Thanks.
MID is a standard - What is an MID energy meter, and how does it differ from other energy meters?- Eastron Electronic Co., Ltd..
The Level 3 bundle you see in the shop is geared towards heatpumpmonitor.org. They are kits typically bought by or for installers. So the focus is being able to compare systems and for the data to be as accurate as we can make it. If you are in the UK getting RHI payments, you would be using similar MID meters.
It is definitely not the only way to monitor a heat pump, you can certainly use CT’s: Heat Pump Monitoring — OpenEnergyMonitor 0.0.1 documentation.
When my HP was installed, they fitted a new CU. I think this is normal. They were going to install a energy meter anyway and agreed to fit a modbus unit. Minimum extra cost for the better accuracy. I use it with a usb adapter on my emonpi v1.
I’m happy…
Thanks for the replies everyone - very useful info. My inclination is to just use a CT for electric power, and calibrate (using the emonCMS feed scale factor) to match that reported by the HP itself as closely as practicable.
I’m not sure I’d be looking to the HP as a reliable source of energy consumption info. For example, the Daikin I have just takes “configured Immersion power” x “hours switched on” e.g. 3000 x 1 => 3kWh, when in fact it isn’t actually working, and adds that into its control panel display values. Duh. Of course, other HPs are different, but if you aren’t going to go MID in-circuit, then you can get ±1% with a CT. Generally, it’s the comparison of before/after config changes you’re looking to compare, unless you want to get into the SPF/CoP comparison wars on heatpumpmonitor.org, in which case you need MID!