OpenEnergyMonitor Community

Heat Pump Monitoring planning - long mbus cable or another Pi?

Hi all,

Here’s what openenergymonitor kit I already have in place:

  • Smart meter main location: emonPi and emonTX (monitoring CT grid, solar, batteries, EV and some DS18B20 probes)
  • Hot Water cylinder location: emonTX (monitoring CT immersion / Eddi PV diversion) and some DS18B20 probes

The distance between the two locations is about 15m.
To future proof I’ve already laid some spare cat6 ethernet between the two locations.

If/when we go ASHP the heat meter and heat pump install gubbins would go next to the hot water cylinder in that second location.
As i’ve only got a emonTX in there i’d need another solution to get the heat meter MBUS connection working.

I’d use the breakout board attached to emonTX to add more temp probes where required.


  1. USB to MBUS converter plugged into my emonPi (at the other location) and connected to the heat meter via 2 wires of the spare cat 6 I’ve got. The emonPi setup is over 3 years old now, likely a Pi2 or 3? Still be okay?

  2. Or am I better off using an old Pi 2/3 and connecting the heatpump hat MBUS directly to the heat meter in the water cylinder location?

There doesn’t seem much in it cost wise if I can lay my hands on an old Pi.
Will one be more reliable than the other? One easy to config / maintain?

This probably isn’t going to happen until we know what is happening with the £5k boiler scrappage government grant, but i’m keen to make sure i’ve got everything in place if that all falls in to place.

Cheers, Mick

Personally, I would get a second device and avoid running long cables. 15m a quite a way, though might be okay. But… if it is not, then you will find it harder to understand what is going wrong.

In my experience, it is best to has a single device to do a single job. It makes upgrades/changes/configuration easier.


Yeah, now maybe thinking a separate Pi with the heatpump HAT might be the safest option.