It looks like the heat meter not correctly measuring the flow. There can be a number of things which can cause this:
- Low system pressure, try increasing to 2 bar
- Air in the system
- Sub optimal heat meter installation location
The heat meter should be installed on a straight pipe run away from sources or turbulence caused by valves, pipe fittings and pumps. It should also be installed so that liquid flows horizontally through the meter or upwards through the meter, not downwards. Could you share a photo of the installation location?
Here’s the emonHP installation guide which include manufactures instructions regarding the heat meter installation.