This a Hard one. Check if your system pressure is between 1-1.5bar when boiler is not operating and heating system is cold. When boiler is operating you flow temperature shouldn’t be jumping up and down. Instead, should be slowly increasing at a steady pace. Your radiators should be evenly hot, bottom should be slightly cooler than the top. In reality, you can’t unless you are a heating expert. However, give us a call and we can schedule an appointment for your appliance/system health check.