I have recently had a new Worcester Bosch Greenstar 29Cdi boiler installed in my medium sized detached house that has 10 small to medium modern sized radiators throughout. there is one bathroom in the house. All the rads are balanced correctly and there is no air in the system .The house is fully insulated and the CH system had a full flush before the install and a magnaclean is also attached to the system. I have a Drayton mistat digital thermostat also linked to the system. I rang WB before choosing that boiler to confirm that it was suitable for my property. The problem is that that when the boiler is on for heating, the rads won't heat up much unless the boiler is set to at least number 4 . Even at the number 4 setting the rads are only hand holding warm so I can place my hands on them for long periods of time and they don't feel overly hot. . Anything below 4 and the rads are virtually cold. The desired temperature we set on the room thermostat is never reached. I called the WB engineer out to check the install had been set up correctly and when he arrived I told him about the lack of heat at lower settings and he told me that I should be using the boiler on the highest setting constantly. i was shocked at this as friends and family only set their boilers to 3-4 and their rads are storming hot with their houses lovely and warm. I cannot afford to run the boiler on the highest setting as I had this install to be more energy efficient and cut down on my heating bills. Any thoughts please?