Back in March 2000 I had a new Vaillant VHR 24-28 combi CV installed. It worked satisfactorily and fairly noiselessly - we could hear the gentle whooshing of water when the heating was running. Then about a year after, the thing began to make a whining noise which I presume emanates from the pump. What is noticable about this is that the noise takes about five minutes to build up when the heating comes on in the morning which indicates that it results in some way from the temperature of the system as a whole. Once the system has been operating, as soon as the heating comes on again, either because the thermostat says so or the hot water is not being drawn, the whining starts.
I have of course bled the system of any trapped air and I have read some of the other messages but I am not sure what the problem is and why a one year old kettle should start making a fuss. I have tried different settings of temperature to no avail. Also, it seems that pump pressure can be a reason for this type of noise but as far as I can tell, this model of kettle comes with a fixed speed pump (it's a Grundfos with a Vaillant rebrand label seemingly).
Would anyone know how to resolve this problem? What is the root cause?
I have of course bled the system of any trapped air and I have read some of the other messages but I am not sure what the problem is and why a one year old kettle should start making a fuss. I have tried different settings of temperature to no avail. Also, it seems that pump pressure can be a reason for this type of noise but as far as I can tell, this model of kettle comes with a fixed speed pump (it's a Grundfos with a Vaillant rebrand label seemingly).
Would anyone know how to resolve this problem? What is the root cause?