Humming pipe from boiler to tank

[syl]

I get vibration in the pipe from the boiler to the hot water tank when the boiler is heating the water. As the hot water is timed to come on before we get up, the noise can be somewhat annoying. The noise is a humming vibration, not the clunking of water hammer.

The boiler (Alpha) is about 4 years old. It's a closed (pressurised) system. The dial by the tank suggests it is currently at 1 bar (and the red marker is set at 2 bar) however the dial on the boiler suggests that the pressure is just over 1 bar (has just been running) and the green zone is 0.5-1 bar. The filling loop is by the cylinder (and the cylinder is one floor above the boiler). Should I fill it until the black line matches the red one by the cylinder?

The pipework is exposed at either end but runs under tiled floors between the boiler and tank.

Any quick fixes or do I need to call someone?

 

[doitall]

No, you shouldn't play with the pressure 1-1.3bar when cold is fine.

The vibration is probably the pump, are the pipes well fixed or floating about.

 

[syl]

They feel very well fixed. I tried to push some insulation between two adjacent pipes where they bend 90 degrees to see if that helped damp the vibration and it's really difficult to increase the separation (a few cm)between them by even a mm.

I'll take some new readings when the system is colder - it has just been running at the minute so its hot.

 

[doitall]

Try turning the pump speed down a notch. What is it on at the moment.

 

[syl]

Is it built into the boiler (alpha CD28S)? I can't see a separate pump.

All I can select is off/frost/on/reset and the radiator thermostat.

Here is the boiler:

Here is the gauge next to the tank:

Slightly concerned one is too high and the other is too low.

The temperature in the central heating is cold. Adding water makes both rise (and bleeding a radiator makes both fall) so I guess this is the pressure in the central heating system rather than the hot water system anyway.

 

[doitall]

Turn the red one so its level with the black one.