halstead sime trio, combi boiler.
has been working fine, if a little noisy - partly the fan, partly the
pump. The pump also vibrates a bit, but I'm not sure if this is
normal or not.
i've tried it set on heating and water, as well as water only, but the
following applies either way.
it runs for about a minute, with the burners firing normally, and then
the whole thing gets progressively noisier within the space of about
20 seconds, then the black screw-down type pressure valve on the
expansion vessel opens.
At that point, I get concerned, and turn the electrical supply off.
My thinking is that its either a blockage or an airlock in the heat
exchanger, causing the pressure to increase, and the valve to open.
I've run the pump with the bleed screw off, and I can see the thing
spinning, so I am inclined to suggest that the pump is ok, if a little
noisy, but I am happy to be proved wrong.
The system had been working fine, with no change in displayed
pressure, and no changes have been made to settings, etc, so I think
anything involving air would be unlikely??
Which leaves a blockage.
Any thoughts anyone?
Also, anyone know a plumber / heating engineer in the Waterlooville or
Havant area of Hampshire, with Combi experience?