"cynic" wrote in message
...
On Jun 1, 12:15 pm, "Grumps" wrote:
Hello

We've got a 28 yr old Potterton conventional gas boiler serving a hot
water
cylinder and 11 rads.
Over the past couple of weeks our old boiler has started boiling the
water.
It has kettled for a few years, but this boiling is a new development.
The British Gas man (we have maintenance on this old thing) said it was
most
likely sludged up either in the HE or pipework around the boiler, and thus
the water is not circulating fast enough so it boils.
I thought we had a Y-plan system but can't seem to figure out the pipes in
the airing cupboard. I have posted a picture
hehttp://i56.tinypic.com/2vnj638.jpg
Physically the boiler is in the direction of the arrow shown.
"This looks like it comes from the boiler" is a pipe that goes to the coil
of the HW cylinder.
"This doesn't go to the boiler" is a pipe that doesn't appear to be in the
direction of said boiler and connects to the base of the pump.
I was expecting the hot from the boiler to go to the base of the pump!
I know it's difficult looking at just this one picture, but can anyone
explain if it is correct?
Ta.

You could try some "boiler noise silencer" gel to deal with the
kettling, and you should also check the boiler thermostat is working.
When these get old and tired they often do not switch the heat off at
the original set temperature but their calibration drifts, Welded
contacts in the 'stat are another possibility. A replacement stat is
significantly cheaper than a new boiler by a couple of orders of
magnitude

OK. Any idea what this stat looks like? I guess it's mechanical and
connected to my front panel dial in some way.