On Dec 21, 8:22*am, " wrote:
I'm about to go away for a few days, and usually I would switch the
central heating thermostat down to the frost setting.

Do you mean you are going to spend a few days sleeping on an airport
floor? :-)

That of course will be sufficient to ensure that the pipework inside
the house won't freeze, but my feed & expansion tank is in the loft -
and with the exceptionally cold weather, I could imagine that might
freeze.

Under present conditions I would say there is a fair chance you are
correct


My system is a thermal store (i.e. large volume of water), so hot/cold
cycling actually results in a fair bit of movement of the water level
in the f&e tank. I'm guessing that because it's never off for more
than 8 hours on the current timer settings, that any ice "skin" in the
tank gets broken up by the movements in water level.

Not if the pipes to the tank are frozen solid


So I think I'm going to play safe as temperatures are remaining below
freezing for days - and leave the system on its normal settings.

Good idea

But I'd like to hear - are f&e tanks freezing a real problem?

They can be, especially if the pipes adjacent burst. You could have no
end of fun then


Are burst pipes elsewhere in the system (due to inadvertently creating
a "sealed system") a possible outcome?

Possible but if there is any trapped air/gas in the radiators etc., to
act as a cushion, only a low likelihood.
If you are a regular winter holidaymaker you might consider installing
self limiting trace heating to the pipes and tank in the loft.