On Tue, 21 Dec 2010 12:40:26 +0000, The Natural Philosopher
wrote:

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.

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.

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.

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.

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


Yes.

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

Yes

Some years ago a neighbour drained their tank in the loft because they
were off to Spain for a couple of months to miss the worst of the
English winter. On their return, in chilly February, they turned on
their main water stopcock and got their c/h running.

After a while there was a horrible rushing noise from upstairs, and
water was seen pouring through the lounge ceiling.

The ballcock in the tank had stuck in the down position....

David J