Feed & expansion tank - danger of freezing?

[dom]

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?

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

[dom]

I should add, the f&e is mounted high on wooden platform on a gable wall inside the loft - not in contact with the ceiling of the heated room below. The tank is insulated to all sides and top (but only with the kit supplied with it - i.e.not that great), and the (copper) pipes to it well insulated with close fitting climaflex.

[cynic]

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

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

Not if the pipes to the tank are frozen solid

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

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.

[Tim Watts]

If you are that worried, leave the heating on a normal or slightly reduced cycle - if it is only a few days.

If not now, can you in the future, insulate the FE tank?

You then have the option to include some trace heating tape around the tank and any vunlnerable pipes, or to complete a box like insulation structure all the way down to the ceiling, but not put a base on it which would allow what little heat is in the room below to rise into the FE insulated space.

After reading all this, I think I might include a short loop of CH pipe under my FE tank so it gets a burst of warmth everytime the heating comes on in frost protection mode.

HTH

Tim

[The Natural Philosopher]

Yes.

Yes

[dom]

Ok - just been up there to check, whilst the water is pretty chilly (that's the SI value for a bit above freezing) - there's no sign of ice at all, even after several days of outside temps continuously below zero.

[dennis]

I would worry then. My main tank is on stilts to increase the shower head. The stilts and the tank are wrapped in insulation right down to the ceiling and the insulation on the ceiling is removed. I don't expect it to freeze as it gets some heat from below, yours can only get colder by the sounds of it.

If you have time you could build a box around the whole thing using insulation board down to the ceiling.

[David J]

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

[dom]

One would hope the overflow could cope with that.

[David J]

Is it designed to cope with full flow input?

[MM]

That's exactly what I have done, although I have a conventional large cold tank and small CH header tank mounted directly on the floor joists. I also opened all the bedroom doors so that the heat from the bedroom radiators should waft up into the loft (left hatch open). I set the radiators to "medium", so they get fairly warm. And the hot water in the airing cupboard will also throw off some warm air to permeate the loft a bit.

I've been leaving the loft hatch open for a few days and placed a thermometer in the loft. Even when the outside (garden) temperature was reading -7C the loft measured +2.

I also ripped up some of the loft insulation covering the joists and placed it around the pipes. The pipes all have the foam rubber tubing around them, but sinc I was going away I thought an extra bit of insulation can't do any harm.

But for next year I am deffo going to investigate warming possibilities, for example greenhouse-type propagation heaters. I'm also going to get a wireless thermometer to put in the loft that I can monitor from the comfort of my living room. Thing to do is see what they do in e.g. Canada and Russia.

Re the light bulb idea, I had also heard of someone using a 100w bulb suspended from a loft beam to just take the chill off. Presumably this would be hung within a few inches of the tank or pipework, but I, too, would be worried about fire risk. In fact, although I had been leaving the light in the loft on for the past few days (it's only 60w filament and mounted on a rafter), I debated whether to leave it on while I was away and in the end just couldn't do it. Let's hope that the CH doesn't fail! Mind you, the weather appears to be getting slightly warmer right now anyway. For example, the BBC weather page for Spalding says the min temps for Wed, Thu, Fri, Sat, Sun are forecasted to be -1, 0, 0, -2, -1

MM

[MM]

When you say "continuously below zero", how far below? In south Lincolnshire nighttime temperatures have sunk as low as -11C and it had been -5 even at 08:00am.

MM

[MM]

(a) didn't the overflow work? and (b) I have an audible alarm that goes off when the water level approaches the overflow outlet. It's gone off a couple of times, too, due to a bit of grit in the ball valve. I got mine from Tschibo, which is now defunct in the UK, but Maplin do a water alarm:

has a rubber sucker that "clings" to the inside of the tank and you just move it about accordingly. Also easy to test because you just make the probes wet.

MM

[MM]

NB: The overflow ~can~ freeze up, thus no longer behaving as an overflow! That's yet another job to take on for next year: What to do to prevent that from happening. Although I have the water alarm mentioned above, I don't hear it very well from 50 miles away!

Maybe that's the next level of technical wizardry: a water alarm-cum- wireless thermometer that "phones home" when there's a problem.

MM

[MM]

Well, my system is a bit weird, although the house is only 6 years old. There ~is~ a large cold water tank, but it doesn't feed the cold taps! It ~only~ feeds the hot water cylinder in the airing cupboard. I know this because if I turn on any cold tap in the house the water level in the cold tank doesn't change, even after 5 minutes, and thus the ball valve never opens. Also, the cold taps all have really high pressure, just like the kitchen cold tap, which traditionally was the one connected directly to the water main. I have high pressure doubries in the toilet cisterns, too.

I tell you what I have been mulling over these past few days: As I go to Germany fairly regularly I can buy the still widely-used Tauchsieder from Karstadt or other similar department stores. I have one at home at the moment and use it for wellying up the water in the bucket when washing the tiles and similar heating jobs. Nifty!

Now, imagine one of these dipped into the cold water tank! On a time switch, you could warm the water a tad every few hours throughout the night during these very cold nights -- sorted!! My Wilkinson electronic timeswitch (=A35.97) has 10 on/offs. (Don't buy the mechanical segment type; they're crap long-term. Both mine stopped working after only a year or so. Unreliable.)

In case anyone doesn't know what a Tauchsieder is, they look like this: