Do frozen boiler-pipes pose a risk?

[Lucky Luke]

Hi experts. Our Vaillant EcoTec Plus 824 combi boiler has had an intermittent fault for a long time (it's been discussed in the DIYNot forum, in earlier months). There does not seem to any certain cure for the fault, and mostly, I find that it must have failed first thing in the morning, when, at about one a.m., it is set to fire up after being merely on frost-setting for a while. If it did not fail (and sometimes, it does not), it would raise the water temperature to about twelve degrees until 7.00 a.m., when it should start to aim for a target temperature of 19 degrees. When I go into the bathroom at about 7.10 am, sometimes, the radiator is stone cold. So, on these occasions, it could have had no heat since about 1.00 am, when it failed to "wake up".

The reason for the above background info is that this boiler is housed in a kind of closet under the stairs. Access to it is via a door in the outside wall of the house. Draughts and cold air generally can go into this closet in winter (the door is not sealed at the bottom — there is a gap of about half an inch high) and, if the boiler has not ignited (let's assume the worst, and think that it failed to ignite at 1.00 am), it seems possible, at least, that in very severe cold, the pipes could freeze (a worst case scenario, I know, but...).

My question is this: if the worst did happen and the pipes to or from the boiler froze, would there be a build-up of pressure after, not knowing about a freeze-up, I manually ignited the boiler and it started to heat up? (I'm thinking explosions.) Or is the worst that could happen be that the pump would not be able to stand the load caused by such a blockage, and cut out?

With thanks in advance, for any helpful replies.
A.W.

 

[terryplumb]

Your pipes could freeze ,burst ,and water would flood out. But the boiler wouldnt explode.

 

[Lucky Luke]

Your pipes could freeze ,burst ,and water would flood out. But the boiler wouldnt explode.

I'm surprised to hear from you that the copper pipes would burst, on freezing (or even burst under the pressure of the pump, circulating against a blockage). I thought that only the old, lead pipes burst when they froze. Anyway, you know best, and I feel reassured. Thanks very much for the swift reply!
A.W.

 

[terryplumb]

Water expands when it freezes and will split just about anything ,car engine's for instance have anti freeze added to the coolant water to prevent the engine from being split.

 

[Lucky Luke]

Water expands when it freezes and will split just about anything ,car engine's for instance have anti freeze added to the coolant water to prevent the engine from being split.

So they do! Of course, of course! I hadn't thought of that.

 

[breadnbutter]

gets some no nonsense antifreeze inhibitor, screwfix sell it, if your worried.

 

[John D v2.0]

Water expands with a practically unstoppable force when frozen, it may be counter intuitive but plastic pipes do have a bit of give in and also fewer elbows to be forced off by the expansion.

 

[KenGMac]

Thawing will allow water to expand by a rather large volume, it it this action that caused pipes to either burst or more commonly a joint, generally an elbow to be shoved off the pipe, no matter what type of elbow, a soldered one or one with a nut and an olive.

One area that caused concern is the Condensate outlet, it has to be plastic, the condensate contains a very, very mildly corrosive liquid, I have seen several insurance claims where the condensate pipe, generally run externally to a drain but the pipe not insulated freeezes and the boiler completly un-aware of this will continue to fire and the resultant burst from the condensate drain can be messy.

Ken.

 

[Lucky Luke]

Thawing will allow water to expand by a rather large volume, it it this action that caused pipes to either burst or more commonly a joint, generally an elbow to be shoved off the pipe, no matter what type of elbow, a soldered one or one with a nut and an olive.

One area that caused concern is the Condensate outlet, it has to be plastic, the condensate contains a very, very mildly corrosive liquid, I have seen several insurance claims where the condensate pipe, generally run externally to a drain but the pipe not insulated freeezes and the boiler completly un-aware of this will continue to fire and the resultant burst from the condensate drain can be messy.

Ken.

Thanks, KenGMac. I shall fix that risk when I can. The bore of the pipe is quite large, so it's not a big worry. However, it will be fixed, eventually. And thanks to everyone else, for their comments.
A.W.

 

[bernardgreen]

Thawing will allow water to expand by a rather large volume,

? ? ?

When water freezes the ice produced has a larger volume than the water it came from. This is when the pipe or joint fails. The ice prevents any water flow out of the burst. Hence the burst is not discovered until the thaw when the ice melts.

 

[John D v2.0]

? ? ?

When water freezes the ice produced has a larger volume than the water it came from. This is when the pipe or joint fails. The ice prevents any water flow out of the burst. Hence the burst is not discovered until the thaw when the ice melts.

Technically the quantity of escaped water is allowed to expand quite rapidly after thawing

 

[bernardgreen]

Technically the quantity of escaped water is allowed to expand quite rapidly after thawing

expand.... NO
increase.....YES

 

[Lucky Luke]

gets some no nonsense antifreeze inhibitor, screwfix sell it, if your worried.

Thanks, breadnbutter. I didn't know that anti-freezing inhibitor was available.
A.W.

 

[Hugh Jaleak]

Boiler explosions are not unheard of, although they were more a thing of the past with the older cast iron boilers. Needed the vent and cold feed pipework to freeze, and the boiler stat fail at the same time, then the boiler could potentially explode.

I'd hope with yours the PRV would operate before any real damage was done, but allowing the boiler to potentially freeze is not going to do you or it any favours.

 

[KenGMac]

I have assumed, as taught in college that it was the Ice thawing that caused the expansion??

Found this on-line 9% in a small diameter long length of pipe work is pretty big??

When liquid water is cooled, it contracts like one would expect until a temperature of approximately 4 degrees Celsius is reached. After that, it expands slightly until it reaches the freezing point, and then when it freezes it expands by approximately 9%.

As for the condensate drain mounted externally freezing? I have seen several kitchens wrecked by a frozen condensate drain when it fills and then bursts cascading dirty water all over the place.

Such are the joys of working up here in at times very low temperatures

Ken.