Condensing central heating boilers and freezing

[ericmark]

Condensing central heating boilers and freezing. My parents have a new Wooster central heating boiler, and the condensate pipe filled up with ice. The boiler made gurgling noises and then tripped out. Lucky the weather was not too bad and I was able to get there, and heat the pipe so removing the frozen condensate. However it would make sense to fit some form of trace heating. It seems the pipe goes through the wall near horizontal then about 30 degrees fall to drain and it was the horizontal section which caused the problem. Since this is in the wall putting any trace heating on outside of pipe will not be easy. This makes me ask what about inside the pipe. There will be a problem with acid I know and any element which can get wet would need to be supplied from a SELV supply. But here is the point. There must be thousands of people with the same problem and it seems inconceivable that an answer has not been found with some special pipe with trace heating built in designed for this very job!

So what have others used to keep the condensate pipe free from ice.

 

[Spark123]

Internal drain

 

[electronicsuk]

More than likely is that it has been installed incorrectly. You would be best confirming this on the plumbing forums, but I believe outdoor condensate drains are required to be run in 32 or 40mm. More often than not, plumbers just continue the 20mm overflow pipe through the wall and do not increase in size for the outdoor portion of the run.

I assume you've tried putting some lagging over the pipe run? As long as the boiler is running for a fair portion of the day, this coupled with the heat from the condensate should be enough to keep it from freezing.

 

[bernardgreen]

Two people I know have this problem. There is not enough heat in the condensate to over come the cold even when lagged.

When there is a risk of a pipe freezing the following idea can save the day.

Thread a length of small plastic tube into the pipe through the area that is liable to freeze and ensure there is no water in that tube.

If the pipe freezes then there are two options, pulling the plastic tube out will leave a small bore through which water above freezing can flow and melt the ice. Or warm air or water can be put through the tube to start the melting of the ice.

4 mm earth sleeving works well as it is strong and shrinks slight when stretched.

 

[pjcomp]

More than likely is that it has been installed incorrectly.

Doubt it. It's a known bug - sorry, feature - of condensing boilers that the condesnate pipe freezes int he winter. Last winter's freeze had every plumber chasing around to callouts for thesse frozen pipes which stopped boilers, and I sauspect this winter is the same. Happily, like Spark123, I've got an internal drain and it hasn't frozen on me (yet...)

PJ

 

[ericmark]

Considering fitting a bulkhead lamp under the pipe. However not sure about lagging as if it does freeze again need to remove it in order to thaw it again.

Yes bad design there is not enough fall through the wall. However big job to correct.

 

[1john]

run a 32mm pipe from outside into the house and have the 21.5mm pipe going into that.

 

[JB666]

Had same problems with my Dear Old Mum's condenser boiler. Ended up with the bathroom extractor ducting bored out next to the condensate drain to give some form of "heat" near the outlet. Hasn't frozen since (i'm touching wood!) with just the passing warm(ish) air

 

[Lectrician]

Larger pipe is the answer...

 

[bernardgreen]

Larger pipe is the answer...

Sadly not in every case. It is 32 mm at one of the places that froze.

In his case he is now having an internal air break installed with an overflow arrangment with a large container for any averflow


http://www.gov.je/SiteCollectionDoc...BoilerInstallationinDwellings 20100910 mm.pdf

 

[tonyelectric]

Can you re-route the pipe in a larger diameter to fall vertical, if water cannot sit in the pipe it can't freeze. I did see one install where the pipe ran a long distance horizontal and the plumber had fitted a length of 8mm microbore copper tubing inside the drain pipe as a loop that in turn connected to the radiator plumbing via a valve that was only a quarter open, this way you had a mini radiator running with the house radiators but restricted so as not to waste heat but stopped ice forming.

You could make up a DIY defrosting unit by running some nickel-chrome wire inside the pipe and connecting it to a suitable isolating transformer, turn on when you need to defrost.

 

[bernardgreen]

Even in a vertical drop pipe some of the water will freeze if it runs down the inside wall of a pipe that is below freezing. This creates a slow build up of ice that eventually closes the pipe. There just isn't enough heat in the condensate to raise and keep the whole pipe above freezing if the outside temperature is too far below freezing.

 

[bernardgreen]

The U bends in the condensate drain pipe work are part of the sealing of the combustion chamber and must NOT be removed or altered.

In simple terms

The liquid in the U bends prevents the fumes formed by burning gas from leaving the combustion area via the condensate drain. It also maintains the correct fan driven pressure in the combustion area. Removal or alteration to the U bends may compromise the correct burning of the gas and may result in the release of carbon monoxide via the condensate drain.