Vaillant condensing boiler freezing - minimising condensate?

ashe

Can confirm it's a very gradual trickle freeze, and once it blocks up it just backs up and more freezes above it. 

We can see the frozen pipe in ours, using a camera phone held with a strong  gripper, but can't get to it. But after window cleaner cleared it, a tube of ice fell out end could see the hollow channel in it he had cleared, but the condensate dripping out the bottom basically did the same thing and froze up to the top and then same happened again 🤣 i put a hot water bottle in it as far forward as I can in the loft and this heated the roof tile gradually - took a while but it eventually transferred enough heat to melt it but a huge pain in the backside. 

ashe

Forgive the random honey dipper in the gutter - I was trying to dislodge the stick of ice so that the heating stayed on longer 🤣 that bit at the back though appears as drops land and freeze and it rises up to meet it. I think the only thing that will sort it is the trace kit.

OP, the closed cell stiff isn't that much more expensive than the cheap stuff - Google armacell. It's not crazy cheap but the price difference isn't huge 

Eldi_Dos

@BooJewels

Could the proximity of the water butt have any bearing?
If water butt has frozen it will act as a cold store helping to keep the condensate pipe cold enough for to cause the freezing.

bjorn_toby_wilde

Someone mentioned solvent welded joins where the condensate pipe is connected - I can't tell by looking at it - but for now, I'm leaving that particular bit well alone - I know my limitations.

Not sure what the internal pipe from the boiler is, but that exterior photo definitely shows solvent welded black waste, which is what it should be as it’s UV resistant.

It’s not what I was expecting to see. As others have said that shouldn’t freeze up anywhere near as easily as the 21.5mm white plastic stuff that you often see outside.

My son’s is routed outside in exactly the same waste pipe and it hasn’t ever frozen - perhaps I should say yet!!

plumb1_2

Just a guess with the OP situation 
1- could be the condensate is dropping onto the grate, and slowly building ice, then gaining height into the pipe, then blocking. Cut the bottom of the pipe so it’s about 40mm up from the grate .
You could drill a 15mm hole in the elbow at the top of the solvent weld fitting, easy access to pour hot water down or a hosepipe.

Belt and braces 
1- Repipe from inside and fit a T branch with a rodding eye instead of the elbow  use 35 or 40 mm pipe
2- Fit stand off brackets down the wall, this will allow you to fit a thicker wall thickness closed cell insulation ( like armaflex).
3- Fit low voltage tracer cable 
4- Keep the pipe off the grating.

Geta local tradesman to do it,

Yorkie1

grumpy_codger said:

Sometimes it can be easy to disconnect the (white plastic) condensate pipe near the boiler and to collect the condensate temporally to a bucket (that you'll have to empty regularly)

I know the thread has got lots of more technical (and longer-term impact) fixes on it, but just to say that this is what I do. (Have just had to do it today!). The flexible hose comes out of the bottom of the boiler and can be put to one side, with the boiler draining straight into a bucket. 

BooJewels

WIAWSNB said:

Blimey, yes, it's astonishing that it's freezing - it looks an ideal setup.
But, once it did freeze, then I think it's pretty clear it never got completely unfrozen again, so subsequent refreezes were much more likely.
So, why did it freeze first time? No idea! The pipe is a good size, so should drain instantly. I guess that a glaze could form on the inside of the pipe wall, and this just builds up with each glug.
Yes, condie is usually dispensed in glugs, I understand because it's via a 'syphon', a bit like a toilet cistern, so that there's always a water 'seal' that prevents combustion gases getting out.
Could there be other water coming out that way? Yes, if the Main Exchanger has failed and is leaking internally, but that would show as a very significant system pressure drop. You don't have this.
Also 'possible' that rain getting in the flue would end up in the combustion chamber and exit via the condie pipe. But unless you have a broken gutter cascading water down on your flue terminal, this is also unlikely.
So, I'd be looking at the bottom of the condensate pipe, and check that it's unrestricted - nowt in t'way.
Then I'd get good quality lagging, and slip a thin layer behind the pipe between it and the wall if theres only a tight gap, and clip the full sleeve over the rest. Almost certainly that's all you'll need. Complete overkill to go heating element in this case, imo.

I don't think there are any faults with the boiler, as everything else appears to be okay - no drop in pressure etc.  I'm wondering if it's occurring from the bottom - if you see later suggestions, as well as your own, maybe the ice is starting where the pipe touches the grate - maybe that is the cold spot that starts the process.  It wasn't blocked there when I first unblocked it yesterday morning - but there's a little angle connector at the bottom that directs the fluid over the centre of the grate, rather than towards the edge where the vertical of the pipe would land it - that was touching the ground, so is perhaps a cold connection. 

But the more I look at it, the more confused I'm getting.  

BooJewels

ic said:

I had this years ago on an older install.  A long 40mm pipe straight down would freeze up.  Fundamentally the pipe was exposed on the side of the house to wind.  The water ultimately doesn't just fall down the middle without touching the sides, but rather dribbles out constantly, then down the side of the pipe.  As it does, that freezes and sticks, then the next dribble, then the next... like a cholesterol blocking up arteries.

I fixed by fitting a Worcester CondenSure under the boiler - this collects the water, then dumps it automatically in larger flushes - rather than allowing a continual dribble down the pipe.  This flushing action gives it weight.  Also whilst it collects, as it straddle the flow pipes it is actually heated before being flushed.  Newer boilers have this built in.

Outside I extended the small 22mm white pipe that exited the house down inside the 40mm pipe, but also wrapped it with some pipewrap insulation.  That way it was insulated inside the 40mm pipe till it got to the floor, and wasn't getting frozen by the wind blowing on the pipe.

These two changes meant I never had the problem again.

I've been trying to remember the discussion about it when it was installed 4 years ago - I think the engineer was asking me where the prevailing wind direction was and we decided to put the drain on the further side of the downspout, to protect it from the main wind direction.  But it was pretty much still (unusually so) on Sunday when the snow fell etc. so on this occasion, I don't feel as though wind chill specifically was a factor.

Your arrangement sounds very efficient and is obviously working well for you.

BooJewels

ComicGeek said:

BooJewels said:

I thought I'd have a quick look before it got too dark.  There was a nice big ice cube in the very bottom angled bit on top of the grate, the whole last angled section came away in my hand as I had a poke round. 

It definitely wasn't there the first time I cleared it yesterday morning, as I did poke a finger up the pipe end thinking it might be blocked with soggy leaves that had then frozen, but there wasn't much room to probe much further.  When I put it in warm water to melt, it came out as five separate lumps, so may be as a result of my earlier efforts and has sintered together in the last section during today.  There was no fluid behind it, so it certainly wasn't actually causing a blockage. 

Given that it hasn't happened before, it's possibly just due to particular wind direction and outside temperature - the wind chill factor can play a key role, particularly when the outside of the pipe is wet. You may find that it never happens again, but I would definitely insulate the pipe to prevent it happening.

Obviously pouring water over the outside of the pipe helps melt the frozen condensate, but also then makes it more likely that it will refreeze in a short time as the temperature of the pipe then drops as the water evaporates. So an easy short term emergency fix but does require you to repeat until the outside temperature rises enough.

Boilers can produce 2-3 litre of condensate per hour in perfect conditions - that would be at around 50 degrees flow and 30 degrees return to the boiler. Even at a lower rate, a blocked pipe can very quickly get filled.

It's happened once before - almost exactly 2 years ago - but didn't happen last winter, but I don't think it was ever very cold last year.  

I did wonder if the evaporation would make it worse - the pipe dried very quickly, as the water was warm.  But I did several passes of hot water - gradually and slowly over the full length of the pipe - hoping that I was being thorough.

I'm really surprised to hear that it's as much as that per hour - that would explain why it repeatedly froze.  But everything I read whilst researching, suggested it was little more than a trickle.  I'll maybe have to watch it carefully one day.

Fobeo

I had the same problem and solved it by fitting a "Pump House Boiler Buoy Condensate Bypass Valve & Hose Kit BB-1". Check Ebay usually about £30. It provides an alternative outlet for the condensate discharge in winter. I use a 5 litre water bottle and empty it every day. Works fine.