External condensate pipe and freezing.

I had a WB condensing combi installed three years ago. It replaced an old conventional boiler which was located on the outside wall of my attached garage.

Because of the location, there was no accessible internal drain available, and so the condensate pipe had to be taken out through the garage wall where it descends vertically for about 14" before running beneath the concrete path at the side of the garage and terminating in a proper condensate soakaway.

That final 'run' is just three feet long and the pipe is just a couple of inches below the surface of the path and poorly insulated. The reason for the poor insulation is that I had to cut a channel for the pipe in the concrete path and the concrete was bloody tough! I did not cut the channel deep enough to enable insulation to be completely wrapped around the pipe - and so I slit a length of pipe insulation lengthways and laid this over the top of the pipe before filling the channel in with mortar. So, whilst there is insulation over the top of the pipe, there is none underneath it.

There was no problem for the first two winters, but last year, during the very cold spell, the external pipe froze up (not exactly sure precisely where in the run this happened) and shut down the boiler. I was able to unfreeze the pipe using kettles of hot water poured over the top of the path along the channel, and I then laid bin liners full of old towels and sheets over the top of the external pipe run - and this stopped the pipe from freezing for the rest of the winter. It didn't look very pretty, however, and the wheelie bin had to be dragged over the top of the bin liners on bin day!

Before winter sets in this year, I want to do a proper job. I don't want to be messing about with kettles of hot water at 10.30 pm on a freezing winter's night again!

Two alternatives: I can improve the pipe insulation, or I can install a trace-heating cable. The latter solution is fairly pricey, however, and I don't want to go to that expense unnecessarily - particularly as the conditions last year when the pipe froze up were exceptional, in terms of the sub-zero temperatures lasting for a prolonged period.

The short 18" vertical run on the outside of the garage wall is not a problem because I have completely wrapped that in pipe insulation and also boxed it in using some left-over upvc (soffit!). I'm fairly sure that that insulation will be protection enough.

So, if I get to work with my club-hammer and chisel, and enlarge and deepen the channel in the side path to enable me to completely wrap the pipe in heavy-duty 22mm sealed-cell foam pipe insulation, will this be sufficient to prevent a repeat of last year's freeze up? How effective is foam pipe insulation in preventing external pipes from freezing in sub -zero temperatures?

Reply to
Ret.
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Not necessarily, although it SHOULD be, As you will probably be using the boiler enough to keep the pipe warm.

Remember no insulation can keep something warm indefinitely: final temperature is down to heat loss versus heat input.

In some ways insulation may make it worse it the end of the pipe is exposed to cold temps: Instead of having to reduce the whole concrete block to zero, its just the pipe..

might be worth just covering the slab with bubble wrap

Reply to
The Natural Philosopher

I had a similar problem with the consensate outlet from a dehumidifier many years ago. I made a heating wire which I threaded inside the pipe, and made sure a small loop protruded from the end so no icicle formed. It was switched on by an external froststat, and for the length and size of wire, I found running it from 18VAC worked just about right. (AC used to reduce corrosion if the water got into it.)

The resistance wire came on a small reel from Maplin (although I can't find it on their website now), and I threaded it (painstakingly) through ptfe tubing which I already had. It probably didn't really need insulating as the supply was isolated, except I had the wire in a long loop to the end of the pipe and back. You could use a bare resistance wire with an insulated return wire, such as a length of standard wiring single.

Another option might be an overflow pipe just near where the pipe exits the wall, depending what it might overflow onto.

Reply to
Andrew Gabriel

Well, after asking for advice - I did the job this afternoon. I decided to just improve the insulation. I chiselled away the mortar I had filled the channel with - then widened and deepened the channel. This enabled me to fit 22mm pipe insulation completely around the pipe and close it up completely with cable ties. I also packed more insulation around the pipe using torn up chunks of pipe insulation before mortaring over and refilling the channel. I'll just have to wait and see if that will be good enough!

Your idea of threading a heating cable inside the pipe was interesting. Would the acidic condensate not affect it after some time?

Reply to
Ret.

Found it, BL64U 28swg Constantan Resistance Wire

Well, mine's in PTFE tubing which certainly won't, but the condensate from a dehumidifier isn't acidic anyway.

I don't know how bare constantan would stand up to it. A few searches just turned up that it's more corrosion resistant than other resistance wire alloys.

Reply to
Andrew Gabriel

Well, is it in a particularly cold spot? A friend has had all this done and it froze at the end nevertheless. I think this condensate issue is going to be a weak link in most installations myself. I understand that they fit a form of heating for the pipe as standard nowadays.

Brian

Reply to
Brian Gaff

I wouldn't have regarded it as a particularly cold spot. The path that the pipe runs under is right next to my garage and between my house and next door house - so sheltered.

I think I may have to get hold of some insulating board of some sort and, if the forecast is for a seriously cold spell, just place that board over the top of the path where the channel is cut.

There was no problem at all for the first two winters after the boiler had been installed - it was only last year, during that prolonged sub-zero spell, that the pipe froze up - and even then only after several days of the very cold temperatures.

I'm hoping that my improvements to the insulation will do the trick.

I did think of cutting a hole in the concrete floor of my garage directly below the boiler and placing the condensate soakaway deep down in that hole so that there would be no external pipework at all. I would be contravening building regs if I did that, however, and, apparently, the condensate can attack foundations!

Reply to
Ret.

on bin day!

temperatures?

I had a similar problem but my pipe ran vertically down and then horizontally to the drain. After trying to insulate it I decided to modify it so that rather than an L shape, run the pipe so it drops for maybe 50cm, then runs at an angle to the drain, t allow any water in it to flow more quickly down the angle and hopefully avoid freezing. This seems to have stopped the problem.

Reply to
Simon Finnigan

have you considered makign it "fail safe". In the vertical run insert a tundish for the pipe to drip in so that if the lower part freezes the condensate just overflows onto the ground rather than stopping the boiler working.

Robert

Reply to
RobertL

Mine's on a NW wall, so gets little sun in the Winter. It does run down all the way at about 40 deg. from vertical and the end, to a gully, is covered. So far it hasn't frozen - fingers crossed!

Reply to
PeterC

have you considered makign it "fail safe". In the vertical run insert a tundish for the pipe to drip in so that if the lower part freezes the condensate just overflows onto the ground rather than stopping the boiler working.

Robert

would work if sufficient space between pipe end and tun dish

I have seen an installation where pipe run was vertical into a gutter on a lower roof

Ice build up in the gutter blocked the end of the pipe

Regards

Tony

Reply to
TMC

That's a good suggestion - but having insulated the 14" vertical drop and then boxed it in, it would require a major rework. I'll see how things go this winter. If I have problems again I will most probably bite the bullet and buy a thermostat-controlled trace heating kit.

Reply to
Ret.

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