Boiler Flue Story

In my last blog I hinted that there was a story to tell about the flue to the new boiler. You may remember that we wanted a vertical flue out through the roof, to follow the same path as for the previous boiler, but that it was not possible. We ended up with a horizontal flue straight out through the wall :

As you know, I asked the builder to come and deal with the stone around the flue, which he did.

Separately, you may also remember that we had a drip from the boiler which the plumber had tried to fix, but failed. He referred the problem back to the boiler manufacturer (Alpha) who said it was a known problem (now fixed, apparently) and that they would send out a field engineer to deal with it. A few days after the builder had been, the Alpha field engineer came and fixed the drip. There is a "bulb" screwed onto a housing at the base of the boiler to collect the condensate. The manufacturing process for the housing was leaving a burr on the threads, allowing water to pass. He simply removed the bulb, filed off the burr and refitted. Problem solved.

However, while he was here I asked him about the flue. The builder had commented about the up-turned nozzle on the centre (exhaust) tube, suggesting it would catch the rain. I explained that this was the "pluming kit" and that I thought it was supposed to be like this to direct the exhaust upwards. However, I thought I would double-check with the Alpha guy.

Alpha guy was happy with the pluming kit, saying that the boiler is designed to deal with any water that gets down the exhaust tube (it is caught by the afore-mentioned condensate trap and directed out through the overflow). However he was not happy with the overall flue installation. You can see from the photo at the top of this blog, or the one below, that it has been installed with a downslope from the wall terminal back to the boiler :

This is incorrect - it should be installed horizontally. The centre exhaust tube has a built-in backslope, but a backslope on the overall tube can lead to water getting into the outer (air intake) tube, and falling back to the boiler. It can deal with a little bit of this, but not a lot, and he explained that there have been examples of boilers damaged internally by too much water getting in. We agreed that, because of it's sheltered location, this is very unlikely to happen, but the key thing is that it has not been installed according to the instructions, hence the warranty could be concluded to be invalidated.

Isn't that typical - a matter of two or three days after the stone around the flue was re-instated somebody tells me it is going to have to come out again !

The plumber was not very happy, but agreed to come and deal with it. This was done last Wednesday, but again he wasn't keen on doing the stonework (they only carry ready-mix mortar and it is the wrong colour for our pointing, apparently) so I need to get the builder back again ! I guess the plumber should pay for this !

While the plumber was here he also tried to fix another minor problem we have. When you shut off a cold tap, the fan on the boiler starts up and runs for a few seconds. This is thought to be some kind of reverberation down the cold water feed to the boiler that triggers the flow sensor, thinking there is a demand for hot water. The boiler does not fire, but it is still slightly annoying. The plumber fitted an in-line shock arrester in the cold water feed just under the boiler that is supposed to absorb this reverberation. However it has not made any difference so, again, this issue is being referred back to Alpha.