DIY: Cleaning my boiler's heat exchanger

[Piwoslaw]

Originally Posted by Daox

Do you think you could post a DIY on cleaning the heat exchanger Piwoslaw? That would be really cool because I don't know how I'd go about doing that.

There's actually nothing to it: I opened my boiler's combustion chamber

took a brush

and kept scrubbing the heat exchanger until the dust and acid deposits stopped coming off. I brushed both from the top and bottom, and tried to get it as deep between the fins (paying attention not to bend them) as possible. Professionals supposedly have better brushes, but the one I had in the garage seemed to work well enough, except that it was hard to get into all of the nooks and crannies. When I was done I used a strong vacuum cleaner to suck out whatever didn't come out by itself. I also vacuumed the burner to clean out its orifices. And that's it.

I also read about the green deposits on the HX: Supposedly they are from the exhaust condensing right after firing up the boiler, when the water in the system is still cold. One source of information claims that a complicated heat exchanger system should be retrofitted to preheat the return from the supply to minimalize the cold time of the return. That source didn't mention how much this would decrease the efficiency of the system. A bunch of other sources claim that this happens in every boiler, especially if the system is large (more than 100-120 liters, mine is close to 300), and just cleaning the HX every year should be enough during the useful lifetime of the boiler.

Now, if I lower my system's (return) temperature, as I plan to do, I may have a problem with too much condensation. But that will also mean that my system is ready for a super efficient condensing boiler, according to plan

[Piwoslaw]

I visited my Grandma today and decided to clean her boiler's heat exchanger before firing it up. Her's is a different make and model than mine, 2-3 years younger and rated at 29kW instead of 23kW, but otherwise similar. The combustion chamber's front doesn't open, so the only way to get to the burner's top or the HX's underside is to close off the plumbing and take the HX off, so I left that for next year. On the other hand, access to the HX's topside is much better, so I could easily scrub it with the brush. Unfortunately, that wasn't enough as the green condensate deposits really clogged the space between the fins in two places, plus many of the fins were bent. I estimate that those two things reduced the heat exchanger's effective surface area by 5%-8%. I used a small, thin file to clean the deposits between the fins, then straightened the fins. I used the vacuum cleaner 3-4 times to both suck and blow the grime out. Once I finished and fired it up I noticed that the water heated up slightly faster during the first 1-2 minutes.
Sorry, no pictures, as I didn't have my camera.

Removing the HX would allow me to see if there are deposits inside the HX's pipes, but I didn't have time for that today.