Barista or Exterminator

Larry (from OSHA)

Well I'm a little late this year, but annual cleaning of the Knight has taken place. I'd love to know what exactly the "coffee grounds" or "mouse turds" actually are. After seeing the Rotting Heat Exchanger thread and picture, I was spurred into action. Hope everyone is having a good year.





Larry

JUGHNE

I just cleaned a KBN 106 today. 2 years since last cleaning had about your amount of coffee grounds. First cleaning after 4 years had much more.

Your first picture must be the target wall cleaning guard installed??

This time I did get brave and unscrew the screw holding the target wall in place. On one of these it felt like the SS screw was going to twist off. So a little WD 40 and coaxing back and forth did remove the Allen head screw (metric BTW, of course), with that out a through cleaning/washing of the coils could take place.
A large sharp tweezers would poke into the target wall and let you walk it out.
The old reliable credit cards with, notched teeth cut into them, would cut the coffee grounds that had passed thru the coils.
The target wall was stained and a little worn so I just turned it over to get more goodie out of it.......anti seize on that wimpy screw before installing....why couldn't they just put a 1/4" (almost) bolt/stud back there like old Munchkens?

A magnet will pick up the coffee grounds, this comes from a boiler that is all stainless steel without magnetic properties.
The only ingredients introduced into the fire box are....condensate from combustion gases (acetic H2O) .....CH4 NG gases.....and a little chloride from the wash down of the PVC vent pipe. (a point I have made here previously) So where does the iron...Fe....come from to stick to your magnet? If it is iron coming out of the SS coils then that seems like it would be an issue towards leaking.
It has been said from re circulation of exhaust gases....but I have some ModCons with 6' of separation with plenty of coffee grounds.

Perhaps my elemental science mind is just too simple.

Larry (from OSHA)

I use anti-seize on everything and it helps a lot. Also, that is what old credit cards are for, right?

Question though, does anyone think that combustion tuning would reduce the amount of deposits and decrease the temperature difference between the flue temp and the inlet water temp?

Paul Pollets

If you do this for a living, there is always the search for the best tool for the job. Credit cards can be useful, but don't last long and have less strength to remove the carbonized debris between the sections. It's the debris left behind that causes the issues. The few HX I've replaced, had pinhole leaks between the sections that were not visible. I've found the Viessmann cleaning tool to be most useful and thought that if the serrated blade were mounted to a Fine tool at an angle, it would be easy and fast way to do a thorough cleaning job. I'd also like to know the long term effects of scoring the HX with a metal blade.

Canucker

What grade of stainless steel is the heat exchanger made of? Stainless can be very resistant to certain acids at room temperature and not so much when it gets raised above that. I'm curious to what the make up of the condensate is. Has anyone ever had the liquid tested?

Paul Pollets

I'm not sure what brand is pictured. Viessmann uses 316Ti SS. Most manufacturers use type 316.

Solid_Fuel_Man

Stainless steel is "self healing". Meaning its oxide protects is from further oxide/deterioration. If you scrape off the oxide, it must "reheal" by which it gets slightly thinner. This is why plastic is a great thing to use in cleaning SS, especially flue liners for wood appliances. So I'd say a credit card or similar tool would be appropriate.

Most stainless alloys gall when threaded with other SS hardware (nuts and bolts) which is why it's usually so hard to remove SS fasteners which show little signs of deterioration.

Larry (from OSHA)

I've been doing this every year and I do use a credit card that lasts longer than my credit. The unit is a Lochinvar Knight 80 floor unit installed in I think 2007. I'm the only person to service it since professionally installed and spend about 2 hours cleaning it fire side and water side as the manual says to. If I worked on these professionally, I'd have a combustion analyzer and know how to use it, but since I'm just a retired OSHA guy, I don't. I'd love to know what the CO, CO2 and Oxygen numbers are, but I had to give back my 4 gas analyzer when I left the Department. The numbers were good a few years ago.

Anyway, it works great but does need more regular maintenance than the old Weil McLain that came out.

Happily retired from OSHA Larry

Canucker

> @Solid_Fuel_Man said:
> Stainless steel is "self healing". Meaning its oxide protects is from further oxide/deterioration. If you scrape off the oxide, it must "reheal" by which it gets slightly thinner. This is why plastic is a great thing to use in cleaning SS, especially flue liners for wood appliances. So I'd say a credit card or similar tool would be appropriate.
>
> Most stainless alloys gall when threaded with other SS hardware (nuts and bolts) which is why it's usually so hard to remove SS fasteners which show little signs of deterioration.

I'm curious about how much gets worn off being bathed in the mild acid solution of the condensate. With the elevated temperatures from the burner, it might be pretty aggressive. Mix the iron getting pulled out with any dust from the air intake might explain the magnetic nature of the coffee grounds when cleaned. We have visual inspections on any equipment we use where I work and you can see where the stainless has a dull surface where it's been chemically etched from the acids. I wonder if it would be good to keep a visual record of the heat exchanger from year to year after a cleaning?