Munchkin High Eff boilers

Rob L_4

I have seen something similar in some Munchkin boilers a few years ago. It was a buildup of what looked like crystalized material. There were several 199M boilers on this job. We found that the boilers were recirculating exhaust flue gas through the intake air pipe.
Not sure if this is what is happening on your job, but it is worth a try to look at.

HVAC1325

Munchkin High Eff boilers

I have three Munchkin boilers that run on propane two 199m and one 399m. Every two to three weeks the boilers go down on an F09 code which is flame failure and when you pull the flame rods and ignitors you find that they are coated with rust which blocks the signal back to the fire control. After cleaning the flame rod and ignitor the bolier comes back on line. I have called tech support and dialed in the boilers with a combustion anaylizer to exactly what factory specs are on ppm CO,O2%, excess air and the factory rep says yes the boilers are running at the numbers they recomend. I have my exact inlet pressure of 13 to 14"wc and my manifold pressure on low and high fire modulates according to factory specs. I have taken burner chamber debris to have it analized and it is coming back high iron content explaining the rust. According to fuel supplier I am receiving grade A Propane. These are condensing boilers and my condensate drains are working properly no water build up. Also after inspecting stainless steel heat exchangers it appears like molten glass crystal like shards have bonded to the surface. Has any one had this problem or know anyone who might help with it. Winter is back and I cannot afford to lose a multi-million dollar client. Engineers at our provider of equipment (The Munchkins) are not helping because I don't think they Know Either. Please Help

WaterHeaterGuy

What are you using to clean the sensor?

If you clean the sensor with steel wool or something metalic (ie: alum-oxide sandpaper) you leave behind pieces of whatever you are using. In that environment, those pieces will rust on the sensor and gum up your signal.

After you clean the flame rod do your rectification signals look good?

If there is a high iron content in the conbustion chamber it is coming from a source other than the boiler. That is why they are questioning your fuel.

Steve Ebels_3

Couple things

I'd check for any possibility of recirculated exhaust gas. Get outside and see if the vent terminations are per manufacturers spec. Sometimes a dusty film on the interior of the boiler will be a clue to this. I like to terminate the exhaust 12" above the intake, blowing straight out, while elbowing the intake straight down. This puts the two air streams at right angles to each other. (horizontal vent applications) For vertical terminations the exhaust should go straight up with no elbow on it while the intake should make a 180* bend and terminate straight down.

I wouldn't mess around cleaning flame sensors for a multi million $$ client. For what they cost, replace them.

The residue in the HX seems to indicate some amount of environmental contamination.

Leo G_101

What

are they heating? I ask because if they are only doing hi temp, i.e. DHW, pools/spas, etc, there will be little condensate to clean the chamber out, thus allowing particulate build-up.

Leo G

HVAC1325

Thank you

Thank you for the professional help, I will check the possibility of recirc of the exhaust gases, however, I think maybe the fuel tanks are rusty on the inside because of moisture getting in when they are refilled thus the moisture is condensing on the inside of the tank and the propane is dissolving some of the rust then during combustion process this iron is being left behind because the heat exchanger is full of coffee ground looking iron debris all three boilers are having the same problem and the 199ms are terminated with the factory concentric termination kit and the 399m exhaust terminates on the side of the building and its intake is on an ajacent peak 10 ft roughly from the exhaust termination. Let me know if this seems likely to be a cause of the rusting. Thanks again guys

tim smith

I agree on recirculation??

It sounds like to me that recirculation may be causing this also, that short of time to oxidize the flame rod is interesting. Now if it is just slightly discoloring I might look at this. Brush out heat ex w/ nylon brush and cleaner. Hood wet vac to condensate drain w/ front off and suck out while flushing clean water through heat x to trap. Then remove burner heads from front plate, clean surfaces of mounting flange on burner on both sides w/ grit, sand paper nuts. Put new gasket on and reassemble, you may just have a bad flame path to ground causing the problematic lock out. I have had this a couple times. Just a thought.

Kevin Gabelmann

Munchkin

All;

Rust on the probe's was caused by condensate backup. A white build up is caused by recirc. The only thing they have recommended for cleaning the probes is a scotchbrite pad. Sand cloth will leave silica behind and will ruin the probe in time.

Kevin