Munchkin Boiler leak

dabineri

I have an 8 year old Munchkin 80M that has sprung a very slow leak from under the front of the combustion chamber but not coming from the seal on the front cover. If this is from a hole in the boiler chamber can this be repaired? Is it alright to continue using the boiler if the leak remains very slow (currently about one drop per 25 seconds)?

Any advice is welcome on this problem?

Dave

Ironman

You need to have a COMPETENT tech that's trained on that boiler look at it. If it's coming from the heat exchanger, it needs to be replaced.

No, it's not safe to run it.

JUGHNE

Does this drip only if the boiler is firing? Have you had the heat exchanger cleaned? If the drain is partially plugged then condensate could be dripping out the front . Usually would cause flame sensor to shut down the burner as the front plate insulation gets wet.
You need a pro to open the boiler, if the exchanger is leaking it would always leak, hot or cold.

jpcallan

I just completed the overhaul of a Munchkin 199M V1 boiler with a Giannoni heat exchanger that had this same failure. In the case of this boiler, the water pressure was not dropping if the automatic feed-water valve was closed, so it was clearly was condensate leaking through the bottom.

The bottom of the external boiler was riddled with pinholes and three significant holes. The leakage began about a week after the annual service to remove the Coffee Grounds (aka Black Rice, Mouse Turds) debris. I am in Portland, Oregon, where we had weeks of record high temperatures for October and November, so lack of heating was not a hardship for the homeowner.


Has your boiler been regularly cleaned? Note the photo of the boiler just after removing the firebox cover to see a two-year accumulation of coffee grounds.

I had a local stainless sheet metal fabricator know for their excellent work building restaurant fixtures (Summit, Inc.) remove the entire radiused bottom section of the boiler and replace it with two gauges thicker of 316L stainless steel. Only about 1/4" - 3/8" of gap exists between the outer jacket and the water coils, so great care was needed removing the rotted old bottom.

Inside the boiler held a surprise. There was a block of solidified coffee grounds that looked like a Vibram cleated boot sole of a size 12 hiking boot where the cleats were where the coffee ground debris went up between the gaps in the water coils. This 199M V1 Munchkin boiler has a number of engineering errors:

Error #1 - There is a flat step at the back of the plastic boiler housing that has the effect of tipping the boiler forward about 1" from back to front. Since the condensate outlet is at the rear of the boiler, the front of the boiler is always immersed in sulfuric acid water, and coffee grounds will naturally collect there.

Error #2 - The condensate discharge fitting is too long to the inside and sticks up above the internal floor of the boiler so even if the boiler had been made to be level, sulfuric acid laced condensate would still be keeping the bottom of the boiler perpetually wet.

The perpetual immersion in acidic condensate and the coffee ground debris virtually guaranty these boilers will fail. HTP provides replacement heat exchangers for some of their boilers, but not all. If you have TIG/GTAW welding skills, I can offer you more advice on how to rebuild the heat exchanger and correct the engineering errors at reassembly.

kcopp

Nice work and good observations... but by doing are you not taking a huge liability?

jpcallan

I don't think liability is a worry. The client is my former dentist of 25 years, now retired. He is a personal friend. I would never have tackled this job for just anyone. We worked side by side on the overhaul. For the first time since I installed the boiler for him in 2004, it now not only operates, but looks right. This was my first Munchkin install and I didn't have the technical sophistication and experience to question some of what I saw that looked odd back then.

There was a lot to do to get the Munchkin 199M back on line besides the new welded bottom.

Summit Inc. machined the condensate outlet shorter to remove the burm that stuck up proud of the boiler's bottom. Now the condensate flows out freely.

The strapping that holds the round manifolds in place had to be remade as adjustable. When the boiler was originally installed in 2004, the heat exchanger clearly leaned to the right, while at the same time on the left side, the inlet and outlet nipples both pitched downward instead of being perpendicular to the side of the boiler. We made a Teflon bar (7-1/2" L x 7/8" H x 3/4" W) that now sits under the front of the boiler on its long axis and holds it up so it doesn't tip forward. The bar is held in place by three countersunk stainless wood screws. This unit's Giannoni heat exchanger uses heavy stainless pipes flatted on one side as manifolds. The three stainless straps pull more down than inward, so the inlet and outlet connections pitched down. We made a telescopic pair of flat bars that are welded to the rear of the two manifolds that keep the manifolds exactly perpendicular to the boiler.

The manifolds have 1" female NPT threads cut into the left manifold. This is the worst threading job I have ever seen in a manufactured product. These female threads had sometimes three consecutive threads ripped out entirely. There was not one entire 360 degree rotation of thread that didn't at least part of the thread torn away due to galling. I don't know how this ever got shipped or how HTP could have chose to use it. The bronze reducing nipples were factory installed loaded with Teflon tape and about a tablespoon of a hardening yellow pipe dope to make them water tight.

The Clamp-All Hi-Torq 80 stainless and black rubber exhaust connection at the rear of the boiler had partially burned out and a small leak was allowing exhaust into the house. The unit is installed in a tiny closet with no room to allow a full inspection. I used a 3-1/2" x 3" high temp silicone tube from a hot rod mail order house to reline the coupling so it will never burn out again.

This boiler is better than the day it was made.

JUGHNE

Jp, how old was this Munchkin?
By rebuilding part of the fire chamber of a water tube boiler, even though it was only the drain pan, would be the liability that kcopp mentions. FWIW.

Now the mystery of the coffee grounds; many theories abound.
The latest to contemplate is that the PVC is outgassing from high temp, with the condensate flowing back into the boiler and than that combining with products of gas combustion.

Or rebreathing exhaust gases back into PVC combustion inlet which would attack the chamber with contaminated air being burned.

I have found coffee grounds in both Munchkin and Lochinvar water tube boilers, every year.

Tinman

If my dentist of almost 3 decades gets a hole in his HX, he's getting a new boiler and without any discount.

Mark Eatherton

I hope you didn't use the Clorox in cleaning the heat exchanger. It will cause chloride stress cracking and additional SS failures...

NY Plumber has been using air filters on his modcons, and has said that it completely eliminates the crud associated with combustion.

ME

jpcallan

I have my theories on the origin of the coffee ground like deposits. The boiler I just overhauled went online about February 1st of 2005 in Portland, Oregon. Portland has a mild marine climate, so this boiler never works really hard, like one say in Toronto. This installation used an oversize 4" concentric vent kit pointing straight up through the roof. There are no dormers or other roof obstructions that might cause eddies and direct the exhaust back at the air input.

If you've read the cleaning instructions in the various editions of the Munchkin manuals a physical description of the coffee grounds or composition of the coffee grounds is no where to be found. I've saved samples and sent them off to the local gas utility with no reply. The character of the deposits have changed over the years. For this boiler, originally they were mostly very black. A few years ago the coloring shifted to more reddish. This last cleaning, the coloring was mixed, mostly reddish and black, but also a noticeable quantity of greenish coffee grounds.

After years of cleanings, I have come to believe CLR and Rydlime are almost a waste of time. Have you ever let coffee grounds soak in CLR or Rydlime? This last cleaning I used Rydlime, then flushed until the flushing water was clear; I then switched to concentrated phosphoric acid, plugging the condensate outlet and letting the acid work for a couple of hours, again then flushed with a garden hose - huge gobs of debris poured forth. After removing the bottom of the boiler during the overhaul, pounds of solidified deposits remained at the front. I now think a stainless steel pickling agent like Bradford Derustit SS-3 Liquid Stainless Steel Pickle, is the best way to not only clean the boiler of all deposits, but also passivate the 316L stainless steel and greatly improve its corrosion resistance. This is a potentially dangerous product to work with as it is mostly nitric acid, but I think the results may warrant the care required.

jpcallan

Mark Eatherton said:

I hope you didn't use the Clorox in cleaning the heat exchanger. It will cause chloride stress cracking and additional SS failures...

NY Plumber has been using air filters on his modcons, and has said that it completely eliminates the crud associated with combustion.

ME

Your remarks about Clorox or any chlorine-bearing product are spot on, and NO chlorine bleach or other chlorinated products were allowed anywhere near the boiler.

I have often wondered about airborne contamination as a cause or at least a major contributor to the coffee grounds, and have been nursing the idea of getting a monster air cleaner from a heavy truck junk yard off a Kenworth or Freightliner, and ducting it into the mouth of the gas valve.

Mark Eatherton

Awesome. A person in your position could make a great living servicing modcons, because no one else is...

ME

Tinman

Some are.

Harvey Ramer

Oooyyy! Did I ever get fussed at for doing this. But it was like giving chemo to a cancer patient. The boiler has remained in remission in spite of the dire predictions by the naysayers. I didn't do the original install, just the air filter and boiler repairs. I was raised on a farm and have first hand knowledge of what kind of crap is in the air around these freestall cow barns.

EBEBRATT-Ed

Welding a boiler HX is a huge liability and it no longer meets ASME........Just sayin

JUGHNE

The coffee grounds I come across will stick to a magnet, what's that all about?

I use the credit card saw, (cut some notches in it) and can feel the crud being cut away. But can't see under the bottom of the coil, only flush with hose sprayer to rinse away.

Harvey is that a dairy vacuum pump inlet air filter?

Harvey Ramer

Jughne
It is an air cleaner from a semi truck.

The coffee grounds are from the metal of the hx ,according to manufacterers. Not from an outside source.

JUGHNE

I am thinking they did not put much extra metal in the HEX, so these are all slowly being eaten away??

With your filter do you still get the coffee grounds?

hot_rod

Axiom sells a cleaner for the fireside of these boilers now, they talked about it on the recent RPA webinar. It sounds like a good addition to the brushing to get the metal back to new condition for optimum heat exchange.

Harvey Ramer

According to manufacturers, that is correct. They are slowly being eaten away. They still have a generous life expectancy, but it's pretty much a certainty they won't entertain the life of a cast hx.

That boiler is a fire tube. I haven't seen coffee grounds in a fire tube.

Alan (California Radiant) Forbes

I service Munchkins continuously and given our Mediterranean climate, get varying amounts of coffee grounds. Even though I badmouth Munchkins, they seem to hold up; even the one in my basement (50M) that heats my 1,200 [] Berkeley bungalow along with my Viessmann indirect for the past 10 years; I'm impressed.

We never use CLR on the drain; always water. Just keep on pouring until it's clear.

I carry replacement circuit boards and blowers with me whenever I service them along with igniters, flame probes, refractories, target walls............ I've even got a few of the original, flashing light circuit board models on my route. Still going strong, but I step lightly and don't look at them sideways.

After Glowcore and Hydrotherm Pulse, Munchkins were the bee's knees. But on new installations these days, I don't do HTP; too many bad memories. I stick with TT, Lochinvar and Viessmann. Just my 2₵.

West Coast radiant is a piece of cake compared to you East Coast and Mid-Westerners and I am in awe of your prowess. Freezing temperatures, glycol..............whew!

xxoo

hot_rod

Assuming the burner is dialed in properly, I thought the coffee rounds were a result of the air they breath?
Roadway dust, pollen from trees, or re circulation of combustion by products

Harvey Ramer

Well, if it sticks to a magnet, it's gotta be metal of some sort. Could be that what it breathes has something to do with the speed of the process. I don't pretend to know. One of the last gianonni boiler classes I sat in, they said they sent the coffee grounds to a lab to be analyzed and determined it contained material from the hx walls.

hotwaterheat

Every boiler that uses that heat exchanger ( munchkin, knight, Laars, NTI, etc) seem to accumulate those "coffee grounds". Well at least every one I have serviced. I just vacuum them out, run a plastic bristle condenser brush between the tubes and flush it with water. Seems to clean them pretty well. Just make sure you clean the condensate trap too, lol, or you plug it up with the crud.

kcopp

I see them (coffee grounds) a lot here. Not just in Munchies but in other coil SS hx ... Just saw this in a Embassy onex this week.
A scotchbrite pad w distilled vinegar helps get the scale off the HX. I do make sure to flush it all out and pull the trap off and give it a good flush. The stuff is pretty greasy.

jpcallan

Mark Eatherton said:

I hope you didn't use the Clorox in cleaning the heat exchanger. It will cause chloride stress cracking and additional SS failures...

ME

I forgot about the Clorox bottle in the 2nd photo, and owe you comment on what is pictured. I apologize for the confusion.

The phosphoric acid I used to clean the boiler a few days earlier loosened or dislodged the heavy cake of coffee grounds covering the front of the insides; the acid and dissolved coffee grounds oozed out of the three larger holes in the bottom of the boiler and dozens of pin-holes, partly saturating the fiberglass insulation. In the photo we were cleaning the acid goo from the boiler and were about to leave for the stainless fabricator to have the bottom cut off and replaced. So yes, a chlorine cleaner was used, but on a part of the boiler that was about to be cut away and discarded.

jpcallan

For those that are interested in the lifespan of the rebuilt Munchkin 199M V1... it just keeps soldiering on. Its been in service for 15 year, 3 months. No leaks in the heat exchanger or the replaced lower outer jacket.

Sadly, my good friend (and boiler owner) Dr. Rushford died in the fall of 2018. The Munchkin continues to keep his widow warm.

The only problem with the boiler since the stainless jacket replacement is the controller died because the PC board cracked. The transformer's weight and a poorly designed mount caused it to stress the board and eventually crack, breaking several traces. I came up with a new and rigid mount design using PC daughter card standoff posts to hold the new controller PC board firmly and prevent flexure. See attached photo.

o.

hot_rod

wow, how do you keep it so clean It looks like the day it was installed.

HomerJSmith

Ya! really clean.

jpcallan

Thank you for noticing and the kind words. The Rushford's are dear friends; I give them my best effort. The boiler was rebuilt in 2016, so some of the tidiness is no doubt left over from then.

Each fall it gets vacuumed thoroughly on the outside and inside. The inside gets cleaned with my shop-made pick tool to get all the black rice between the water jackets.



Some years I go over the interior with a fine stainless wire wheel on a long-reach die grinder. After wire wheeing, it gets flushed with gallons of tap water, normally followed by Rydlime; although lately I changed to cleaning with phosphoric acid mixed 1:1 with water. This is the same acid used in Coca-Cola and liquid toilet bowl cleaner, and no threat to 316L stainless. The phosphoric acid wash does a substantially better job of removing adhered crud. Another flushing with a garden hose spray gun, then back together it goes.

Working on this boiler installation is something like watchmaking - the boiler closet is almost that tiny.

Gboiler

I have a munchkin 199M boiler that needs repair in Portland Oregon

any chance you could work on it?

the service tech says needs a new heat exchanger ...no longer available
looks like it needs just what you did in the post here.

EBEBRATT-Ed

@Gboiler

If the heat exchanger is leaking then you need a new boiler. If it hasan't been cleaned in a long time you may not be able to save it. Is it leaking?

mattmia2

The replacement model for that boiler has been discontinued, at its age it doesn't make sense to repair it even if you could find the HX. It is time for a new boiler.

Tim_D

ASME applies to pressure vessels only. Replacing the none pressurized shell would not effect the ASME rating.

Gboiler

the heat exchanger does not leak and some cleaning and continued use makes a lot of sense compared to the $15,000 a new boiler costs with install.