So Why Did MY Munchkin Leak?

90!

is that a typo...

When I installed the unit three yr ago I put a 125# relief valve. The unit leaked on the coil inside. I discovered the leak the other day on a no heat call. I got a signal of flame fail and when I took out the flame rod water came out of the hole beacause the drain was clogged. I cleared the drain and restarted the boiler. At that point I decided to clean it and when I removed the burner I could see a pinhole leak spraying across the cumbustion chamber. I changed the boiler today and am really worried about this happening again.
Thanks
Jim

Hmm I don't know. I have a good chem co. in that building, they do a lot of other buildings I am involved with. As faf as flow the boiler is in the basement and the loop pump and fill/expansion tank are all the way up in the penthouse. I have a b&g pl66 pump on the boiler.
The leak wasn't really spraying but there was flow at enough rate to go from about 10 oclock to about 4 across the cumbiustion chamber. I think with the burner on it was getting real steamed up in there. Could it just be defective?
Thanks
Jim-

Chelini, how often did you open up the boiler and clean out heat

exchanger, trap etc. I am guessing not since install?? If not then read the lonnnnnng thread by perry which talks about under iron deposit corrosion. Left that long with acidic moisture sitting on top of deposits, that will eat right into the stainless and bye bye to heat exchanger. If cleaned at least annually they might make 10 yrs is what might guess is.

Tom, of course I have contacted HT. I explained the installation and problem. All they told me was a heat exchanger is not replacable and to replace the boiler which I did. What sounds "screwed up" about the system to you? When I installed the Munchkin 3 yr ago I was replacing a Hrdro Pluse that had been in there for 15+ yr. All I changed was the piping to primary/secondary and installed the hv pump (also increased pvc to4"). I bought the first Munchkin from Thos. Sommerville when I contacted them for a replacement I was told they won't sell any more Munchkins Due to "issues". I had to get this one from R.E. Michel as per HT co. I sure hope I am not going to get a run around on the warrenty. I really think I have it installed correctly. I been around 35+ yr and am very careful with instructions and installations. Also master D.C, Va.,Md.
This job sure does have me worried tho.
Thank for your input
Jim

Mike/ Mark, First thing I did was contact munchkin BEFOR I did the orignal install and discussed the high pressure. Their resopnse was "no probblem the 399 is rated @ 160 working pressure. The 125 valve is ok" I am going to have one more chat with this so called operating engineer(not sure if he hold 3rd class or not, law in D.C. I have 3rd but no time)if he still refuses to lower the pressure I am going to have the Mangment show him the door. There is leaks all overr the build. Not sure if 40# will do it though as this building has water sorce heat pumps and may need a little higher? I guess at this point I am going to consider the high pressure the most likley suspect. Calling HT in the AM
Thanks for your input guys!
Jim

It is not the presssure...

I would not worry about the pressure as it relates to the leak. The tubing the boiler HX is made of will not rupture until at least 5000 PSI and more likely 10,000 PSI.

Commercial HXs use the same tubing at multi-thousands of Lb of pressure - with no leaks even with 50% - 70% through wall pits.

As per mentioned above - the boiler is actually rated for this pressure so the other pressure parts should also be OK too.

While I cannot specifically state why this HX failed. I am sure that it is one of the reasons in my long post on practical mod/cons. As such, this is likely to occur again. Just don't know how long.

If you could, on close visual inspection - does this look like a pit or a crack?

Perry

Why I said what I said

Mike:

I am quite aware that the pressure rating of a boiler includes all pressure boundary parts - and not just the HX. In this case the boiler was officially designed to handle pressures at either 150 or 160 PSI, which is well above it current operating pressure. Pressure design and certification is actually for at least 125% of the nameplate design pressure under current ASME Code.

In this case - the other pressure parts includes the headers that the HX tubes go into, and any piping and sensors to the boiler connections.

I do point out though - that even if the rest of the boiler pressure boundary was not designed to handle this pressure - or up to thousands of PSI. The fact is that the HX coils themselves can handle that kind of pressure without leaking - so much as to make it a moot point in any discussion on leaks. If this was a pressure related failure I would have expected the leaks to occur elsewhere in the boiler pressure boundary.

As far as why this has no effect on leaks - and that it is likely to occur again (even if I cannot state exactly why it failed).

The failure is from one of 3 causes: Original defective material. Pitting. Cracking.

Defective material in HX tubing is very rare; and would not explain why a number of this type of boilers have been developing leaks.

Pitting and cracking are caused by specific degradation mechanisms. I consider the material that this HX to be constructed of - in the application it is being used for - to be vulnerable to a whole series of well known degradation mechanisms.

Whatever mechanism it was that caused the pitting and cracking is still there - unless things were reconfigured.

Waterside chloride pitting/cracking can be protected against by installing a carbon filter on the initial fill/makeup water.

Chloride leaching from PVC or CPVC condensate runback can be eliminated by not using PVC or CPVC for exhaust vent materials.

You can insure that you are using relatively clean air for the intake and reduce chloride (or halide) attack by proper sourcing of the combustion air (normally should be outside air - and away from a pool, garage, or area the can pick up chloride dust (sea mist, road-salt dust, etc).

But, even if you do all of that - I'm still not sure you can protect this construction from early failure due to other issues I see. See my post on Can a Practical Mod/Con be built.

Has anyone noticed that these post about failed HXs with this design appear with some regularity. When did this design boiler hit the market - about 5 years ago (does anyone have a better date).

Perry

I disagree! While regular annual service is a good idea this boiler will not fail in a year due to lack of service. My company has over 4000 out there through the state and i'm guessing 75% are not being serviced annually or ever. I open them up all the time and as long as the combustion is set right they look great inside. I opened one up that was 6 years old the other day and it was pristine.

Tim, I have never opened the boiler or serviced it. I am the contractor and that building is under contract to a company that claims to be operating engineer. This is the same company that insists that the pressure be at 90#. I went by there today to post a copy of my installation/gas permit (D.C.). While I was there I went up to the penthouse and adjusted the loop presure to about 65# ie. 8# in front of the 5hp pump up there. I would be willing to bet if I go by there tommrow the operating (so called) engineer will have the pressure right back up where it was this morning.
Jim

Chelini, where is the boiler located, basement or penthouse.

a little confused here. Are the pumps up at penthouse and boiler in basement?

Where are you located? This is a regional thing. I'm in CA (Big territory) and we do have a few in some metro areas that get this. We call it the coffee ground problem but there few and far between.
Are these natural gas or propane?

Please don't get me wrong service is good but I have never seen holes in HX due to lack of yearly service. There has to be another explanation. I'm still going with water quality. I bet there is high iron content mixed with high pressure spells doom.

Flat like looking at the coil and its pointed towards the combustion chamber. I am sure I am the first person to open that boiler.
I sent it back to Munchkin today. It will be interesting to see what they say if anything.
Jim

Make up water test

This is a must for me on any install. In my area I can get the water tested for free a few diferent places. I recenty had a 140M with three pinholes. The make up water was mean to say the least. A leaky T+P valve had make up water incoming for as long as six months. I am convinced this was the problem. Mean water + lots of fresh O2 loaded make up=bad things. In short a small leak means more than some wasted water.

Your right Perry but on the sides only if memory serves me. Not on the face! I show samples of the HX often and I don't remember them being flat on the face.

Not exactly .... but perhaps close

Excess O2 will not degrade the SS HX, and all normal hard water will do is scale the HX - and perhaps plug it up.

However, the fill & makeup water likely contains chlorine - and chlorine will pit and potentially crack the tubes - and do so faster under a deposit layer (hard water deposit).

Also, the water likely contains some bacteria - and other trace elements. These can also pit the tubes.

Small flakes of iron can also cause a pitting attack (this starts as a galvanic attack).

There are other issues that can occur on the fireside as well.

These mechanisms were not a problem with steel and Iron boilers (although excess O2 could rust them and they would still scale up). They are common issues with 300 series SS alloys - especially at elevated temperatures typical of a boiler.

Perry

Good call Perry

Couldn't have said it better myself!

Because it's a HTP product

right?

Are you sure?

?