So Why Did MY Munchkin Leak?

Brad White_191

First of all the pressure sounds way too high- adding a 125 pound relief valve on what should be a 30 pound boiler is like putting a penny in a fuse box. You are losing all protection. Right of the bat, if I were the manufacturer I would tear up the warranty. Forget what caused the leak, that pressure is not helping you. Randy is right, about 40 pounds at most and that requires a higher than standard pressure unit rating.

Also, little things are important like not using dielectric unions, stuff like that. I agree with Tom what did the manufacturer say? Nothing we really could add to that without seeing the install.

EDIT- just saw your other post that you did talk to mfr.

Jim_108

why did munchkin leak?

Ok so I just finished installing a new replacement(3 year old) Munchkin 399 boiler. Can't figure out why it leaked. Its piped correctly ie. primary/secondary no other problems since I installed it. The only thing thats somewhat unsual is that the engineer that is running the building is rumming about 90lbs psi on the closed loop. I have asked him to bring it down cause it is only 9 story build. Any ideas out there?
Thanks
Jim

kpc_49

90!

is that a typo...

Randy_30

what model 399

Were is it leaking and has the relief been upgraded to handle the extra pressure. Unless it's a VWH model (rated 150psi)the relief is rated for 30 and on a 9 story building you need 36-40psi.

Jim_108

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

Randy_30

Two things

The two things that I've seen is bad water chemistry or a flow problem. If the boiler is going to steam it will stress the boiler and crack the exchanger over time (like a year). If it is truly a pinhole than I would focus on water quality.

Jim_108

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-

Randy_30

It's extremely rare that there is a defect but yes its possible. You need to rule out the other two items so you don't go down this road next year.

tim smith

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.

Mark Hunt_6

You have issues

Have you contacted HTP? What did they tell you? Do you really think anyone on this forum will be able to diagnose your issue? If you haven't contacted the manufacturer, you had better do so and let THEM tell YOU how to keep this from happening again. Your system sounds totally screwed up and you are just changing parts rather than fixing the real problem. Tom

Jim_108

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

Mark Custis

One needs

to watch what you get here on weekends.

I vote lower the pressure or sign off on any future leaks.

Jim_108

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

jcarta

boiler

the 399 munchkin boiler he is talking about is a commericial munchkin-it has a rating of 160 psi working pressure-it is not a residential model-the residential model is only rated for 30 psi

Brad White_191

Pressure

Did not know it was good to 160- I usually assume 30 res. or 60 comm. with the right ASME stamp on it. Had not seen one that high, new to me.

Leaks all over the building? Not just the boiler? That has me more worried, the boiler may be just a bystander.

The pinhole part of the story got me thinking about electrolisis (sp?) and how small leaks develop like that so I asked about the dielectric unions. Did you ask htp about those too?

Jim_108

Mike it closed loop just brown nasty water but no o2. The leaks are pressure related ie. weak sweat joints that normally would not leak. I repiped the feed on the building loop system a few years ago up in the penthouse and set the pressure up there at 10#. Everything was working ok, was pushing about 30 out of loop pump and ending up with about 40 in the basement 10 floors down. I made the mistake of installing a bypass and sure enough a week later he had the bypass open and I got 90# on the boiler. I called this guy on a friday night around 8pm after I made that discovery. I could tell he was in a bar due to the back ground noise. He gave me a real earfull about calling him "after hours" and hung up.That was about a year ago or so. Yea I think tommrow is his (or mine) last day in this building
Jim

Perry_5

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

Brad White_191

Agreed but

that the heat exchanger itself may be so rated but as far as the warranty, boiler code and conditions of a leak once started, having higher pressure than necessary cannot help matters? I was happy to hear that this boiler does carry a higher pressure rating than what they have though. But once they have a leak are you saying that pressure no longer matters? Agreed it probably did not cause it.

I am curious how you can say you do not know the reason yet know it will happen again at a point unknown. That seems to cover just about anything.

When you say that because the boiler can handle thousands of pounds, the other parts should be good as well? How can you possibly know? That was built by no one any of us probably knows.

Perry_5

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

tim smith

Chelini, you still have not answered the question as to

regular cleaning of combustion side, was this done. If this boiler is not cleaned at least annually, you will have a failure for sure.

Randy_30

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.

S Ebels_2

RE \"leaks all over the building\"

If the boiler has had continuous make up water added to the system, you may have a situation where fresh deposits of mineral are clogging or partially clogging the HX. This will cause a hot spot and eventual burn through. I would tell the building manger the leaks have to be taken care of or he'll likely lose another boiler in a couple years. i wonder if the leaks were present the entire time the previous boiler was in service or if they have shown up more recently

Jim_108

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

tim smith

Re: regular maintenance and proper combustion

Randy, I have several, not 1000s like you have but every one is set up right and I have found they block up w/ iron deposits if we go even to 15 mos or so. We service many more than we ever installed and the same holds true on needing annual service. I would be hard pressed to buy off that all of yours are clean as can be if never serviced. Not disbelieving you just my 1st hand experience in our area. Tim

tim smith

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

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

Jim_108

Tim, The loop pump,primary is located up in the penthouse(tenth floor) and the boiler and secondary pump are down in the basement. There is a check valve at the bottom of the primary loop. there are two tees and a cir pump that "inject" heat into the building loop for the water sorse heat pumps, basically this is a second primary loop that ties into the closely spaced tees on the secondary loop of the boiler. The second primary loop also continues over to a side arm heater that supplys hot water to a 1000gal tank for domictic hw. I use the side arm heater only in the summer as of now beacause I have to install a three way valve for the heating loop. When I install the three way valve I will increase the water temp from the Munchkin to 180f from 90f and will use the Munchkin for both systems. The 1000gal hwh is equiped with eight 18kw elements for winter heating. I don't know why a three way valve was never installed. I just walked into this building three yr ago on the first Munchkin install. I hope you are not sorry you asked. I wonder if the piping arrangement had something to do with my hx fail. I took a close look at it today, could not find a hole (looking down into the combustion chamber) but it was easy to tell where the leak was by the lime etc deposits. In that area the round coils were sorta flat, like someone took a hammer flattened them and then wound them back into the shape of a coil?????
Now do you see why I am worried?
Thanks
Jim

Randy_30

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.

Randy_30

The only system I saw leak would only leak when it was warm. if it was cool the metal would contract and seal itself. Like you it was obvious that there was something wrong due to staining on the burner.
When your talking about flat like someone hammered it is that on the face pointing to the burner or on the sides. if it is the face something is wrong. Like someone used a hammer to knock of calcium build up or something....HMMMM

Jim_108

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

Randy_30

That does sound like a material defect. Who did you talk to at HTP and what was there response?

Big Will

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.

Perry_5

Probably not a defect - the tubes are \"Squashed\" by design

During Mfr the tubes are squashed pretty flat.

The Mfr who makes this HX has a video of the process on their home page - after you get past the first minute or so of building shots...

So get some popcorn and enjoy the movie...

http://www.giannoni.fr/

Perry

Randy_30

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.

Randy_30

I'd put a $100 on bad water quality...

Perry_5

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

tim smith

Randy, again 1st hand knowledge. We have found pinholes under

the (coffee grounds) ie iron deposits. This was referred to in the epic thread by Perry. This is what I have seen. PS, Seattle, natural gas.

Wayne_29

Good call Perry

Couldn't have said it better myself!

Brad White_191

But

hard water (lime) also creates hot spots on the heat exchanger surface and can that be a good thing? Flashing to steam? Does that not, over time, cause damage beyond plugging?

Wayne_29

Because it's a HTP product

right?

Perry_5

Not normally

Scale deposits and hot spots were not a normal issue with iron or steel tubed boilers.... Why would they be for SS (keep in mind that Stainless Steel is nothing but a modestly modified form of steel).

The material in this case has the basic structural strength to actually handle the production of steam (same as steel) - and even handle the production of steam with a scale layer (just like steel). 304 SS tubes are commonly used in industrial steam generation heat exchangers (reboilers). The difference is that in industrial settings control of impurities and trace elements is such that they are not worried about pitting or cracking attacks on the SS tubes.

If you cannot control these impurities and trace elements their are different tube materials readily available - if you cannot use a normal steel alloy: Depending on the impurities & trace elements the most common groups of alloys looked at are the Superferritic SS alloys [AL 29-4C, SeaCure], Inconel, or Hastalloy. There are also about a dozen other lessor common alloys readily available.

So no - you would not normally expect hot spot damage on a SS tube just from heat - even with scale - unless you get to the point where you have bulk metal temperatures above 1000 F (which is almost always caused by lack of water inside the tube).

However, many of the various forms of chemical attack that 300 series SS is succeptable to (and normal steel or Iron is not) - do in fact happen faster at hotter temperatures. Thus, they progress faster in a tube with an inside deposit or scale layer because the bulk tube temperature has gone up modestly.

Edited to add: Hotspots under scale are more of a potential problem with Aluminum due to its lower material strength transition and melting point. You could much more easily sag or melt an aluminum HX that had heavy scale on it in this application.

Hope this helps.

Perry

Wayne_29

Are you sure?

?