3rd failed heat exchanger in Burnham Series 3

bmc321

We just had a 3rd heat exchanger fail in our Burnham Series 3 boiler. The first one lasted less than 5 years, the second less than 2 years, and this one is less than 4 years old. Definition of insanity.
US Boiler replaced the first one & we paid labor. The second time, we got a whole new boiler for free.
This time, our heating company took water samples and the boiler system water came back highly acidic. Our tap water tested fine - we live in a city. Unclear why acidity would cause a thick cast iron heat exchanger to crack...seems more like a thermal shock issue? Not to mention, why is the water so acidic in the boiler system?
Seems US Boiler may not honor the warranty this time however...and our contractor is being evasive. It has been a month already and we've gotten NO answers.
Everyone tells us this NEVER happens.

Jamie Hall

I would agree -- three cracked boilers in that span of time does look like the definition of insanity. It also looks like you -- or somebody -- needs to look beyond the boiler for the problem. This is a hot water boiler, yes? What, if any, treatment are you using in the boiler water? What materials are used in the rest of the heating system -- pipes, valves, etc. What controls do you have available and operating to prevent slugs of cold water getting to the boiler when it's hot?

bmc321

Yup, hot water, gas fired boiler.  We have mostly radiators, but added 2 small bathroom hot water, in floor heat 10 years ago. 

There’s a mixing valve to prevent cold water from shocking system on return. System was most recently drained & refilled a year ago after said mixing valve failed. A F-1 system cleaner was added then. 

House built 1919 for what that’s worth. 

pedmec

cracked or pitting from corrosion

pedmec

?

bmc321

I think it’s cracked. Leaking small amounts of water steadily. 

kcopp

Do you have some pictures of the set up?

bmc321

MikeL_2

   What type of tubing is installed in the radiant floors?

mattmia2

Especially the tubing for the radiant floor and any markings on said tubing.

clammy

I would gather that the mains are large and even though it s not a gravity conversion I would think you have a hi water volume in your system the addition of a danfoss thermic return valve would be in order to protect against prolong operation below flue gas condensation temperatures . As for you acidic water in the system water that may be the product of the water treatment they added personally it is a simple ph test that you yourself could do and if they did not flush the system and add a cleaner and flush again and test and add a inhibitor then it possibly bull to cover there butts . What type of floor radiant tube was used ? If your drink water where acidic you would certainly see pitting on your water lines . I would guess your on well water due to the fact most if not all supplies water systems are never to much below neutral pd 6.8 to 7.5 in my experiences ? I have only seen acidic water from well systems and usually the first time is the replacement of the steel welltrol tank w a fiberglass type . . Personally at the 3 boiler i would have zero confidence in the installer and from the looks of the install I would not personally have put my name on it . Do you know if they did a heat lose or a edr on the existing radiators to determining the proper boiler size? I ve been in the heat business for close to If not more then 35 years and I ve yet to see a boiler go so often as for it relating to he boiler quality so it’s either cold return water shock from the way it zoned and piped ,running prolong at below condensation temps or possibly a combination of the 2 .
At the 3 rd boiler I would suggest find possibly a better heating contractor who is a lot more knowledgeable then who you have for sure
Peace and good luck clammy

bmc321

We live in a major metro area - city water. Our tap water tested fine. The tubing for the radiant floor heat is pex. 

Glycol was in the system for awhile due to some frozen pipes, but after adding insulation around those pipes, that has theoretically been flushed out of the system. 

Jamie Hall

This is a closed system. If what you have is PEX, and not oxygen barrier PEX or PEX-Al-PEX, however, you are getting oxygen diffusing through the pipe wall into the circulating water. Unless you have an effective corrosion inhibiting treatment in the water, and maintain it, that oxygen will attack any metal -- particularly the boiler -- and cause pinholes which leak. Further, if there is even a trace of the old glycol which hasn't been flushed out, that will cause the water to be very acidic -- which won't help.

Your feed water composition is almost irrelevant, unless it has high chlorides (which you don't mention -- city water often does) which also attack unless there is an effective corrosion treatment.

That you have tried three boilers in a short time. Those boilers are high quality. That all three have failed on your system in much the same way suggests to me that the problem isn't the boiler, it's the system.

bmc321

Thank you for all your thoughts. It is oxygen barrier pex. I have no idea about the chloride levels in our water. 

We’re not getting any joy from our heating company and the little they have said is that Burnham won’t replace due to acid levels. But heating company created whatever levels are in there when they refilled it a year ago?  And it doesn’t seem like acid should crack an inches thick heat exchanger after only a few years?

We’ve spent $$$$ on this over past 10 years. Beyond angry. Yes, clearly we need a new heating contractor.

Sorry to complain, but honestly, I’m a mom who knows way too much about her boiler. And I still don’t understand much of it.

I appreciate all your wisdom. Thanks again 

Jon_blaney

How many zones? Is the in-floor on a zone seperate from the radiators.

GGross

Not every time, but generally speaking if it was water quality killing your boiler you should see other component failures of items that are ferrous metal (changing pumps constantly for example). I am not one to make assumptions, but it sounds more like a thermal shock issue to me.

Enough about that though, we can all troubleshoot this thing remotely and it will do you no good. What you really need is to get a new heating contractor in there, someone with excellent reviews and a focus on hydronics. No doubt anyone worth their title would be able to determine what is causing your failures, that should be step one. Then they can replace your boiler. It never hurts to try warranty again either.

bmc321

5 zones, and yes in- floor has its own 2 zones (2 baths). Kitchen toe kick blower, basement, and rest of house are the other 3 zones. 

Pump has been fine but we did replace the mixing valve a year ago. 

Off to find a new heating contractor. 

Thank you!

clammy

Just a though has your heating contractor removed the boiler jacket n possibly burner tray to try and locate where the leak is . I ve had it where the piping into the boiler was leaking behind the jacket ,also stay rods being loose . If it where I ,I would be trying to locate the leak and confirm . I de also be looking into system water volume ,looking at there piping I’m not to impressed . Peace and good luck unfortunately clammy

Jon_blaney

I do not know how but would guess that one or more of those small zones is calling for heat, the boiler gets hot and them those old gravity zones calls for heat and dump large amounts of cool water on the boiler shocking it.

pecmsg

bmc321 said:

Thank you for all your thoughts. It is oxygen barrier pex. I have no idea about the chloride levels in our water. 

We’re not getting any joy from our heating company and the little they have said is that Burnham won’t replace due to acid levels. But heating company created whatever levels are in there when they refilled it a year ago?  And it doesn’t seem like acid should crack an inches thick heat exchanger after only a few years?

We’ve spent $$$$ on this over past 10 years. Beyond angry. Yes, clearly we need a new heating contractor.

Sorry to complain, but honestly, I’m a mom who knows way too much about her boiler. And I still don’t understand much of it.

I appreciate all your wisdom. Thanks again 

MOM
Dans got quite a few books that will give you a better understanding of what’s going on. 

Possibly more then your service provider!

pedmec

i doubt thermal shock. cast iron is not gonna get that hot with the water circulating and pulling heat off of it. unless there is a delay on make relay for the circulator, causing it to have delayed start but i doubt it. judging by the size of the piping and that he has cast iron radiators i'm guessing that your getting a lot of condensation of the flue gases on the cast iron. your return temperatures are most like coming back to cool and are cooling the flue gas temperatures below the dew point of the flue gas. depending on the sizes of the radiators you can heat your house with the lower temperature supply water most of the winter. some heating systems never see 180 degree supply temperature until it gets below 20 degrees ambient. i can't tell if there is a system bypass or three way mixing installed or ball valve bypass. you need something to increase the boiler temperature to prevent the condensation.

you need to break the boiler down to locate the leak. if its from the condensation it most likely will be under the flue collector hood. as most everyone has stated you need to get a good company in there to see where its leaking from. this will give you a better idea of whats happening. a crack is different from a corrosion hole. you don't need a fourth heat exchanger leak.

i would suggest a stainless steel mod/con but certain acids would eat that up too if its the boiler water. but i'm in agreement with gross that you would most likely see other failures on your ferrous metals. i truly believe your corroding from the outside in. rip the jacket off and whatever else you need to do to expose the leak. good luck

mattmia2

I was also thinking condensing when i saw the converted gravity system. Now I'm wondering are you sure it is leaking and it isn't just condensation?

Tinman

pedmec said:

i doubt thermal shock. cast iron is not gonna get that hot with the water circulating and pulling heat off of it. unless there is a delay on make relay for the circulator, causing it to have delayed start but i doubt it. judging by the size of the piping and that he has cast iron radiators i'm guessing that your getting a lot of condensation of the flue gases on the cast iron. your return temperatures are most like coming back to cool and are cooling the flue gas temperatures below the dew point of the flue gas. depending on the sizes of the radiators you can heat your house with the lower temperature supply water most of the winter. some heating systems never see 180 degree supply temperature until it gets below 20 degrees ambient. i can't tell if there is a system bypass or three way mixing installed or ball valve bypass. you need something to increase the boiler temperature to prevent the condensation. you need to break the boiler down to locate the leak. if its from the condensation it most likely will be under the flue collector hood. as most everyone has stated you need to get a good company in there to see where its leaking from. this will give you a better idea of whats happening. a crack is different from a corrosion hole. you don't need a fourth heat exchanger leak. i would suggest a stainless steel mod/con but certain acids would eat that up too if its the boiler water. but i'm in agreement with gross that you would most likely see other failures on your ferrous metals. i truly believe your corroding from the outside in. rip the jacket off and whatever else you need to do to expose the leak. good luck

And if it is condensing, that may explain how the contractor came up with the acidic water story? As the OP said, the water quality is fine. It’s easy enough to check your tap water versus what’s dripping on the floor. 

bmc321

Yes, our tap water pH is fine. Boiler water pH very low/acidic, around 4. Original contractor has spent all of 30 seconds looking at it. We’re getting bids/ideas from new contractors. Frustrating, because we’ll wind up paying for everything if we go with a new contractor. 

Also, they measured total dissolved solids in boiler water, which are very high. 150, I think. 

bmc321

Correction - Total dissolved solids measured at 301ppm.

Jamie Hall

Assumptions. Can send one off on a possibly odd trail.

@pedmec had a very good observation up there. Are we sure that the technicians are measuring the pH of the heating water, and not condensation from a presumed "leak"? No, in fact, we are not. Worse, it would appear that no one has actually verified that we have a genuine leak.

Let's go back and check that first: Exactly how much makeup water is being used by this system? If there is no water meter on the makeup line -- which there probably isn't -- note the system pressure and then close the shutoff valve on the makeup water. Then observe the system pressure over time. Has this been done? If it has, what were the results?

EBEBRATT-Ed

And previous glycol use that was not flushed properly, glycol can cause acidic water...especially old glycol

bmc321

I'm back again....not much progress to report. We've now had 2 new contractors come out to take a look and give us a quote. But none of them are willing/able to diagnose the problem. And frankly, they're all hesitant to do any work on our system at all (including replacing the boiler).
I'm waiting to hear back from the city inspections office to see if they have any ideas, but thought I'd check back here to see if anyone here might have suggestions? I've also reached out to a local private testing and inspections company to see if they can help diagnose.
If heating contractors can't diagnose this problem, who can?
Obviously, we'll get a new boiler at some point here, but it seems silly to keep replacing if we don't know what is causing 3 heat exchanger to crack.
And the local Burnham distributor is ignoring us, too.

mattmia2

Did you ever determine exactly where it was leaking? Does it continue to leak if you don't run it and keep it at pressure? You could even open the fast fill lever and let it get up to just below the relief valve setting. If it really is leaking it likely will leak and continue to leak if you let it sit under pressure for days.

On the other hand if the controls are set up so it is running short cycles and is satisfied without ever getting all that mass of water, pipe, and radiators very hot it may condense whenever the burner is on unless there is a bypass at the boiler to keep the boiler hot especially when the outdoor temp isn't near design conditions.

GGross

bmc321 said:

I'm back again....not much progress to report. We've now had 2 new contractors come out to take a look and give us a quote. But none of them are willing/able to diagnose the problem. And frankly, they're all hesitant to do any work on our system at all (including replacing the boiler).
I'm waiting to hear back from the city inspections office to see if they have any ideas, but thought I'd check back here to see if anyone here might have suggestions? I've also reached out to a local private testing and inspections company to see if they can help diagnose.
If heating contractors can't diagnose this problem, who can?
Obviously, we'll get a new boiler at some point here, but it seems silly to keep replacing if we don't know what is causing 3 heat exchanger to crack.
And the local Burnham distributor is ignoring us, too.

If I am not mistaken there has not really been much done to troubleshoot this beyond the fact that there is water under the boiler. Has anyone actually found a crack in the heat exchanger? Has it been confirmed that we are in fact dealing with a leaker, and the water on the floor is not stray condensate (still a problem) but is in fact water from a leak? That should be step one. You can't solve a problem until you first know what the problem is.

bmc321

No one has been willing to even look inside the boiler. We're in Minnesota and spring has not sprung here yet, so we've been running it.
Maybe this week now we could shut it down to see if it continues to leak.
It started leaking in mid-March. We've added water twice since then to maintain at about 20 psi....it's now back down to about 15 psi.

mattmia2

That doesn't seem like a leak you would notice if you have only added a few gallons in a month and a half. What makes you think it is leaking at the boiler?

It is leaking a little somewhere if you have lost pressure but that is likely at a valve or pipe joint and leaking so slowly it evaporates faster than it is leaking.

Mid march would be when the heat load would get smaller and condensation problems would get worse because of shorter cycles.

bmc321

There’s fresh (rusty) water on the basement floor every day. This has happened twice before (Dec. 2017 & late 2018) and was replaced under warranty both times. 3 contractors have been here this spring and no one has questioned that the heat exchanger is cracked. 🤷‍♀️

mattmia2

Open that valve on that diagonal pipe across the top all the way and see what happens.

Jamie Hall

I hate to say this, but if you have only added water twice since mid March, @bmc321 , you do NOT have a major leak in your heating system. Period. Regardless of what your three contractors say. Nor do I doubt that you are correct in saying you have fresh water on the basement floor every day.

Since, however, you are totally determined to blame the boiler, go for it. Put in a nice new boiler. Then when you are done with that, find the actual leak and fix it.

STEAM DOCTOR

Replaced a bunch of leaking boilers over the course of this heating season.  Those customers were adding water more then 2X a day. Does not sound like a boiler. 

GGross

@bmc321 Have you tried the contractor locator on this site to see if there are any contractors on here in your area? I feel bad you are getting the run around from so many, there must be someone who knows how to properly service boilers in your area.

STEAM DOCTOR

My bad. Didn't read carefully. You have hot water, I was talking steam. Boiler is dropping from 20 PSI and maintaining 15 PSI? Certainly does not sound like boiler is leaking. 

pedmec

To give you an example of what we are trying to tell you so you don't get really frustrated. Shut the gas off. Drain your water heater (i'm assuming you have a tank type, natural draft) completely and refill with cold water. After bleeding all the air out turn the gas back on and the thermostat up to have a demand. listen closely. You will hear snap, crackle, and pop. flame turning yellow. sizzling. and walla, mostly likely water on the floor. Is it a leaker? no its not. its flue gas condensation due to the cold water reducing the flue gas temperature below the dew point. it is a normal process. this is what could be happening. but without taking the jacket off the boiler its just educated guess. TAKE THE JACKET OFF

mattmia2

Another way to test this is to disable the circulator and let the boiler heat up to high limit. That will thermal cycle the boiler without the mass of the system water causing potential condensation. If there are valves to the system, shut them to make sure you don't get gravity circulation but make sure the boiler is still open to the expansion tank. If it still leaks there is a leak somewhere. If it doesn't leak it is probably condensation.

bmc321

Thanks for the tips. I’m only reporting to you what my heating contractor told me - that it’s a cracked heat exchanger. I know very little about any of this stuff. 

Contractor & Burnham are offering us a discounted replacement boiler or heat exchanger- details TBD. Obviously we’re not getting a 4th one of the same ilk without understanding the problem at hand. 

I’ll keep searching for someone who’s willing to look under the cover - like I said, 3 contractors out so far (including the original) none interested in investigating.