Stainless Steel flue liner corroded

Steven Murray

Background: I've got an Energy Kinetics EK-2 oil-fired hot water baseboard system with 5 zones, also heating a water heater indirectly. The 8" round pipe that comes out of it turns into a 7" ovalized 316L stainless steel liner made by Columbia A-Flex as it enters the wall/thimble. From there, it's a 35-40' run to the top of the chimney. The liner is insulated with a poured vermiculite-type mixture. There is no laundry facility in the basement.

Situation: After only 2 years, the bottom 4' of the liner is highly corroded/deteriorated. The liner had a lifetime warranty, but the company's no longer in business, apparently due to a divorce. Without a clue as to the cause of the rapid deterioration though, it doesn't make sense to simply replace the liner and risk a problem in another 2 years. Any ideas? Ever seen this before? Some have suggested using AL-29-4C, but admitted that it's performance is only marginally better. TIA.

Jacob Myron_9

Corroded stainless steel flue liner

Just a shot in the dark.

Energy efficient boilers, direct fired units, and energy efficient fuel fired hot water makers take all the heat out of the flue gases. Typically these unit have flue gases with temperatures below 120 degree's F.

At such low flue gas temperaures leaving the fuel fired equipment the flue gases carry a lot of moisture.

This moisture deposits on the cool liner and condense. All fuel fired equipment that use hydrocarbon type fuels are acidic.

The products of combustion depending on temperatures have some sulfur, nitrogen and some clorine based acids.

To simplify what acids are present we can say some sulfuric acids differnt chemical make ups. Some nitric acids different chemical make ups and occasionally depending on how far away a laundry is some hydrocloric acids different chemical make ups.

Unfortunately, there is no way to raise the flue gas temperature to 140 degree's and and above.

Higher flue gas temperatures heat the liner and cause the moisture to stay in a vapor state. When the moisture is in a vapor state it will leave the chiney and not allow the small amount of acid present sufficient time to corode the stainless steel liner.

Acid resistant stainless steel line are vey expensive and are only slightly better than what you have.

High eficiency fuel burning equipment due to the low flue gas temperatures cause more costly problems than what they save you in fuel expense.

jake

BillW@honeywell

Jake is right...

Here's another angle to consider. I don't know where you are located, but you could contact a Certified Chimney Sweep in your area. They are chimney experts, and knowledgeable in what causes all manner of chimney woes. Make sure they have a current picture ID with the Certified Chimney Sweep logo and a member number on it. That's your assurance you're getting what you pay for. If you are in The NY-NJ metro area, email me & and I can provide you with some contacts.

H. Green

Before re-installing anything you might want to verify sizing. 7" that has been ovalized - depending on how much it is flattened (think kinking the garden hose)- has substantially less capacity than the 8" flue collar on the unit. This probably left you with positive pressures as well as condensing temperatures as pointed out in the previous posts.

The 316L is probably the best commercially available relining material for an oil fired - higher efficiency unit. The amount of sulpher present in fuel oil in some regions will eventually attack any stainless steel alloy.

A suggestion would be to find the thickest material you can. Thickness will buy time before failure - all other things being equal.

You should also eliminate any sources of contamination of the combustion air for the appliance.

I echo my collegue @ Honeywell's recommendation - call a certified sweep for advise and help.

Dan Peel

Killer condensate

Oil fired equipment requires a flue temperature above dew point (typ 130F) for the full length of the chimney to prevent flue gas condensation. You may need to waste a little fuel up the chimney to prevent self-destruction in the smoke path. Enjoy...Dan

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kevin

in addition...

to what good advice you have recieved, a question...is this chimney in the house or on the outside of the house? Outside exposed chimneys will cool down the flue gasses faster and warm up slower giving you condensation. This could be a contributing factor.Hope this helps...kpc

Bob Bona_4

let's

start at the boiler, Steve. EK's have a manual bypass that needs to be set "just so" to keep the return water temps up and minimize short cycling. Could it be that your boiler is turning into a condensing boiler? That would account for the apparent low stack temp (BTW I wonder what yours is, anyway)and the premature liner failures.

I'm also thinking that the OEM 8" pipe just aggravates things by slowing the flue gasses down, but we can't change that. I know that I was much chagrined to see the amount of coke/ash the first EK2 I installed produced after a season of running. That was back in '91 and it still haunts me:)

Although this is a long shot, I thought I'd mention it anyway. Again, it would be hard to believe someone would downfire this boiler to a huge degree, that would also contribute to the problem.

Something to check out!

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Joe_13

8\" flue seems large for an EK-2

I can't find the specs of the EK2 but the EK1 only uses a 4" flue. I would thing the EK2 would use a 6" at most. Again, bad draft could be causing the problem also.

steve_6

flue gases

flue gases under 300 degrees will condense and cause this problem. EK recomended that you keep them above that temp

Steven Murray

More info

First, thanks to everyone that's taken the time to respond. It's greatly appreciated.

I thought I'd post the answers to some follow-up questions and ask some more of my own. Please forgive my ignorance.

Dan Peel offered the following advice: You may need to waste a little fuel up the chimney to prevent self-destruction in the smoke path.

What method are you recommending?

kevin asked: is this chimney in the house or on the outside of the house?

The best way to describe it would be that it is inside, but within a couple feet of the exterior.

Bob Bona asked: Could it be that your boiler is turning into a condensing boiler?

I don't know; how could I tell?

Bob Bona commented: I know that I was much chagrined to see the amount of coke/ash the first EK2 I installed produced after a season of running.

Interesting you should say that. This is how the problem was discovered. During a cleaning an unusually large amount of ash was found in the pipe, all very white and fluffy, not black and sooty, so I guess the combustion is complete at least. If it hadn't been for the buildup, the deterioration may have gone unnoticed for some time.

Jacob Myron explained: the high-efficiency / low flue gas temperature / acid condensation connections.

Thanks. I was actually aware of that. In fact, it's why I had the chimney lined in the first place.

BillW suggested: contact a Certified Chimney Sweep

Thanks for the idea. Anyone that can look at it and offer advice is a welcome resource.

HF Green referred to: positive pressures

Here's some more info on that topic... The EK-2 has a puff switch to detect a lack of draft, which I've had to disable/bypass since the lining was put in. The system was working fine in the winter months, but in the fall/spring when the boiler would still be heating, but less regularly, it would shut off due to lack of draft although it would always work right away after a manual restart. My take has always been that in the winter, the system runs often enough to maintain draft, but that in the transitional months, it takes a bit longer than the 30 seconds (?) the puff switch allows. The time it takes for a manual restart, and the additional firing of the second attempt, were always enough for proper drafting.

Joe commented: I would thing the EK2 would use a 6" at most.

Thanks for the idea. I'll check to see if it has been oversized.

steve pajek states: EK recomended that you keep them above that temp

Do they recommend how to accomplish that?

Would a fan to boost the draw help?

TIA.

John@Reliable_2

Steve, If draft is a problem........

they do make draft inducers. But a better way I think is with a different cad cell relay. They make these controls so that before burner fires, it will come on to start a draft(pre-purge) but the flame is delayed for a few seconds and upon shut down flame will stop but burner will post-purge flue gases. Their are other benefits with this type of control and the cost is a less than a inducer. You also need to know what the flue gas temp.If the right nozzle wasn't installed it could lower temp. causing allot of your problems. Your service company should be testing for this and leaving you the results always! John@Reliable

Bob Bona_4

answer

for Steve, and John said it as well- your burner tech should have instrument readings to indicate the stack temp, along with the CO2 and draft. This will paint a pretty good picture. Of course the EK is not a condensing boiler, but if the bypass valve isn't set right, and there is a flood of cold return water coming back to the boiler, the combustion gasses will cool way before they should, leaving the aggressive byproducts to corrode. Years ago, I remarked to the EK rep how much ash these things produce and they said it was the quality of the oil.. (eyeroll:))

I like John's suggestion about the pre/post purge primary control..this is becoming standard on a lot of new boilers, and it really helps performance. I'm pretty sure the 8" pipe is OEM, I remember thinking what a large pipe for a small boiler the last EK2 I put in. I have seen a lot of puff switches disabled due to nuisance lock-outs. A lot of the time the lock-outs were justified due to partially blocked flues or downdrafts, etc..once draft conditions were improved, the puff switch was put back in service.

Bottom line, I think, is to get some instrument readings. The EK has specific nozzle and set-up parameters-they are not as flexible and forgiving as other boilers can be.The CO2 MUST be checked over the fire, and there is a port for that test. Checking the CO2 in the smokepipe will lead to errroneous set-up.

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Scott Nichols

columbia a flex

I could be wrong, but I believe Columbia A Flex was a distributor for Ventinox stainless chimney liners. If I'm right, Ventinox would be the company to contact. They are still viable and active with chimney liners.

Scott Nichols

come to think of it

Sorry this didn't occur to me before. We worked on a job with an Energy Kinetics boiler connected via 10' of horizontal run to an 30' outside chimney. Condensation was a huge problem. We got together with a plumbing and heating contractor to come up with a solution that for the past three years has worked. We ended up relining the chimney with Ventinox Al29-4c or whatever the acronym and insulated with with Thermix poured insulation. The plumbing and heating contractor replaced the boiler with a Viesmann, not sure which model, but they claimed to be getting a higher stack temperature while maintaining higher efficiency. It sounded fishy to me, but maybe the boiler had a higher water volume which would have required a longer firing, which would have heated up the exhaust more. Sorry I can't be more helpful than that. I know about wood boilers, but have not studied up on our liquid fuel brethren.

BillW@honeywell

Pre & Post Purge

Honeywell makes an oil primary that has an adjustable pre & post purge, and a Flame Quality monitor. Contact your oil supplier/service provider, ask them to install an R7184U primary and a QS7100F1001 Flame quality monitor, and as John et al said, make sure they set this up using instruments! You can't set an oil burner up "by eye". What the terms mean are that when a call for heat comes in, the burner motor starts and gets the fan up to full speed, getting the air moving thru the burner, firebox & chimney, then the flame ignites. When the call is over, the ignition shuts down,flame goes out, but the fan continues to run to purge all gases from the firebox and chimney, and then shuts down.The flame quality monitor gives you an early warning of flame degradation, helping to prevent soot-ups.