Summer corrosion, humid air brought in via vent

I've used a Pioneer top vent for three seasons now, love it!

However, it is in the family room at basement level, thus cool in the summer. It is vented via a Stainless Steel chimney.

Last summer was extremely humid and the black pipe including the $$$ Stainless chimney to stove pipe connection corroded badly despite a 25W bulb to keep some heat in the unit. There was severe internal pipe corrosion and condensate buildup before there were any externally visible signs.

I believe the problem is a power exhaust vent in my home creating negative pressure. The path of least resistance most likely is down the SS chimney and convection from 25w of heat wasn't enough to overcome the negative pressure. I use a dehumidifier but that has no effect on the inside of the pipe or stove.

I have two thoughts and solicit comments. For cosmetic reasons, I don't wish to leave the stove pipe disconnected.

1 - Somehow fashion a plug for the chimney and stuff it up the clean out T. This is difficult since the bottom of the T is very close to the ground and impossible to inspect.

2 - Disconnect the black pipe (can't remove the plain steel adapter to SS chimney) and insert a plug into the SS there. Reconnect the pipe for the summer

In 1 & 2, put a sign on the burner "chimney has a plug"

3 - Use a manual speed control and run the combustion fan at a slow speed during the summer.

Two questions if I do either:

What model fan is the combustion blower should I wear the fan? (actually both fans). I get a discount on HVAC equipment.

Any ideas what would make an air tight tight plug?

gerry

I'll take a shot at the "Plug the pipe" one...

Use a small hand pump to inflate a "heavy duty" party balloon inside pipe...either @ top or bottom or even @ both locations.
And there is such a item designed for plumbing w/ a valve stem arrangement from the plumbing supply house for more money.

And "Hang the Sign" as you mentioned.

SMITTY wrote:If there's any kind of humidity in the basement, you need to get that pipe out of there & into a dry environment. My basement is on the extreme end of this spectrum, but I learned my lesson .... even with stainless!

Guess you missed "I use a dehumidifier but that has no effect on the inside of the pipe or stove." in my original post. Dry air in the basement won't help since I also stated "There was severe internal pipe corrosion and condensate buildup before there were any externally visible signs."

The problem is clearly that the dew point of outside air ingested via the chimney was below the temperature in the basement, thus the condensate was actually internal, not external.

I suspect your SS issue is not simply humidity, rather acidic water/condensate.

gerry

McGiever wrote:I'll take a shot at the "Plug the pipe" one...

Use a small hand pump to inflate a "heavy duty" party balloon inside pipe...either @ top or bottom or even @ both locations.
And there is such a item designed for plumbing w/ a valve stem arrangement from the plumbing supply house for more money.

I like the plumber's supply idea, I don't really trust even heavy duty balloons.

I disconnect the black pipe each year anyway to clean out the fly ash in the 2' horizontal section of SS chimney. I could easily reach in a foot and place the plug such that it keeps all outside air in pipe at outside sections of the chimney, thus at near outside temperatures (some thermal conduction will occur)!

So either that or a blower set up (extra fan or combustion blower run slowly off a speed control)

The advantages of a fan seem to be it is easily inspected during the summer and will be blowing dehumidified air since I use a dehumidifier in the basement level family room.

gerry

The Hastelloy C alloy can handle just about anything you can throw at it. It would laugh at sulfuric acid corrosion. Inconel is right up there also. Tubes are available in both materials, but you might find that being independently wealthy is a prerequisite to ownership.

304 Stainless and 316 Stainless are listed as"not usable" in an environment of sulfuric acid.

SMITTY wrote:

gerry_g wrote: suspect your SS issue is not simply humidity, rather acidic water/condensate.

Nope - just humidity - which will result in condensate.

Regardless of where it comes from, humidity + fly ash = sulfuric acid.

Thus NOT JUST humidity. You did state "Nope - just humidity - which will result in condensate." although, to be fair you then added + fly ash in the next sentence.

Just, curious, your photos show deep pitting without holes on the outside of the pipe. How did fly ash get there?

However, I'm aware most SS doesn't like acid liquids. This conversation is proving very helpful to me. Since I can't get ALL fly ash off the SS chimney interior, I'm leaning toward forced air (extra fan or reduced speed combustion fan) which will blow dehumidified air from my conditioned space where the stove is located.

A solution with chimney pipe in place is a must. I can't remove the chimney for the summer. It has a horizontal section that penetrates an exterior wall, and weather sealed to that wall. It extends into the room to meet fire codes.

I ran two years with a 25W bulb for heat which worked fine. It was last year only where we had sustained outdoor dew points well above the temperature of the room the stove is in and a light bulb didn't cut it.

gerry

My solution is that as soon as I turn the stove off I take the powervent out of the wall and clean up the stove thoroughly and pack it and the dissmantled stove in a warm dry place for the summer. Damprid in the stove and saran wrap over the chimney and other holes. That is one of the things I don't like about a static chimneys in this part of the world but the stove is never exposed to the elements if it is not on. IT'S ALSO ONE OF THE MANY THINGS I DON'T LIKE ABOUT HYDRONICS (oh,oh war will break out here - wait for it - but, but, it's the most efficient way of transferring heat and I love to make Peru miners rich - yes I know - you think I don't know that one and no the alternative is not scorched air). Little grasshopper has grown up and enough time has been spent at the feet of the masters. Don't get me wrong I am still learning every day thx to this wonderful board but I have my own opinions now.

Sulphurous acid is a horrible thing and I learned that in high school (or was it kindergarten) and I am old fart so that was a loonngg time ago. I read about broken SS coils, LP3 sprays etc. etc. I'm sorry but the few bucks I spend a month on juice for the powervent is money well spent and don't get me started about the imputed cost of building and maintaining a chimney (and ugly). I never seem to read about how wonderful powervents are as they are somehow nonsense. Well let me clue you, I think they are a great invention and their use has been made possible by rolling roads stoves (as I call them) and coaltrols. Those three wonderful and unique things form the basis of a modern anthracite burner and I love it. Let's not forget safety (I can't turn them into a puddle of iron thx to the WVO unit) either. Now I am going to hide under a rock and wait for the yelling. William is going to be ticked off here!!!

DUPLICATE

DUPLICATE

coalnewbie wrote:My solution is that as soon as I turn the stove off I take the powervent out of the wall and clean up the stove thoroughly and pack it and the dissmantled stove in a warm dry place for the summer.

I fully understand taking everything apart, removing the sealed vent to the outside and storing the stove in a humidity controlled situation would solve any such problems. That is not an option for me, I am disabled (although I installed it all including the chimney w permit and inspection) dismantling and packing the setup along with breaking the weather seals in the wall (and doing something cosmetically to fill the hole) is not an annual option. My stove (as mentioned before) is in a finished, dehumidified family room we use and we do care about cosmetics.

I honestly believe coal stoves would become very unpopular to many is the process you practice was needed! There has to be a solution sans such extreme measures.

coalnewbie wrote:My solution is that as soon as I turn the stove off I take the powervent out of the wall and clean up the stove thoroughly and pack it and the dissmantled stove in a warm dry place for the summer. Damprid in the stove and saran wrap over the chimney and other holes. That is one of the things I don't like about a static chimneys in this part of the world but the stove is never exposed to the elements if it is not on.

I agree with you 100%. I don't have a power vent but I do have a SS chimney and I want that to last a long, long time. Have you thought of making a removable cover for the power vent opening? I bet you could come up with something not too very ugly. Every year as soon as I lose the fire, I take off my black pipes and put a pipe end cap over the thimble opening. Then I vacuum up as much ash as I can out of the stove, put another pipe cap on it, put a DAMP Rid inside and let it sit that way until the fall. Last year I did wash it down with baking soda but this year I'm not going to because the humidity is controlled by my AC and the Damp Rid. In theory there should be little or no humidity in the room or stove to react to the flyash. The external SS chimney is another story. Every year I spray that out with a hose and try to get some baking soda down it. Not much else I can do - I do wash the thimble down with the baking soda.

My issue with corrosion is on the exterior of the SS chimney. Apparently, the flayash is carried by the draft and deposited on the outside of the chimney near the top. The chimney cap prevents the rain from removing that flyash. That accumulation is causing the corrosion I'm seeing there. I am going to try to remove as much of the corrosion that I can with steel wool and baking soda before I treat the SS with a rust preventative product. I hope that will slow down the corrosion but we'll see. I'm open for suggestions if anyone has one. Take care, Lisa

Does a piece of crap plywood and chewing gum over the hole qualify as an aesthetic covering for the powervent hole. After all it comes off Labor day. I did send a photo to Architectural Digest but they did not seem interested.