Problem with condensation

[Mark in VA]

Hello everyone,

I discussed this with Camfan by PM recently, and since it appears to be a somewhat unusal issue, I thought I would post to the forum to see if anyone else has had a similar experience.

I've had about a dozen or so fires in my Baby Bear so far this fall and after about the third use, I started seeing a few brown drips around the crown of the chimney that were coming from the underside/corners of the chimney cap. Since this year is the first time I've used a cap, I thought that this was probably somewhat of a normal condensation issue and figured I would simply keep an eye on it. However, soon after that, this same condensation began dripping from the cleanout door on the chimney and staining the block below it.

The liquid is basically like a brownish rusty water, that on a couple occassions has actually puddled onto the concrete base below the flue. It's not sticky, and it will wipe almost completely away if you catch it before it dries. The flue and stove pipe themselves are not showing any abnormal build up, thankfully, so I'm scratching my head at why this is happening. (It's also not a rain issue... When I first noticed it, we had not had rain for over two weeks.)

I've also been running the stove at, or above, proper temperatures and have let it run even hotter since noticing this hoping it would clear up, but the drips return each time I use the stove. The wood I'm burning is all hardwood that has been split and stacked for going on two years, so I don't believe that's the issue either.

I realize that with a small stove like the Baby Bear, an exterior masonry flue is not optimal, but the I.D. diameter of the flue is only 6 3/4, and it's about 15 feet tall from the thimble to the top, so it's not that terribly over-sized. The flue also has a very strong draw, even when cold. Upon starting a fire, I let the stove burn for 25 - 30 minutes with the draft cap nearly all the way open, then only turn it down to two turns open for the remainder of the burn. The only time I've set it lower is for overnight burns and still I've left it one full turn open. I've also experimented with and without a pipe damper to allow as much heat up the flue as possible. I know this may not be the best for conserving wood, but I just wanted to see what the effect would be on the condensation problem, but so far there's been no change.

Sorry for being so long winded, but this has me puzzled. I've burned several different types of stoves over the years on identical flues and never experienced this. I don't think I would as puzzled if I were having build up on the inside of the chimney, but the drips on the outside are something I haven't seen before. A certified chimney sweep was also unable to give me any solid answers, so any advice y'all can offer is appreciated!

(BTW, the flue is less than a year old and I have looked into lining it with S.S., but since it's barely over 6 inches as it is, I don't see that making much difference. That would also require milling out the clay tiles, so that a liner would fit, and I really hate to do that to a brand new flue!)

Thanks in advance,
Mark

 

[coaly]

A spring at the top of a chimney is unusual.
I'd remove the cap since the moisture started after installing it. This will verify if it dries up that it is certainly the cap causing it. Then it's why ??? Condensing on the bottom side of cap and running down to where you're seeing it ?? Plus dripping back to the bottom off the top ?? Maybe tilt it if possible to see if the drips only form on the lower side?
Logical explanation ( or a guess) is byproduct of combustion since it's not that cold where you are and the cap is condensing it where it used to vaporize out the top ? I wonder if the cap top is staying that cold to condense on and not heating up enough to evaporate? Like maybe the lid is too high above the flue top?
Lets hear Camfan's guess !

 

[Mark in VA]

Thanks for the reply, Coaly!

I forgot to mention in the first post that I did remove the top cap a few days ago, thinking the same thing. That did seem to stop the drips at the top, but had no effect on the clean out.
I guess at this point its more of a cosmetic issue than anything, buts its really frustrating!

 

[CamFan]

Mark sent me a PM about his double skirted adapter and hooking up his stove. After he completed it this started, he has already asked me. The problem is the last house I had had a Papa in the basement with a masonry chimney and it did the same thing. I never figured out what was wrong. I was like Bill Murrary in the "Caddy Shack" trying to get it fixed. I suggested he post it here and someone has to had the same problem, and hopefully a solution to fix it.

My guess is has to be something to do with the chimney......but what? I am at a loss. As smart as you are Coaly I told him you would know. lol

I googled it and this was found http://www.chimneys.com/smoke-signals/water-in-chimney-with-wood-stove I did not search long as I have a busy morning and neeed to get things started.

 

[Mark in VA]

Well, I don't want to jinx myself, but it looks like the condensation problem has just about cleared up. I'm still not exactly sure what was causing it, but the brick mason who built the flue stopped by a couple weeks ago to tell me he had another customer recently who had the same problem, but it cleared up after a few hot fires. After 30 years of building chimneys he had never seen this before, but had calls from me and the other gentleman within a short period of time, so it does seem a little more than coincidental! It's only a guess I suppose, but he seems to think it's some type of residue or new chemical that's being applied to the teracotta tiles, and simply needs to burn off. Again, that's only an idea, but it does seem to be clearing up, so I'm keeping my fingers crossed that it doesn't reappear!

I am seeking Coaly, Camfan and others' opinions on another matter; however, as it looks like the Baby Bear is just not going to be able to cut it when it comes to the heating capacity that I need. My house is only about 980 Sq.ft., so I had thought the Baby would be the perfect size, but I think the fact that the house is old (=poorly insulated) and has a somewhat broken up floor plan, the little stove is just up against it! The short burn cycles are also another factor...

I realize that the obvious solution would be to up-size to a Mama Bear, but I'm a little bit restricted when it comes to space. The Baby fits just shy of the 36" clearance requirements, but I think I might be pushing it with the extra 6 inch depth of the Mama on the rear wall (I'd be fine on the sides). I have durock and ceramic tile fastened directly to open, rough-cut oak stud (2x4) framing on the rear and side walls, with no insulation, so there is an air gap (just not open, at the top and bottom), so I'm wondering just how close I could safely get? Currently, the tile barely even gets warm with the Baby Bear running full bore at about 30" away.

I've read the NFPA guidelines, etc., but my grandparents had a 1940's era Ashley Automatic in this same spot for over 40 years (much, much closer to bare sheetrock walls) and never had an issue. I've since removed the sheetrock and added the durock and tile to the bare studs, so I'm wondering just how much protection that would actually give me, without the prescribed "open" one inch air gap? I realize a lot of unsafe things were done in the past and folks may have just been lucky, but I'm just looking for a "real world" opinion from some long time wood burners.

Thanks again,
Mark

 

[Mark in VA]

I meant to add, if you look at my avatar picture, that's my Baby Bear in its current location, showing the tile hearth, rear and (short) side wall protection. It's basically a partial corner installation. The left rear corner of the stove is actually out further from the white trim than it appears in the photo. I can post more pics if that helps with what I'm describing.

Mark

 

[coaly]

Perhaps the flue liners were not kiln dried enough and had a lot of moisture to evaporate still?

Technically the cement board attached directly to studs is not an approved heat shield. Cement board actually transmits heat through to the other side quite readily. So your installation doesn't offer a clearance reduction. Solid 4 inch brick against combustible allows I believe a 33% reduction. So that gives you a reference for heat transmission through masonry. It's not that great like a 1 inch air space.The factor is the heat applied over time to the studs dries the wood to the point where the ignition temperature is lowered, increasing the danger. The clearance measurement is from stove to wall, not to the added heat shield. So an added shield in front of what you have with air space under and behind for circulation is what would technically be required.

The Mama VI with a bottom and rear heat shield has a reduced clearance of 32 inches in a corner installation and in a sidewall, backwall installation 30" to rear, 36" to side.

 

[CamFan]

I did one once with the durock on wood. When I took the Sheetrock off the wall behind the stove in a remodel the wood was scorched. So be careful

 

[Mark in VA]

Coaly and Camfam, thanks for the replies! You both pretty much confirmed my own thoughts that if I go with a larger stove, that modifications are going to be needed to do it safely. I will say however, that when we originally removed the sheet rock from the walls to put up the durock, there were no signs of scorching or charring of the wood after many years of even closer exposure. Again, maybe they'd just been lucky... One scary thing I did find though, which I had brought up to code immediately, was the fact that the clay thimble had been run straight through the combustible wall to the old (now demolished) flue with no masonry around it whatsoever. The builder of the old chimney had stuffed the empty mortar bags around it; however, and they were charred!! Needless to say, I had the proper masonry installed around it and have since replaced the flue itself as I've mentioned in other posts.

Anyway, I guess I'm going to have to look into some type of additional shielding for the walls, or if y'all can offer any additionals advice on how to get more efficiency out of the Baby Bear, it would be much appreciated. I really like the little stove, but it just doesn't seem to hold enough wood. It puts off some pretty decent heat if you run it with the draft cap about 1 1/2 to 2 turns open, but at that rate it needs reloading about every two hours or so. That's not a problem during the evening hours, but not so great for overnight burns or while we're away at work. I can make it hold a fire for the night with the draft at about a half turn, but the drawback is the obvious reduction in heat output and lack of radiation to the rooms that are further away...

 

[jatoxico]

Well, I don't want to jinx myself, but it looks like the condensation problem has just about cleared up. I'm still not exactly sure what was causing it, but the brick mason who built the flue stopped by a couple weeks ago to tell me he had another customer recently who had the same problem, but it cleared up after a few hot fires.

Just to chime in here, when I first installed my stove (insert) during my first full fire I went outside to check things out and give it the once over. What I saw was what looked like smoke coming from all over the brick chimney but especially from where the masonry met the siding. Naturally I almost lost it and ran up to the attic and got a step ladder, did that about 20 times. After much feeling of brick and smelling and agonizing I decided it was steaming off. The brick itself was never even warm to the touch.

In my case the fireplace had not been used for a while, must have soaked up water and had probably never had flue temps that the stove could achieve. Hasn't happened since. I would be willing to guess that it happens more often than people realize (maybe weather conditions need to be right) but that a lot of people are just not very observant.

 

[Mark in VA]

Wow, Jatoxio!! I'll bet that was something that would make your heart skip a beat!!

You're probably right about most folks not being very observant, and/or conditions having to be just right for something like this to occur. I'm probably on the extra careful (sometimes worrying too much) side of things, but I figure better safe than sorry!