chimney frost

[lightecho]

New member here. Hiya!
Husband and I both work full time. We ran out of wood a month ago and haven't used our freestanding Lopi steel stove since then. (Even with plenty of wood, we only use it on weekends and days off). Our set up is black stove pipe inside, double wall stainless outside for 20 ft through the soffit. No chase - bare pipe on the outside of the house (I know, bad... but we're building in a few years and have no intention to spend more on this old farmhouse). Have had an issue a few times with starting a new fire after no activity in weeks, the heat melts frost inside the chimney and water drips down the inside of the chimney. Occasionally it drips from where the black stove pipe meets the wall onto the floor behind the stove. I can hear it melting during the first 10 minutes of operation, then all water noise stops. After the chimney gets warmed up, the chimney dries out and the dripping stops. Since we don't use the stove all the time, the chimney has a chance to get cold (this winter= super cold!). There's no way around that.
My question is... is this frost melt dangerous to operation? Is there some sort of creosote sludge being made inside the chimney with this occasional melting going on?

 

[red oak]

Welcome to the forum lightecho!

I'm sure smarter people than I will be along to help but I'll offer my first impression. Have you checked the chimney to see if creosote is there?

I wouldn't worry as much about the melting as the fact that the pipe is on the outside of the house. This is because creosote forms when gases from the fire condensate before leaving the chimney. This is why so many on here are adamant about burning dry wood. The more moisture in the wood, the higher the chance that the fire will be cooler. This is also why the most creosote is typically found at the top of the chimney, above the roofline.

So, given that you don't want to work on the house and that you probably don't want to burn more than you are now, I would check the chimney and run a brush through to clean it out. I would check it every couple of weeks if possible and clean as needed. I hope this helps!

 

[lightecho]

We had the chimney prof cleaned in Oct after not using it all spring/summer/fall. With the little that we run it, we also check it once a month with our own poly brush, run up the clean-out that is accessible from outside the house at the bottom. Mostly it's fluffy ash. The prof guys did scrape a half inch of black sludge off the clean-out plug. Granted, this was after all the summer rains washing down the stovepipe. We have a Vacu-Stack high wind chimney cap with bird guard.
Mostly, I'm worried about the moisture buildup inside the cold stovepipe, combined with the occasional use and leaking into the black stovepipe inside the house. If we don't have much issue with creosote, is that melting presenting a problem in itself??

 

[red oak]

We had the chimney prof cleaned in Oct after not using it all spring/summer/fall. With the little that we run it, we also check it once a month with our own poly brush, run up the clean-out that is accessible from outside the house at the bottom. Mostly it's fluffy ash. The prof guys did scrape a half inch of black sludge off the clean-out plug. Granted, this was after all the summer rains washing down the stovepipe. We have a Vacu-Stack high wind chimney cap with bird guard.
Mostly, I'm worried about the moisture buildup inside the cold stovepipe, combined with the occasional use and leaking into the black stovepipe inside the house. If we don't have much issue with creosote, is that melting presenting a problem in itself??

Just to clarify, did you have the chimney cap on during the summer? You mention the summer rain, but the cap would have prevented that??

I'm thinking that the main problem would be deterioration of the stove pipe over time, also anywhere where the water could run out of the pipe (into your wall mainly). But I'm certainly no pro, and it may be prudent to call one to check it out.

 

[Highbeam]

That's not melting frost, it's just condensation from cold smoke hitting your cold chimney. Even super dry wood is still more than 10% water and during the early part of your fire you are boiling that off and sending it into a cold chimney where it cools to the dewpoint.

There is nothing you can do except be sure that each time you burn that you burn hot and long enough to burn off all the built up condensate.

I have a shop stove and the stove and chimney are often well below freezing when i start a fire there. I will actually get condensation forming on the inner firebox and dripping out past the gasket onto the ash lip before the temps go up enough to ensure the steam makes it to the flue cap without condensing.

 

[lightecho]

redoak, yes the chimney cap hasn't been touched since install. It's always on. We're on top of a hill and get major wind especially during storms. We had a wind meter at one time and clocked a gust at 65mph during a June storm, which is the reason for that specific chimney cap. A few times we've had rainwater in the stovepipe during a big summer blow. Not always, just occasional. Anything left in the chimney in May is washed down to the cleanout plug by Fall, I assume.

Highbeam, thank you! Makes sense. I always just assumed the moisture was from warm house air meeting cold chimney while it's not in use. We have always cut and split our own wood in the past but this year is different. I went back to school and we had little time for wood all year. Now, we're left with buying from a dealer last week. It appears their definition of 'seasoned' and our definition is different. It's great wood (oak, red elm) but hardly any cracks in the ends, and bubbles when in a hot stove. We have no moisture meter, but I'd guess it's above the 20% it should be. No choice though. Trying to burn hot fires with this is a challenge. I suspect we'll only burn if we have to and keep the rest of the delivered load for next fall. It should be great by then.

 

[Highbeam]

Split it smaller, stack it looser, and with a good bed of coals you can burn that green wood. Sure beats being cold.

 

[lightecho]

Highbeam, yes, it beats being cold. Especially with the price of LP going through the roof in the midwest! At this point, electric space heaters would be cheaper than running the furnace. Considering most of these delivered pieces are Yule Log sized, looks like we'll be doing some splitting. Thank you for all your help.

 

[bag of hammers]

I have a shop stove and the stove and chimney are often well below freezing when i start a fire there. I will actually get condensation forming on the inner firebox

That's a great sanity check for me. I'm a weekend burner - my place is kept above freezing but well below normal room temps during the week. The (steel) stove isn't freezing but it is cold. When I light the fire sometimes I can see a tiny bit of condensation on the inside of the firebox near the door. It's gone in a few minutes as the fire kicks into gear. I guess it's part of the reality of doing these cold starts. It doesn't take long before the chimney temps want to climb over 800 deg. so that bit of moisture does not last long or make me worry too much - as long as I get the fire rolling fast and hot on startup.

 

[Highbeam]

That's a great sanity check for me. I'm a weekend burner - my place is kept above freezing but well below normal room temps during the week. The (steel) stove isn't freezing but it is cold. When I light the fire sometimes I can see a tiny bit of condensation on the inside of the firebox near the door. It's gone in a few minutes as the fire kicks into gear. I guess it's part of the reality of doing these cold starts. It doesn't take long before the chimney temps want to climb over 800 deg. so that bit of moisture does not last long or make me worry too much - as long as I get the fire rolling fast and hot on startup.

Yes, I actually will get a puddle of water on the ash lip. What happens is the cold smoke condenses on the airwash plate that hangs down into the loading door. Then the condensate drips down between the glass and the outside of firebox. The puddle stays a while since the ash lip is relatively cold and boy does it stink if you wipe that puddle off with your hand. I've got to imagine that the whole flue system is prone to the same condensation until things warm up.