Outdoor Wood Furnace Info
Outdoor Furnaces - Manufacturers WITH EPA-Certified Models => HeatMaster => Topic started by: Sluggo on February 06, 2015, 04:46:54 PM
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Has anyone experienced a sweating stove by chance? I have a 20,000 heating 8,000 sq ft in western Wisconsin. Just switched to this stove this year and like it but the past month and a half or so it's sweating or leaking or both. About a month and half ago I noticed clear water dripping from each front corner. I was getting a crystal clear inverted icicle. Then I noticed one corner on the rear doing it. I unscrewed the corner trim and my insulation was soaking wet. The insulation again the stove has a foil vapor barrier and that was bone dry. Bone dry. Now a few weeks ago I go out and hear a dripping noise. Look under the stove and I'm getting about a drip a second. This water seems to be dirtier. I opened the back door and looked and again everything is bone dry. Open the ash pan and that's bone dry. By the way the drip is coming from directly in the middle of the bottom of the stove. Dead ass center there is a seam in the cover metal and that is where the drip is coming thru. On the bottom side of the firebox/water jacket there is about a six inch air space. I can see clear as day there is no leaks under there and there is no water jacket under the ash pan. I go to lift up the insulation on the bottom of my stove and I can't budge it. It's froze down solid to the metal pan covering the bottom from the elements. My water indicator varies slightly but not enough compared to what's dripping out. If no one has experi need this could you guys do me a favor this weekend and go feel around both sides of your insulation and see if it's wet on the cold side? Heat master says they have never heard of this before. It's not a huge deal just like to know what's causing it and be damn sure it's not a slow leak. Thanks a lot.
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Is there a chance snow could be getting behind the siding or under the roof somehow, I have seen what you are taking about in other models when there was a place for the wind to blow drifting snow into the insolation.
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There's no chance for that,for one I don't think we get snow in Wisconsin anymore and two it's in a covered shed.
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OK how about the water temps, do they occasionally drop below about 140 degrees F, I have seen sweating occur on other models when the water temps get that low.
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There's no chance for that,for one I don't think we get snow in Wisconsin anymore and two it's in a covered shed.
Covered or enclosed? If it was enclosed maybe enough temperature variation moisture in the air is condensing.
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Temps are 160-170 any higher and I boil the water,that is a different topic though. SlimWhen you encounter your first heat master 20,000 I will explain! She'd is covered and enclosed on three sides. Temp in the wood shed is same as outside temps. I'm going to try some charcoal in the back of the stove and see if that helps dehumidify.
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Cancel the charcoal idea,I'm leaving the back access door open to see if that helps.
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I think we may have a more serious concern if you can't run higher than a 170 cutoff without causing a boil over! Is this what you meant?
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Little bit of a design flaw in the stove I believe. To much volume on the sides and not enough on top. Sweating problem cured by cracking the door on a side note. I added a seperate pump strictly to circulate the stove water which helped but still must be a dead spot on top.
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When my 5000e is half way into the cycle and the fire is roaring I often hear the sound of water boiling near and around the extra bypass. Should I be concerned about this? It has never boiled over. My setting is 160 on and 180 off in Jan/Feb when really cold and 170-180 otherwise.
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No worries. The front of the stove is where the first turn is to start heading back. There is a lot of heat that gets concentrated in that one spot. It is localized boiling that only occurs right there. If you watch your water level pipe closely you can see tiny wisps of steam that pops out. It's minimal and shouldn't affect your water level at all.
Just as a note, I would bring up your low point a bit. If you have a 20 degree delta T, you're getting really close to that sweating mark. I rarely go lower than 170 for my low set. When it gets cold I bump up to 185 if I'm not burning hedge or coal. I basically run 170 on and 185 off when cold and 170 on and 177 off when it's more mild. In October and April I'll bump down to 165 172.
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Thanks CountryBoy. I changed my setting to 170-185.
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Another thing I do I just remembered, is I don't stack any wood 6"-8" right inside the door. This prevents any direct flame from hitting that portion of the water jacket.
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Way to go CBJ, Great info.
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Never thought of that. Good idea!
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Just my personal experience here so please don't shoot me if it seems odd.
We got a MF5000e last year. Located in Ohio the house is a brick 2800sq ft with dhw. We started the stove and quickly learned that it only took between 4-7 pieces of wood to last 12 hours depending on the temps (burning cherry and oak pieces of 8-10" dia) This proved more efficient than "filling" the stove and seemed to save wood. The stove started dripping water out of the ash door almost immediately. I work in the tech support business for Fujifilm and started a K-T problem solving sequence-try to identify the root cause and eliminate it. Finding the root cause is difficult when you are not a stove tech so experimenting was the next step.
It was thought that the wood was too wet and the water was condensation. We were burning wood that was down for 2 years but only cut and split for 6 months. We had done some remodeling and had a bunch of scrap wood so the test was to burn 40 year old dry 2x4 and 2x6 pine for 3 days with no "seasoned wood". Issue remained- Wet wood not the cause.
The air intake was changed from 100% to 20% in 2-3 day increments-no significant change.
I had been burning wood since the 70's and thought this should be easy but grasping for straws wasn't getting anywhere so I started reading and researching.
The on/off point was changed to higher and lower temps for 2/3 days at each test. 160-170, 170-180, 175-185. 180-185. The thought was that the stove idled too long at too low of an internal temp and the air leaks were exaggerated. Trying to keep the stove needing heat was the goal. lower temp would require that the fan on my furnace would run longer to heat the house to the same temp. This would cause the stove to run more frequently and also not go out. A 5 degree differential might accomplish the same thing. All offered no improvement.
Research suggested air leak- Cold moist air coming in around rope gaskets could meet hot dry air and condense at point of contact. Gaskets were repositioned and doors and latches readjusted to minimize air leaks. (The ash door gasket gets pushed to the side due to the ash pan resting on the bottom of the channel that it rests on. It should be centered better but that would take some redesigning). This appeared to provide some relief however never completely stopped the phenomenon.
As this experimenting went on the stove started going out during the day after about 2 months of working fine. I was ready to pull the stove out! My dealer was great to work with and called me about every other day to check on my progress. He offered to come out and check it out but I declined. Stubborn...Proud....Stupid....lol. Our house is pretty well insulated and didn't really need too much help maintaining heat. One of the main symptoms was that when we opened the door to check or fill the stove there was no pile of coals in the fire box. All that was left were the pieces of charred wood. On top of that the ash pan was filled with 1/4" to 1/2" chunks of charcoal-no ash. The thought was that the fan was blowing the fire out and I left the ash pan full for longer periods and it improved the fire going out but still had water dripping out of the ash pan. Working with my dealer and Woodmaster we checked other items that offered no help to the sweating but improved the fire going out some.
About this time it got to -20F outside and I was going to be gone for the week leaving my 110# wife to tend the stove. We decided to forget about saving wood and had her fill the stove as full as she could get it so that it wouldn't go out on her. After a week of doing this I returned home to find about 6-8" of coals in the bottom of the fire box. On top of that the ash pan was only 1/4 full after a full week of heavy burning. Hmmmm. We then went back to putting just enough wood to maintain a 12 hour burn and keep the same amount of coals in the fire box. Back to 6-8 medium pieces of wood per load and the coals stayed and the dripping stopped and never came back. This easily lasted 12+ hours.
Through all this a guy looks at the input and the results while taking in subtle clues along the way that may go unnoticed if not paying attention. Through this all I can do is speculate what was the cause and repair. It appears that our lack of need for heat caused the stove to run infrequently. When it would burn it would do so feverishly and the water temp would recover quickly and thus no coals/ash generated. On top of that, our desire to save wood led to fewer pieces of wood in the box from which to burn. When the fan would come on it appeared to blow all the particles that might accumulate in the box down into the ash pan. I never touch the shaker grates. While all this happened the stove was leaking water from the ash pan at up to a cup a day filling a 5 gallon tub 1/2 full of water in a week. Once the firebox was full of coals and stayed that way, the water stopped even though we used wood that I know was wetter than previously used wood.
I know what stopped the issue, however don't know the root cause. Were the coals insulating the doors and gaskets from the air leaks? I'll probably never know but when I fire it up in the fall it'll burn like a mad man until I get a good bed of coals-that's one thing for sure.
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Great story Suzukidad! Glad you got it figured out, sorry I wasn't more help with our product but I think you may have nailed it with the coals and ash insulating the ash door, somebody recently posted on
P and M section regarding the same issue and resolved it by placing a brick just inside the ash pan door, this may be just enough to keep the ash door cool and stop the condensation, this is exactly the type of stuff I like to see, we can all learn from it! Thank you for taking the time to post it!
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This is an "issue" that I believe HM has remedied. The flanges for the door and ash pan stick out so far from the stove that it's bound to condense. The "C" models have reduced this flange to the minimum amount necessary to hold the hinges and door latches, I've been told. I use air quotes for "issue" because I don't really see it as an issue. The only moisture I get is in the very front of the ash pan, hardly a critical component of the stove. It may shorten the lifespan of the rope gasket, but that's not a big deal. Some things make it better, some done. Just like you found. However, I believe that all stoves condense and drip at the door. Every time I load I scrape off the flange and move on.
I discuss this very issue in my in-depth review video that I haven't uploaded yet.
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Exactly right. I have never seen my C375 sweat.