How hot does the last bit of cob get, on the outside and near the duct?
Can you tell where the water is condensing?
If your exhaust is still 180 F as it exits the last mass
Is it possible that the condensation is happening in your chimney and running back into the mass?
How well insulated is the chimney?
Is the ductwork level, or where are the high and low points?
Phil Holbrook wrote: I live in Alaska with temps in winter usually down to minus 50 or 60. I've been heating water with a wood stove in my house for 40 years now and usually have plenty of free hot water all winter. I have about 20 feet of 1/2" OD copper tubing right in the fire box and it circulates to the hot water heater upstairs. No pump, it circulates by itself, but if I start the fire from cold I have to not get it hot real fast or it pops and snaps till it gets to circulating, then it doesn't matter how hot the stove gets, it just makes the water go faster and heat the tank sooner. So I am sure you need more copper tubing and in a hotter place to get enough hot water. I know about all the warnings about the dangers and plan to change things nest summer, but don't consider it an emergency now after 40 years.
That brings me to my other system I have in my airplane repair shop which is a stove made of a 30" x 42" pipe with if I remember right 50 feet of tubing and it circulates to an open 30 gal. tank sitting on top of the stove. Another 60 feet of tubing is in that tank and circulates to the tubing in the concrete floor. I'm out of time now, have to leave. But want to say a little more about it later.
Glenn Herbert wrote:If your exterior chimney is uninsulated, that would absolutely be where the condensation is happening. It will also cool off immediately when the fire peters out, so you would get no draft without the strong heat source. Replacing the chimney with an insulated one, or if budget is tight, adding section by section an 8" duct jacket and packing it with perlite or rockwool (joints arranged to shed water to the outside and top edge capped off to keep the insulation dry) should make a big difference in your condensation and in your ending draft.
I would also put in a drain vent to let any water running down the chimney drip outside instead of continuing into the mass ducting. A T fitting at the bottom of the vertical chimney instead of an elbow will make this easy.
F Styles wrote:
this is amazing information. do you think my water tank diagram design will work then? how much copper do you have in the "firebox" how hot does you firebox get and is your system open or closed system? my diagram to heat water is a concept i would like to add and the copper will be about 10' long inside the exhaust duct 220 degrees at one end and 180 at the other end and circulating up inside a tank outside of a mass bench. should i keep the copper line there or should i move it closer to the heat?
Phil Holbrook wrote:
But I'm a little jealous of your stove, which is like what i've got in mind to make next using firebrick. I like the long burns you're getting and it sounds like it is burning pretty clean and using the heat for the house instead of the great outdoors like most stoves. I'd love to cut my wood use in half too. Or better than that? Haha.
Glenn Herbert wrote:I'm happy to hear that adjusting your chimney tee solved your condensation problem.
I would not jacket any of your exterior chimney in concrete, as that is not a good insulator and would cool down the chimney for a long time until it got warmed up, and even then in cold weather would be sucking heat out of the chimney, if not as fast as bare metal does.
Glenn Herbert wrote:Sometimes non-technical people demand changes to systems to satisfy their fears or tastes. It is often wisest to comply when the change will not have a serious negative impact on the system
Bacon Lee wrote:
I bought QUIKRETE Portland 47-lb Gray Type-I/II Cement Mix to use for my bench coating. How do I mix it, what ratio did you use for your coating please
John McDoodle wrote:Thanks for the link to your stove. I admire the fact that you have your own ideas. The water heating is a good idea and you could definately make that work, in more than one way. The thermal siphon that Phil H mentioned seems like a good idea, and perhaps a copper coil could even be mounted at the hotter end of the exhaust? Anyway I think water for a mass is a great idea. Kill 2 birds with one stone, so to speak. Every custom unit will require testing and tweaking, so its no big deal. You will get the kinks out in no time.
How does the 10" metal duct work around the riser? I plan on the same idea. And mine also has a 6" riser
Bacon Lee wrote:What do you call refractory cement? I want to know so I can buy. Would you please take a picture of the bag and upload so I can see