Piping hot stove air to back rooms?

[stevec77]

I have a cabin with a 20' cathedral ceiling that collects the heat my stove puts out. I want to pipe that heat to 3 back rooms ideally but would settle for one. I'm on batteries and an inverter so running a powerful fan would drain them quickly. The in-line booster fans are low wattage but too wimpy, I was told, to push air in this application.

What if I installed a cold air return duct in the back room, ran the duct under the cabin and had it come up or return to the floor behind my wood stove? Do you think that the upward movement of the air around my stove would "pull" air from the cold air return as it rose up above my stove and thus create air movement in the back room that might result in pulling some warm air into that back room? It is a crazy idea maybe but what do you folks think?

 

[pen]

I like idea 2 much better. Moving the cold air to the hot place is wiser.

Picture this, you have one finger to push with and you need to push 2 things, a marshmallow and a brick. Which would you push on first? If you tried pushing on the marshmallow first, it having less density will cave under the pressure of needing to push the more dense brick. Go vice versa, and let the heavy hitter (cold air) do the moving, and you'll have no problem.

pen

 

[stevec77]

Thanks, Pen. I get that and will do. Did you understand that I did not want to use an in-line fan, just natural convection?

 

[pen]

yep, got that electricity is at a premium for you in that spot.

That ceiling is beautiful I'm sure but certainly a heat movement killer.

Duct size will be crucial for that cold air return. You'll also have to be careful with how this is done as I believe that any open ducting has to be a good distance (10 feet is sticking in my head but someone else will chime in here) from the stove by national code. If you go closer I'd imagine it would work better but you would be taking a risk in the experts opinion.

pen

 

[Bigg_Redd]

I have a cabin with a 20' cathedral ceiling that collects the heat my stove puts out. I want to pipe that heat to 3 back rooms ideally but would settle for one. I'm on batteries and an inverter so running a powerful fan would drain them quickly. The in-line booster fans are low wattage but too wimpy, I was told, to push air in this application.

What if I installed a cold air return duct in the back room, ran the duct under the cabin and had it come up or return to the floor behind my wood stove? Do you think that the upward movement of the air around my stove would "pull" air from the cold air return as it rose up above my stove and thus create air movement in the back room that might result in pulling some warm air into that back room? It is a crazy idea maybe but what do you folks think?

Not necesarily, but if you manage to do it, you'll be the first.

 

[stevec77]

Pen, if there is a code caution on the cold air return,s proximity to the stove then there must be a good reason for it. I don't know what it might be, though. Carbon dioxide concerns?

I think proximity is key. A return could hug the backside of the stove and act as a heat buffer to the back wall. The return metal would heat up,the return air there would heat up and float up creating air flow through the system. Lordy! How well theories works on paper!

What don't I know?

 

[pen]

Pen, if there is a code caution on the cold air return,s proximity to the stove then there must be a good reason for it. I don't know what it might be, though. Carbon dioxide concerns?

I think proximity is key. A return could hug the backside of the stove and act as a heat buffer to the back wall. The return metal would heat up,the return air there would heat up and float up creating air flow through the system. Lordy! How well theories works on paper!

What don't I know?

Agreed, on paper the theory is great. You'll know how it works in practice when you put it into and try it. I think your biggest problem would be that the hottest air will still be trapped in that cathedral part, and you won't have the hottest of the air easily being able to move to your back room.

If nobody posts the official numbers (i just searched google and the site quickly and couldn't find it) make a new post w/ that as the title on here and someone in the know will respond.

pen

 

[Renovation]

I have a cabin with a 20' cathedral ceiling that collects the heat my stove puts out. I want to pipe that heat to 3 back rooms ideally but would settle for one. I'm on batteries and an inverter so running a powerful fan would drain them quickly. The in-line booster fans are low wattage but too wimpy, I was told, to push air in this application.

What if I installed a cold air return duct in the back room, ran the duct under the cabin and had it come up or return to the floor behind my wood stove? Do you think that the upward movement of the air around my stove would "pull" air from the cold air return as it rose up above my stove and thus create air movement in the back room that might result in pulling some warm air into that back room? It is a crazy idea maybe but what do you folks think?

Hi Steve, and welcome! It sounds like you're living the good life, off the grid in your cabin.

Here are my thoughts--I'm not an expert on codes or HVAC, but I am a scientist and have done a little nosing around. Anyway, it happens that I made that exact suggestion in another thread, and no one had a heart attack, so that's a helpful sign. Folks have reported that moving the cool air around is the way to go, and hot air will replace it. Most do it with fans, but I have heard of more than one doing it with ducts, and being pleased.

I believe it was BattenKiller (please correct me if I'm wrong), who said he did such an arrangement for a friend, and it worked so well that the friend still gives him beers in thanks.

There are two key innovations:

1. Running a separate powered duct, independent of the central heating system.

2. Moving cold air from a distant area, and dumping it near the stove.

I'm betting the air movement by convection would be better than nothing (insulate the **** out of that duct!), and that you'll need an inline duct fan to get useful flow. But I bet that useful flow doesn't need to be very much, and that a battery could run it. Just a little movement would make a difference over time.

Regarding your cathedral ceiling, and your lack of electricity, you may have to just accept the inefficiency. You could use the same principle, and aim a floor fan upward. Actually, I believe large fans are quite efficient, and don't use a lot of power at low speeds. You could consider putting a big ceiling fan up there, and running it on low if you can spare the juice. But even a flow fan on low speed might make a big difference.

Regarding code, I believe the rule is you cannot have a *return* inlet for your central HVAC within something like 10 feet of a wood stove. I'm guessing the reason is that if the stove belches carbon monoxide, it won't get recirculated in concentrated form and kill you in your sleep. Seems like a good idea.

But I know of no such restriction for outlets, which is what you are proposing, other than not having combustibles within the specified clearances for your stove. I'm planning on having an outlet behind my stove, for the same reason--I'm planning on locating it behind the metal wall shield behind my stove, to cool it and augment natural convection.

And of course, you should insulate the Dickens out of your cabin and ductwork to make it work. If you're gushing heat to the outside, no low-power fixes are going to work.

The short version: I think your idea is great, and that you should go for it with an insulated and powered duct, and make sure to come back and tell us all how you made out so we can learn from you.

HTH, and good luck!

 

[Dune]

The cold air return duct pipe is a great idea. You don't need much flow to make it work. An inducterator should do fine. The only problem I can see is the cathedral ceiling. You may need a ceiling fan turning slowly to make it work.

 

[Renovation]

The cold air return duct pipe is a great idea. You don't need much flow to make it work. An inducterator sound do fine. The only problem I can see it the cathedral ceiling. You may need a fan turning slowly to make it work.

+1 Wow, you said what I said in five sentences.

 

[Dune]

The cold air return duct pipe is a great idea. You don't need much flow to make it work. An inducterator sound do fine. The only problem I can see it the cathedral ceiling. You may need a fan turning slowly to make it work.

+1 Wow, you what I said in five sentences.

Sorry, too many Jerzey Kozinski novels as a youth.

 

[pen]

If there is no code for cold air plumbing back to the stove, then why not just bring the cold air duct right back to the rear heat shield of the stove. On mine, there is a plate I can remove for installing a blower which could also work well for mounting the ducting directly too. Then, as the air is heated at the back of the stove, it would be pulling directly from the cold air in your rooms.

pen

 

[Renovation]

If there is no code for cold air plumbing back to the stove, then why not just bring the cold air duct right back to the rear heat shield of the stove. On mine, there is a plate I can remove for installing a blower which could also work well for mounting the ducting directly too. Then, as the air is heated at the back of the stove, it would be pulling directly from the cold air in your rooms.

pen

+1 Great idea. Then you get air circulation to your back room *and* a stove blower with one fan. WIN!

 

[Renovation]

Duplicate post, sorry.

 

[Fake coal burner]

I have a cabin with a 20' cathedral ceiling that collects the heat my stove puts out. I want to pipe that heat to 3 back rooms ideally but would settle for one. I'm on batteries and an inverter so running a powerful fan would drain them quickly. The in-line booster fans are low wattage but too wimpy, I was told, to push air in this application.

What if I installed a cold air return duct in the back room, ran the duct under the cabin and had it come up or return to the floor behind my wood stove? Do you think that the upward movement of the air around my stove would "pull" air from the cold air return as it rose up above my stove and thus create air movement in the back room that might result in pulling some warm air into that back room? It is a crazy idea maybe but what do you folks think?

That is how I have mine. Use a small bath fan to move cold air. If you are using gravity feed system air might just settle in the low spots in pipe. all though the gravity coal furnace we had with no fan worked good. Try it both ways. Mine is 3 inch pipe 50 feet long. no isolation around pipe. You only have to move a small amount of cold air to be replaced for warm air to take its place.

 

[stevec77]

Hi Everyone,

Awsome perspectives and advice by all. Many thanks!

 

[Renovation]

Hi Everyone,

Awsome perspectives and advice by all. Many thanks!

Thanks for the fun topic. I'll reiterate my suggestion of insulating the duct.

If you really want to thank us, report back if you try something! (smile)