Creative thoughts on moving air

[68 Couper]

I have a Napoleon 1100cp being picked up later this week. It's been 15 years since I lived with wood heat and I have learned allot thanks to this forum. Thanks...
I'm thinking about setting up the 1100 in front of a hearth which is not called for at all by the manufacturer. They call for 6" on a wall and 2" on a corner to combustionables. I'm thinking about sealing the hearth on sides and bottom just to leave the top open. On the wall, inside the hearth would be a cold air return for my forced air furnace. This is where the cool air comes from. Then, I'll set up feeds from the non-stove rooms from their low return vents. I'll leave the upper vents out of the systen because of AC returns in the summer.
What do you think? I'm still toying with the best way to get heat transfer to the 1" air gap. The hope is to create a convection heat pump that moves air around the house??? What do you guys think?

DISCLAIMER: This is a very specific application following manufacturer's minimum clearances. Don't try this at home. LOL

:coolsmile: ,
Couper

 

[mayhem]

Wouldn't doing this actually bring air towards the stove when your furnace is running? I'm assuming your intention is to heat the air going into your ducts with the wood stove and maybe just run the air pump, not the furnace to move warm air around the house. I'm skeptical that you'll get significant warm air out the other end of the ducts...I just don't think the stove will heat the air fast enough or hot enough for it to be particularly warm on the other end of the duct.

I may be reading this backwards but when you say a cold air return duct in the hearth, to me that means that will be where you're pumping air into the HVAC system, is that correct?

Might be better off reversing the flow and put an outlet in the hearth to help gently push the warm air away from the stove while using the returns in your more remote rooms to fed the ducts. Moving heat from a woodstove seems to work best by pumping cold air out of rooms you want to heat up towards the stove instead of trying to force warm air from the stove into the ducts. By pumping the cold air out of the distant rooms you're creating a low pressure area where its cold and a high pressure area where its warm...since the system will make every effort to equalize pressure throughout the house the only thing it can do is push alot of warm air into those rooms in an effort to return the system to equilibrium.

Its actually a pretty good idea...I may have to try it myself, got two rooms that just don't want to heat up that much...40 feet of ducting and a squirrel cage fan might do wonders for me.

 

[68 Couper]

I'm thinking no furnace fan, just convection.

Couper

 

[begreen]

There are definitely code and safety issues to consider here. I believe code states that the air returns must be at least 10 ft from the stove. If you describe the current setup, stove room location and first floor plan we may be able to suggest an alternative.

Here's an article that should help:

https://www.hearth.com/econtent/index.php/wiki/Move_Stove_Heat_around_house/

 

[68 Couper]

There are definitely code and safety issues to consider here. I believe code states that the air returns must be at least 10 ft from the stove. If you describe the current setup, stove room location and first floor plan we may be able to suggest an alternative.

Here's an article that should help:

https://www.hearth.com/econtent/index.php/wiki/Move_Stove_Heat_around_house/

Thanks for your input but the article did not address what I'm talking about. My home is a 1000 sf ranch on a crawl. The Nap 1100 will go into the living room on the interior wall. There is an air return on that wall and it pulls from both the living room and the bedroom on the other side of that wall. This is a square hole streight through. So I'm thinking if I block off the connection to the furnace and build the hearth over it with an air gap, the colder air from the bedroom would be pulled up the air gap in the hearth by a warming effect on the hearth from the stove. Then exit at the air gap opening on the top of the hearth. It's not all that different than the 1" gap on the bottom on the non- combustible heat shields that folks use to reduce clearance. Except the air is pulled through a hole in the wall from another room. The main difference would be I am not shielding the wall from heat to combustibles. I would be encouraging it by use of a heat conducting material like hammered thin sheet copper. Or something else cool and a good conductor.

All clearances to combustibles will be by the book. I'm not subject to inspection according to the building inspector. Code is not a concern of mine. Safety is important. But I fail to see any issues there.

What do you think, will it circulate air?

Thanks,
Couper

 

[68 Couper]

Wouldn't doing this actually bring air towards the stove when your furnace is running? I'm assuming your intention is to heat the air going into your ducts with the wood stove and maybe just run the air pump, not the furnace to move warm air around the house. I'm skeptical that you'll get significant warm air out the other end of the ducts...I just don't think the stove will heat the air fast enough or hot enough for it to be particularly warm on the other end of the duct.

I may be reading this backwards but when you say a cold air return duct in the hearth, to me that means that will be where you're pumping air into the HVAC system, is that correct?

Might be better off reversing the flow and put an outlet in the hearth to help gently push the warm air away from the stove while using the returns in your more remote rooms to fed the ducts. Moving heat from a woodstove seems to work best by pumping cold air out of rooms you want to heat up towards the stove instead of trying to force warm air from the stove into the ducts. By pumping the cold air out of the distant rooms you're creating a low pressure area where its cold and a high pressure area where its warm...since the system will make every effort to equalize pressure throughout the house the only thing it can do is push alot of warm air into those rooms in an effort to return the system to equilibrium.

Its actually a pretty good idea...I may have to try it myself, got two rooms that just don't want to heat up that much...40 feet of ducting and a squirrel cage fan might do wonders for me.

I have the 2 same rooms, both are bedrooms. The problem with trying to duct warm air is the cooling effect of the ductwork on the slightly warmed air. My ducts go through the crawl and attic. Be Green brings up a good point on creating low pressure in the stove room as well. I don't want to create smoke spilling nonsense. Especially in shoulder seasons where the draft is not as intense.

I think in the cold room situation it might also be good to seal the windows up extra well. Lets face it, the air that goes up the chimney has to come from somewhere....

Any other ideas?

Couper

 

[mayhem]

I think we both misunderstood each other. I thought you were trying to forcibly duct warm air from the stove to the bedrooms...effectively using your woodstove instead of your furnace, which is why I was pointing out the cooling effect in the dsuct would probably make any warm air movement negligible.

Combustion air does need to come from someplace, true. In the cases of a really tightly sealed house you probably want to consider an outside air kit which will bring in cold combustion air from outside the house directly to the stove.

I think ducting returns from your cold rooms and using a small fan to move air into the stove room will do wonders for you. You take cold air out of the bedrooms as low as possibe on the wall and push it into the stove room in a location that mees whatever offset regs you're subject to. That air will create a low pressure area in the bedrooms and high pressure in the stove room. Nert result is that cool air will forcibly displace the warm air out of the stove room and it will move towards the low pressure area you created in the bedrooms. To test it just put s box fan on the floor int he doorway of your cool room and blow cool air out of there towards the stove. If you stand behind the fan you'll actually feel a warm breeze blowing in your face.

I hadn't considered the ducting idea before, but now the gears are turning in my head. Could be a nice solution, at least for my particular setup.

 

[begreen]

It would probably help to post a diagram or two to understand what the goal is and how it would be done. There are too many questions that a simple picture or two could explain. Blocking off part of a ventilating system return is not a good idea. It will unbalance the system. Another return of equal size would have to be added. Having a ventilation system return duct within 10 ft of the stove is also against code. If the idea is to increase heat circulation to the other rooms, it doesn't sound like it will work, but it's possible I'm missing something or have not visualized the idea well. Please post a diagram.

In a ranch house, passive distribution of the stove heat is often unsuccessful. However good results have been achieved with using a fan on the floor blowing air from the cooler room into the room with the stove.

 

[68 Couper]

It would probably help to post a diagram or two to understand what the goal is and how it would be done. There are too many questions that a simple picture or two could explain. Blocking off part of a ventilating system return is not a good idea. It will unbalance the system. Another return of equal size would have to be added. Having a ventilation system return duct within 10 ft of the stove is also against code. If the idea is to increase heat circulation to the other rooms, it doesn't sound like it will work, but it's possible I'm missing something or have not visualized the idea well. Please post a diagram.

In a ranch house, passive distribution of the stove heat is often unsuccessful. However good results have been achieved with using a fan on the floor blowing air from the cooler room into the room with the stove.

Here's a link to the floor plan I drew up. The stove can be on the interior wall as represented or a corner install the left of the square icon. But that is pulling it even further away from the other rooms. The corner install would be best for space with a small home. That area was a book shelf before I began the living room remodel. I'm re-finishing the hardwood floors and maybe opening a hole to the kitchen for a breakfast bar. I'm thinking that would help a little. It's not load-bearing and would be pretty easy to accomplish.


http://www.floorplanner.com//projects/18470412/floors/18490744/designs/19806456?guest_pass=q4gpoe

Just to simplify the circulation idea, put a hole thru the wall into the bedroom, build a hearth over it sealing the bottom and sides, whatever air rises from heat in the air gap, displaces from the bedroom pulling air from the living room. Move warm air to cold room...

Thanks,
Couper

 

[begreen]

Link seems to be missing.

 

[68 Couper]

This program is acting up, sorry...

Couper

 

[begreen]

That link works. Nifty little program. I see your dilemma now. I could be wrong, but suspect that the simple fix will not be that effective. But if you don't mind the extra hole in the wall, it probably won't hurt to try it. Keeping the bedroom door open or installing a return air grille though it would probably help. Let us know.

If not, then a small fan blowing from the room into the living room should make a difference. This could be a 4" muffin fan, set in low in the wall.

 

[68 Couper]

BeGreen- Thanks for your input.

I'm still in the brainstorming mode for material and constriction on the hearth. I have to have non-combustible floor protection so I picked up 3 sheets of durarock and will probably do a 2" tile over dura raised deal. I like the look of flush to the floor but I'm not very excited about cutting out my hardwood to put down the durarock and tile.

The hearth's material is what I'm looking for ideas on. There is a couple directions I see available. Heat transfer is the goal of course. So right now, I've come up with 2" vertical durarock strips with hammered copper plate on it. Edge it with stone maybe? I read on here that marble is a poor insulator but I don't know what I could affix it to so it would warm the air gap well.

I know it is different thinking along the lines of heat transfer and not insulation from the stove but that is what I want to go for.

Any ideas?
Couper

 

[EL DRIFTO]

this is a repost, but it might be easier to search "cold air return"

i've tried this recently
yesturday, while the wife was at work i tried to light the furnace, reuseable air filter on fire
i tried it with the fan running too, it cleaned out all the deeply embedded dust, but no ignition
how'd that smell?

although the convection is the obvious goal,
my main issue is heating my house quickly
my stove is in the unfinished basement, concrete walls & floor
with steady use, the hvac fan is unneccessary
but when i haven't been home all day, it's 67 upstairs...

my first attempt was rerouting the cold air return to the two joist spaces directly above the stove
this resulted in very low outlet temps, very drafty feeling with the hvac fan on high @ 67...
not to mention the electricity & noise

i used an additional hvac thermostat, set on ac, to come on when the top of the hvac furnace reaches 91+
it feeds off the existing hvac htr thermostat upstairs,
only the fan comes on, no gas heat & this way the fan stops "helping" once the upstairs gets over 71-72

i may have knocked a % off of the 120" min here...
my master hvac friend mentioned keeping intake temps below 100 for the fan motor's sake
so i located a thermometer in the cold air return, it hasn't gotten over 92 @ 500
i have a metal screen over inlet, i can touch most of metal
i throughly cleaned out the vents before i rerouted them & the only thing that could catch fire in the huge all metal encased hvac furnace is the filter
i contemplated if it would do more than smoke damage the house if i threw in a cup of gasoline, match & fan on...

it seems to be working now, with the two thermostats
the fan shuts off mostly since it's fed off the existing hvac programable thermostat
only comes on if the stove is rollin, or intermittantly (bsmt ac thermostat)
literally on top of the furnace is a good location, keeps it from cycling excessively

the proof is in the fact that i used to come down stairs & was hit by the heat...
now it's the same temp down stairs & stairway
furthermore, i had the bedroom end of the house vents shut off since the stove is under them
but after my most recent cold air location change, the bedrooms above the stove were the only cold ones until i opened their vents back up
i'm new @ the stove this year, but this season has the fan running from 5-10 pm every night
then it doesnt need to run over night obviously, or the next morning, or all day with no one home...