Cold Air Return?

Av8r:

I placed a small fan on the cold air return that I just finished yesterday and you know what I found: I had two sources of cold air coming toward the stove instead of just one across the floor. The temps in the furthest two rooms did not increase at all. I have an old farm house which I have all of the upstairs closed off except the stairway. Last night I closed the two doors leading to the stairway. I had 1060sq.ft. and I am now down to 850 sq.ft. of room to be heated and this is down from the total of 2500sq.ft I have. Even with this small amount of space I still had the draft across the floor and now an added draft coming up out of the new cold air return. Closing off the stairway made no difference in the total temp of the rooms. My coal stove is running at 100 percent( 575 degrees) 24/7. The room where the coal stove is located is 80 degrees and the furthest room was 59 degrees this morning. Right now I am at a loss as to what I can do to get the heat into the last two rooms. I think I wasted an entire day yesterday running that cold air return. The only solution I can see right now is to turn on the oil heat for those two rooms. Let me know how you make out with any changes you do with your setup. I hope you have better luck moving the heat than I have. I'm always open to crazy ideas.

wayne.

When I was working on my cold air return, I tried several things before concluding the project.

After exhausting the possibilities of natural convection and fans blowing this way and that, I decided I needed a "cold air return path". My first step was to cut a hole, and place a return register into my basement, from the cold end of the house. Pictured here >>
http://nepacrossroads.com/download/file ... &mode=view The rest of that story can be seen by following the "project" links below.

This didn't work well, as the air in the basement wasn't heated, and had there been a "flow loop", the air would have lost a bunch of heat to the basement. Next, I ran a flexible 6" duct, through the basement space and back to the stove room. This worked better, but the cold end of the living space was still chilly.

Next, I built and included a "duct fan" into the return air duct. The reason I built a duct fan, was because I didn't like what was available. They were either real flimsy or very expensive, plus I had a fan. The fan I had was a two speed fan from a Broan Range Hood. http://parts.broan-nutone.com/broan/Shop?DSP=30115&PCR=1:1000&IID=413001 .. See first item #9, p/n 97011220 @ $35.46. I bent the ends of the mounting arms to 90* angle and mounted it in a piece of 8" pipe. The wire was brought through a grommet in the pipe sidewall into a small junction box, with a "single pole, double throw, center off" switch for the two speeds, with a cord from there. The 8" pipe was fitted with two 8" to 6" reducers to marry up with the flex duct. This fan runs continuously, as the coal stove makes heat "continuously". This set-up will pretty much bring the heat to the end of the house, furthest from the stove.

Edit: Maybe I should say, "This set-up will pretty much exhaust the cold air from the far end of the house, to allow space for the warm air."

Diagram of whole heat flow. Really temperamental stove/draft !! ... Duct fan not shown.

the snowman wrote:
Even with this small amount of space I still had the draft across the floor and now an added draft coming up out of the new cold air return.
wayne.

It sounds like this cold air, being pulled from the basement, is needed for your stove's "combustion air". Here again, if you look at my "projects" links, you'll find "outside air source".

Another thought, I had: Do you have a barometric damper on your stove set-up? Is it open most of the time, exhausting house air up the chimney?

Dallas:

I do have a barometric damper on the stove and it is closed almost all of the time. The only time it opens is when I am adding coal or I have wind gusts outside. The chimney is pulling a constant .05 according to the manometer which is hooked up all of the time. The cold air return is hooked up directly to the furthest room from the stove and it travels directly to where it exits next to the stove where the distribution fan I have picks it up and blows it around the stove. The duct is a solid six in diameter pipe with all seams screwed and taped. It does run through the cold celler. It is a forty foot run through the cold cellar. I had a fan installed on the underside of the grate in the furthest room blowing down into the duct. It did move a lot of air to the stove, however, the rooms still stayed cool and I still had the cool air coming across the floor to the living room. After I post this I will look at your links. Thanks.

wayne.

Is your newly installed duct, connected directly to the return grate in the bedroom? In other words, is it a closed loop from the bedroom to the stove, with the exception of the short distance, right at the stove? The reason I ask, is in regard to, your "fan right underneath the grate".

Dallas:

Yes the newly installed duct is connected directly to the grate. I took the grate out so I could install the fan in the duct just under the grate. I reinstalled the grate. It is a closed loop except for the short distance at the stove (four inches). I did a smoke test so I could see the air flow and found out that the smoke source had to be within six inches of the grate to show any sign of air flow towards the grate. Any further distance and the flow was flowing across the floor towards the direction of the stove in the living room. I have a good flow coming out of the duct at the stove. Tomorrow I will crawl under the house and take a look at the entire run just to see if I am missing something. I will have the fan on when I do this so I can see if I have any leaks in the duct. I will keep you posted as to what I find. If you have any ideas please let me know. I appreciate the feedback. Thanks.

wayne.

I think, any minor imperfections, which you might find, are NOT going to be the cause of the problem.

My circulation system has a total of three fans involved: the circulation fan on the stove, the duct fan on the head of the cold air return, and another fan from the output of the return, across the room to the stove. The other thing to keep in mind, as you progress, faster moving warm air, gives the feeling of being chilly.

Dallas:

I have a distribution fan at the stove, one in the top of a doorway pushing warm air towards the two cold rooms. and one at the head of the cold air return and a ceiling fan moving warm air down from the ceiling in the living room. Last night I crawled under the house and checked the entire run. I did not find any problems with the duct. I then installed a higher cfm fan in the duct. I did another smoke test to see the air flow. I only had air flow towards the cold air return within one foot of the vent. Any further distance and the flow flowed towards the coal stove across the floor. The air coming out of the return at the stove was ice cold. Maybe since the return is forty foot long and it has to travel the entire distance through a cold cellar and cold crawl space the air is being cooled. I know that I don't like running the coal stove at 100 percent 24/7 at 575 degrees. I am reloading the stove every four hours. I am burning between 70-80 pounds of coal per day trying to heat 1060sq. ft. of space and I have not reached the coldest part of the winter yet. This is double the amount of coal I figured I would use per day this season. Today I shut the fan in the return off and was forced to turn on the furnace to heat the last two rooms. Unless I find a solution to efficiently move the warm air into the last two rooms and eliminate the cold air across the floor, I will have no alternative but to run the furnace this winter. I am still open to any crazy thoughts.

wayne.

I'm pondering this whole situation and I can't quite get my head around it.

First of all, you are using way too much coal, it seems. ... but, taking that a step further, with a burn like that, the stove has to be pulling a ton of air out of the house for combustion. This could explain, the cold air coming "up" out of the floor grate and heading toward the stove. At this point, I would try cracking a window about 4" in the vicinity of the stove, at the same time observing the air activity at the grate, without any fan running. If the open window satisfies the air need and the flow at the grate stops or reverses, the stove is using the air. So, now we'd have to look at the need for outside air or (Greg, take another Nitro tab!) possibly a MPD to keep some of the heat in and reduce the flow up the chimney. ... I'm sitting here thinking ... when the furnace runs, what happens to the air flow in the grate? If the furnace is in the basement, the air at the grate might go down.??

I'll ponder some more.

I went back to see, once again, what we are dealing with. ... An old farm house, such as mine. Have you insulated the attic and done other weatherization? Does the house sit on an old drafty field stone foundation?

Well I bit the bullet and bought the stuff to vent directly back to the stove. I have a blower in line below the register, used flex duct back to the blower on the stove. I cut out a piece from a rigid duct and fit it over the blower on the stove. So, in theory, I hope the stove is sucking cold air from upstairs, reheating it and blowing it back through my heat registers. If I knew then what I know now, I would have bought a totally different stove. Oh well, at that time I was only trying to heat the basement and have some radiate upstairs. Here's some pics.....

Qball wrote:Well I bit the bullet and bought the stuff to vent directly back to the stove. I have a blower in line below the register, used flex duct back to the blower on the stove

Neat!

I assume the floor register (pic 1) is the return to your blower intake, but where does the stove blower (heated air) duct to?

It sure does look familiar I never had the Harley in next to my stove, though.

The reason you have gone through , what you did, is probably because you bought a "room heater", saw that it had more potential and went from there.

Good job! You didn't say how it seems to be working.

Hey guys, getting ready to drop a couple of registers into 2 back bedrooms. 80 in the basement with the stove, back bedrooms 63 to 65. My question is, if I put the register on the far end of the room with my sons bed inbetween the door (where the warm air will come in from) and the register, will he be feeling the slightly cooler air and thus making him feel cold? or will the cooler air move along the floor. Also would it affect in any great way if the vent was put under a dresser... I'm pretty sure I read somewhere to put the vents on the outside walls under a window, butt he is above my garage and above my garage door, so I might have to put the vent where his dresser is nearer to an inside wall. thanks

Chris