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: Wood Stove and HVAC Return Duct Proximity


dieselscout80
12-02-2011, 09:27 PM
I want to install a wood stove in our home's basement.

My basement HVAC return duct/grill/filter is in the ceiling of the basement.


Can I install a wood stove directly under the HVAC return duct? My thinking is that we can run our heat pumps blower fan in the constant on setting and circulate the heat from the wood stove throughout the house.

Is this possible?
Is this ok per code?
Is this a good or bad idea?

Do I need to provide the wood stove a fresh air intake out side the basement?

Tencubed
12-02-2011, 09:54 PM
When we were in the HVAC/R business it was a common thing to use the central heating ducting and fan to circulate heat from a wood or pellet stove. I've never installed a RA directly over a wood stove so can't comment on any codes in that regard. Some, not all, insurance companies require a temperature limit switch be installed in the RA duct close to the grill to detect high temperatures. I've never seen a code that required this option. This switch is designed to shut down the fan if temperatures exceed what the duct is designed to safely handle. This will keep the duct system from blowing fire thru the house in case of a fire. Well worth the investment in my opinion.

It's also possible, and I believe desirable, to install a low temperature sensor that will shut the fan off if the stove goes out and the air temperature drops. Why paddle cold air around?

These switching systems are not hard to install and should be wired to allow the central heating system to operate normally.

As with any wood, or other heating system, it's important to have up to date and properly operating smoke detectors.

I'd suggest you contact your local code officer and insurance for a definitive answer on this, it's a good question.

Mike

paul52446m
12-02-2011, 10:28 PM
I want to install a wood stove in our home's basement.

My basement HVAC return duct/grill/filter is in the ceiling of the basement.


Can I install a wood stove directly under the HVAC return duct? My thinking is that we can run our heat pumps blower fan in the constant on setting and circulate the heat from the wood stove throughout the house.

Is this possible?
Is this ok per code?
Is this a good or bad idea?

Do I need to provide the wood stove a fresh air intake out side the basement?
I don't think you should put the wood stove directly under the return opening.
I don't know how far it is from this opening to your heating blower. What you have to watch is every blower motor has a temp. range that they can work with. So if you get too hot of air going into the blower, you will damage the motor and it could keep turning off on internal over load or over heat switch.
If you move the wood burner a ways away from the return so it mixes more of the house air, this way you will not over heat. Wood burner ducts should be at least 2" from and wood and i would bet your are closer than that.
Do you have a open stairs to let the house air get to the basement. Even if you do you will still be pulling a little vacuum in the basement to pull the house air down to the basement. So you will need a air tight wood burner
that can take it burner air from out side. Paul

dieselscout80
12-03-2011, 04:42 PM
I don't think you should put the wood stove directly under the return opening.
I don't know how far it is from this opening to your heating blower. What you have to watch is every blower motor has a temp. range that they can work with. So if you get too hot of air going into the blower, you will damage the motor and it could keep turning off on internal over load or over heat switch.
If you move the wood burner a ways away from the return so it mixes more of the house air, this way you will not over heat. Wood burner ducts should be at least 2" from and wood and i would bet your are closer than that.
Do you have a open stairs to let the house air get to the basement. Even if you do you will still be pulling a little vacuum in the basement to pull the house air down to the basement. So you will need a air tight wood burner
that can take it burner air from out side. Paul

The return duct goes through the unheated crawl space and the return duct is +20' long.

I have a open stair case that is right by where the stove will go if it goes there.

Is it okay to pull outside air for the stove from the unheated crawl space?

LLigetfa
12-03-2011, 05:04 PM
Always check with the AHJ but I'm sure most places, code says the stove needs to be at least 10 feet away from a return duct.

Is the crawlspace vented and insulated because you will be drawing a lot of really cold air through the space. Probably better to pipe the OAK to the outside so you'll have warmer floors.

paul52446m
12-03-2011, 06:07 PM
The return duct goes through the unheated crawl space and the return duct is +20' long.

I have a open stair case that is right by where the stove will go if it goes there.

Is it okay to pull outside air for the stove from the unheated crawl space?

Are you saying that you don't have any return air up stairs?
In a cold area there in no such thing as a untreated crawl space. I am sure you close your vents in the winter time. We have treat this space so pipes don't freeze.
So pay attention to my first post and also the post that LLigetfa posted.
i don't have too much to do with wood burners, but i have been a heating dealer for over 40 years. Your wood stove needs to be a air tight unit that can duct it burner air from out side. Paul

likes old stuff
12-03-2011, 06:35 PM
I have the wood stove in one corner of the house, and the return air is in the middle. I thought that running the blower fan of the furnace should work.I still do it but it not all that effective. If you find something that works let me know. One side is warm the other side fair. Good luck

dieselscout80
12-03-2011, 10:25 PM
Are you saying that you don't have any return air up stairs?
In a cold area there in no such thing as a untreated crawl space. I am sure you close your vents in the winter time. We have treat this space so pipes don't freeze.
So pay attention to my first post and also the post that LLigetfa posted.
i don't have too much to do with wood burners, but i have been a heating dealer for over 40 years. Your wood stove needs to be a air tight unit that can duct it burner air from out side. Paul

I do have a return upstairs.

The crawl space is insulated and I do close the vents.

I can run the outside air vent to the outside rather than the crawl space.

paul52446m
12-04-2011, 07:30 PM
I do have a return upstairs.

The crawl space is insulated and I do close the vents.

I can run the outside air vent to the outside rather than the crawl space.
So if you are putting hot air from your heating system in the basement and you are taking return From the basement. If the amount is the same then you will not pull a vacuum on the basement. But when you burn wood use use up a lot of air ind the wood stove is made to work in a pos. pressure area, not a neg. area.
This is why i said you need to take the burner air from out side so it will burn right. There is not a real good way to put the heat from a space heating wood burner to where you want it The only way to do that is to buy a wood burning furnace and duct it in line properly with your other heating unit. Paul

LLigetfa
12-04-2011, 07:52 PM
I have an RSF Onyx with central heat option but rather than trying to push hot air to remote parts of the house, I reversed it and push cold air from the far end of the house to the stove.

dieselscout80
12-06-2011, 10:42 AM
may have to move the return duct to get the 10'.

My upstairs return filter is 20"x30" and the HVAC unit is a 5 ton heat pump and the total home is 2700 sqft (1920 sqft upstair).

The current basement return duct is a 10"x20" filter opening attached to the main return line.

I can run it between the floor joist, but can I fit a big enough duct between 2"x10" floor joist on 16" centers (basically a 9.25"x14.5").

What size return ducting and vent is needed for 780 sqft?

If one run in the space between the joists is not enough would it work to do two runs side by side to a common grate/filter?

Curly69
12-07-2011, 02:49 PM
Heat is going to rise no matter what. I have my R/A high in the ceiling. So about 7-10' away from my wood stove I but a thermostat that closes on temp rise. I wired it to turn on my furnace blower on low speed. Works pretty well.
Should mention that my R/A is about 15' from the stove.

TractorJoe222
12-14-2011, 02:50 PM
My dad has a wood/coal stove in the basement. He took a deadend of a heat run and put a small fan on it. It was out of a Air Cleaner machine. He runs filters on the blower and pulls heat from the basement. He has done this for years and never had a problem. May not be code but pushes a warm air throughout the house.