Furnace fan only use?

[nshif]

Im about to install my backup propane furnace system in a new construction house so now is the time to get it right. My stove selection at this point is a Quadfire 4300. It a 2000 Sq Ft house which will be 2200 Sq in the next year. 2 story, 16'- 26' cathedral ceiling in a 400 Sq great room open to a loft above with bedrooms in the back on 1st and 2nd levels. Stove will be in the great room opposite end from the bedrooms. What Im thinking of doing is adding a second cold air return(which I could close off)from behind or next to the stove to the furnace. Then when the stove is up to temp run the fan on the furnace to circulate the warm air. What do you think?

 

[elkimmeg]

First of all removing combustion air so near the stove will not help the stove functioning. Second on a new home, there is no excuse to ignore code and place a return near
another combustion appliance. Third of all I would hope you install a balance system supply = returns. You are now preposing to have an un balance system?

When you use your returns, what are your supplies doing. Did you also know if your HVAC system is not listed to extract heat from another appliance then it is non code compliant to use it in a manner to which it is not listed to be used. Since you are now using an open combustion source, doyou intend to alarm that duct system to your smoke fire supression system with automatic shut down and alarmed smoke dampers? With open combustion system code requires contanment or prevention the spread of smoke and noxious gasse

finally many have tried and just as many have not suceeded using returns to distrobute heat The only thing the suceeded was to expose them and their familly to greater life safety issues
Why do we draft stop everything, then ignore the value of containment? the whole purpose of draft stopping

 

[nshif]

My combustion air will be from outside so that is not an issue. I did not intend to be so close to the stove as to draw HOT air but just warmed air from around it. My only thought was to try to "balance the heat flow through the house.

 

[Mike Wilson]

You are not directly connecting the return to the stove, so code is not an issue, absolutely, not whatsoever, period, end of statement. You need neither alarms nor smoke dampers. We had this out last year in a thread so long that it had two area codes, and the verdict was, that so long as the stove is not directly connected to the duct, code re: HVAC ducts is not an issue.

Now, on a practical matter, it won't work. Or, it won't work as well as you think it might. You have the liberty of installing a duct there, so if it works into your plans, try it. I'll let you know this, I have 29' and 34' cathedral ceilings in several areas, and have used my HVAC system to move warm air from the insert (return is close to the insert). I lost more heat bringing the air through the ducts than it was worth. In other words, the house was considerably warmer without the air handlers running, than with... by about 6 degrees. You wind up warming the duct work.

Now, what I would consider is putting a single run from the top of your cathedral down to the ground, or wiring up a fan up there. Gets the air moving where you want it. But... note this... the natural convection from the cathedral will cause some of the warm air to stream down on the walls oppsite the stove (assuming stove is on the "low" side)... and its more than you'd think.

YMMV...

-- Mike

 

[nshif]

Mike,
I agree good point. But this return will be in insulated space and not subjected to alot of heat loss. Just thought it might help to balance things out. I will have ceiling fans in in the great room (2) 1 in the loft and in both bedrooms ( up and down stairs)

 

[Mike Wilson]

Mike,
I agree good point. But this return will be in insulated space and not subjected to alot of heat loss. Just thought it might help to balance things out. I will have ceiling fans in in the great room (2) 1 in the loft and in both bedrooms ( up and down stairs)

Understood. My returns are in insulated space as well. Not trying to crash on your idea, just that I had high hopes for the same idea, and it wasn't what I expected.

-- Mike

 

[nshif]

Just re read your reply and yes the stove will be on the low side. my concern is that the heat wont get to the back of the house so this was the reason for the idea. Its a pretty cheap test ( in the grand scheme of things) to try.

 

[Marty]

Has anyone ever tried a stand alone cold air return from the furthest, coldest reaches of the house to the vicinity of the stove in order to create more natural heat migration to the further vacated places?

 

[nshif]

Marty,
that is what im trying to do.

 

[elkimmeg]

On the design end IT has been prover that flattening off the cathedral ceiling instead or a v shape Apex, allows better flowing of heat around the ceilings better overall air movement.
The Apex also traps heat and disrupts flow patterns. The conclusion Mike posted are his conclusion Not shared by me. By using you system to move air from near a open conbustion vestel you also increase the risk of excellerating spread of smoke poisoneous gasses and fire be drawn into that system and spread into your sleeping quarters. In comcercial code, This is addressed, the ability to contain or stop transmission of such to other areas. Alarmed smoke dampers and fire dampers are used. No this is not mandated in residential codes yet. I do not feel as Mike does it is ok I feel one should do everything possible to reduce risk. Mike on the other hand advocates risk taking. Mike are you denying the potential of smoke and fire gettting sucked into the return system
Are you telling everone it is a safe practice?

I think every home duct system should be alarmed to induce automatic shutdown upon detection of fire or smoke. I have taken it to my State advisory board to be consider.
IT is not cost prohibited and really not much more that an oxogen depletion device to trip shutdown except smoke is now detected. I am working on a post where part of it deals with HVAC ducting and too much wasted energy mostly to poor design and leaky delivery systems.

I have the latest energy star Homes p publication on my deck in front of me

Ducts not sealed?
1 Contributes to air leakage in homes
_ adds 300-305 to air changes while blower is runninbg
2. Reduced confort in home
- increases drafts
-reduces air delivery/ unbalanced airflows
Can contribute to backdrafting.

I wish I could publish the entire pamphlet

I have followed some of you other post or responses and I appreciate your willingness to help and share knowledge

 

[Roospike]

Has anyone ever tried a stand alone cold air return from the furthest, coldest reaches of the house to the vicinity of the stove in order to create more natural heat migration to the further vacated places?

Thats my thoughts too.......

Cold air is harder to move then warm air so if one was to put a cold air return as its self from one side of the house and pull the cold air to the stove room then warm air should flow to the rooms that the cold air is being pulled from.

 

[elkimmeg]

Has anyone ever tried a stand alone cold air return from the furthest, coldest reaches of the house to the vicinity of the stove in order to create more natural heat migration to the further vacated places?

this will only work if warm air is also routed to replace the removed cooler air. Supply without returns are useless returns without supplies equally useless

 

[Roospike]

On the design end IT has been prover that flattening off the cathedral ceiling instead or a v shape Apex, allows better flowing of heat around the ceilings better overall air movement.
The Apex also traps heat and disrupts flow patterns. The conclusion Mike posted are his conclusion Not shared by me. By using you system to move air from near a open conbustion vestel you also increase the risk of excellerating spread of smoke poisoneous gasses and fire be drawn into that system and spread into your sleeping quarters. In comcercial code, This is addressed, the ability to contain or stop transmission of such to other areas. Alarmed smoke dampers and fire dampers are used. No this is not mandated in residential codes yet. I do not feel as Mike does it is ok I feel one should do everything possible to reduce risk. Mike on the other hand advocates risk taking. Mike are you denying the potential of smoke and fire gettting sucked into the return system
Are you telling everone it is a safe practice?

I think every home duct system should be alarmed to induce automatic shutdown upon detection of fire or smoke. I have taken it to my State advisory board to be consider.
IT is not cost prohibited and really not much more that an oxogen depletion device to trip shutdown except smoke is now detected. I am working on a post where part of it deals with HVAC ducting and too much wasted energy mostly to poor design and leaky delivery systems.

I have the latest energy star Homes p publication on my deck in front of me

Ducts not sealed?
1 Contributes to air leakage in homes
_ adds 300-305 to air changes while blower is runninbg
2. Reduced confort in home
- increases drafts
-reduces air delivery/ unbalanced airflows
Can contribute to backdrafting.

I wish I could publish the entire pamphlet

I have followed some of you other post or responses and I appreciate your willingness to help and share knowledge

How well does this "alarmed duct system" work in your house ?
How much did it cost to install into your home ?

 

[Sandor]

This issue comes up all the time.

When I designed my WV Chalet home, I put my return in the highest part of a huge open room, where the woodstove was. My net effect of moving heat around was almost zero. I warmed the duct work up, like Mike Wilson said.

I should have known better, because in my previous home in MD, I put a big return above the woodstove. Same. Zero.

Many on this site has tried using central HVAC to move woodstove heat around.

It JUST DOES NOT WORK. Period. So many of us have tried and failed. I agree, it makes no sense, but it just does not work.

 

[nshif]

Marty.
Ij ust got what you are suggesting, and my primary cold air return will do just that ... pluse mix the cold air with the warm air from the stove

 

[elkimmeg]

How well does this “alarmed duct system” work in your house ?
How much did it cost to install into your home ?

All that is involved is a sensor wire from one of your smoke detectors to a sensor when ararmed shuts down the power or curcuit
Many boilers are wired for this for comercial usage For instance the same redidential furnace and one used for comercial applications, cost about $50 more to be prewired for automatic shutdown. ITs not a lot of money for the safety it provides. The smoke detection system is there it could be wired to the heat detector usually found above the furnace

 

[Roospike]

How well does this “alarmed duct system” work in your house ?
How much did it cost to install into your home ?

All that is involved is a sensor wire from one of your smoke detectors to a sensor when ararmed shuts down the power or curcuit
Many boilers are wired for this for comercial usage For instance the same redidential furnace and one used for comercial applications, cost about $50 more to be prewired for automatic shutdown. ITs not a lot of money for the safety it provides. The smoke detection system is there it could be wired to the heat detector usually found above the furnace

Well the price dont seem too bad for what it does.
How log have you had yours installed Elk ?

 

[elkimmeg]

My heating system is oil fired forced hot water system no duct work here. If I were to do it again, I would be considering radaint heating

 

[nshif]

OK didnt mean to start a war. Ill give up on the idea and just use a few 19$ box fans to move heat around, I just had a thought.

 

[webbie]

I remember servicing a coal stove in a house that had a return in the same room. This was in NJ where it is common for systems not to be properly designed.... the return was BLACK from soot which had been pulled from the coal stove! Yes, outside air would help, but creating a negative pressure is usually not a good idea around stoves.

Aside from the tech end, the other folks are correct in that the air dilution is so great the the effect is lost.

 

[Marty]

Has anyone ever tried a stand alone cold air return from the furthest, coldest reaches of the house to the vicinity of the stove in order to create more natural heat migration to the further vacated places?

this will only work if warm air is also routed to replace the removed cooler air. Supply without returns are useless returns without supplies equally useless

I remember reading your comment from another thread that ducted cold air would infiltrate into a warm room better than the reverse scenario because of the greater density of the cold air.
My thought is that if you could bring the cold air to the warmest end of the opperation it would effect enough displacement to accelerate the natural migration of warmer air back to the negitive area that had been vacated. Assumeing there were no significant barriers (like closed doors or excessive distances) in its path.

 

[Mike Wilson]

Once more unto the breach, dear friends, once more...

Mike on the other hand advocates risk taking. Mike are you denying the potential of smoke and fire gettting sucked into the return system. Are you telling everone it is a safe practice?

No Elk, I'm not... But what I am doing is telling everyone that using an HVAC system to move warm air is not against code, as you specifically said it was.
To wit, I offer the following:

on a new home, there is no excuse to ignore code and place a return near another combustion appliance.

Please, tell us how doing this is ignoring code... because its not. Code does not address this, period. Like I asked last year, and the year before, if you can provide a citation to where it is stated in a residential code, in any of the 46 states and 4 commonwealths in this union, I will gladly concede the point. Otherwise, it is simply incorrect information.

-- Mike


Oh, and trust me, Elk, I can tell people what I advocate on my own, I don't need help.

And sorry NSHIF, its a touchy subject :coolgrin:

 

[begreen]

Elk, I have to side with Mike on this one. While I don't use the HVAC system to distribute the heat, it certainly can come on if the thermostat calls for heat while the stove is firing up or cooling down and should be considered safe. This happens in our house frequently. I hear the furnace or heat pump now kicking in and say, why don't I start a fire? It will be maybe 30-60 min. before the stove takes over the heating load. Should I shut off the furnace each time?

If the stove fails, what is the greater risk here, the woodstove, or the HVAC system? By these standards ducted heating systems should be banned outright or forced to all have smoke detectors connected to fire dampers and system cutoff. I suspect that would add an average of $500 to most installs.

More helpful might be understanding what is the incidence of woodstove failures creating fatalities due to HVAC air distribution systems. Perhaps this is a higher figure than I am aware of.

 

[Roospike]

Has anyone ever tried a stand alone cold air return from the furthest, coldest reaches of the house to the vicinity of the stove in order to create more natural heat migration to the further vacated places?

this will only work if warm air is also routed to replace the removed cooler air. Supply without returns are useless returns without supplies equally useless

I remember reading your comment from another thread that ducted cold air would infiltrate into a warm room better than the reverse scenario because of the greater density of the cold air.
My thought is that if you could bring the cold air to the warmest end of the opperation it would effect enough displacement to accelerate the natural migration of warmer air back to the negitive area that had been vacated. Assumeing there were no significant barriers (like closed doors or excessive distances) in its path.

Again ........my thought as well . If your going to put a box fan at the end of the hall and shoot cold down the hall to the wood stove room then why couldn't you run duct work that pulls cold air from one side of the house to the wood stove room. Both ways is going to pull the heat back to the other side of the house as its own return ......will it not ?

 

[Roospike]

My heating system is oil fired forced hot water system no duct work here. If I were to do it again, I would be considering radaint heating

True that .