Fan Use on Insert

[velvetfoot]

I don't usually crank the fan up on my insert because it's noisy. Yesterday I did however and the room did seem to warm up faster. Is the heat being lost, like going up the stack, when the fan is on low or off? Any other observations on fan use, other than say, high air flow cools off the fire box,etc. I'm thinking mostly a pretty hot fire.

 

[Rhone]

I keep my fan on high, to maximize heat transfer creating turbulance and having a larger temperature difference will net you more btu's in the living space. The fan on high creates the most turbulance and keeps the temperature differential higher so should get you more miles per gallon.

 

[The Patriot]

I always leave my fan on high. Of course, I don't have the stove in a room where the noise is a problem.

Yeah, I believe it wastes heat if you lower the fan.

 

[PAJerry]

If we cut the fan speed down, the masonry of the fireplace above the insert gets pretty warm, so I assume a lot of heat is being lost up the liner. The only time we cut it back is when removing ashes or when the room becomes unbearably hot. When buying an insert, it is wise to see one in operation or at least turn on the fan in the stove shop to see how noisy it is. That kind of swayed me from purchasing the small Regency when I was looking.

 

[ozarkjeep]

lately, I have even been using a small circular fan blowing straight into my inserts built in fan.

With a full load of wood, and the cat engaged, if I leave the air intake open the top of the insert has gone over 950 degrees.

With the extra fan, the room stays warmer, and the its hard to get the stove top temp over 600.

when I bought this back in November, I commented on adding additional fans, it supposedly has 2 -125 CFM fans, a total of 250 CFM fans, variable speed, I would like to at least double that, with variable speed.

in my experience, its difficult to move TOO much air thru the insert once its hot, I have not had any trouble keeping a clean burn moving ALOT more air thru it than its designed for.

it IS noisey though.

Wife gets aggrevated when she cant hear the TV, so I turn the fan off, pretty soon she is complaining about being cold.

haha

 

[treeman08]

My thoughts are that as you lower the fan with the same fire, you will get higher stove top temps.
That would give higher natural convection due to temp diferential, so the total heat to room might be a wash.
However the heat is concentrated at the stove. With the fan on high you get circulation through the house.
I usually keep my fan on high unless a low fire has dropped the temp at the top of the insert below 300 degrees.

 

[velvetfoot]

Another member, I forget who, had a setup where he had a fan in his basement duct air through the insert. This could be a solution, but you would have to draw suction from the basement, and even if that was okay, you'd have to punch a hole in your hearth, I imagine.

 

[Corey]

I went from no fan to a 12", 220CFM model. The insert went from a radiant space heater to a forced air whole house heater. I think that 'cooling the firebox' is largely a non issue with modern stoves (or retrofitted ones like mine) as all the combustion and secondary burn happen in an insulated 'fire box' the flue gases then wrap around some type of baffle and are exposed to the actual metal firebox. By the time the flue gas is exposed to the metal box, all secondary combustion is (or should be ) done. At that point you want to get the maximum practical heat out of the stove and into your house. You still need enough heat in the stove for proper draft, but anything beyond that is just waste. With big fans, I suppose it is possible to cool everything off enough that you start to loose draft, which means a lower fire and less overall heat - a downward spiral.

Corey

 

[laynes69]

We have our main lp furnace blowing at all times on our woodfurnace. We have a ton of airflow going around the firebox, and we still achieve secondary combustion. We have a clean chimney and a clean flue. I know in our situation our blower doesn't affect the rate of burn or temps at that in the firebox. I have seen stuff in the past that they were talking about blowers pulling too much air, or heat from the stove. Water will act as a heat sink and of course cool the walls. The air just pulls the heat that the firebox is producing away from the stove. Maybe someone could explain this better, but we have very good results with our wood furnace.
Im sure different designs and materials affect this. One thing that I think really helps is the firebrick help hold the heat into the firebox. We can easily get 120+ degree heat from our registers through the house.