Blower use?

[nola mike]

Normally I run my insert with the blower on high. I monitor my temps with a thermometer in the air jacket--obviously this temp is dependent on blower speed. Question is, what exactly happens if I don't use my blower? I've never actually tried it because I'm afraid of getting something too hot--should that be a concern?
My thinking though is that nothing else should change much--the stove should be about the same temp (maybe somewhat less heat loss given less of a differential inside/outside stove). Heat output of the stove should be about the same. The distribution of the heat may be different; more might go towards heating the masonry/walls/whatever rather than convective heat into the room, but overall the heat should make it into the room eventually, no? The air jacket around the stove will get much hotter, and the differential with the room should cause a convective current around it...
My owner's manual is largely silent about blower use.

 

[velvetfoot]

The one time I saw glowing red steel through the room air outlet was when I didn't have the fan on. Plus, it might not do that much good for your blower.

 

[mellow]

If noise from the blower is of concern then I would turn the fan to a lower speed before turning it off altogether, especially during a peak burn to keep air moving and the blower cooler.

I have been using this to control my blower fan for the past 2 seasons and it does a great job: http://www.harborfreight.com/router-speed-control-43060.html

 

[nola mike]

Using the blower isn't an issue. Just curious, especially during a power outage.

 

[mellow]

During a power outage you should pull off your surround to help get hot air out of the fireplace, some of us use UPS backup batteries or Deep Cycle batteries till we can get the generator started for longer outages.

 

[iamlucky13]

Heat output of the stove should be about the same. The distribution of the heat may be different; more might go towards heating the masonry/walls/whatever rather than convective heat into the room, but overall the heat should make it into the room eventually, no?

Heat transfer depends on temperature differences. If the fan is off, the metal is not being cooled as much. Therefore the metal is hotter, which means there is less temperature difference between the metal and combustion gases going up the flue. That means more heat going up the chimney. It's usually a reasonably modest difference with a free-standing chimney, but can be significant with an insert.

 

[David.Ervin]

My zero clearance Northstar can be run with the fans off, and the hot air will move via convection in from the bottom and out of the top vents. I'll do this if we're trying to watch a movie with quiet dialog in the living room, since the white noise is just enough to make it tough to hear some parts. That said, I find that it makes the mantle above the fireplace uncomfortably hot to touch, and even with the ceiling fan on, the end of the room with the fireplace is much warmer than the other end. If I were going to be without power for a protracted period of time, I think I'd be wiring up my generator to run the circuit that feeds my stove.

 

[nola mike]

Heat transfer depends on temperature differences. If the fan is off, the metal is not being cooled as much. Therefore the metal is hotter, which means there is less temperature difference between the metal and combustion gases going up the flue. That means more heat going up the chimney. It's usually a reasonably modest difference with a free-standing chimney, but can be significant with an insert.

Interesting. So you're saying that most of the heat from the stove comes from the exhaust stream, rather than the heat in the firebox?

 

[EJL923]

The first time we had a power outage with the stove i didnt have a generator yet. I pulled off the surround and had to add 1-2 logs at a time. The stove warmed the immediate room and a little of the adjacent. Without blowers, i would never run full loads especially in cold weather with more draw on the stove. Depending on your house size, you may be able to get away with no blowers, but mine is too big for the stove so i really rely on them to move the heat along with a ceiling fan

 

[iamlucky13]

Interesting. So you're saying that most of the heat from the stove comes from the exhaust stream, rather than the heat in the firebox?

I'm not making quantitative statements, even as loosely as "most," although in older designs, you can definitely lose most of the heat out of the chimney. A properly operated modern stove should transfer most of the heat into the room.

I'm referring to the process of how that heat transfer takes place, which is primarily a multi-step process where heat moves from the air and wood that react to release the heat to the walls of the stove by both convection and radiation, and from there to the room.

Most of this heat transfer takes place in the area of the firebox and the baffle. You want to get as much heat out of that exhaust stream as practical before the exhaust gases go up the chimney. The blower helps move that heat away from the stove, which in turn, allows the walls of the stove to absorb more heat.

 

[nola mike]

I wasn't talking about the chimney, but the top of the stove. I always wondered about insulation in a stove, and its purpose. But it makes sense to keep the heat in the box, and release it mostly in the top of the stove as it exits the firebox and travels back to the chimney. The insulation will initially keep the heat in the firebox and allow it to get up to temp quickly, but will eventually transfer the heat to the outer walls. Now as far as heat transfer, that's dependent on the differential between the metal and the air, so what you're saying makes sense. It would seem then that without the blower the stove would be less efficient, but shouldn't be dangerous. The effects of no blower should be greater then the hotter you run the stove...

 

[weatherguy]

When I had my insert I ran my stove without the blower for a week when we lost electricity, just kept an eye on it when I loaded it up so I didn't over fire it. Also used to run it without the blower in shoulder season a lot.

 

[Lumber-Jack]

If you don't use the blower you are going to lose some heat up the chimney, there is no getting around that. As to whether it's safe or not? It is. Or at least it should be if your install is built to code. When the manufacturer comes up with clearance specs for stoves and flue components, they do not assume you will be running a blower. They realize that can be power outages, or that the blower will eventually stop working, or that people will simply choose not to run the blower, and so they must come up with clearance specs based on the stove operating without a blower. Not only that, they must base their clearance spec on the worst case scenarios, meaning they must assume that the eventual users will occasionally fill the stove with wood and forget to close the draft.
Clearance specs are set according to max running conditions, not moderate operating conditions, and they still have safety buffers built in.
None of this is to say that running your stove at max all the time is good for your stove. If you over heat your stove every time you put a fresh load of wood in it, you will significantly decrease the life of your stove and likely void any manufacturer warranty.
Again that's not to say just because you don't use your blower you will over heat your stove. Just realize that turning it off is not going to burn your house down, but you will lose a certain amount of heat up the chimney, and running it will help remove excess heat when you are running the stove a little to hard.