does turning up the blower on an insert affect burn times?

The fan in my insert cools the firebox.

Sometimes in a very handy way.

My stove has a bi-metal thermostatic air control so the blower does affect it. I also have an OAK so the cold air affects the thermostat as well. The flue temperature also affects the draft and the draft affects burn time. I have a large 650 CFM central heat blower that moves a lot of heat. I push cold air from the crawlspace floor up to the stove.

I think mine cools the fire box also so I turn it off at the start. Withe that said if your fire box is cooler it should increase the burn time..?? Kind of a thought.

wood spliter said:

I think mine cools the fire box also so I turn it off at the start. Withe that said if your fire box is cooler it should increase the burn time..?? Kind of a thought.

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If you have a thermostatically controlled air intake, no. When the blower cools off the firebox the thermostat will respond by opening up the air to burn faster and try to maintain the set temperature.

Im stuck on this one, one part of me says that running the fan on high will take more btu's from the stove requiring it to be burned hotter to produce the heat, other part says its going to produce the heat no matter what the fan speed is, your going to get really hot air on low or cooler hot air on high.

mellow said:

Im stuck on this one, one part of me says that running the fan on high will take more btu's from the stove requiring it to be burned hotter to produce the heat, other part says its going to produce the heat no matter what the fan speed is, your going to get really hot air on low or cooler hot air on high.

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If the blower takes the stove out of the sweet spot by cooling it too much, the stove's efficiency could drop, resulting in less heat per cord. Of course YMMV.

LLigetfa said:

mellow said:

Im stuck on this one, one part of me says that running the fan on high will take more btu's from the stove requiring it to be burned hotter to produce the heat, other part says its going to produce the heat no matter what the fan speed is, your going to get really hot air on low or cooler hot air on high.

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If the blower takes the stove out of the sweet spot by cooling it too much, the stove's efficiency could drop, resulting in less heat per cord. Of course YMMV.

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Right. In general, running the blower(s) fast will pull heat out of the firebox and put a greater load on the fire which will reduce the draft. When you are in the peak of your fire, with healthy yellow flames and secondary combustion, there's nothing that you can do with the blower to slow things down. The blower will have an insignificant impact on the fire. However, after you transition to coals, depending upon how much air your blowers move, it is possible to cool the firebox enough to slow the fire and even to put the fire out. I know this because I can do this with my Napoleon 1401 that has more powerful blowers after the originals died.

It's all because draft is proportional to the temperature of the gasses going up the chimney. If heat is removed by blowers, you'll reduce draft.

+1. I have the Montpelier too, and the blower definitely cools the firebox. This is a good thing: if you want to get more heat out the insert, let it run a roaring fire (primary air 1/2 to full open) and turn up the blower fan. It really kicks out the heat, but you burn the fuel much faster.

I personally think it definitely makes a difference turning up the blower speed. Here is why I think so... If I load the stove with oak and damper it down in the morning there are more coals then when I put it on high. This theory has been proven time and time again with my stove. No idea if you would get the same result with a different stove/chiney set up but my guess is yes... Now this info and a buck will get you a cup of coffee :lol:

I should also add to support my findings are that stove manufacturers will never tell you its ok to up the air speed. I know about the epa test etc, but if they thought they could get more efficency and heat out of it don't you think they would have done so? JMHO...

I know that with the fan speed on high I get many more unburnt black coals.

jharkin said:

wood spliter said:

I think mine cools the fire box also so I turn it off at the start. Withe that said if your fire box is cooler it should increase the burn time..?? Kind of a thought.

Click to expand...

If you have a thermostatically controlled air intake, no. When the blower cools off the firebox the thermostat will respond by opening up the air to burn faster and try to maintain the set temperature.

Click to expand...

I'm not sure if my air intake is thermostatically controlled. I am going to check today.

I recenlty purchased a fan for my 13 with some interesting results. Since my wood is "marginal" it's tougher to keep it going all the way through the burn without some primary adjustment. With the blower on low after the stove hits 500 seems to keep the stove steadier. I do leave the primary open more than normal to hold good hot flue temps, but the secondaries are actually better than without the blower. On the 13 the blower blows right on the channel for the secondary air, so it actually cools the secondary air before it enters the stove. I always thought you wanted to super heat the secondary air before combustion. I don't have and OAK so maybe the fan robs the 3" air intake of air since they are in close proximity. I would say my burn times increased because I can load it more and leave the primary open enough to burn the entire load without lettng the stove overheat (remember marginal wood). When things are working the stove stays around 500 with the blower on low. So I imagine that the top is somewhere around 550-575 without the blower.

I still need to go buy some dry wood from Lowes to see how much better it burns (I know it will). Then see how the blower works with good dry wood. The dry wood problem is fixed for next year. Either way I like the results from the blower not the noise.

With my stove once the temp drops below 275-300 the thermodisc shuts off the blower, so I am left with the same amount of coals in the morning if I run it on high or low.