Effects (if any) of adding a larger blower fan

I'm adding a larger blower to my indoor wood furnace because I added on to my house. I'm going from ~550 cfm to ~1100 cfm. I got into a discussion with a friend from work as to the effects it will have on the burn cycles and cleanliness of the burns. Now, my furnace is controlled by a bi-metal thermostat located on the front. It has infinite adjustments from "Off" to "High". As the fire and furnace cool, the t-stat opens a draft door and lets more air in. With the small blower, the blower would run until the coals were out. The furnace is designed to shut down the blower when the air jacket drops to less than like 90 degrees or something like that.

Now, my friend says that the increase in air is going to cool things off too much and I'm going to make more creasote. I am saying that the temps will swing more and will allow the t-stat to open sooner and open more, which will create hotter burns than I've usually maintained. So I am saying that I will either burn cleaner or the same.

Anyone care to enter a comment?

It's an add on blower kit from the manufacturer. It is recommended when the furnace is a central furnace and not just an add on. The manufacturer offers three different options: a 550 cfm (standard), an additional 550 cfm blower (to get the 1100 cfm), and then a 1600 cfm. So, I'm not reinventing the wheel as the manufacturer has already tested and approved my install.

Regardless of if the burn cycles or emissions output remains the same or changes, I can say that the temps in the house should be better regulated with what I am doing. The furnace was oversized for my house, but should be perfect now that I've added 500+ square feet of living space.

The blowers turn on with a snap disc t-stat. When the temp of the air jacket hits 110 degrees, the blowers kit on. When it drops to 90 degrees, they kick back off. So the furnace is actually designed to have the blowers cycle on and off. With just the one 550 cfm blower, the blower never shuts off until the coals are almost burned out. The bi-metal t-stat that controls the intake air has infinite adjustment up to a designated "HIGH" point. If you need more heat output, just turn that up.

I don't think I'll need to crank the heat up though. I just need the extra cfm to get the heat through a longer duct run. The extra space I added is completely open to the original house, so it will not be hard to evenly distribute the heat.

The furnace has two 8" ducts coming out of the top of it. I might build a sheetmetal plenum to sit on top and then put the 8" ducts off of that, but I'll see how it does this way first.

Well, I'm going to revive my old post.

Got my first real taste of "winter" here. Temps this AM were -11. When I started the wood furnace last night, it was 62 in the house. Temps got up to about 64 before I went to bed and were back to about 62-63 when I woke up. Doesn't look like the small 550cfm blower can handle below zero temps by itself. I'm guessing it would have been fine had I built my fire when it was 68 in the house and it could have maintained that. Now that I know what it's doing, I guess it's time to order the additional blower.

I found a honey of a deal on another 550cfm blower that is exactly the same as DAKA sells. That should get me to 1100cfm. If that doesn't do it, I believe my FIL has a few old blowers from some old furnaces that I could try out, but I think this one will do. Stay tuned!

Daka's kit consists of a Dayton 1TDT2 blower, some wire, and some conduit and costs $199 plus shipping. I already have wire and conduit, so all I really needed was the blower. I found the blower on ebay for $100 to my door. Now I see that someone has some cold air/filter boxes on ebay for a little cheaper than Daka retails them for. Maybe I'll just spend the extra $100 and pick one up rather than fiddling around with making my own.