Chimney size?

I have aquired a free woodburner with 4 blowers, and some misc piping (stove pipe and 8" duct pipe). I have the thing in place, one blower (more than enough) attached and wired in, and the ducting is piped into my furnace ducting and to a room that is notably cold all winter long (french door, garage door, very little insulation on a concrete floor). All is well.

I have it up on low bricks right now on a cement floor 30" away from the back wall and will be putting a cinderblock wall around it just to be safe. Next year I planned an addition to the garage that will put this thing in a full masonry chimney, but that is going to have to wait another year as I will be deployed then. So this has to last safely for two years.

I was told by others I am being too safe as it is a "cased" burner (?) which I guess doesn't have the same exterior temps as my little fireplace insert. Better safe than sorry.

The opening is 7" right off the back of the case. The previous owner put an elbow right there, but that can come off. I would run the pipe the same size, but getting a hold of 7" stuff is so hard and expensive. Not to mention they need 3-6 weeks to get it out.

I am considering either going up to 8" or down to 6". I need some advice on this. It is a large piece compared to others I have seen and is rated for coal burning as well though I doubt I ever will. I was told it would heat the entire house (3000sqft), and was used to heatr a 1500sqft garage before with no ducting, just blowing out the two eight inch outlets.

Any help would be apreciated. I am trying to do this both economically and safely. I can get pics once I figure out how the wife messed up the camera, but things are a mess right now out there as I take care of a few projects before bow season opens.

So your bow season starts late huh....we opened two weeks ago, guess we have a really bad deer issue.
The piping you are increasing is usually not an issue if it is only one size bigger than the opening at the stove, just do not decrease in size.

I have had wood stoves all my life with only two chimney fires, and I cleaned the flues every two months. Once I switched over to the double walled insulated pipe(which is expensive) I do it once a year.
Masonary chimneys are really not made for wood stove use. They take to long to heat up and if they are on an exterior wall build up creosote much faster than an interior chimney.
As far as being safe with the stove, building a wall around the area is fine, you creat a large thermal mass that continues to hold heat after the stove is done burning. A better thing to have would be a carbon monoxide and smoke detector in the living areas, the house can always be rebuilt.

Another thing to think about is the weight of the block around the stove, unless of course it is on a concrete floor.

Good luck , check out www.woodheat.org they have a good site.

Yes, it is on the garage floor (slab) so the weight won't be an issue. I hope the heat will heat it too this winter, but the house is the big thing.
Thanks for the advice. I do plan on going double or triple wall as I want to make sure my insurance company doesn't have a fit.
Deer season opens this weekend and I hoped to have this done by then, but...

Any heating contractor can answer your questions about sizing chimneys as they all have the appropriate charts and know how to use them.