Thanks, loger. I wouldn't have ever found this, so I've "bookmarked" it in my browser.

Just bought a beautiful new wood stove (Hearthstone Mansfield) and am getting ready to hook it up. However, the only flue I can vent it to already vents a wood boiler/furnace (Tarm 500 series) in my basement. I also have a second flue that vents an oil furnace/boiler. Now, the instructions for both the wood stove and the wood boiler say not to hook up 2 wood appliances to the same flue. However, my homeowner's insurance company and the owners of the local heating appliance store both say it's fine, and there will be no increase in my insurance premium. SO, can I or can I not vent the wood stove out the same flue as the wood boiler? I am really confused!

Side wall venting of an oil fired 80%, which is most common, appliance is called "power venting". There are two manuf of power venters. Field Controls and Tjernlund. In my business I represented Tjernlund for 20 years and have a lot of them installed in the Northeast, where 80% of oil heat is located. As I noted previously, back in the 80's I represented a company who made a condensing oil fired furnace. They had other excellent products but the condensing unit put them out of business. Power venters are excellent products BUT, they have to be installed and serviced by a real tech. The biggest problem with PV is that the servicing company will clean the furnace or boiler and not touch the PV. Everything that goes through the furnace goes through the PV. When properly serviced they are an excellent exhaust system for oil appliances Power venters on oil boilers which also provide hot water are an occasional problem if located where the fumes from combustion are venting close to your deck or by a window which you want to open. The flue gases get blown out of the building but then waft along the wall to your BBQ and, well, if you can believe it, some people don't like the smell. If it is a winter only operation the odor issue is much reduced as the patio is not used and the windows are closed. Of the two manuf of PV, while I am biased, I think Tjernlund makes the best. I can defend that technically, but wlll offer one point. The Field's unit blows the gases straight down against the side of the house where the Tjernlund blows them straight away from the building. A properly set up condensing oil furnace is a very efficient appliance. That said, they are service intensive and have not been embraced by the oil companies. This is after 30 yrs on the market. If the techs don't like them, then you had better not like them either. My biggest problem with oil heat is that there has just not been any technology advances in the business. Why after all these years is there not an effective reliable modulating burner? Oil has 140kbtu, vs 100k for NG and 92 kbtu for LP. My feeling is that the modulating technology common in gas appliances makes up the difference in heat potential in the benefits of modulation. For the OP I just can't see trying to save a chimney that has deteriorated to the point that it is separating from the building. That is the result of decades of condensation and acidic consumption of the flue itself. There is no way that chimney passes the requirements of NFPA 211-Chimneys & flues, NFPA 54-Gas Code or NFPA 31-Oil Installation, all of which have an inspection requirement which this flue simply will not meet. Lining a structurally sound chimney makes sense. Lining a compromised chimney is throwing good money after bad, imho!

Restarting this discussion- does anyone have photos or additional info about venting 95% efficiency gas furnaces through a chimney flue? Got 2 bids for high eff furnaces. Both recommended Lennox G61MPV. One company said furnace will be vented via PVC out front wall of (brick) house- horizontal distance of about 10 feet. Would exit below hall window near front door. Another recommended venting through existing chimney flue. Chimney service just put steel cap on fireplace flue and confirmed there is room on furnace flue for 2 PVC pipes, but questioned why vent is vertical rather than horizontal. Also said PVC out chimney would be ugly on old house. Can anyone comment on venting through chimney versus wall?