I have had this insert installed a month and half ago. It was very hard to decide which stove insert should be installed and there was not many people has been using this model and we could not find anyone have this installed that we could see its operation. Finally, it was installed by a local dealer with 5" s.s. flex pipe inside the existing clay oval 8"x6" at about 15ft long. My brick chimney is located outside but we do not feel warm touch on the outside of brick chimney. It works very well with good heat and good draft too. During the start, the door is left open about an inch to make up the quick fire for about 20min. The thermal sensor switch is working perfectly once the stove heats up to the operating temperature. We never had burned wood to heat the home before and this is a new experiment for us. Hopefully this message will aid to potential osburn users to make up their mind.