Just ordered a Condar probe thermometer for my Excel double wall pipe. I have been running without one, but after recently purchasing a new IR gun im amazed on how hot my outside temps are on the pipe. On the straight section about 3 feet above the stove it hovers around 350* and the small piece that is 45 degrees into the ceiling support box is about 450*. This is with the draft just about closed. Seems a little to warm to me for double wall. So, in goes the probe. My stove drafts like crazy so maybe a pipe damper is needed... although i really dont want one. Thats another thing i have to teach the wife to use!