I have 2 thermometers on my Englander 13NC..One is a probe type and the other is a surface thermometer. I do have DVL pipe on my stove and the probe thermometer is 18"above the stove, drilled into the stove pipe. The other thermometer is a surface thermometer made to go on single wall stove pipe about 18" above the stove. I do have this surface thermometer mounted on the front of the stove. I don't know which one to believe as the surface thermometer reads way into the Hot Zone of the stove while the flue gas thermometer is still about 150-200 degrees below the Hot Zone. I know the surface thermometer is located in the wrong place, but as i have double wall stove pipe I just stuck it on the front top of the stove....There is a large discrepancy between the two thermometers. I have a new stove and do not want to overfire it. Am I wasting my time with the surface thermometer?