The other night I saw my new P68 doing something my P38 never did. It was the first significantly cold night since I installed this stove. Temps were around 15 degrees overnight, following a day of 30 degree temps. I looked over and saw the stove cranking pretty good, a bit more than I thought it should've been. About 10 min later it was back to an idle. I figured I'd just come in and out a few times bringing in groceries and the stove was simply reacting to the sensor temp. About 10 min later and the beast was CRANKING this time. 10 min after that and it was back to an idle, dist fan OFF. Hmm. Sure enough the cycle kept repeating for an hour or so, until finally, it calmed itself down and behaved like a good little Harman. I recently had a 5 day old ESP replaced, so I knew that wasn't the issue.
I figured 2 different things were happening, both combining to cause the issue in a cause and effect sort of way. Repeatedly opening the door caused a bunch of cold air to reach the sensor, which told the stove to ramp up significantly for about 10 min, followed by the first idling down. During that burn ,a sizable slug of hot air made its way upstairs, displacing and forcing a slug of cold air back down the stairs, through the fan at the bottom and back towards the stove, where the problem soon compounded itself. In reaction to the extended cooler than normal temps the sensor was reading, the stove maxed out for another 10 min, this time, I think, heat sinking the sensor in the process. This is when the stove idled down again, this time turning off the distribution blower. This behavior went on 3-4 more cycles.
Since Harman decided to foolishly skimp out on the sensor wire length, my options for placement were limited. I ended up extending the wire another 10', putting the sensor about 14' feet from the stove. Problem solved.
My P38 also had a short sensor wire, although maybe 1' longer, but never had this issue. I don't think it was capable of heat sinking the sensor, and certainly didn't have the output to displace as much air in the same amount of time as a P68.
So, if any of you guys are noticing your stove doing this, especially if you're in a 2 story house, you may wanna reassess your sensor location.
I figured 2 different things were happening, both combining to cause the issue in a cause and effect sort of way. Repeatedly opening the door caused a bunch of cold air to reach the sensor, which told the stove to ramp up significantly for about 10 min, followed by the first idling down. During that burn ,a sizable slug of hot air made its way upstairs, displacing and forcing a slug of cold air back down the stairs, through the fan at the bottom and back towards the stove, where the problem soon compounded itself. In reaction to the extended cooler than normal temps the sensor was reading, the stove maxed out for another 10 min, this time, I think, heat sinking the sensor in the process. This is when the stove idled down again, this time turning off the distribution blower. This behavior went on 3-4 more cycles.
Since Harman decided to foolishly skimp out on the sensor wire length, my options for placement were limited. I ended up extending the wire another 10', putting the sensor about 14' feet from the stove. Problem solved.
My P38 also had a short sensor wire, although maybe 1' longer, but never had this issue. I don't think it was capable of heat sinking the sensor, and certainly didn't have the output to displace as much air in the same amount of time as a P68.
So, if any of you guys are noticing your stove doing this, especially if you're in a 2 story house, you may wanna reassess your sensor location.
