Picked up a used Harman Invincible, installed it Friday. I burned it a little Friday to see how it would work, but with temperatures being in the high 60's, I didn't run it real long. I fired it again Saturday evening, and left it run all night, it ran great, and the temperature in my living room (where the stove is installed) was almost 80F whenever I woke up this morning, so I turned it back a bit. Now this evening, it doesn't seem to be burning quite as hot as it was last night. Last night the temp in my living room was in the very high 70's, and that was with the stove set to about 1/2 of the temp setting. Tonight, it doesn't seem to be burning as hot, and I've even cranked the settings up to the highest and have had it operating like that for over 2 hours now. The only thing I've noticed different is that the flames today don't seem to be quite as large as they were last night when it was firing hard. They seem to "switch" back and forth from a large, high flame to a smaller, less brighter flame if that makes any sense. When the flame changes, there is a noticeable "clinking" noise in the stove that corresponds with it. I'm not sure if I'm just doing something wrong, if its some bad pellets, etc. that's making this difference, but the stove is definitely heating differently than it was Friday night. Anybody have any ideas/suggestions?