I put a brisket on my YS 640S last night at 11:00, pit set for 225. I went to bed planning to finish late his morning. Instead, the low temp alarm work me up at 6:00 a.m. as the pit was below 200. I got dressed and went out to check and the hopper was still almost full, but the temp was still dropping. I shoveled out most of the pellets and saw that the auger was turning, but temp was still dropping. Finally, I started the shut down on the Yoder, removed and wrapped the brisket and put it in the oven.
I removed the door to the two piece diffuser and found the firebox overflowing with white, charred pellets.
I have now found out that the Texas Mesquite Grilling Pellets (made nearby in Hamlin, TX) are 100% mesquite wood. While this may sound good and does provide a lot of flavor, those of us who live in West Texas know that mesquite wood does not burn clean at all and leaves a lot of ash and residue. This may be why many of the better pellet brands only use a small percent of flavor wood in their pellets while the bulk is made of oak. I am sure that was the problem with my July 4 cook. These pellets will be going in my smoke tube, but not in the hopper.
Since you have Academy down there, try the B&B Comp blend. They're made by BBQ Delight for B&B are high quality and only $15 for 40# bag. Works very well in my past pellet cooker and my new YS640s.
I just experienced the same issue with Shuping/Hamlin's Texas Beef blend (Mesquite, Oak, Pecan mix). They were new and opened 5 minutes before the cook.
Fortunately it was a shorter cook, but I had a huge pile of ash and unburnt pellets in the burn grate. Big temperature fluctuations during the cook too.
Used some older Treager Pecan pellets for the next cook, and held much tighter temps with almost no ash.
I'd stay away from Shuping/Hamlin pellets. Seems to be more than just a mesquite issue.
Want to try B&B. Anyone have thoughts on LumberJack? Seems to be popular amongst some other forums.
I've burnt nothing but lumberjack for 4 years and haven't had any issues. I buy in bulk with some buddies and have 40lb bags sitting on steel shelves in my Illinois garage for months and have never seen an issue like above.
I now use only B&B. I can buy them at Academy for $9 /20lbs. and have never had a problem.