Somerset pellets from Lowes burning goodnhot. Englander PDVC25 with OAK did not like them until turned up low feed air up by 2. Burning hotter than ever, but still seem to get a half moon shape of crusty ash built up over 4-5 hours. It builds up right in front of the auger - most of the ash is fine but this half moon crust shape is about the size of big coffee cup and continues to grow. Is this how it should be? Does it need more air? I have been burning Marth (good) Pennington (ok) and Valley Forest (poor), but they all burned to fine ash. I like the Somersets because they burn a lot hotter and throw more heat. What should I try?