Hello,we had our Jotul GF 300DV Allagash recently installed and I have one question, on the initial ignition when it's cold, there's a bit of a pop and a slight rattle to the unit, is that normal? Because I'm assuming it's when the hot air and flame hits the cold metal.. if I turn it off and turn it back on it fires up silent,and still silent after it's been heated up, it's not a big bang or anything just like a slight pop, everything else works fine... Thank you in advance