I am getting frustrated, I hope that the experts here can help. I have a CharBroil H2O and I can't keep the temperature up. In fact, I haven't been able to get it above 200 for any length of time. I have used 3 chimneys of charcoal since I started 4 hours ago. Anything I can do to get the temp up? How far should the door be open? How about the top thingy? Any help appreciated!!