Hi, I am very new to wood heat. I have an osburn 1600 insert. The other night I was burning a load of those wood fuel bricks. I had it about two thirds full like they recommend. Up until then I only put in some and some regular wood, after about an hour I noticed the tube in the front getting red. I did a searchon here and it seems like that's normal, but I am wondering if it is for just some stoves, is it a common thing for all of them. I burned about a cord of wood so far and it didn't happen with the regular wood.