i have a 6220 furnace and i noticed today with the fire going that the top right hand side of the door was not sealing up as i can see the fire through the gap. so my question is how critical is it that the door seals completely up on a pellet furnace or pellet stove? i know on a wood burner if it doesnt seal completely that it will eat more fuel.

Its actually fairly important..... will it work with the gap, yes.

Will it work effiently, no. You will waste a lot of fuel with the extra air.

Will it work safely, also no. You stand a good chance of carbon monoxide getting where you don't want it if the door doesn't seal.