This is a Super Sized Super Smelter, it's great for smelting a large amount of items in a rather small amount of time. In this tutorial I will be using various wood planks to help with understanding on how to build this, and how the redstone works, but when you build it you can use a block of your choosing.

Spruce Wood Planks: Long Gone Steps
Birch Wood Planks: Previous Step
Oak Wood Planks: Current Step

Step 1: The Railing/Output Chest

You will want to build this railing module for this super smelter, this will be the base of this build.

Step 2: The Furnaces/Chests

For this step you will need to place the furnaces right above the powered minecart tracks. Then after you have done that, place hoppers above the furnaces pointing into the top of them, and then place chests on top of the hoppers. Keep in mind that when you place the chests, you will have to have trapped chests in between the normal chests so they don't connect.

Step 3: The Hoppers

First you will need to place hoppers pointing into the back of the chests. Then after you have done that, then you place hopper along the top of the hoppers pointing into the chests, but make sure you have that line of hoppers running over into the oak wood plank, and not into the hoppers below them.

Step 4: The Redstone Menace

Now you will need to place blocks next to the hoppers that are running into the chests. then place a half slab with a redstone comparator on top next to the blocks, and have them pointing into another block.

Step 5: Attack of the Redstone

You will need to go down 2 blocks from the birch wood planks that the redstone comparators are pointing into, and then place 4 blocks along the length of the build. After that you need to put redstone dust ontop of those blocks, and then redstone torches along both sides.

Step 6: Revenge of the Redstone

Now you need to go down two blocks from the wood planks with the redstone torches on both sides. Now place a three by four block platform, and place repeaters on the end closest to the minecart tracks and have them pointing to the minecart tracks. Then fill in the rest the the platform with redstone.

Step 7: A New Redstone

Now you need to place four blocks in front of the repeaters and then place repeaters on top of those blocks, and have the repeaters pointing towards the furnaces. Then you want to place redstone torches on front of those blocks.

Step 8: The Redstone Strikes Back

Now you need to place 4 blocks in front of the second set of repeaters, and then place redstone torches on top of the blocks.

Step 9: The Return of the Redstone

This part of the redstone is to turn the hoppers off when there is no more items in the input hopper. To build it you will need to put 2 blocks out of the input hopper and put a redstone comparator pointing into a redstone repeater which is pointing into another block in front of it with a redstone torch on it. After that you place a block 2 blocks below the redstone torch and put some redstone dust on that block, and then put down another block diagonally from the that one, then put a piece of redstone on it. Now the last thing before we move into the autofuel portion of this build, you want to place a hopper minecart onto the powered minecart tracks and push it to get it moving.

Step 10: The AutoFuel Portion

This part is completely optional, but I thought it would be a nice addition to the Super Smelter design.

Step 11: The Hoppers Yet Again

First you need to put hoppers pointing into the front side of the furnaces, then you put hoppers going across the top of those furnaces. Make sure you have them pointing to the oak wood plank and not down into the other hoppers.

Step 12: The AutoFuel Portion of the Matter

First you need to put a furnace on top of the last hopper in the line that is pointing to the left and then bellow that hopper put another hopper pointing to the right. Then you want to put down two droppers next to the two hoppers below the furnace. Then put another hopper above the two droppers and have it pointing into the furnace.

Step 13: The Little Parts

First you need to place two blocks one block down from the furnace and place a comparator running out of the hopper, and a repeater running into the bottom dropper, and set the repeater for 2 ticks. (one right click). Then you need to place two blocks in front of the comparator and the repeater and then one block diagonally and place a redstone torch underneath the diagonal block and one on the side of it, and then place a peice of redstone dust in front of the redstone torch. Now place a block above the repeater and place a comparator on it and have it pointing into another block that is right above the piece of redstone dust.

Step 14: Even More Redstone

This part of the Super Smelter is just for making sure that the fuel is evenly distributed. Keep in mind that this is the same redstone set up that is used to evenly distribute the items. So to do this just go back and do steps four through eight.