My best guess here is the admin of the server require the users to be logged in for the chunkloaders to work (its an option in the chickenchunks config file and I guess all the chunkloaders have some kind of system like that too), when the user isn't connected the chunkloaders he placed in the world are deactivated until he's back online, this preserve the memory and bandwith for the other users and help a lot to keep the server lag to a minimum...
And I think the boilers would keep eating the charcoal for a real long time depending on what you use to automate the boilers, they may be loaded for longer than the chunkloaders staying active... Or if there's anyone near your base that happens to be connected while you're not the automatic system is back online and can cause this, even if your chunkloaders aren't online if someone is around, it loads I think 10 chunks in each direction for a player...