Keep in mind as has been said, the only purpose of the fuse is to protect the 120v heating elements - there may be two fuses on the 1200. If they blow, you may as well buy a new heating element before you replace the fuse.
My previous MH had 1200 and it used to trip the GFI when I tried to start the refrigerator to cool it down. It would switch over to propane and cool down before I'd notice the GFI had tripped. After I reset the GFI and the boiler on the 1200 was good a hot, it continued operation on 120v with not issues. The fuses never blew.