11A PTC Replacement fuse for RAMPS which protects the heated bed output against over-current.
The Bourns positive temperature coefficient (PTC) MFR1100 is a resettable fuse that shuts down when overheating, albeit slowy. In cool state the carbon in these fuses conduct electricity, allowing current to flow through the fuse. When the current passes the threshold for the fuse i.e. when a short occurs, the fuse gets too hot causing the carbon pathways to disintegrate, resulting in heating faster until all pathways are disintegrated and the current flow stops. When the short is removed, the fuse cools down restoring the current flow, although the resistance is higher afterwards for a longer period of time.
The hold current, or current at which the fuse is guaranteed not to trip, is 11A. The trip current (current at which the fuse will trip for certain) is 22A for the MFR1100, although that may take 30 seconds seconds. See the datasheet for more specifics on the trip current.