Is it practical to put this fuse in a device running at 120VAC?
I am not seeing the “TKP-R-15a” listed in our system.
However it would be recommended to select a fuse that has a higher voltage rating.
As the 120vac is a maximum rating. If the voltage it sees goes above 120vac every so often it can shorten the life of the item.
The link works for me–the device in question appears rated for 600VAC, and as such it would suitable for protecting a 120VAC line. In fact, it would be over-rated for such use in most cases and as such might not be as “practical” as a fuse in either of the 5x20mm or 3AG formats that are typically used for 120VAC applications
Under normal conditions, there is no appreciable voltage across a fuse; that only happens when they blow open to interrupt a circuit. Fuse voltage ratings exist to indicate the maximum circuit voltage that a fuse can be depended on to interrupt. Further discussion on this and other fuse-related topics can be found here.