another name could be "dual-element fuse" as these are the slow-blow type.
It depends on the precise type of slow blow fuse, but in general terms a fuse with a slow blow characteristic will take longer to operate (blow) at high overload currents than one with a normal characteristic. For low overload currents it will operate in about the same time as a normal fuse.
no A FRN fuse is a slow blow fuse where an non is a fast blow fuse. In a pinch a slow blow fuse can be use in a fast blow circuit but not the other way around.
If the fuse is labelled F it is fast-blow or T OR S it is slow-blow, the letter should be on the metal cap on the ends of the fuse.
The fast blow fuse will generally only have a straight wire between the terminals, while the slow blow version will have part of that wire coiled up as a spring.
The time it takes for a fuse to blow, either "fast blow" or "slow blow" is determined by the design of the fuse and is described in a table or graph provided by the manufacturer. In general, the higher the applied overload current, the faster the fuse will blow. Fast blow fuses can open in milliseconds, slow blow fuses can open in several seconds. The fuse used depends entirely on the application and what kind of circuit it is protecting.
slow
Slow burning fuse usually to alot time to evacuate an area
Any piece of machinery that is designed to use a fast blow fuse should only use a fast blow fuse. For safety reasons this could save your life instead of taking it.
There's really no general way of knowing, it's all down to how sensitive the equipment the fuse is hooked up to is. There should be recommendations on what type of fuse to use.
Check to insure that you are replacing the fuse with the same fuse size and type (fast blow fuses don't substitute for slow blow.) If this is ok the either the pump relay or the pump is going bad and drawing too much power for the fuse to handle.
It should be a 1.25 amp (1250ma) "slow-blow" fuse.