Fuses are made of a ceramic or glass cylinder, with a central metal wire inside. Used to protect the circuits of your electronic devices against short circuits and overloads.

If your fuse blows, it must be replaced by a new fuse of the same type. If the power fails on your hot tub, to ensure that the fuse's wire (which is not always visible, especially on ceramic fuses) is broken, you have to to test them one by one to determine which one (if any) is responsible for opening the circuit.

Fuses are divided into two categories:

Slow-Blow, or time-delayed
This fuse is used to start a device, since it "handles" the transient overcurrent when you power up a pump, for example. This type of fuse is designed to withstand these very short bursts of high intensity.

This type of fuse where power surges are damaging or dangerous, even very short ones. It is a very effective protection against the effects of short-circuiting. The fast-blow fuse melts as soon as the current flowing through it exceeds the set value.


The IEC 60127 standard provides four types of fuses depending on the time it takes for these devices to cut the current. Two are rapid-acting (FF, F) and two are slow-acting (T, TT), each type being defined according to the time required to cut ten times the rated current:

  • FF (Very fast acting), less than 1 ms
  • F (Fast acting), from 1 to 10 ms
  • T (Slow acting), from 10 to 100 ms
  • TT (Very slow acting), from 100 ms to 1 s

You will also find some fuses named according to their operating mode: gG fuses protect against short circuits and overloads, aM fuses protect against short circuits only.

To make your search easier, we have sorted the fuses by length, the most standard being 20 and 32 mm.

If you are looking for a replacement fuse for your control system, we have listed all the fuses installed on our systems to make it easier for you.