why do these not have a fuse?

 

I think you need to specify what type of connectors you are talking about???
IP44 specifies solids ingress and water proofing on housings... so where does a fuse come into this??

 

ip44 site plugs



EDIT: this question is about the 110V and 230V connectors. the 3phase plug was the first image i found

 

Almost no plugs have fuses, the UK 13A one is one of the very few that does, the use of these connectors on site include fusing elsewhere - so it's not needed.

Certainly the way builders treat wires the fuses wouldn't last more than a couple of minutes either 8)

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The type of plug your picture is for wet locations, like comercial kitchen use, or outdoors, and having fuses would require opening the plug body and possibly damaging the watertite design. I would imagine that since it needs to remain watertite to meet its safety rating, it is not meant to be opened after intallation, execpt by qualified persons who know how to reinstall it properly.

I use a similar plug called an "Arktite" for disconnecting live loads, and there is a required procedure on installation that the average "consumer" would not likely follow, possibly rendering the plug unsafe.