If the sprinkler is usually operating a type 4 is required. If it is for fire protection then any enclosure appropriate for the area without spriklers is ok. The normal use is what we determine the enclosure type not for a fire.
Now having said that there still are requirements for enclosures and equipment where a stream of water from a sprinkler head is required then 26-008 but that applies to the panels, transformers, switch boards etc.
A normal outlet box or JB where only wire and devices are installed would not require a special enclosure or every sprinled building would need to be completely wired per section 22.
In the case of a fire I presume we don't want the distrobution or transformers to fail from the sprikler putting water on the equipment. A fire pump or emergency lighting might be at stake. A wet location JB is overkill as this is a dry location except when a fire is present.
