What do you call equipment delivered as parts to be assembled on-site?

I think kit is a suitable word, as suggested in a comment.

However, there is a sense of the word assembly that can be used as well:

6 a: the fitting together of manufactured parts into a complete machine, structure, or unit of a machine
        the assembly of an automobile
   b: a collection of parts so assembled
_{Merriam-Webster}

Sense 6a is the sense used in the term assembly line, but sense 6b is used to refer to the partially constructed item as it moves through the line.

An assembly line is a manufacturing process (often called a progressive assembly) in which parts (usually interchangeable parts) are added as the semi-finished assembly moves from workstation to workstation where the parts are added in sequence until the final assembly is produced.
_Wikipedia