234.267—Insulation resistance tests, wires in trunking and cables.
(a)
Insulation resistance tests shall be made when wires or cables are installed and at least once every ten years thereafter.
(b)
Insulation resistance tests shall be made between all conductors and ground, between conductors in each multiple conductor cable, and between conductors in trunking. Insulation resistance tests shall be performed when wires, cables, and insulation are dry.
(c)
Subject to paragraph (d) of this section, when insulation resistance of wire or cable is found to be less than 500,000 ohms, prompt action shall be taken to repair or replace the defective wire or cable. Until such defective wire or cable is replaced, insulation resistance tests shall be made annually.
(d)
A circuit with a conductor having an insulation resistance of less than 200,000 ohms shall not be used.
(e)
Required insulation resistance testing that does not conform to the required testing schedule of this section shall be completed in accordance with the following schedule: