Are 2 or 4 locknuts required if I use a RMC close nipple in this situation:

Two small dry-type tranformers are bolted together (back-to-back) and a close nipple used a a raceway between the transformers. There is about a 3/4 inch gap between them, which is too long for a chase nipple. A ground wire is pulled between the two transformers and terminated properly. Article 250.97 does not apply because the voltage is only 120vac to ground (230 phase to phase). Insulated bushings are required because the wire size is #2AWG.

I would say 4 unless you devise some sort of spacer. Otherwise you wouldn't be able to properly tighten up the locknuts without distorting the transformer case.

Many manufactures produce metal bushings with insulated throats. these satisfy the requirements of 300.4 F . These types of bushings also have a serrated face that will grip like locknuts.

in situations not requiring double locknuts ( over 250V ), one of these bushings on the inside and a locknut on the outside should do it


charlie P