I want to hook up two 120 V rectifiers in diffrent enclosures but I want to run one 4 conductor teck cable instead of 2 2conducotors cables and run a nipple between the two.Bring the teck cable to one rectifier and run the other conductors through the nipple to the other rectifier.One person tells me that I have to put the rectifiers on a double pole breaker because they are in the same cable instead of a single pole breaker for each individual rectifier.

The rule for this is 14-010,(b). If I'm reading the rule correctly, you should be okay with two seperate circuit breakers, as it appears you have two seperate circuits. If you were feeding the equipment with a 3 conductor teck cable (a 120/208V 3-wire circuit), I believe you would need a 2-pole breaker.

Is the termination enclosure of the first rectifier approved as a raceway? If not you won't be able to use it the way you're planning.