Reesh14
Electrical
- Aug 3, 2005
- 38
I know that there are calculations to determine the minimum conduit size required for conductors, but is there also a maximum size that can be used? I am replacing a handful of 208V,3 phase rooftop units. The new units have significantly less load than the existing. Therefore lower rated circuit breakers and wire sizes will be used for the new units. I would like to reuse the existing conduits if possible. In a few cases the existing conduit size meets the size of the required load, but in most cases, the existing conduit is 1 to 2 inches larger than the minimum conduit size required for the load. Length of the run varies between 50-175 feet. Can over sized conduits be used? or is there some issue with insulation or something else?
example: existing rooftop unit: 350 mcm wire size, 2-1/2" conduit, and fed by 300A circuit breaker. The new rooftop unit has an MCA of only 34A and a recommended 35A MOCP device. Thus #8 wire will be installed and only 3/4" conduit is needed. Can the 2-1/2 inch conduit be reused?
Thank you.
example: existing rooftop unit: 350 mcm wire size, 2-1/2" conduit, and fed by 300A circuit breaker. The new rooftop unit has an MCA of only 34A and a recommended 35A MOCP device. Thus #8 wire will be installed and only 3/4" conduit is needed. Can the 2-1/2 inch conduit be reused?
Thank you.