Moving all the electrical panels on the roof of a fairly large commercial building. There is a shed on the roof with SES diconnect panel and 120,208, 277/480v, 225a regular panels. I should be able to splice the 4/0, 350MCM, etc. wire with special crimps or connectors. They want to rerun the pipe coming from A/C's AH, Fans, etc raised about a ft and a half above the ceiling outside so roof repair work can be done now and later for leaks on the roof. Any ideas on the best way to do this? Is splicing the main panel feeders ok? The switchboard (SES)disconnects, ..can they be changed to a panel with breakers? They feed machines and some panels. Any help would be apprieciated. Hope I discribed this good enough. I've been doing elec work a long time and this one is challenging. I thought I would start with one panel at a time, and move to the next.
Is running the pipe above the roof, feeding the panel ckts sound ok? or should I stay below the roof inside and run the pipes? I will need quit a few junc boxes to splice the circuits and panel feeders. The panels on the roof are fed from down inside SES disc's.
I could put a junc box splice below the roof and poke up through the roof and run the feeder wires to the wall which is upstairs inside the bldg, or run them below the roof, then poke up through, where the panels will be above the ceiling inside.
Splicing large 350MCM feeder wires should be ok?
Should I use the same type, but new service section disconnect switches in the new wall inside.?
There are also contactors in the shed, I might try to illuminate them, unless needed.

Conduits on a roof are subject to derating in 08 code.Not sure if you're on 08 or not

Sounds like alot of work, to acomplish what exactly? also if you put alot of splice boxes below the roof deck, there are more penetrations to seal up. Another thing would be a pain to trouble shoot depending on height of inside ceiling, can you get a lift in there, now? in the future?

The idea is to be able to do roof repairs and also have the panels inside instead of in an outside shed.

I don't know how much wiring is involved, but how about if you take the old wires out, extend the conduits at a desired height and repull new wires?
It may be a bit costly, but it will be a cleaner installation and less connection to worry about.
Depending on how the roof will get re-done, I would do the junctions on the roof, it is easier to work on VS inside on the high ceiling with a lift. (assuming it is a high ceiling)