sizing conductors for a R.T.U

[johneymac]

i need to wire 9 rtu,s. 3 phase 208v mca is 23.9a max ocpd is 35a.Do i have to use the max ocpd or could i use a lower size such as a 30a breaker with a 30a non fused disconnect at the unit.

 

[augie47]

For the individual units you may use a 30. Fuses would only be mandatory if the unit specified fuse protection or did not allow HACR breakers for OCP..
For the feeder for all (9), you might find this thread useful:
http://forums.mikeholt.com/showthread.php?t=115831&highlight=Units%22

 

[hurk27]

When I have that many, I start thinking about setting a local r-3 panel, such as in this case, 225 amp, load center, then run your RTU feeds from it, placing the loads closer to the panel you can avoid voltage drop problems, and more closely size the branch circuits.

but this would depend upon the distance your talking about back to the nearest panel to start with.

If these RTU's have there own built in OCD's then wire for the minimum, and breaker for the max, #10 with a 35amp breaker will do just fine.

See 440.22