Hi guys. Project I'm working on, I have an apartment building that has a 400A service inside the building. In the utility room it starts with a 400A 3ph main breaker. From there it goes in a 3" s40 pvc pipe about 100' direct to the city transformer undergound. We are working on putting a 400A fused disconnect and meter socket outside for emergency disconnect.
The bad part about this, previous electrican installed a single run of 250 URD in the 3" pvc pipe. How it got passed inspection and turned on is beyond me, undersized and no outside disconnect.
I only get the 1 pipe to work with, its buried under concrete. I did the conduit fill and if I did a parallel run of 250 AL thhn the fill would be 36%. I've done that before, but I regret it. There's 2 90s and an LB, honestly getting all that stuffed in a LB is a sob.
What I'm thinking about doing, is running a parallel feed of 4/0 AL thhn. If I do the derating is knocks me down to 320A, but if I put 350A fuses in my disconnect. Would this pass feeding the 400?
The bad part about this, previous electrican installed a single run of 250 URD in the 3" pvc pipe. How it got passed inspection and turned on is beyond me, undersized and no outside disconnect.
I only get the 1 pipe to work with, its buried under concrete. I did the conduit fill and if I did a parallel run of 250 AL thhn the fill would be 36%. I've done that before, but I regret it. There's 2 90s and an LB, honestly getting all that stuffed in a LB is a sob.
What I'm thinking about doing, is running a parallel feed of 4/0 AL thhn. If I do the derating is knocks me down to 320A, but if I put 350A fuses in my disconnect. Would this pass feeding the 400?
