A Subpanel from another Subpanel?

[REFLEXX]

Hello all,

I'm posting all my questions as new threads in hope that these answers will be easier for future searchers to find.

Here's my next dilemma:

400a panel at house that feeds a 200a panel at detached garage. Among all the 30a 220v and 20a 110v breakers and circuits I have a need for another little circuit.

I need to feed a CNC machine 125amps across the building from the 200a subpanel.

What's best? Another subpanel, run in conduit (along the outside of the building (I've got finished interior walls and don't want conduit showing). and back into the building where I want the sub? Do I need special conduit when outside? what size conduit for 2AWG x3 (2 hot + 1 ground).

Is there any way to put the 2AWG in the walls? 2AWG romex??? Or is conduit my only choice???

Should I just run it inside? along the drywall? I cannot run it inside the drywall because of the size of conduit.


thanks in advance,

REFLEXX

 

[TOMWELDS]

I dont have a code book in front of me, but #2 (im guessing copper) is too small for 125amps. It's probably 1/0 CU. Whats the distance (voltage drop)? Is there a future need for other circuits (if so, install a subpanel)? EMT or PVC would do though i dont know if you have local code restrictions. The only difference between in/outdoors are the fittings with EMT...set screw inside and compression outdoors. The size of the conduit: 2-1/0 and 1-#6 ground would be 1 1/2" conduit. Try to put the 125amp breaker at the top of the buss in the subpanel as to not heat up the buss (EX: in spaces #1&3).

 

[TOMWELDS]

I dont have a code book in front of me, but #2 (im guessing copper) is too small for 125amps. It's probably 1/0 CU. Whats the distance (voltage drop)? Is there a future need for other circuits (if so, install a subpanel)? EMT or PVC would do though i dont know if you have local code restrictions. The only difference between in/outdoors are the fittings with EMT...set screw inside and compression outdoors. The size of the conduit: 2-1/0 and 1-#6 ground would be 1 1/2" conduit. Try to put the 125amp breaker at the top of the buss in the subpanel as to not heat up the buss (EX: in spaces #1&3).

 

[TOO Z MAXX]

They do make a #2 romex in copper. That stuff is heavy and a pain in the *** to work with. Like said above it may not quite be big enough for 125 amps. I will try and find my code book later and post back.

 

[TOMWELDS]

Also, if there are no 120volt outlets near the machine, run 2-#12's also. The outlet is required for servicing.

 

[REFLEXX]

Tom & Too,

Found 2/3+G Romex (it is huge and it cost me $2.50 a foot for 60 feet. It is a PITA to work with, but since I dont have my building's "skin" on yet, it worked out much easier. Since it's "Romex" it's legal to run inside a wall (AFAIK). It's also going to work better than conduit (time/effort/looks/etc...)

NOTE TO OTHERS: Always do electrical BEFORE putting up the metal/stucco/plywood on your interior/exterior walls. SO easy to be able to step thru a wall and get to something from the outside.

I ran it into a 100 amp fused discon box near where my cnc will be. The breaker is 125amps ($50 !!!) My machine only needs a 60 amp breaker (3phase) but since I'm hooking up a (20hp) DIGITAL phase converter and it needs a 100-125 amp (1ph) circuit.

All of this is incredible overkill. I've NEVER had my CNC running over 40% of full power (which equals about 20-25 amps of draw). But I gotta keep it all legal and safe.


thanks again,

REFLEXX

 

[TOMWELDS]

Are you feeding #2 copper with a 125amp breaker? It's only rated for 100amp.

 

[muddy]

In st. louis........

In my old shop in st. louis I had a 400 amp service at back of house. 200 went to house and a 200 in the shop. Off of that 200 in the shop I also had a 100 amp disconnect run about twent five feet from the panel for my welder, and the disconnect that my electrician used allowed you to just change the fuse size in the disconnect for whatever application you needed.
I'm no electrician so this is just from memory but know it worked well....... Keith

 

[TOMWELDS]

Another idea, if the #2 is already installed. Put the phase converter at the panel.Now the #2 will only see 60 amps.