Garage Sub Panel


  #1  
Old 11-25-04, 06:26 PM
J
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Garage Sub Panel

Have a main 200 amp panel in garage (it's own meter), non attached garage.

Am going to run a sub panel to the other end of the garage.
Installing 4 ton a/c/heat pump.

Question??

1) If amp draw to sub panel is not over 100 amp at "one time"
can I still have more than 100 amp total of breakers in panel, any panel as far as that goes?

2) Plan to use Sch 40 PVC, am assuming 11/2" pvc, 35 ft with #3 THHN wire is enough, ok??

3) Can you "surface mount" any panel vs between studs?

4) I know not to connect neutral and ground in a sub, so do I run two hot, one neutral, one ground back to the main panel?

5) Can the ground be undersize of the two hots?

6) Does the sub panel require an "in ground" bare metal ground if the ground is already going bak to the main panel??


Thanks
John
 
  #2  
Old 11-25-04, 07:27 PM
SkyKing
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Instead of a subpanel, why don't just run a disconnect?
 
  #3  
Old 11-26-04, 03:18 AM
J
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Have that now, but need more service at that end and would be cheaper I think than more conduit/conductors.
 
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Old 11-26-04, 07:47 AM
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Originally Posted by John1
Have a main 200 amp panel in garage (it's own meter), non attached garage.

Am going to run a sub panel to the other end of the garage.
Installing 4 ton a/c/heat pump.

Question??

1) If amp draw to sub panel is not over 100 amp at "one time"
can I still have more than 100 amp total of breakers in panel, any panel as far as that goes?
Yes you can. The size of the feeder is based on calculation rather than the size and number of breakers in the panel the feeder supplies.

2) Plan to use Sch 40 PVC, am assuming 11/2" pvc, 35 ft with #3 THHN wire is enough, OK??
You should check with the local Authority Having Jurisdiction (AHJ) to see if the use of exposed PVC is permissible. It would be better practice to use Electro Metallic Tubing (EMT) which is often called thin wall conduit if the conduit will be exposed indoors. The problem with PVC is that it will produce a lot of dangerous smoke when exposed to fire.

3) Can you "surface mount" any panel vs between studs?
Yes you can surface mount the panel.

4) I know not to connect neutral and ground in a sub, so do I run two hot, one neutral, one ground back to the main panel?
Yes, you run four conductors back to the service disconnecting means which in your case is the "main panel".

5) Can the ground be under size of the two hots?
The size of the Equipment Grounding Conductor (EGC) is matched to the rating of the Over Current Protective Device (OCPD) that protects that circuit. Your one hundred ampere feeder should have a number six American wire gage (AWG) EGC.

6) Does the sub panel require an "in ground" bare metal ground if the ground is already going back to the main panel??


Thanks
John
No grounding electrode system is required for feeder supplied panels that are in the same building as the OCPD that protects the feeder that supplies them.
--
Tom H
 
 

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