50A to 100A SubPanel

[jocool1585]

I am finally getting around to finishing the upstairs of my coachhouse style garage. My garage is being fed 70A from my 100A main box in the house. I figure that I need a max of 50A in the finished apartment upstairs, but I want to have a seperate box up there so all power can be shut off when doing work in the space. Can I purchase a 100A subpanel and simply feed it with a 50A breaker from my main garage box?

[mmg440]

:thumbup: should be fine.

[Damon L.]

I did that with a basement subpanel. I'm feeding a 100A panel with a 60A CB from the main panel. I did swap out the 100A breaker that came with the panel for a 60A one to match them.

[jocool1585]

Seemed ok to me, just wanted to check. They have 100A Square D panels on sale at Menards right now for $49.00 with the 100A breaker + 5 20A breakers included.

What gauge wire is most suitable for the run from my current sub panel to this panel?

Merry Christmas All!

[LoRollinLS]

12 or 10 gauge... at least 12

[hidollartoys]

For 50 amps you will need #6 wire. For the 20 amp breakers you will need #12 wire.

[tfi racing]

6/3 is what you need.You may want to consider running 3/3 or maybe conduit instead,that way if your loads increase in the future,the ampacity can easily be increased.

[Torque1st]

You will need 4 wires, 2 Line, 1 Neutral, and 1 Ground. The sub panel must be set up for an isolated Neutral.
Check this:
http://www.selfhelpandmore.com/home-wiring-usa/accessory-structures-to-dwellings/wiring-a-detached-garage-2002.php
Some of the info above may help.

[precisionsc54]

If anyone has any questions let me know. Im a union Electrician and I have the NEC book right here lol

[jocool1585]

Thanks for the info guys. I'm going with a 60A breaker feeding my 100A box. I couldn't pass up the deal on the box. I will post some photos of the project I'm working on next week sometime.

[jocool1585]

Ok,

I've got my cable run and now have one more question about the final connections from my garage sub-panel to the one upstairs.

This is the current setup in the downstairs part of the garage. It is being fed by a 70A breaker from the house.
http://www.jtaylormarketing.com/bbnetimages/IMG01204_2.jpg

I did not install the current configuration, but it appears that they started with the smaller box to the right and then upgraded. The previous owner ran a lot of large powertools. Note that the lines coming in are only: H-H-N - there is no ground to a rod. The lines going back to the box in the house connect both hots to the breaker and the neutral to the neutral bar. This is an older (70's) house. The ground from the house box goes to the water line.

Here is what I am installing upstairs, being fed by 60A from the garage box.:
http://www.jtaylormarketing.com/bbnetimages/IMG01215_2.jpg

What method should I use for a ground to earth or is one necessary with this setup?

Thanks in advance for the advice!

[jocool1585]

I think that at the very least I need to install a ground bar in my new box and run that ground to a grounding rod, but do I need to add one to the existing box in the garage as well?

[Mr_fixit]

They say a picture is worth a 1000 words. Is that a sub panel feeding a sub panel feeding your new sub panel....?

You better hope one of the code prophets don't get ahold of you...

[jocool1585]

The main house panel feeds the large garage panel. The large garage panel is feeding the original panel to the right (which I will eventually eliminate). I'm just trying to solve the grounding question. The existing boxes were installed before there was a requirement for an earth ground for subpanels in detached. There were no other conductors (ie: water lines, cable, telephone) between the house and garage at that time.