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Discussion Starter #1
I am very much a novice so please speak verrryyy sloowwlyy! :) I would like to run a sub panel out to my garage to run an 80 gal (4hp) compressor. -- I have a 200 amp shut-off panel on the outside of my house which runs to a 200 amp breaker panel in the house. I was told to think of the outside box as the "main" panel and the one in the house as a "sub-panel." So, I am essentially running a sub panel from a sub panel. - Any problems with that?

I'm thinking I'd do a 60 amp panel in the garage. The compressor would need a "dual 30A" breaker - correct? Can I still have another circuit in that panel for a 20A outlet and or a lighting circuit? Or would that require a larger sub-panel?

How many wires of what awg would I need to run from the house panel to the garage in each case?

Thank you (in advance) VERY much for talking me through this...

In response to question - Total distance from indoor panel to garage panel is about 100 feet.

and, the plate on the motor says 230 volts -- 16.5 amps....

I also use a welder very intermittently that "works" on a 20a circuit.

As I continue to browse on this subject... I've learned that I can have four 6 awg wires in my 3/4" conduit... Am I correct that I will need 2 hots, a neutral and a ground running to my sub panel? At just under 100 feet, will 6 awg suffice for a 60 amp sub panel? Then the question becomes, what circuits will I be able to run out of that sub panel? My compressor, plus what?...

Thanks.

Chuck
 

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I am essentially running a sub panel from a sub panel. - Any problems with that?
not a problem

I'm thinking I'd do a 60 amp panel in the garage. The compressor would need a "dual 30A" breaker - correct? Can I still have another circuit in that panel for a 20A outlet and or a lighting circuit? Or would that require a larger sub-panel?
30 amp should be fine for the compressor. Check the manufacturer specs for better info.
No problem installing lighting and receptacles from the garage panel.

I think you have the rest figured out.

Is the garage attached or detached?
 

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Naildriver
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Hey, Chuck, welcome to the forums. Breakers are not additive, so you will need a 60 amp double breaker in your main (sub as you call it) panel. I would run 1" PVC conduit, although the wires may truly fit in the 3/4", it is a PITA sometimes to pull 100' with limited capacity.

In the garage, you would install a sub panel with a 60 amp main and space for several breakers. You can run your lights, receptacles on single breakers, and your compressor on a double breaker.

Remember you must run a #6 bare grounding wire from the subpanel to two grounding rods spaced approx 8' apart outside. You must also isolate your neutrals from the grounds in the sub panel by using two buss bars. This is for detached garages, and at 100' I assume it is detached.

Joed types faster than I do.
 
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Welcome to DIY chat frawg. Agree with previous posts, good info in both.
But, to make certain you're getting relevant advice you should consider
adding your general location to your profile.
 

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Discussion Starter #5
Thank you very much for your responses! - I will reply to one or two tomorrow.:smile:
 

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Discussion Starter #6
Hey, Chuck, welcome to the forums. Breakers are not additive, so you will need a 60 amp double breaker in your main (sub as you call it) panel. I would run 1" PVC conduit, although the wires may truly fit in the 3/4", it is a PITA sometimes to pull 100' with limited capacity.

In the garage, you would install a sub panel with a 60 amp main and space for several breakers. You can run your lights, receptacles on single breakers, and your compressor on a double breaker.

Remember you must run a #6 bare grounding wire from the subpanel to two grounding rods spaced approx 8' apart outside. You must also isolate your neutrals from the grounds in the sub panel by using two buss bars. This is for detached garages, and at 100' I assume it is detached.

Joed types faster than I do.
Okay... so I think I've pretty much got it. When you say "grounding rods 8' apart", is that "at least" 8'? or should I shoot for as close to 8' as I can get? I'm assuming those are those copper rods at Home Depot? Also, is there anything I should know about "bonding" (what is that?? :) ) -

Thanks! - This is a great forum!
 

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Naildriver
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Check with your inspector. He will have the last say so on the rod spacing. Some allow "over" 6', while others say 8'. Was your garage pad poured with a UFER embedded? You can tell by the copper grounding electrode sticking out of the side of the pour. In such a case you would only need it and one ground rod. I doubt you will have a bonding issue in a garage.
 
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Discussion Starter #8
Check with your inspector. He will have the last say so on the rod spacing. Some allow "over" 6', while others say 8'. Was your garage pad poured with a UFER embedded? You can tell by the copper grounding electrode sticking out of the side of the pour. In such a case you would only need it and one ground rod. I doubt you will have a bonding issue in a garage.
Thanks!
 

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Discussion Starter #9
Check with your inspector. He will have the last say so on the rod spacing. Some allow "over" 6', while others say 8'. Was your garage pad poured with a UFER embedded? You can tell by the copper grounding electrode sticking out of the side of the pour. In such a case you would only need it and one ground rod. I doubt you will have a bonding issue in a garage.
Okay - I'm feeling lost again... What sort of box do I need for my panel in the garage? The big box stores seem to have a lot of 70A "2 space - 4 circuit" boxes. (I read that a 70A service requires 4awg) and I see some 60A 2 space 4 circuit boxes on line... but if I need a double 30A breaker just for my compressor, what good is that? Where would I put other breakers? Can I use a 100A box with more spaces and just run 60A to it?? Can you point me to what I need?
- also, just curious - I've seen some applications where the ground doesn't have to be as heavy as the load wires. Is that true running a sub-panel? i.e., can I use 6 awg for the load wires and 8 awg for the ground?

I'm in Minnesota by the way...

Thanks again.
 

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Okay - I'm feeling lost again... What sort of box do I need for my panel in the garage? The big box stores seem to have a lot of 70A "2 space - 4 circuit" boxes. (I read that a 70A service requires 4awg) and I see some 60A 2 space 4 circuit boxes on line... but if I need a double 30A breaker just for my compressor, what good is that? Where would I put other breakers? Can I use a 100A box with more spaces and just run 60A to it?? Can you point me to what I need?
- also, just curious - I've seen some applications where the ground doesn't have to be as heavy as the load wires. Is that true running a sub-panel? i.e., can I use 6 awg for the load wires and 8 awg for the ground?

I'm in Minnesota by the way...

Thanks again.
You can use a panel with any rating equal to or greater than your feeder ampacity. A 100A panel with a 60A feeder is fine. A 200A panel would be fine. I'd definitely use at least a 12-space panel to allow for future expansion. Since the price difference is minimal there's no reason to use a tiny panel.

For a 60A feeder under the current NEC, you can use a #10 or larger grounding conductor (see table 250.122).
 
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Discussion Starter #11
You can use a panel with any rating equal to or greater than your feeder ampacity. A 100A panel with a 60A feeder is fine. A 200A panel would be fine. I'd definitely use at least a 12-space panel to allow for future expansion. Since the price difference is minimal there's no reason to use a tiny panel.

For a 60A feeder under the current NEC, you can use a #10 or larger grounding conductor (see table 250.122).
Okay - Thank you, so - define "feeder" as you're using it here? Do I need something other than the "panel"? (I get confused looking at the boxes that say "main lug" etc....

It sounds like I can have my #6 red/black/white and a # 8 (or #10) green wires travel through a 3/4" conduit directly to a 100 amp "main panel"... - correct?
 

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Okay - Thank you, so - define "feeder" as you're using it here? Do I need something other than the "panel"? (I get confused looking at the boxes that say "main lug" etc....

It sounds like I can have my #6 red/black/white and a # 8 (or #10) green wires travel through a 3/4" conduit directly to a 100 amp "main panel"... - correct?
A feeder is wiring ahead of the last overcurrent protective device before the load (it's defined by code), like the circuit which serves this subpanel. Whether you want a main lug panel or one with a main breaker is a matter of personal preference, unless this is a detached garage. Your selection of conductors is good. There is no real need to buy both black and red wire though. Most people would probably just use black for both hots. 1" conduit is a better idea. Plan for multiple pull points unless it's a straight run.
 

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Discussion Starter #14
A feeder is wiring ahead of the last overcurrent protective device before the load (it's defined by code), like the circuit which serves this subpanel. Whether you want a main lug panel or one with a main breaker is a matter of personal preference, unless this is a detached garage. Your selection of conductors is good. There is no real need to buy both black and red wire though. Most people would probably just use black for both hots. 1" conduit is a better idea. Plan for multiple pull points unless it's a straight run.
Regarding above - This IS a detached garage so, "main lug"? or "breaker"? --- and "feeder" (?) So, in this case the "feeder" is just the wires leading from my panel in the house to the one in garage, correct?
Thanks!
 

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Regarding above - This IS a detached garage so, "main lug"? or "breaker"? --- and "feeder" (?) So, in this case the "feeder" is just the wires leading from my panel in the house to the one in garage, correct?
Thanks!
Yes with the feeder....

You'll want a disconnect at the garage, so the easy way and likely cheapest way is just get a breaker panel. As your feeder is allready protected by the 60A breaker in your upstream sub, your panel can be anything equal/above 60, and that breaker just serves as a disconnect.

You'll be able to pick it up off the shelf at a BigBox, probably come with some 15/20 breakers allready packaged with it, and you can pick up your 30/double right there off the shelf.
 

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Discussion Starter #16
Yes with the feeder....

You'll want a disconnect at the garage, so the easy way and likely cheapest way is just get a breaker panel. As your feeder is allready protected by the 60A breaker in your upstream sub, your panel can be anything equal/above 60, and that breaker just serves as a disconnect.

You'll be able to pick it up off the shelf at a BigBox, probably come with some 15/20 breakers allready packaged with it, and you can pick up your 30/double right there off the shelf.
Thank you!
 

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Discussion Starter #17
Another question re. all this.... This is a detached garage, 100' away from the house panel. Does any part of this set up have to include any sort of GFCI capability?...
 

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Discussion Starter #18
Yes with the feeder....

You'll want a disconnect at the garage, so the easy way and likely cheapest way is just get a breaker panel. As your feeder is allready protected by the 60A breaker in your upstream sub, your panel can be anything equal/above 60, and that breaker just serves as a disconnect.

You'll be able to pick it up off the shelf at a BigBox, probably come with some 15/20 breakers allready packaged with it, and you can pick up your 30/double right there off the shelf.
Sorry - another follow up question (well, a few of them).
1. - To clarify above - so I can by a 100A breaker box and just leave the 100A breaker as the disconnect in the garage?
2. - Does any part of this set-up require that anything be protected by GFCI? - perhaps individual circuits in garage?
3. - If I'm using flexible liquid tight conduit or just the gray stuff you glue together, can I run it into the house into a metal junction box? Or does it have to be a water tight box? and/or does that box have to be outside?
Thanks!!!
 

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1. yes
2. Garage receptacles need to be GFCI protected.
3. Inside the house a metal box is fine. Outside needs to be waterproof.
 

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Discussion Starter #20 (Edited)
Okay... I really appreciate all the help so far! I'm delaying this job for another month or so but collecting parts along the way. I will probably pull a permit in the end so I'd like to get it right and not look (too much) like a fool... - hence this next question: (refer to the two attached photos. One shows the brown "ground level" deck leading to our front door. To the right of our door - below the deck - is where the wiring for this panel will leave the house. When I was re-decking a year or twp ago, I put a 3/4" flexible conduit under there thinking I'd just run a 20a circuit to the garage. Now, with putting the panel in and using an inspector, I'm wondering:
1. - Is it "legal" to just lay that flex cable under the deck framing like that?
2. - Since I have determined that there is no easy way to transition from 3/4" flex to 1" flex, I'm wondering if:
a. -- Should I replace it with 1" flex(?) or 1" pvc conduit(?) (which is preferred?)
OR - should I leave it as is and put a weather tight junction box on the side of the deck there (at almost ground level) and transition that way...?
3. The 2nd photo shows the route toward the garage from the edge of the deck. I understand this will have to be buried at least 18" Would there be a preference for PVC conduit or liquid tight flex?...
Thanks VERY much for any thoughts on all this!!
Chuck
- Edited - PHOTOS are in my "album"
 
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