Opinions and advice: Feeding a detached sub panel.

[KissMyWhiteSS]

Ok so I have had a few questions on here in the past dealing with electrical work. One post was a rather dumb post mostly because of my lack of experience and knowledge, but mostly because I wasn’t using common sense. I was quickly told to call an electrician or somebody who has more experience, to help me. That is fair. Up until I have been able to handle everything on my own, ie: running wire, connecting outlets, and preparing my sub panel. But now I am at a stopping point where I will be calling an electrician to come out and “finish” it. Before I do that though, I want to make sure that I am educated enough to know what the guy is doing, and WHY he is doing it. So I am going to do my best here to explain my plan and what I have done, or what has been done to my detached 20x24 garage.
First, the garage is a detached 2 car in a Charleston style neighborhood. What that means pretty much is that the house faces a street and the garage is about 15 feet behind house and faces an alley.
Goals:
I want a clean, simple place to store/work on things such as cars, wood work etc. I do not have any crazy tools, just mostly circular/chop saws, a drill press, and a shop vac. I also have a fridge for the brewskies and do plan on having a wall for a tv and stereo set up.
The garage has a 20amp 110V 12/3 feed wire coming in from the panel inside my home which runs directly into a 4 gang light switch box. 1 switch controls the light on the outside main door, 1 switch controls the light on the outside of my service door, 1 switch controls the 2 – 4’ fluorescent light fixtures and the other switch controls my attic light up above.
Now, there is also a 12/2 wire coming into the garage in the same conduit that is wired into a 3-way switch at the back door to my house. This feeds a switch that reads “Main Disconnect” that then feeds the only gfci that THEN runs into my 4 gang box. I have not pulled the cover off the box to look inside yet so I do not know how that is wired.
How can that single switch cut off the power to the 4 gang box switches? Would that make it a 4-way switch? I am trying to fully understand this.
I hope you can picture everything I am explaining.
I purchased a 125 amp 6 space circuit panel with the intentions of using at least 5 for now.

1 circuit will control the light switches
1 circuit will be dedicated to my fridge
1 circuit will be dedicated to the right side of the garage
1 circuit will be dedicated to the left side of the garage
1 circuit will be dedicated to the tv wall.

Everything is wired and ready, except for wiring the feed wire into the sub panel.
My father in law, who has enough experience that I trust his word, told me that I should run 220 out to the garage. So I bought a 30amp 2 pole circuit breaker to replace the single pole 110 amp breaker. My issue that I see now is that where the single pole garage breaker is in my panel, there is no room near it for a 2-pole. So I have to have the breaker for the garage moved to a lower location in the panel, which will result in my wires being too short. How many of you have used wire nuts in your panel to splice in your wires? I know it is ok by code, it just seems like something could go wrong? My other option is to shift all the following breakers down in the panel. I could get away with not having to use wire nuts then….but I’d have to re label every location on the door. What would you do?
Lastly, after the feed wire is connected to the sub panel in the garage, what wire should be ran to the light switch from the new circuit? 12/2 or 12/3 and why?

I know this is a lot, and I promise I have done more research on this stuff than I have running the wires in the garage. Some things just haven’t been very clear. School me if you can, but dumb it down. I’m not an electrician. Thanks in advance.

 

[Gary S]

You need to check your local bulding code, but as I understand it, most locales do not allow more than one feed to a detatched garage. If yours is like that, you can't use a 12/2 and a 12/3 from the house to the garage. You need to make it one single larger line. That fits right in with running a 240v line and a sub panel in the garage like your father in law suggested.

I would pull out both small wires and replace with a single larger feed.

 

[matt151617]

Gary S is correct, but you can have more than one if the 2nd is strictly to control a light, and not used as a feeder.

You are definitely going to need bigger than 12 gauge. Many go with 2 gauge aluminum to get 90 amps. Personally I went with 6 gauge aluminum to get 50 amps.

Now on to the basics. Hopefully you have somewhat large conduit coming into the garage. If so, all you have to do is pull the new feeder wires. You need 4: 2 hots, 1 neutral, 1 ground. Also, you'll need 2 ground rods. Home Depot has a decent 100 amp Square D subpanel kit with a main breaker for about $48.

As far as your circuits, all of them need to be GFI protected now, including the door opener. The TV and fridge don't really need to be on their own circuits; I would combine them. Also, you may have better luck alternating outlets on circuits instead of dividing the garage in half.

 

[pattenp]

You can use wire nuts in the panel, but I would try shifting breakers around so not to have any splices. As has been stated you are not to have more than one power feed to an outbuilding per NEC. You can have a wire that serves as a switch loop for controlling lights from the house but the switched power source needs to originate in the outbuilding.

The 6 space panel you bought can it use tandem breakers? If so, and you put more than 6 breakers in the panel, then it needs to have a main disconnect breaker.

 

[royalton10]

I would look to put in an at least a panel with 20 or more spaces. Five filled at install with six spaces gives you very little room for expansion.

Panels are cheap, put that to your advantage.

 

[MN Falcon]

Also, you'll need 2 ground rods.

Its been a while since I did my garage, maybe 15 years, but I was only required to have 1 ground rod for the garage sub panel. Has this changed recently?

 

[pattenp]

Its been a while since I did my garage, maybe 15 years, but I was only required to have 1 ground rod for the garage sub panel. Has this changed recently?

By NEC you only need one rod if you can show that there is 25 ohms or less resistance to earth. If you use two rods then you don't need to worry about the 25 ohm rule. I believe this was changed with the 2011 NEC. At least this section is highlighted in my 2011 NEC which indicates a revision to the code.

 

[matt151617]

Its been a while since I did my garage, maybe 15 years, but I was only required to have 1 ground rod for the garage sub panel. Has this changed recently?

I usually just say 2, since no one really has the equipment necessary to test for the resistance required with only 1 rod.

 

[wyliesdiesels]

....As far as your circuits, all of them need to be GFI protected now, including the door opener. The TV and fridge don't really need to be on their own circuits; I would combine them. Also, you may have better luck alternating outlets on circuits instead of dividing the garage in half.

Though it is not advisable nor do I recommend putting a motor load such as a refrigerator, on a GFCI. I get service calls almost every week related to a GFCI that keeps tripping because of a fridge or other motor device plugged into it.

 

[eljefino]

I'm going to reiterate what's said above and that you need to run a bigger thicker wire if you want "more power", your 12-2 is limited to 20 amps. If you really have 12-3 that ends in a convenient spot (eg in or within reach of your main box) you can run a 240V, 20 amp breaker in your main box which will double your power when appropriately hooked up to a subpanel. You'll lose switch control from within the house. If your 3-way switch is on the other side of the house from the main panel you can add a 'handy box" to splice the world together and run some more 12/3 across your basement or however it would go. Still beats fishing through conduit (probably).

I think you have the purposes reversed on your 12-2 and 12-3, the 12-2 (probably) presently brings in the power and the 12-3 makes "travellers" for the 3-way switch. If you want to "instantly double your power" using the 12-3 you'll want to hack into it in your house, which beats digging a ditch.

Personally I think if you use one side of your 20 amps (at 120V) for power tools (there's only you in there) and the other side for lights and TV you'll do fine.

The "good news" in all this is your "main disconnect" switch and GFCI mean someone building the garage was trying to meet code and/or pass an inspection. This kind of stuff is often left out by homeowners/ hacks.

 

[matt151617]

Though it is not advisable nor do I recommend putting a motor load such as a refrigerator, on a GFCI. I get service calls almost every week related to a GFCI that keeps tripping because of a fridge or other motor device plugged into it.

I agree, but unfortunately code doesn't say otherwise. The other huge downside is risking loosing what's in the fridge if the GFI trips. Not a problem with just beer though. Personally I will not put a fridge, freezer, or sump pump on a GFI circuit.



Also, I just noticed this. Do not use the 30 amp breaker you purchased if you decide to keep the 12/3 wire. 12 gauge wire needs to be protected at 20 amps.

 

[KissMyWhiteSS]

I think you have the purposes reversed on your 12-2 and 12-3, the 12-2 (probably) presently brings in the power and the 12-3 makes "travellers" for the 3-way switch. If you want to "instantly double your power" using the 12-3 you'll want to hack into it in your house, which beats digging a ditch.

I know that I have one of each coming through the conduit into my garage. But now that I think about what you are saying you are probably correct. That would make sense. If I have a 3-way switch at the back door of my house then it would require a 12/3 wire right? If so, that would explain why that 12/3 runs directly into the 4-gang box and the 12/2 is connected to a switch for a disconnect. Does this sound correct?

 

[eljefino]

^ spot on!

 

[KissMyWhiteSS]

hmm...well that makes everything make sense. So then the 12/2 will feed my panel and I can leave the 12/3 alone, considering that I am ok with it wired the way it is. The switch and gfci are no longer needed for that application, since I can disconnect at the sub panel?

No on to my next question/dilemma. I'd like to run 220amp to the garage as suggested in the OP. But since the 30amp breaker I bought will not protect the 12 gauge wire, should I buy a 20 amp two pole?

As much as I'd like to run a higher amperage and thicker wire, it will be damn near impossible to do so with little actual benefit/use out of it.

 

[KissMyWhiteSS]

I just thought of this...

If I plan running my lights off of a circuit in my sub panel, do I wire that 12/3 coming from my back door any differently?

 

[wyliesdiesels]

I agree, but unfortunately code doesn't say otherwise. The other huge downside is risking loosing what's in the fridge if the GFI trips. Not a problem with just beer though. Personally I will not put a fridge, freezer, or sump pump on a GFI circuit.



Also, I just noticed this. Do not use the 30 amp breaker you purchased if you decide to keep the 12/3 wire. 12 gauge wire needs to be protected at 20 amps.

Yup, I'm fully aware that code doesn't allow that. On one of the service calls I had related to this, I didn't care about code because if I did, the folks wouldn't have hot water. They had a fridge, a freezer and a tank-less water heater in the garage and the GFI would trip every-time the blower on the heater would kick on or the compressor in the freezer would kick on. I had no choice but to re-wire the circuit!

 

[matt151617]

hmm...well that makes everything make sense. So then the 12/2 will feed my panel and I can leave the 12/3 alone, considering that I am ok with it wired the way it is. The switch and gfci are no longer needed for that application, since I can disconnect at the sub panel?

No on to my next question/dilemma. I'd like to run 220amp to the garage as suggested in the OP. But since the 30amp breaker I bought will not protect the 12 gauge wire, should I buy a 20 amp two pole?

As much as I'd like to run a higher amperage and thicker wire, it will be damn near impossible to do so with little actual benefit/use out of it.

If you decide to keep the 12/2, then you can only run 120v. This also means only 3 out of the 6 circuits in your panel would be energized. You cannot get 240v from the 12/2 wire.

I had the exact same issue as you; one 12/3 switch loop powering outside lights (controlled from both inside the garage and inside the house), and one 12/2 feeder line. What I did was remove the switch from the garage but left the one in the house. Used the 12/2 as the new switch loop and the 12/3 as the new feeder to a new 6 space panel. This lasted about 4 months before I needed more space in the panel and more than 20 amps. When I dug a new trench for conduit I discovered they had direct buried regular indoor Romex for the 12/3.

You still aren't exempt from all circuits being GFI, along with the 2 ground rods. A double pole 20 amp breaker is appropriate if you decide to use the 12/3 as the feeder, otherwise, a single pole 20 amp breaker.

 

[pattenp]

If you decide to keep the 12/2, then you can only run 120v. This also means only 3 out of the 6 circuits in your panel would be energized. You cannot get 240v from the 12/2 wire.

If you do just use the 12/2 for 120V you can split the hot to both legs in the panel to utilize all 6 of the spaces at 120V. Be sure to place a information label on the inside of panel so no will come behind you in the future and put in a 2 pole breaker.

 

[eljefino]

No on to my next question/dilemma. I'd like to run 220amp to the garage as suggested in the OP. But since the 30amp breaker I bought will not protect the 12 gauge wire, should I buy a 20 amp two pole?

As much as I'd like to run a higher amperage and thicker wire, it will be damn near impossible to do so with little actual benefit/use out of it.

Er, you mean 220 Volts. If you go this way you or your electrician (get help! pleeeeaaaase) will need to scrounge up some more 12-3 and run it from your box to your inside switch where the 12-3 starts, or to intercept it in the basement. Yes you'll need a 2 pole 20 amp breaker.

 

[KissMyWhiteSS]

Er, you mean 220 Volts. If you go this way you or your electrician (get help! pleeeeaaaase) will need to scrounge up some more 12-3 and run it from your box to your inside switch where the 12-3 starts, or to intercept it in the basement. Yes you'll need a 2 pole 20 amp breaker.

Yes you are right I mean 220 volts...not amps. typo.

 

[KissMyWhiteSS]

So this is what I am understanding.
I now know that the sub panel HAS to be fed with at least 12/3 and not 12/2. This will give me black(hot), red (hot) white (neutral) and bare (ground). The red and black wires will feed the two hot buses and the white will feed the neutral bus bar. Now my question comes in about how to properly ground the sub panel. I have read and understand that in a sub panel the neutral and ground CANNOT be bonded together. Then I am reading that the ground has to be connected to ground rod outside of my garage. In my panel I had to buy a grounding bar kit for all my ground wires coming from my CBs. Can the ground wire from the feed wire be grounded to this or does it get grounded to a rod outside? The neutral and the ground bus bars are NOT bonded with a bonding strip.

 

[KissMyWhiteSS]

http://www.lowes.com/pd_105718-7686..._?productId=1001509&Ns=p_product_avg_rating|1

http://www.homedepot.com/h_d1/N-25e...&keyword=GE+ground&storeId=10051#.UQS3Yr_iyrh

 

[matt151617]

There's a screw that came with the panel that would bond the neutral and ground, throw it away. The ground on the incoming feeder goes to the ground bar you purchased. In addition, you need to run 6 gauge copper (or smaller gauge but inside conduit) off the ground bar to 2 8 foot ground rods, at least 6 feet apart.

 

[vartz04]

Glad the home inspector never mentioned any of.that to me looks like I've got some work to do. Everything is bonded together in my sub panel

 

[pattenp]

Another way of putting it is the neutral bar is isolated/insulated from the box and ground bar, and only the neutrals connect to the neutral bar. The new ground bar is screwed directly to the box grounding it to the box. All the ground wires are connected only to the ground bar in the sub-panel. That means all the circuit equipment grounds, the feeder equipment ground, and the ground rod ground wire.

 

[eljefino]

So this is what I am understanding.
I now know that the sub panel HAS to be fed with at least 12/3 and not 12/2. This will give me black(hot), red (hot) white (neutral) and bare (ground). The red and black wires will feed the two hot buses and the white will feed the neutral bus bar.

Well you could use the 12/2 but it would gain you zero capacity. The 12/3 would double it and let you brag that you have 240V in your garage, even though it wouldn't be enough to do much with. (My welder takes 40 Amps for example.)

Now my question comes in about how to properly ground the sub panel. I have read and understand that in a sub panel the neutral and ground CANNOT be bonded together. Then I am reading that the ground has to be connected to ground rod outside of my garage. In my panel I had to buy a grounding bar kit for all my ground wires coming from my CBs. Can the ground wire from the feed wire be grounded to this or does it get grounded to a rod outside? The neutral and the ground bus bars are NOT bonded with a bonding strip.

IDK why sub panels don't come with the ground bus bar, it's required in pretty much every situation. Like said above mix all the ground wires together: the one coming from the house, the one from the rod, the ones from your garage wiring. Keep the neutrals on their bus bar. It will be real simple, whites to whites, bare to bare. You need 6 gauge stranded copper grounding wire to go off to the rods. THey sell it by the foot at HD/Lowes, get a few feet more than you think you need. It can't be spliced.

 

[KissMyWhiteSS]

Let me make sure I'm getting this clear...
I can use the 12/2 feeder wire to feed one leg of my circuits and use a jumper to other? Then all whites go to neutral all grounds go to ground bar (feed, circuits) then run 1 section of 6 gauge bare stranded copper from my ground bar through conduit outside to 2 - 8' ground rods 6' feet apart?

I would love to be able to brag about having 240v to my garage. However, at this present time I have no need for it. I do not plan on needing it either. For me to get 240v it would require rewiring my main panel in the house and feeding about 100' of at least 10/3 through conduit that has 12/3 in already. The wire runs out the tip of my panel in between my subfloor down a wall outside in conduit under a sidewalk and into my garage. Not an easy task for something that is not necessary. My garage will be nothing more than an addition to the house with nothing running anything more than 15 amps at once. I want to make sure what in have will work.

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[KissMyWhiteSS]

You guys have been great BTW. Thanks for all the advice.

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[pattenp]

The ground rod wire can be #6 solid bare copper, and if not exposed to possible damage it does not need to be in conduit.

 

[vartz04]

I pulled 3 #6 and a 10 thru 3/4" conduit which had 6 90s in it. Pull 10 gauge you'll thank me later.

 

[wyliesdiesels]

Your plan is correct other than the bare stranded copper. You want to use solid #6 cu for the GEC to the ground rods. Bare stranded #6 cu doesn't exist other than if u striped the insulation off #6 THHN cu. #6 bare cu. doesn't need to be in conduit if not subject to damage. If u use wire smaller than #6 it needs to be in conduit!

I pulled 3 #6 and a 10 thru 3/4" conduit which had 6 90s in it. Pull 10 gauge you'll thank me later.

We're talking about the GEC wire for the ground rods NOT the EGC in the feeder!

 

[KissMyWhiteSS]

I pulled 3 #6 and a 10 thru 3/4" conduit which had 6 90s in it. Pull 10 gauge you'll thank me later.

Yikes.

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[Norcal]

I pulled 3 #6 and a 10 thru 3/4" conduit which had 6 90s in it. Pull 10 gauge you'll thank me later.

A conduit run is only allowed 4- 1/4 bends totaling 360 degrees between pull points, yours exceeded that by 180 degrees & even when a pull complies w/ the 360 degree max requirement it can be difficult.

 

[vartz04]

I guess it might have 4 I was guessing the layout since its existing and under ground.

 

[wyliesdiesels]

A conduit run is only allowed 4- 1/4 bends totaling 360 degrees between pull points, yours exceeded that by 180 degrees & even when a pull complies w/ the 360 degree max requirement it can be difficult.

Good catch! I missed it!

 

[KissMyWhiteSS]

Your plan is correct other than the bare stranded copper. You want to use solid #6 cu for the GEC to the ground rods. Bare stranded #6 cu doesn't exist other than if u striped the insulation off #6 THHN cu. #6 bare cu. doesn't need to be in conduit if not subject to damage. If u use wire smaller than #6 it needs to be in conduit!



We're talking about the GEC wire for the ground rods NOT the EGC in the feeder!

10-4

If your panel is inside your garage, how would you do it?

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[wyliesdiesels]

10-4

If your panel is inside your garage, how would you do it?

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Without pics of your setup, its hard to give a specific answer. But one of the ways I've done it before is to follow the conduit to the outside. You could even strap the #6 to the conduit. If that's not an option, you could surface mount the #6 cu, drill a hole through the wall and then run it through to the outside. Use clear silicone to seal up the holes after the wire is through!

 

[KissMyWhiteSS]

This is what I was imagining. Thanks again for the help.

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[eljefino]

If you're going to keep 120V 20A service to your garage I don't see why you're messing with a subpanel, unless you want control over single breakers within the garage. 20 Amp service is adequate for any "normal plug equipped (15A)" device plus a few lights.

But if you have a 20 Amp breaker for your circular saw, and a 20 AMP for your lights, and you overload the saw, the combined load of saw + lights is going to blow the 20A breaker in your house first and leave you stranded in the dark.

 

[KissMyWhiteSS]

It's really just to have control over the circuits. In case I'm working on lights and still want my fridge and radio to work at the same time. I'm not saying that I'll never upgrade the service to it either...If i felt that running new wire could be done without tearing up walls and such, i'd do it now.