30Amp Sub in a garage?

[Abj87]

I'm about to buy the supplies i need to wire up my 24' x 24' detached garage, and want to run it by the experts before i do anything dumb.

My electrical loads are not huge a few tools,lights, Lincoln AC225 welder on low amp settings and my wife's pottery kiln.


Right now im looking at running a 10AWG Underground feeder cable feed from a 30 double breaker to a 6-8 space panel in the garage. I would setup the sub as follows:

15 amp single CB feeding 6 15amp outlets.
15 amp single CB for the door opener.

10 amp single CB for 2 150W lights and one T4 florescent over my work bench.
10 amp single CB for outside security light. (probably doesn't need its own breaker but i want to be able to turn it off)
30 amp double CB for the welder.
30 amp double CB for the kiln (draws 22amps)


Is this crazy?

 

[jrsulo]

Not enough juice !

 

[aandpdan]

Up the feeder. 30 amps is cutting things just too close when you have a 22 amp draw.

Just a few lights with that on and you'll trip the main.

There's really no difference in the labor but definitely spend some more on the feeder, use AL if you have to. You could run #6 CU and put in a 60 amp subpanel.

Is this an attached or detached garage?

Missed it, detached. You need 4 wires and you'll need a ground rod too.

 

[Alchymist]

I'd jump it to at least a 60 amp feed and 12 or more slots for breakers. Down the road you will be glad you did. Breaker price is about the same, only extra expense is for heavier wire. And I would go conduit with individual wires.

 

[Abj87]

If I went with individual wires what size should I use
2 #6 for the hot
1#8 for neutral
1# 10 for ground?

Is it ok for these to be not in conduit inside my basement?

 

[pattenp]

From the questions you are asking you need to do a lot of research before doing anything. One thing is you need the lighting circuits to be a minimum of 15 amp not 10 amp. And it all depends on the wire you use to feed the garage as to whether in has to be in conduit inside and or outside. If the wire is not a cable such as 4 individual wires it will need to be in conduit inside. You also need to decide if you are doing direct bury wire or wire that needs to be in conduit to the garage. No matter if it's direct bury or not it's best to put it in conduit. And you should do at least 60A. I also recommend aluminum wire for the feeder such as Mobile Home Feeder at a size of 2-2-2-4 which is common.

Edit: Oh..also do 20A for the outlets.
Next edit: You need two ground rods at the detached garage.
Third edit: Also would help to know where you live. Country/State.

 

[ForceFed70]

I agree that you should go to a 50-60A subpanel. Not being able to weld while the wife is using the Kiln (don't those things run for like 12hrs at a time?) would ****.

I'm not an expert, but I think individual conductors need to be in conduit even in your basement. I'd run a cable of some sort.

And like mentioned, don't run 10A circuits. You'll find that the materials for 10A circuit actually cost more than 15A circuits because they arn't commonly used.

And yes, it sounds like you really need some help here. I'm not going to say don't try to do it yourself... we're a DIY board for goodness sakes. But please make sure you take out a permit and get it inspected. The inspector should be happy to answer all of your questions along with those of us here at GJ.

 

[megalo]

Is it ok for these to be not in conduit inside my basement?

You have to either run the conductors in conduit or use a cable rated for indoor use and splice it to the individual wires out to the garage.

 

[Norcal]

30A is not enough, 10A circuit breakers are a standard size but good luck finding them.

 

[theoldwizard1]

Right now im looking at running a 10AWG Underground feeder cable feed from a 30 double breaker to a 6-8 space panel in the garage. I would setup the sub as follows:

15 amp single CB feeding 6 15amp outlets.

Up that to a 20A and wire all outlets with 12 guage.

15 amp single CB for the door opener.

Why does a door opener need a separate circuit ?

10 amp single CB for 2 150W lights and one T4 florescent over my work bench.
10 amp single CB for outside security light. (probably doesn't need its own breaker but i want to be able to turn it off)

Never seen 10A breakers at HD or Lowes (that does not mean they don't exist)

30 amp double CB for the welder.
30 amp double CB for the kiln (draws 22amps)

You don't need these on separate breakers (you can not use them at the same time anyway without tripping the main). If they are going to be on the same breaker, there are some rules about wiring.

Is this crazy?

Yes.

This a do it right the first time job. You really need 50-60A. If something goes wrong with the welder/kiln it could possibly trip the 30A main and leave you in the dark !

 

[theoldwizard1]

If I went with individual wires what size should I use
2 #6 for the hot
1#8 for neutral
1# 10 for ground?

Depending on the distance, 2 - #8 for hot, might be adequate for 50A service.

 

[JakeKohl]

This a do it right the first time job. You really need 50-60A. If something goes wrong with the welder/kiln it could possibly trip the 30A main and leave you in the dark !

And your wife will not be happy with her partially-fired pottery!

 

[pattenp]

Can't put my finger on the current NEC section, but I think it's now required to have the garage door opener on its own circuit.

 

[Abj87]

Depending on the distance, 2 - #8 for hot, might be adequate for 50A service.

Is it ok to use a smaller neutral? The big loads will be 240.


It's 50 feet

 

[pattenp]

It's okay for neutral to be smaller.

 

[megalo]

Is it ok to use a smaller neutral? The big loads will be 240.


It's 50 feet

The price difference between #6 and #8 for that distance is probably negligible.

 

[aandpdan]

Can't put my finger on the current NEC section, but I think it's now required to have the garage door opener on its own circuit.

It's not in the NEC for a dedicated circuit. It does have to be GFCI now and readily accessible. You can't put the GFCI in the ceiling.

 

[theoldwizard1]

Is it ok to use a smaller neutral? The big loads will be 240.

It's okay for neutral to be smaller.

The price difference between #6 and #8 for that distance is probably negligible.

Yes, if your only going to use #8 on neutral only, you only going to save about $20.

As for going 3 - #8 for 60A service @50', someone else will have to comment.

More is better in this case!

 

[theoldwizard1]

It's not in the NEC for a dedicated circuit. It does have to be GFCI now and readily accessible. You can't put the GFCI in the ceiling.

Hmm. Inspector did not say anything about the GFCI first outlet that was mounted near the ceiling on a multi-drop run, including garage door opener.

 

[Alchymist]

Yes, if your only going to use #8 on neutral only, you only going to save about $20.

As for going 3 - #8 for 60A service @50', someone else will have to comment.

More is better in this case!

3 #8 AWG won't cut it for 60 amp service. The hots will have to be at least #6 & copper for all.

 

[aandpdan]

Hmm. Inspector did not say anything about the GFCI first outlet that was mounted near the ceiling on a multi-drop run, including garage door opener.

2011 NEC 210.8

ground fault circuit interruption for personnel shall be installed in a readily accessible location.

What is considered "readily acceptable" can vary by inspector and how high the ceilings are.

 

[Abj87]

I decided to bump it up to 60amp, bought 50 feet of 6/3 with ground.

I'm confused do I need a ground rod, if it's grounded at the main panel? Sounds redundant.

 

[Alchymist]

I decided to bump it up to 60amp, bought 50 feet of 6/3 with ground.

I'm confused do I need a ground rod, if it's grounded at the main panel? Sounds redundant.

Yes.

 

[aandpdan]

I'm confused do I need a ground rod, if it's grounded at the main panel? Sounds redundant.

You do require two ground rods.

The simple explanation is, it's required by Code.

Also, you bought 50' of 6/3 with ground - what type of cable???

 

[Abj87]

You do require two ground rods.

The simple explanation is, it's required by Code.

Also, you bought 50' of 6/3 with ground - what type of cable???

I was wondering why? With two ground rods it's possible to get a voltage potential between the two.

I don't remember off the top of my head but it's indoor cable which I will run through conduit.

 

[Alchymist]

I was wondering why? With two ground rods it's possible to get a voltage potential between the two.

I don't remember off the top of my head but it's indoor cable which I will run through conduit.

If you bought an "NM" type cable, it can't be run in conduit underground.
As to the ground rods, with a #8 or heavier wire between them, no voltage potential between them.

 

[IONH]

Lets clarify for OP.

When people say you "can't" run X wire in conduit, it is because the electrical code states that wire can not be run in wet locations. This includes buried conduit as water will likely penetrate and fill the conduit making it a wet location.

This said, in the unlikely event there is a disaster which is determined to be caused by the improper wire being used without a permit, you will likely not get paid from your insurance or at a minimal have that payment significantly delayed.

 

[Abj87]

If you bought an "NM" type cable, it can't be run in conduit underground.
As to the ground rods, with a #8 or heavier wire between them, no voltage potential between them.

Then what's point in the second ground rod? The sub will have a separate ground busbar that's tied into the ground/nutral in the main panel. Sounds like a good way to lose the main ground at the service entrance and back feed the garage ground rod.

Am I wrong?

 

[Alchymist]

Then what's point in the second ground rod? The sub will have a separate ground busbar that's tied into the ground/nutral in the main panel. Sounds like a good way to lose the main ground at the service entrance and back feed the garage ground rod.

Am I wrong?

You are.
http://ecmweb.com/design/10-worst-grounding-mistakes-youll-ever-make

Pay particular attention to #8.

The more grounding rods, the lower the resistance to earth.

 

[megalo]

Your subpanel ground and neutral will be separate. The ground rods and the equipment ground from your new cable will be tied together.

From what I understand, the ground rods are more for lightning protection than grounding - that's what the equipment ground is for.

 

[Abj87]

You are.
http://ecmweb.com/design/10-worst-grounding-mistakes-youll-ever-make

Pay particular attention to #8.

The more grounding rods, the lower the resistance to earth.

If its under 25 ohms I don't need a second? The article doesn't tell you how to measure it?

What does the code say?

 

[aandpdan]

If its under 25 ohms I don't need a second? The article doesn't tell you how to measure it?

What does the code say?

It says special equipment is needed:

"You cannot use a simple ohmmeter because that would require a known perfect ground. Special equipment and procedures are needed, so it's common practice to simply drive a second ground rod."

The special equipment is an "earth ground resistance tester".

Just drive the other rod. By the time you find someone with the equipment to test your ground, if it passes, you'll spend more than you will on the other ground rod.

You can always ask your AHJ about this, or any other question. You are pulling a permit, right?

 

[Abj87]

If you bought an "NM" type cable, it can't be run in conduit underground.
As to the ground rods, with a #8 or heavier wire between them, no voltage potential between them.

It is nm-b which I understand it its THHN in a jacket. THHN which is ok to use in conduit? This is confusing....

 

[Alchymist]

It is nm-b which I understand it its THHN in a jacket. THHN which is ok to use in conduit? This is confusing....

Needs a "W" (waterproof or wet) in the designation THWN.

Like this:
http://www.southwire.com/products/THHNTHWNTWN75T90OEM.htm

 

[aandpdan]

It is nm-b which I understand it its THHN in a jacket. THHN which is ok to use in conduit? This is confusing....

Also, each conductor needs to be marked as to type/gauge/etc. It usually isn't in a cable assembly.

 

[Alchymist]

It's beginning to sound like it would be cheaper and easier to hire an electrician....?

 

[Abj87]

It's beginning to sound like it would be cheaper and easier to hire an electrician....?

I like this kind of stuff!

I will return the wire and get the UF rated stuff.

I will need to check more on the ground rod issue.

 

[pattenp]

Just a FYI. #6 UF is rated at 55A, but you can push the breaker to the next size of 60A. The ground rod issue should not be an issue. Just install 2 rods six feet apart from each other using a #6 solid copper conductor. This is the standard practice instead of trying to prove the resistance is 25ohm or less to get by with one rod.

I like this kind of stuff!

I will return the wire and get the UF rated stuff.

I will need to check more on the ground rod issue.

 

[Alchymist]

Just a FYI. #6 UF is rated at 55A, but you can push the breaker to the next size of 60A. The ground rod issue should not be an issue. Just install 2 rods six feet apart from each other using a #6 solid copper conductor. This is the standard practice instead of trying to prove the resistance is 25ohm or less to get by with one rod.

Nah, we need to make this harder than it is!

 

[IONH]

Just a FYI. #6 UF is rated at 55A, but you can push the breaker to the next size of 60A.

Is that because you should not wire a circuit with more than 80% of the breaker capacity. This said, a 60A breaker should not have more than 48A of juice and anything between 55-60 is probably going to be momentary and pop it as it'd be a failure of some component?