AGAIN with the wiring questions

[Keith Hooks]

The good news: I'm moving into a new house this weekend.

The bad news: The garage will become my shop, but it only has 1 receptacle in it. Yes... one receptacle. I know, try and hold back the tears.

Anyway, I'm of course intending to add more, both 110 and 220v. The existing receptacle is a GFI and its location in the garage basically renders it useless to me. The 220v circuit is easy. I'll just add a breaker and run some wire. However, I'm wondering if the additional 110v will need to be GFI protected. Would it be wise to tap into the existing circuit?

I plan to run 12 Ga everywhere with a 20A breaker and 20A receptacles. I only have one tool, the TS, that uses 220v. I do plan to buy a bandsaw in the near future that uses it as well. Aside from that I just have the 6" jointer, 13" planar, and 1.5hp dust collector.

Wish me luck...

[Hoa Dinh]

While you're at it, may as well add a 60A panel. It gives you room to grow if needed.

If not, add at least two 240V circuits - one for the power tool and one for the DC. I'd add at least two 20A 120V circuits. Ask you city if codes require GFI.

I would not tap into the existing 120V circuit, especially if it shares with lighting or garage door opener. I would use that outlet for small stuffs (battery charger, portable power drill, ROS, ...).

The lighting should be separated into two difference circuits. If one breaker pops, you still have some light in the shop.

[Don Baer]

Keith,
I'd run seperate 110 Volts plugs and I'd run 2 circuits. alternating between circuits. Check you local codes since they may or may not require GFI's on those circuits. If so then make the first receptical in each circuit a GFI. and you should be OK. If your going to run your DC (off of 220 ( I would) then run a seperate 220 for it and then one for your planer etc.

[Mike Henderson]

Put GFCI on all your 120 volt outlets. Why would you risk your life to save a few dollars?

Mike

[Don Baer]

Put GFCI on all your 120 volt outlets. Why would you risk your life to save a few dollars?

Mike

Michael, by putting the GFI's first the other recpticals on that circuit are also protected.

[Mike Henderson]

Don, yes, I'm aware of that. What I meant was to protect each 120 volt outlet with GFCI. I guess I wasn't clear. Sorry.

And just to clarify, you have to wire the first outlet equipped with the GFCI outlet in a certain way in order to get the advantages of GFCI on the downstream outlets. The instructions will tell you how to do it.

Mike

[Chuck Trisdale]

When I moved to Memphis, I moved all the tools in, and noticed very quickly I had a power problem. There I was staring at one 120V recepticle. So after fighting it for about 2 months the "wiring new electricity" project vaulted up the list.

I left the circuit that was in there alone so I would have another breaker for that one. I wish at the time I had run 220V while I was at it, so do that for sure. I ran one 30A 120V circuit over 10G or 12G wire (cant remember - I think I went with 10G bc of the 30 amps) to 3 recepticles and it has done fine for me. I did make sure that I had recepticles that were rated for the higher amps running through them though.

As far as the GFCI. I didnt have one there to begin with so I cannot speak to that.

[Brian Triplett]

I had the same thing, one outlet, not includig the garge door opener. I checked my panel and it was full. I add to run a new sub-panel - 60 amp I believe. It was worth it. I now have 3 - 220 outlets (ts, Bs, DC). I would plan were you want to put certain items. for example my air compressor, 15amps, well thats about all a 20 amp breaker can take at one time, no running the window AC off the same breaker or jointer or planer. Stuff like that. I've been told to add a safety factor into was is going into which breaker, 20 amp breaker should see no more than about 18 amps.

[Rob Russell]

Current electrical code as adopted in most areas requires that the garage receptacles be GFI-protected per NEC article 210.8(A)(2).

GFI receptacles are cheap, so I'd echo Mike's comment about trying to save a few $ vs. having the protection.

I also agree with Hoa - if you're going to run a new circuit to the garage, install a subpanel. It's just about the same as putting in a 240v circuit - except it has the neutral conductor. That gives you the flexibility to add circuits as needed without running all the way back to the main panel. If you do add a subpanel, make sure that you put it in a location where you're not going to store stuff in front of it. You need a 36" deep x 30" clear "working space" for the subpanel.

Rob
Addy protocol - unlicensed, but experienced homeowner electrician

[Chuck Trisdale]

I mainly would like to add some more circuits in there now and am stuck with what I ran. I had no idea about the GFCI. I think I will go get new recepticles now though. I knew they werent very expensive at the time. I just never thought of it since the 1st one wasnt.

[Doyle Alley]

I may be in the minority here, but I hate GFCI outlets. Don't get me wrong - I like the idea of the protection. It's the implementation that has got me fuming. I have had nothing but problems with them. When I remodeled the bathrooms, I put in GFCI outlets. I had to keep going back to Home Depot until I got outlets that would actually hold the reset button in. Just last week, I had to replace one of them because it simply stopped working.

When I bought my electric pressure washer, it wouldn't run more than half a second before tripping the GFCI built into the power cord. I finally cut it off and replaced it with a standard grounded plug.

It seems like they just aren't built with the same kind of durability that is built into the other outlets. Until I find some that actually work dependably, I'm hesitant to put them in my shop.

[Chris Padilla]

I think a #4 for the 60 A sub-panel is right?? I ran a 50 A sub-panel on #6--it then feeds my A/C and some shop outlets on that side of the garage and the crawl space lights/outlets.

You'll want some dedicated circuits for various items like an air compressor and the dust collector as these items could well be running at the same time as your ww'ing equipment (TS, Jointer, Planer, BS, etc.). Also, think about adding copious lighting; I don't think you can have enough light so save a circuit for the lights, too.

[Rob Russell]

I ran one 30A 120V circuit over 10G or 12G wire (cant remember - I think I went with 10G bc of the 30 amps) to 3 recepticles and it has done fine for me. I did make sure that I had recepticles that were rated for the higher amps running through them though.


Chuck,

I sort of skimmed over this before and happened to go back and see it.

FYI, it's specifically against the NEC to run a 30 amp circuit and put normal 15 or 20 amp receptacles on it. Article 210.21(B)(2) and the associated table specifically say that a 30 amp circuit must have 30-amp rated receptacles. The plug configuration on a 30-amp receptacle is different than 15/20-amp receptacles, so you can't use the 30-amp receptacle as a "general purpose" receptacle for the normal plug configuration on all of our tools.

If you had a typo and really ran a 20-amp circuit, that's fine. Also FYI, you can use 15-amp rated receptacles on a 20-amp circuit.

Rob

[Chris Padilla]

I may be in the minority here, but I hate GFCI outlets.

I have the same problem in my garage with a particular circuit. The GFCIs are always tripping. I have another circuit where they are just jim-dandy fine so I know it is the GFCI that is the problem.

I thought I heard/read that they are good for one-trip...after that they aren't guaranteed any more! :eek:

I also don't think they are too cheap at ~$12...especially when they aren't working well. :mad:

[Rob Russell]

I think a #4 for the 60 A sub-panel is right?? I ran a 50 A sub-panel on #6--it then feeds my A/C and some shop outlets on that side of the garage and the crawl space lights/outlets.

You'll want some dedicated circuits for various items like an air compressor and the dust collector as these items could well be running at the same time as your ww'ing equipment (TS, Jointer, Planer, BS, etc.). Also, think about adding copious lighting; I don't think you can have enough light so save a circuit for the lights, too.

Chris,

#6 copper individual THWN conductors (obviously run in conduit/"raceway") have a rated ampacity of 65 amps per table 310.16. #6 NM cable would be good for 55 amps, even though it's copper conductors.

Rob

[Chris Padilla]

Yes, Rob, it was #6 NM. I'm sorry that I neglected to put the TYPE of wiring in my post but I knew you'd correct any "sub-par" info. ;)

[Rob Russell]

Yes, Rob, it was #6 NM. I'm sorry that I neglected to put the TYPE of wiring in my post but I knew you'd correct any "sub-par" info. ;)

You just provide sooooo many opportunities! :D

[Mike Henderson]

I may be in the minority here, but I hate GFCI outlets.

I don't know why you're experiencing trip failures on your GFCI - I have them all over my house and shop. I even have the lights in my shop on GFCI so that if I ever forget to turn the power off before I work on them, I'll be protected. I've never had a GFCI failure - defined as a trip for no known reason.

If I were experiencing the trips that you are experiencing, I'd find out why. GFCI works by monitoring the current in the two wires and tripping when they are not equal (meaning that some current is flowing to ground). Perhaps you have some slight leakage to ground, but not enough to trip the GFCI all the time.

GFCI really can save your life, especially in a wet environment like you describe with your pressure washer.

Mike

[Randy Meijer]

I may be in the minority here, but I hate GFCI outlets.....It seems like they just aren't built with the same kind of durability that is built into the other outlets.....

With the millions of GFCIs in use all over the country, it would seem that they are reliable in general. Given that assumption, perhaps your "defective" GFCIs "ARE" operating correctly and you have an undetected problem with your wiring?? Or perhaps, your Home Depot got a bad lot of the recepticles??

I would never eliminate a legally installed GFCI.....either find one that works correctly or correct the fault in the wiring that causes the units to trip.

As to the pressure washer, removing the GFCI in favor of a 3 prong plug is not the best solution unless the PW is always plugged into a GFCI receptacle. My home does not have any outdoor recepticles so whenever I have to work outdoors the extension cord is plugged into a non-protected outlet indoors. I bought a box, GFCI, several feet of wire and a plug and made a little GFCI "patch" cable which I always plug in ahead of the extension cord so I am always protected when working outdoors!!

[Jim Becker]

I wouldn't depend too heavily on that existing outlet, anyway...it's certainly not dedicated to the garage and may have "other things" on the same circuit that could cause annoying problems. IMHO, get a sub-panel added for the "shop needs" (leave lighting on the existing panel) and it also gives you a complete shut-off for the shop...a nice safety feature.

[Don Baer]

I wouldn't depend too heavily on that existing outlet, anyway...it's certainly not dedicated to the garage and may have "other things" on the same circuit that could cause annoying problems. IMHO, get a sub-panel added for the "shop needs" (leave lighting on the existing panel) and it also gives you a complete shut-off for the shop...a nice safety feature.

The single outlet that came with my garage was tied into the hall bathroom GFI. DAMHIKT...:D

I now have 26 outlets on four seperate circuits.

[Bret Olmsted]

It seems like they just aren't built with the same kind of durability that is built into the other outlets.
I agree. I had a GFCI outlet that would occasionally trip every few months. I replaced it with a new one and have not had any problems since. Before anyone gets excited, I did buy a GFCI tester and used it to verify that the outlet was properly installed (before and after replacing it).

[Alan Tolchinsky]

Your specs on the #6 THNN are what I've seen too and that's what I'm using in my upcoming electrical project. But why can you use 15 amp. outlets in a 20 amp. circuit? Doesn't make sense to me. Do you know?

[Mike Henderson]

I believe the logic of using 15 amp outlets on a 20 amp circuit is that you have multiple outlets on the string. I think that if you only have one outlet on a 20 amp circuit, it has to be a 20 amp outlet.

Maybe one of the guys who knows the code well can clarify.

Mike

[Keith Hooks]

Thanks for all the replies, folks. Just to clarify, the panel is in the garage and there are still 5-6 circuits available. I think I'm going to take the advice of splitting the 110 receptacles into 2 seperate circuits. I wish I could do everything I wanted right now, but I'm going to have to settle for the most bang for the buck.

For the install, I'm planning to cut a 6-8" strip from the drywall near the floor giving me access to the studs so I can run the wire. I plan to install the 110v receptacles just above bench level ~3' and the 220v closer to the floor.

The plan is to acquire a bandsaw later that will need the other 220v receptacle. There's no chance I'll be running them both at the same time so I'm going to plan on having them on the same circuit.

All of the receptacles will all be rated at 20A. I would really like to run another dedicated 220v circuit in case I pick up a stationary DC one day, but right now I'm dismissing it as a luxury (plus I'll be running out of room in the panel).

I've also decided to put all the receptacles on GFI. The installation is no more complicated than a regular receptacle and the only downside is the extra cost of the single receptacle per circuit - worth it in my opinion. I'm curious about 220v GFI receptacles - I can't remember seeing them on the shelf. However, I have seen GFI circuit breakers. I wonder if that would be an acceptable alternative.

Again, thanks for all the comments and suggestions.

[Jim Becker]

If you want GFCI for your 240v circuits, you'll need to use a GFCI breaker and they are darn expensive. Give the 240v circuits are "dedicated" to "a" tool, you could probably skip them relative to GFCI...I could be wrong, but I don't think they are required in that case.

[Gary Sostrin]

For woodworking, after installing a subpanel in my garage with 2-0 cable from the main (other circuits used for new addition), I wired one set of 220v on both sides near the front of the garage on the same circuit knowing I would not have more than 1 220/240v application at a time. Also most important, I ran in parallel 2 sets of 110/120 V 20 amp circuits to make a 4 plug box (2 recepatcles side by side; one set grey color/the other set white) in 5 different places around the garage. 2 on sides in front near door, 2 on sides in back, and 1 in back wall. I knew that from the same location I could have 2 circuits being used at the same time, like if I was running a vacuum and belt sander. I did not want to run extension cords to bring over a new circuit. Also, I have 4 spare 110/120 v (or 2 220/240v) circuits in box for more future upgrades even though I would have to go into the drywall to do it. Also do not forget that some 220/240 volt equipment may run on a 20 amp circuit steady state, but initial turnon may exceed this limit which can cause tripping and weakening the breaker.

[Luis Oliveira]

Hi all,
I also have the same need. Basically I have no 220v
or greater in my garage.
I would like to put 2 or 3 220v, add a new sub panel 65amp,
and have these outlets on their own circuit.
I am hopping I am saying this right;
I don't know anything about electricity.
I would like to bring a license electrician.
However I would like to know, considering the work,
what kinds of questions should I ask to make sure
the proper receptacles, wire, sub panel, etc.. gets installed.
What is the difference between 220v and 240v?
I am planning to use them to run my TS, DC, jointer and BS,
one tool at a time.
How much does this kind of work cost ... ballpark?
I know a life is more important that money and I want it done right,
however I want to be prepare for sticker shock.
Any help you be appreciated.
luis

[Rob Russell]

A couple of comments:

The GFI in garage requirement applies to 120v circuits, not the 240v circuits. Motors don't even use a neutral, so putting a 240v GFI breaker in for pure motor loads would be a waste of money. An example of when the 240v GFI breaker is effective would be for a spa/hot tub. The pump motors are 240v, but the lights are 120v and that's what the GFI breaker would be able to detect current leakage on.

The reason that we can use 15 amp receptacles on a 20 amp circuit is definitely because there are 2 or more receptacles or outlets. When you install a 20 amp laundry circuit and use a single outlet receptacle for that circuit, it must be rated at 20 amps. The NEC article is 210.21(B)(2), if anyone cares. Even a single receptacle with 2 outlets in it means that you can have 2 loads connected, each capable of pulling 10 amps -like a pair of hair dryers in a bathroom shared by teenage girls.

[Mike Henderson]

The GFI in garage requirement applies to 120v circuits, not the 240v circuits. Motors don't even use a neutral, so putting a 240v GFI breaker in for pure motor loads would be a waste of money.

I don't think putting GFCI on a motor would be a waste of money - it can save your life. GFCI works by monitoring the current in the two current carrying wires and tripping when the currents are not equal and opposite. In a 120 volt circuit, the wires are a hot and a neutral. In a 240 volt circuit, the two wires are both hot. (hot means there is voltage referenced to ground)

If you have GFCI on a 240 volt circuit (with any kind of load), and you grab one of the hot wires, current will flow between the hot wire and ground (through you). Since the currents are not equal and opposite in the monitored wires, the GFCI trips and you live another day.

If you grab the two hot wires in a 240 volt circuit, maybe one in each hand, and you have very good rubber sole shoes on, you could be fried and the GFCI will not trip because the current will flow between the two wires (through you) and the currents in the wires will be equal and opposite. The same thing can be said of 120 volt circuits if you grab the hot and neutral wires.

That said, I didn't put GFCI on the 240 volt circuits in my shop, mainly because of cost.

Mike

[Cliff Rohrabacher]

Every year it seems my power needs increase.
this year I installed a new sub with 16 breaker slots.
It was nice of the old electrician to use the huge multistrand copper cable he did when he put the old sub in.
The only think I didn't like was the BX cable ground he relied on. I kept the BX of course, I just don't trust it all that well. I preferred to run a ground from the ground strip in the new sub to the main ground wire that just happens to pass close to the sub box on it's way to the earth.

I am running all my lights off 15 amp breakers with 14 guage wire, my outlets are 12 guage at 20 amps and my big baldor motors are 30 amps dual throw with #6 wire.

[Rob Russell]

I don't think putting GFCI on a motor would be a waste of money - it can save your life. GFCI works by monitoring the current in the two current carrying wires and tripping when the currents are not equal and opposite. In a 120 volt circuit, the wires are a hot and a neutral. In a 240 volt circuit, the two wires are both hot. (hot means there is voltage referenced to ground)

If you have GFCI on a 240 volt circuit (with any kind of load), and you grab one of the hot wires, current will flow between the hot wire and ground (through you). Since the currents are not equal and opposite in the monitored wires, the GFCI trips and you live another day.

If you grab the two hot wires in a 240 volt circuit, maybe one in each hand, and you have very good rubber sole shoes on, you could be fried and the GFCI will not trip because the current will flow between the two wires (through you) and the currents in the wires will be equal and opposite. The same thing can be said of 120 volt circuits if you grab the hot and neutral wires.

That said, I didn't put GFCI on the 240 volt circuits in my shop, mainly because of cost.

Mike

Mike,

You're partly correct.

GFI's work by comparing the current flowing in the hot leg(s) vs the current flowing back out the neutral.

On a 120v GFI circuit, there is 1 hot leg and 1 neutral - so the GFI is comparing the current flowing through the 2 current-carrying conductors.

On a 240v GFI, the sensor compares the net current flowing in the 2 hot legs to the current flowing back out the neutral. Remember that, in our single phase systems, the 2 hot legs in a 240v circuit are 180 degrees out of phase with each other, so the current flowing in 1 hot leg negates the current flowing in the other hot leg. What the sensor in a 240v GFI circuit sees is the difference in current between the 2 hot legs and that's what is compared to the current flowing back out the neutral.

To use a 240v GFI example, assume you have a spa with 240v motors and a 120v underwater light. Assume the motors draw 10 amps @ 240v and the light draws 60 watts @ 120v or .5 amps. The current flowing in the hot leg with just the motor would be 10 amps and the current flowing in the leg with the motor and light would be 10.5 amps. The current flowing back out the neutral would be .5 amps. The GFI will compare the net current flowing in the hot legs (10.5 - 10 = .5 amps) with the current flowing back out the neutral. .5 amps = .5 amps and the GFI doesn't trip.

For a motor-only load - where the neutral isn't used - the GFI generally has nothing to detect because there is no current flowing back out the neutral. To put it differently, if you have a 240v tablesaw wired through a 240v GFI breaker and the motor has a short in the motor windings such that the chassis of the saw becomes hot with 240v and you stand barefoot in a puddle of water that makes a connection to ground and touch the saw - you're gonna fry and the GFI will let you cook until you're toast. Why? Because there is never any current flowing back through the neutral for the GFI to monitor and the net current flowing in the 2 hot legs completely negates each other, so 0 = 0.

I agree that, if you had a situation where you contacted 1 and only 1 leg of the circuit coming in so that current was flowing in that leg, nothing was flowing in the other hot leg and nothing was flowing out the neutral, the GFI would trip.

Rob

[Chris Padilla]

For a motor-only load - where the neutral isn't used - the GFI generally has nothing to detect because there is no current flowing back out the neutral. To put it differently, if you have a 240v tablesaw wired through a 240v GFI breaker and the motor has a short in the motor windings such that the chassis of the saw becomes hot with 240v and you stand barefoot in a puddle of water that makes a connection to ground and touch the saw - you're gonna fry and the GFI will let you cook until you're toast. Why? Because there is never any current flowing back through the neutral for the GFI to monitor and the net current flowing in the 2 hot legs completely negates each other, so 0 = 0.
Rob

Well, let's hope the bare/green wire is hooked up!! :o

[Mike Henderson]

Mike,

GFI's work by comparing the current flowing in the hot leg(s) vs the current flowing back out the neutral. Rob

I don't believe that's correct, Rob. The GFCI compares the current in the two current carrying wires, no matter whether one of those wires is a neutral or not.

In your example of a motor wired for 240 volts where one side shorted to the case (assuming you didn't ground the case), if you touched the case and current began to flow through you, the current in the two current carrying wires would not be equal (and opposite) and the GFCI would trip. GFCI really does work on 240 volt circuits without a neutral. It would not make sense to design GFCI otherwise.

Mike

[Randy Meijer]

I'm not an electrician or an EE; but I am having a hard time accepting the idea that a GFCI is useless on a 240V circuit without a neutral. Guess I am going to have to do some outside reading to see if I can satisfy myself as to what is the correct information.

[Rob Beckers]

GFCIs don't need a neutral at all. All they need is for the current through the wires they're measuring to cancel out, so if current is diverted (for example because you grab a hot wire and send a bit to ground) the net current through the GFCI is no longer zero and it trips. Consequently, 240V GFCI breakers work just fine without a neutral.

To make this even more interesting, GFCIs don't even need two wires, there are versions that work on 3 or more. To take my shop as an example: I wired up the shop with a run of 12/3 MC cable around the entire shop, two of the wires are hot 120V phases, the third is neutral (and there's a fourth for ground). Every few feet there's a duplex 120V outlet, hooking up to one of the 120V phases and neutral (I alternate phase between outlets to balance the load), and every other outlet there's another duplex hooked up to both 120V phases, making for a duplex 240V outlet. Ground fault protection is important to me, this is a basement shop and I have no desire to electrocute myself, but a regular 240V GFCI breaker won't work since there's current going through neutral as well in case of a 120V load. To solve that I used a Leviton 8895-00E and a 50 Amp contactor to create a GFCI that handles any type of ground fault. Here's a picture of the device:

http://www.levitonhelpdesk.com/catalog/productimages/device8895.jpg

Both 120V hot wires and the neutral wire pass through the donut, which is just a transformer. As long as total current going through those wires is zero there's nothing for the transformer to work with and all is fine. When a bit of current is diverted to ground the total is no longer zero, and the transformer produces a bit of voltage on its windings, telling the electronics to drop the contactor, and presto, the voltage going to my equipment is dropped. Only specific contacters/relays are approved for use with this GFCI to guarantee it will drop its voltage in case of a fault within a few miliseconds. Cost is not all that bad, I paid $31.54 for the GFCI controller plus $54.39 for the contactor, making for a total of $85.93 for very reliable and flexible ground fault protection. Of course, one still needs a 20 Amp double breaker (regular one, not a GFCI breaker) to protect the wiring from shorts, another $45 in my case.

Works like a charm!

-Rob-

[Keith Hooks]

A 220v circuit doesn't have a neutral wire at all. All of the current is designed to flow through the two hot leads. Of course, there's still the bare ground, but this conductor isn't meant to carry electricity unless something goes wrong. It's there as a failsafe.

Thinking about a 220v circuit, I don't think a typical 110v GFI, current balancing configuration, would work at all. If you you get a short to ground anywhere in a complete 220v circuit, then that connection essentially becomes like the neutral in a 110v circuit and starts to carry current to ground. Equal amounts of current will flow from the two hot leads into the new ground as it alternates back and forth. So technically, the currents in the hot leads would remain the same (equal and opposite).

The reason it works on 110v is that there's no voltage on the neutral and connecting neutral to ground doesn't create a current sink. Current won't flow on the neutral without a voltage. So, if there's a difference between the hot and the neutral then you know it's going somewhere else. In the 220v, you get the same amount of current flowing into the "fault" each time the juice cycles back and forth effectively summing to zero.

Anyway, this is how it works in my head...

[Mike Henderson]

Rob Russell and I communicated via PM and I think we both agree that a 240 v GFCI works essentially the way Rob Beckers described in his post. That is, the three wires are monitored (two hots and a neutral) and it will trip if the net current is not zero. This allows unbalanced loads as well as balanced loads. An unbalanced load would be as Rob R described when a 120 v circuit is derived from one side of the 240 v circuit and the 240 volt is also used to supply a load (Rob R's spa example). A balanced load would be a motor where the neutral is not used.

As Rob B explained, if the three wires are run through the sensing coil, the GFCI will work in either configuration.

[comment on Keith's posting] If you get a short from hot to ground, the current returns via the earth and not through the neutral or the other hot so the currents in the monitored wires are not balanced and the GFCI trips. If you get a short from hot to neutral, the circuit breaker trips because of excess current. This is true of both 120 v and 240 v circuits.

Mike

[Rob Russell]

What Mike said. :)

Rob