Detached Garage Wiring

[64mgb]

I'm preparing to wire my newly built detached garage and have several questions. First, the situation. The new garage is 24 x 28, and the wiring will enter it approximately 30 feet from where it exits the home. The exit from the home is approximately 20 feet from the home's circuit box. There are no noncurrent carrying metallic connections between the 2 structures. I intend to install a 220v outlet for a welder, and have a compressor and a radial arm saw. Other than that all loads should be typical garage/workshop power tools and such. I want to install a circuit box in the garage with at least 4 circuits besides the 220 for the welder. Now the questions: What size wire do I need to use between the home's service panel and the garage? What's the best way for the wire to exit the home...I intend to bring it out about a foot above ground...what materials should I use? (I've buried flexible plastic conduit in the concrete for the wires to enter the garage). Should I use direct bury, or run it in PVC? Do I need to install a grounding rod at the garage? If so, how do I do that?

Sorry if these questions are repeats on this forum...I just discovered it and it looks like a great resource.

All advice is greatly appreciated!

Thanks,
Rich

[Wgoodrich]

Is this a 20 amp wire welder or a 50 amp arc welder. What size horse power and voltage is your air compressor. Are you planning on an electric water heater or any type air conditioner window or central.

This flexible conduit was it approved for contact or buried in concrete?

Curious

Wg

[64mgb]

Hi Wg -

I plan on being able to use an arc welder. The compressor is 110v...I meant to check the horsepower but forgot...I think it's 5HP. I'm not planning on installing a water heater or air conditioner. I'm not sure about the flexible conduit...my brother gave it to me and said his company uses it all the time for burying cable, although I think it is used for communications cable, not ac cable. I've been concerned about it's proper use, since we didn't check ahead of time. Worst case, we plug it up and enter the garage a different way.

Thanks,
Rich

[Wgoodrich]

A 5 horse power motor 120 volt would make your garage service size jump way high. Confirm the horse power and voltage of that motor before we can come up with an accurate service size for your garage.

Also confirm is you are the only person planned to use equipment at any one given time in your garage. This also would make a difference in service size required.

Curious

Wg

[64mgb]

I just checked the compressor...it's actually 5.5 HP, and it's 120v (plugs into a standard receptacle). As a rule, I'll be the only one using the garage at any one time.

Thanks for your time.

Rich

[Wgoodrich]

You are not looking on the right location. You need to look on the name plate of the motor for your horse power and voltage. The sticker on the tank has nothing to do with motor horse power. That is compressor horse power rating not motor horse power rating. I am expecting your electric motor name plate found on the motor yourself to say either 1/2 horse power or 3/4 horse power. Look again you used the sticker on the tank and you don't have the proper horse power rating yet.

Wg

[64mgb]

Thanfor your patience and attention to this Wg. I'll check again tonight.

Rich

[Wgoodrich]

See you then

Wg

[64mgb]

I was unable to find any other markings...I suspect I need to take the plastic cover off the motor/compressor (but it's cold here in Iowa!). But, here's what it says in the manual:

======================================
These compressors can be operated on a 15 amp circuit if:
1. Voltage supply to circuit is normal.
2. Circuit is not used to supply any other electrical needs (lights, appliances, etc.)
3. Extension cords comply with specifications in owners manual.
4. Circuit is equipped with 15 amp circuit breaker or 15 amp time delay fuse.

If any of the above conditions can not be met, or if operation of the compressor repeatedly causes interruption of power, it may be necessary to operate it from a 20 amp circuit. It is not necessary to change the cord set.
======================================

Does this tell you what you need to know? If I need to, I can go out and figure out how to get the cover off and see if there are markings on the motor. The compressor normally works fine, even on a circuit used for lights, except when it's cold out. Then it will occasionally trip the 15 amp breaker.

Thanks again for your help!

Rich

[Wgoodrich]

If you welder is a wire welder with 240 volts then most likely it will be 20 amp 240 volt.

If your welder is an arc welder then most likely it is a 60 amp 240 volt welder.

You are compresser we will take as 15 amp load but advise you install a 20 amp branch circuit from your garage panel to that air compressor for reliable service of that air compressor.

Also chances are if you install that air compressor in an accessible location you should be able to unplug your air compressor and plug in your wire welder.

If you have an arc welder then you will need 6/2wGrnd [no neutral wire used reidentify the white as a hot wire for this arc welder] Then use a 50 amp welder plug and a 50 amp double pole 240 volt breaker.

To size your service we would take the 50 amp arc welder as your largest load increasing it 125% = 62.5 amps then add you air compressor load of 15 amp to that. I picked up no other loads that would be used at the same time other than general lighting. so lets add approximately 10 amps for lighting say. This would require a garage service 87.5 amps adjusted up to a 100 amp service.

If you do not have an arc welder and only have a wire welder at 20 amp 240 volt then you would take that welder at 20 amps increase 125% = 25 amps add 15 amps for the air compressor and 10 amps say for general lighting and you have a minimum service size of 60 amp service.

Now you need to decide how much more than minimum service size you want to install.

Keep in mind that you garage may be served using TAble 310.15.B.6 allowing 4 awg coppper or 2 awg aluminum wire to serve a 100 amp panel in your garage.

You may use a 6 awg copper or 4 awg aluminum feeder to serve a 60 amp panel in your garage.

Suspect that you can buy with little cost difference between the 60 amp service and the 100 amp service in the garage, the 4 awg wire in a conduit using 4 awg copper wire using three conductors as your feeder in a 1 1/4" PVC conduit buried a minimum of 18" deep using a 100 amp service panel in the garage and marry the neutral bar and hte grounding bar together due to no equipment grounding conductor ran with the feeder between the two buildings due to no metal water pipes etc. connecting the two buildings.

Let us know what you decide

Good Luck

Wg

[64mgb]

Thanks, Wg -

I think I understand all of this, and will go with the 100 amp service. If I understand correctly, you're saying that I do not need to bury anu sort of grounding system for the garage, right (just connect the grounding bar and the nuetral bar together)? What's the best way to exit the house (I plan on exiting about 1 or 2 feet above ground)? Are there PVC fittings for this purpose? I've always done all my basic home wiring, but have never tackled anything like this!

Thanks for all your help.

Rich

[Wgoodrich]

Sorry I skipped the grounding part. YOu must drive a ground rod at the garage and create a new grounding source by doing so. Then install a 8 awg copper wire from that ground rod and connect to the grounding bar in the garage panel. Also you must bond the metal case of that panel to the neutral bar or grounding bar so all neutral and grounding bars and metal case of that panel is one entity.

If your panel is on the outside wall most commonly you would pass through the back of that panel to the side of the meter base through the wall to the outside and install a PVC LB with a cover plate. This LB allows you to make the bend flat to the wall and keep your conduit against the wall. You will need to install a PVC terminal treaded adapter and use a locknut to secure that terminal adapter to the panel in the house. Then glue a piece of PVC conduit from taht terminal adapter through the wall and glued ot the PVC LB. Then glue a sch. 80 PVC to the bottom of the LB and run down the outside wall into the ground. Then install a sweep 90 PVC conduit piece preformed allowing the 90 degree turn into the trench bottom. Change to sch 40 PVC using 1 1/4" PVC all the way between the two panels. Then trench the conduit 18" deep to the garage and again install a preformed sweep 90 to make the bend out of the trench along the outside wall of the garage. Forget you unknown buried flex leave it unused doubt it is approved for use as you thought you could use it.

Run sch80 PVC up the wall again using an PVC LB to turn through the wall into the back of your garage panel.

The LB has a cover plate to assist you in pulling your wires through the conduit.

IF you are coming out of the crawl or basement do the same as above using conduit all the way from one panel out that buliding into the trench again using LBs like above to complete your conduit run.

HOpe this helps

Wg

[64mgb]

I've got another question. From the reading I've done in NEC 1999, I've determined that I can have up to 8 receptacles on a 15 amp circuit. My question is, is a standard duplex receptacle considered one receptacle for this calculation, or is it considered 2?

Thanks,
Rich

[Wgoodrich]

A duplex receptacle is considered as one receptacle.

Now what rules in the NEC did you use to come up with the number 8 per circuit?

Did you calculate using a 15 amp branch circuit then reducing to 80% then dividing that by 180 volt amps per outlet getting your 8 outlets per 15 amp branch circuit?

Below you can find your confirmation about an outlet being a point of the wiring system where current is taken to supply utilization equipment. Notice it say point meaning outlet box.

Outlet. A point on the wiring system at which current is taken to supply utilization equipment.
An example is a lighting outlet or a receptacle outlet.

I question what is the setting of this detached garage? Is this an accessory structure of a residential setting zoned as a dwelling? If so then the detached garage being an accessory building of a dwelling is also considered a part of that dwelling estate.

If this is a separate building such as a farm [ag] building in an agricultural zoning for use to raise crops or animals, and has its own power source then the dwelling unit would be considered as dwelling and this ag building would now be a commercial garage under its own rules.

Again if this building is as the last paragraph above yet power is coming from the farm dwelling then again it is a mix occupancy that carries even a third set of rules that shares new calcualtions for farms only.

Which garage do you have?

Curious

Wg

[64mgb]

Hi Wg -

Actually, I got this information from a combination of sources, but primarliy from an article I found on the internet, authored by you: "Example of Wiring a Detached Garage or Detached Building Designed as a Storage Garage". In it, you state that If you have a question as to how many receptacles are allowed on a circuit, then you may wire your dwelling's garage by designing your general use receptacles in that garage with no more than 10 receptacles on a 20 amp circuit or no more than 8 receptacles on a 15 amp circuit".

I believe my garage is as described in your first example: "an accessory structure of a residential setting zoned as a dwelling". I live in a residential area, and the garage is for storing cars and a workshop.

Thanks for all your help,
Rich

[64mgb]

I forgot a question, Wg. The way I read the definition of a receptacle, it would infer to me that a double box with 2 duplex receptacles would be counted as 1 receptacle when determining the number of receptacles in a circuit. Is this right?

Thanks again,
Rich

[Wgoodrich]

Receptacles are counted by the mounting yokes. If you have three mounting yokes each being a receptacle whether one, two, or three plugins in each certain device you would have three receptacles by counting the mounting yokes that mount the devices to the box.

Hope this helps

Wg

[Wgoodrich]

I did not imply that you were wrong just questoned why you hit the 8 so accurately concerning commercial wiring styles. From what you explained I see where you got it.

Actually if it is a residential garage and convenience outlets it would be the same as in the house. Yet most areas respect the commercial number as you hit originally. This garage has been argued in many different manners commercial and residential.

You stated as I would have wired it you just surprised me that you hit the 8 directly first said on the subject. Figured you picked it up somewhere.

Good Luck

Wg

[64mgb]

Thanks again, Wg - I really appreciate all of your help. I've included a picture of my wiring plans in this post...what do you think? Any suggestions/tips?

http://rdfrahm.home.mchsi.com/wiring.jpg

(Hope I inserted the image properly).

Thanks again,
Rich

[Wgoodrich]

Make sure you have a minimum of 30" width dedicated wall space for your service panel.

Outside plugs are not required in a garage but you may install them if you like. Remember that these outside plugs now must be with in-use bubble shield weather proof covers.

You might consider daisy chaining your welder plug installing a welder plug on each end of the garage near the over head door so you can have an either or choice of where you can weld. You can use the same breaker just daisy chain from welder receptacle to welder receptacle.

YOu are exempt from being required outside lights at over head doors. These outside lights are required only at human doors. YOu may install them if you like but you are not required to install outside lights at service doors.

You seem a bit low on light fixtures. You may want to consider adding a light over your work bench [flourescent hanging is usually the best for this or under cabinet if cabinets above the work bench.

Area lights should be placed not over where vehicles are sitting but over the sides of the vehicles so they can light the bottom and side of the vehichles for working on them. Also you might want to install lights wrapping all four sides front and rear included holding the lights out a bit further so they will light under the engine hood and trunk hood.

Also a thought would be add a couple of ceiling receptacles for a hanging retractable trouble light plugged into the ceiling.

Also a thought is to install Garage door opener receptacles for each over head door about the location of where the overhead doo will come along the ceiling where the door opener motor will be. Also may want to consider running door bell wire about a 5 wire door bell wire from each garage door opener receptacle location to the human door location for door opener controllers.

You may wire this garage in Romex if you like. I would install a 10/2wGRnd to the air compressor then install a 20 amp 220 volt breaker and receptacle for your smaller air compressor. This way if you have growing pains you already have the wire for a much larger compresser. Easy to do now.

Hope this helps

Wg

[64mgb]

Hi again, Wg -

You must really like all these questions from amateurs...you keep coming back for more :wink: I really appreciate all your advice.

Sounds like I will have to change my plans for the location of the circuit box...it measures 28" between the front (south) wall and the edge of the service door frame. I assume the door is not considered part of the wall. I can either move it to the other side of the door (still on the east wall), in which case it cuts into my wall area above the workbench. Or, I can move it around the corner to the short wall next to the 18' overhead door. My preferred position would be between the service door and the window on the east wall because it would be an easier and cleaner entrance (the wire from the house will be coming from the east side). Any suggestions?

What's a "in-use bubble shield weather proof cover"? I bought some weather proof covers...I think they are aluminum. The box itself doesn't have to be weather proof does it?

I assume the best way to daisy chain the 6/3 for the welder is to use a junction box before going into the box for the first one? I've never worked with 6/3, but I assume it would be pretty hard to splice in the outlet box.

Yea, I know I'm a bit low on indoor lights. I can't decide what I want to do. I do plan on installing flourescent fixtures over the workbench...just forgot to draw them in. I was going to install 4 incandescent fixtures (although I plan on using flourescent bulbs...they come on quite dim when cold, but come up to full light in a few minutes, and use less energy). But, 3 of them would be hidden under the overhead doors if the doors were both open. Granted, you usually won't need to have lights on when the doors are open, but sometimes you do. Also, there isn't much clearance between the bulb and the door when it's open, especially on the 8' door. How about 3 fixtures straight across in the position I have the 2 drawn now?

I also had planned on installing ceiling receptacles for the garage door openers...just forgot to draw them in. What circuit should I put them on? I figure either the outdoor outlets circuit or the lights circuit.

Great idea for the 20A circuit (using 10/2 w/g)...I'll do that!

A design question...Can I combine the lighting circuit and the outdoor outlets circuit, thereby leaving a spare in the box for the future? Although, I guess this isn't really a concern...I bought a box with 8 spaces, 16 circuits, so I could use the narrow breakers to add circuits. Also, I plan on using isolated ground outlets for the computer equipment...do I still need a GFI outlet ahead of these?

Thanks again...and have a great holiday season!

Rich

[64mgb]

A couple more questions, Wg. I'm running wiring for cable, computer network, phone, and speakers. None of this is governed by the permit is it?

I'm building "troughs" that lay across the top of the trusses for the wiring to lay in (9.5" wide OSB, with 2x4 sides). Is this ok? Do I still need to staple the wires in the troughs, or can they just lay in them?

Is there a limit on the number and size of holes drilled in the top plate to run wires through? Above the curcuit box where many wires will be exiting through the top plate, as well as above the junction box I bought for the phone, cable, and computer network, I can see that I will need several holes. Any guidelines?

Thanks again,
Rich

[Wgoodrich]

YOU SAID;
Sounds like I will have to change my plans for the location of the circuit box...it measures 28" between the front (south) wall and the edge of the service door frame. I assume the door is not considered part of the wall. I can either move it to the other side of the door (still on the east wall), in which case it cuts into my wall area above the workbench. Or, I can move it around the corner to the short wall next to the 18' overhead door. My preferred position would be between the service door and the window on the east wall because it would be an easier and cleaner entrance (the wire from the house will be coming from the east side). Any suggestions?

REPLY;
The panel may be anywhere within the 30" dedicated wall space. This means the panel can be right in the corner as long as 30" of dedicated wall width is reserved unobstructed wall space. The panel does not have to be 30" from the edge of that space it only has to have 30" wide dedicated space with the panel set anywhere within that 30" space.

YOU SAID;
What's a "in-use bubble shield weather proof cover"? I bought some weather proof covers...I think they are aluminum. The box itself doesn't have to be weather proof does it?

REPLY;
The older weatherproof cover is no longer allowed for outside receptacles. Outside receptacles now must be with a weatherproof cover plate that is bubble shield style so that you may plug in a cord and the bubble will cover and make weather proof that receptacle while the cord is plugged in. This is required whether a receptacle is plugged in unattended or not. All outside receptacles now must have INUSE weatherproof cover plates.

YOU SAID;
I assume the best way to daisy chain the 6/3 for the welder is to use a junction box before going into the box for the first one? I've never worked with 6/3, but I assume it would be pretty hard to splice in the outlet box.

REPLY;
Use a nonmetallic 4 x 4 nail on box then run your 6/2wGrnd into that box. then make a black, red, and bare pigtails about 6" long. Then use blue plastic wing style wire nuts designed to accept 6 awg wire. Then just wire nut the 3 black wires extending to the second welder receptacle using the pigtailed black wire to connect to the welder receptacle that is to mount to that box. Then use what is called a plaster ring or a welder receptacle designed to mount directly to that 4 x 4 box. Easy as wiring a duplex receptacle you have done before.

YOU SAID;
Yea, I know I'm a bit low on indoor lights. I can't decide what I want to do. I do plan on installing flourescent fixtures over the workbench...just forgot to draw them in. I was going to install 4 incandescent fixtures (although I plan on using flourescent bulbs...they come on quite dim when cold, but come up to full light in a few minutes, and use less energy). But, 3 of them would be hidden under the overhead doors if the doors were both open. Granted, you usually won't need to have lights on when the doors are open, but sometimes you do. Also, there isn't much clearance between the bulb and the door when it's open, especially on the 8' door. How about 3 fixtures straight across in the position I have the 2 drawn now?

REPLY;

Decide where you would park a vehicle or other machinery in that garage to work on it. Then place receptacles around that area. Then install your incandescent fixtures as you planned if you like. When you decide you need flourescent fixtures later and you can afford them then buy 8' HO type flourescent fixtures that are desigend to work in sub zero weather. Bit more expensive but well worth the money.

YOU SAID;
I also had planned on installing ceiling receptacles for the garage door openers...just forgot to draw them in. What circuit should I put them on? I figure either the outdoor outlets circuit or the lights circuit.

REPLY;
Any branch circuit 15 or 20 amp 120 volt rated. You don't have enough of a load long enough to make a difference to a branch circuit concerning loading of amps.

YOU SAID;
Great idea for the 20A circuit (using 10/2 w/g)...I'll do that!

A design question...Can I combine the lighting circuit and the outdoor outlets circuit, thereby leaving a spare in the box for the future? Although, I guess this isn't really a concern...I bought a box with 8 spaces, 16 circuits, so I could use the narrow breakers to add circuits. Also, I plan on using isolated ground outlets for the computer equipment...do I still need a GFI outlet ahead of these?

REPLY;
You most likely will not be working outside when working inside and vice versa. Kind of an either or situation concerning load. You can add the outside receptacles to any branch circuit incuding the inside receptacle serving the outside receptacles. That way you can use the same GFI protection saving on cost.

Even isolated grounding receptacles must be GFI protected unless placed inside an office having a dual occupancy building being the garage area and the office area separated by a minimum of a 1 hour fire wall.

HOpe this helps

Wg

[64mgb]

Hi again, Wg. I passed my homeowner's electrical test last week, so I can legally wire my garage. :-) I have a couple more questions:

1) Instead of using 10/2 w/ground for the 20A air compressor circuit, can I use 10/3 w/ground and leave the red lead disconnected, in case I want to get a 220v compressor some day?

2) Can I use plastic adapter plates (to adapt a 4x4 junction box to accept a single receptacle) on metal boxes?

Thanks again!

Rich

[Wgoodrich]

10/2wGrnd is fine to use for either a 120 volt or 220 volt air compressor circuit. A motor does not use a neutral wire if 220 volt so the white wire is allowed to be reidentified as a hot wire when using 220 volt on the same wire. 10/2wGrnd is find for both 120 or 220 volt circuits.

Normally a steel plaster ring is used on a steel box or a plastic plaster ring is used on a plastic box. However there is no rule against using a plastic plaster ring other than you will have to install an equipment grounding jumper for either because the steel or plastic plaster ring is not approved as a grounding path.

Be sure to bond those steel boxes as well as the devices with a green grounding screw in the metal box.

Hope this helps

Wg

[64mgb]

Hi again, Wg. More questions today:

I'm assuming I can use 6/2 with ground (as opposed to 6/3 with ground) for my welder circuit, as long as I don't use metal boxes for the receptacles...is this correct?

Can I run 2 cables (12/2 w/ground) through one cable clamp into a metal box?

Take a look at these pictures:

http://rdfrahm.home.mchsi.com/garage_20030106_01a.jpg
http://rdfrahm.home.mchsi.com/garage_20030106_02a.jpg
http://rdfrahm.home.mchsi.com/garage_20030106_03a.jpg

Is the location for the circuit box ok? Is it ok to have an outdoor fixture, switches, and receptacles near the box? I hope the answer is "yes"...it's a major problem if not. Also, does my wiring inside the box look ok?

Thanks again for all your help!

Rich

[Wgoodrich]

YOu have shown the whites on one side and the bares on the other side as if you were running a 4 wire feeder with grounding conductor ran with feeder to this panel, yet you have left the jumper between the two bars as if you were running a 3 wire feeder without a grounding conductor. Which are you going to install.

Yes you panel and switches are fine as you have them. YOu may start your 30" to the right edge of the panel and measure to the left with teh panel offset in the 30 wall space. Also if you got technical your switches are flush and do not extend past the front of the panel and would not be counted as an obstruction anyway.

The metal box makes no difference. What counts is that the welder does not use a white wire at all. No 120 volt components are inside this welder needing a neutral conductor at all. The bare wire in the 6/2wGRnd is your equipment grounding wire only. The black and white [reidentified as red] wires are both hot wires. No white neutral is used at all.

Some cable clamps are listed for two romex cables and some are listed only for one cable. Check you installation instructions on the clamps.

If you drywall you will have to deenergize and take the switches and romex cables loose from the boxes and shove in longways so you can maintain your 1/8" gap max from box to drywall.

I also do not see you big green grounding screw that is supposed to be screwed from the grounding bar to the metal case of the panel.

Looks like a nice clean square to the world wiring installation.

HOpe this helps

Wg

[64mgb]

Hi Wg -

I just put the box up the way it came from Menard's. I assume the metal bar across the top of the nuetral bar and the grounding bar is the jumper you are talking about? Which way do I need to wire this?

In an earlier post you wrote:
"YOu must drive a ground rod at the garage and create a new grounding source by doing so. Then install a 8 awg copper wire from that ground rod and connect to the grounding bar in the garage panel. Also you must bond the metal case of that panel to the neutral bar or grounding bar so all neutral and grounding bars and metal case of that panel is one entity."

I assume this means I should leave the jumper in place and run a 3 wire feeder without a grounding conductor, right?

Thanks again,
Rich

[Wgoodrich]

It does not matter whether you install a four wire with equipment grounding conductor or three wire without and eqiupment grounding condcutor with the feeder you still must install the grounding electrode [commonly a ground rod] at that accessory building.

You did not have your feeder yet and you got me in trouble. I ASSUMED you were running a four wire feeder. My mistake.

If you have no noncurrent carrying metallic paths [including a grounding wire in a phone cable or computer or antenae cable] then you may install a three wire feeder.

Problem is you need to think ahead. If any time in the future you plan to install a phone line or other type line or pipe that makes a noncurrent carrying metallic path between those two buildings then you need to consider a four wire cable.

If you have no nor never plan to have a noncurrent carrying path between the two buildings then yes you panel is fine as it is if you install the three wire cable.

Good Catch

Wg

[64mgb]

Hi again, Wg -

Sounds like the safest thing for me to do would be to run a 4 wire feeder, even if I think I don't need it now. The only negative I can think of if doing this is the extra cost, right? How do you connect the 4 wire in the house's panel?

I am planning on running phone, cable tv, computer network, and possibly wires for a security system to the garage, so maybe I should go ahead with the 4 wire? If I understand correctly, if I do that, then I need to remove the jumper between the nuetral bar and the ground bar, right? Then I connect the grounding rod and the box to the ground bar.

On to another subject. I'm planning on installing an isolated ground circuit for the computer. Is this really necessary? Does it really do any good? If so, is there such a thing as an isolated ground gfci receptacle? My local Menard's doesn't have one. Can I run regular (non-isolated ground) receptacles off the same circuit as the isolated ground receptacles? If so, I assume they need to have there own gfci protection.

Thanks again!

Rich

[Wgoodrich]

In the main service rated panel in the house you would connect the black and red wires to the 220 volt double pole breaker. The white wire and the grounding wire bare can be connected to the same neutral or grounding bar in the house main service rated panel.

In the garage you would connect the white to the neutral bar with the neutral bar isolated from the grounding and the metal case of hte panel.

The grounding electrode conductor from the ground rod to the panel and the bare and green grounding wires are connected ot the grounding bar of that panel that is connected to the metal casing of the panel.

An isolated grounding circuit is in affect already done if you run Romex directly from the garage panel to a nonmetallic receptacle box to a normal receptacle. The box is non conductive and the yoke is connecting to nothing that is conductive [being the plastic box].

A dedicated branch circiut to a single duplex receptacle with the branch circuit being 12 or 14/2wGrnd Romex cable using a plastic box allows that bare wire to make contact with nothing else conductive except at the receptacle and at the grounding bar where you isolated ground would connect anyway. To make this a true isolated grounding circuit you may run the grounding conductor directly through the panel not connecting to anything until you reach the ground rod. If this grounding wire is insulated and marked with green tape then you would have a true isolated grounding receptacle if wired as discribed using a plastic box and using a 12/3 removing the grounidng wire and marking the red with green tape as the insulated grounding conductor connected directly to the ground rod.

A normal 12/2wGrnd branch circuit using a plastic box essentially does the samething as an isolated grounding receptacle. That ground wire touches nothing that conducts electricity thus you have an insolated grounding conductor.

Hope this helps

Wg

[64mgb]

Thanks a bunch Wg! I'll just run a normal 12/2 w/gnd to receptacles in plastic boxes and not worry about the isolated ground receptacles. I really appreciate all the help you've given me. All i have left to wire (besides running the cable from the main box to the garage) is the computer/stereo circuit and the welder circuit. plus i still have to run some of the "utility" wiring (phone, network, etc).

Thanks again,
Rich

[64mgb]

Hi again Wg...it's been a few weeks since I posted, so I figured you probably missed me :lol: Anyway, I'm working on the welder circuit. You recommended that I daisy chain the two receptacles I'm putting in by tying the wires together in a junction box at the first receptacle then running on to the second one. I wasn't comfortable trying to stuff all those wires in a 4 x 4 junction box, along with a receptacle, so I bought a 6 x 6 junction box and mounted it on top of a 2 x 6 spanning a couple of trusses. This gives me much more room to work, although it'll be less accessible if I need to get to it.

Now the questions. You recommended I tie the wires together with blue wing type wire nuts, but they say they will handle up to two 6 awg wires. Can I really use them to tie 3 wires together? I tried it with some short wires and it seemed to tie them securely, but is it safe? And will it pass inspection? Are there any other alternatives?

Is there a recommended height to mount 220v welder receptacles? I already mounted the last receptacle in the circuit with the center of the box about 42" off the floor. Is this ok?

Thanks again!

Rich

[Wgoodrich]

REad the installation instructions on the box. I thought the blue Ideal brand wing nut was approved for three 6 awg copper wires. If you have the hard bakelite wire nut it may be limited to two 6 awg wire. Do not exceed the manufacturer's instructions concerning number of 6 awg copper conductors in that wire nut.

If you manufacturer's instructions forbid you to use three wires in that wire nut, then buy three split bolts and a roll of filler tape and a roll of electrical tape. Make the connections using the split bolt connector for each sets of wires. Then use filler tape wrapping each individual split bolt. Then use electrical tape to seal the filler tape making a secure connection for all three connections.

There is no set hieght for receptacles what you discribed is fine.

Hope this helps

Wg