As far as your ground rods, you will need two of them spaced 8' apart and fed with a continuous #6 bare copper from the panel, through acorn nuts on each rod. No splices.

If you are planning on future proofing it, I would go ahead and bury 2" conduit so you can pull larger wires for more amperage later on. Better than digging it up and re laying it.

Don't forget to get your permit for it. Once you dig your trench, the inspector will want to see it. He will probably tell you to cover it up, but lay in yellow tape about 4" above the conduit to warn others that wiring exists below it.

 

I'm a master electrician. $2400 is a little steep. At 30 feet distance, I would have done this job and gave you a full 100 amps to your garage for probably like 1400-1600. That wouldn't include trenching and backfilling though. I always offer my clients the opportunity to gain some sweat equity in that area, otherwise I would just refer you to answer another contractor.

You can do a 30 foot trench by hand but it's a lot of back breaking work. For probably around $200 you can rent a walk behind trencher with a 4' blade. You can only get so close to the foundation with it and then you'll have to finish the rest by hand. So you'll want a trenching shovel (a very narrow shovel).

As for circuit sizing, 46 amps on a 50 amp breaker would be in violation. You can't load a circuit more than 80% of rated ampacity. Also, I don't even think you can put #4 wire on a 50 amp breaker. I think the max is #6. Also #4 copper can be OCPDed at 85 amps. But forget all that. Here's what you need to do.

Up your pipe to 1-1/2 or even 2" like the other guy mentioned. Instead of #4 copper THHN, you'll run #1 aluminum XHHW. It may not be available at your local big box store so you'll have to visit your local electrical supply house. With #1 aluminum you can run that off a 100 amp breaker, so you'll have a full 100 amps out in your garage. The price difference is unreal. #4 THHN is about $2/ft and #1 AL XHHW is about $0.50/ft. Aluminum is a fine conductor if installed properly. You'll need to get a small tube of antioxidant paste to apply to the terminations at both ends. The reason is aluminum wire oxidizea easily and aluminum oxide is a really good insulator and can cause the termination to fail over time.

You are correct to use SCH 40 at burial depth, which is 18" to the top of the pipe. So the elbows and riser pipes emerging from grade need to be SCH 80. You'll need 2 LB conduit bodies to make the sharp turn into the building on each side. You can run the pipe up the side of the garage and then LB in right into the back of the panel. You'll need duct seal to seal the pipe where the wires come out on both ends. The reason is because warm moist air from inside the building will get in the pipes and condense, causing the pipes to fill with water.

I would recommend your equipment ground wire be #8 copper. That's the size you need for a 100 amp feeder. I always recommend copper for a ground. You certainly can use aluminum if you want, but you'll need #6 XHHW. The wire for the ground rods must be copper though as you cannot bury bare aluminum wire. The other poster was correct about the ground rods. You need 2 spaced 8 ft apart and connected to the ground bar in the panel via #6 bare copper. You really only need #8 copper for ground rods but it has to be in pipe. #6 doesn't have to be protected so it's cheaper and easier just to use #6.

You may notice that in your main panel, all the ground and neutral wires are probably terminated on the same bus bar. This is ONLY allowed in the main panel because the neutral is bonded to ground at that point. In sub panels, the neutral and ground wires must be separated. Most panels do not come with a separate ground bar so you'll need to purchase one separately. They are specific to the manufacturer of the panel. I usually put two ground bars in, one at each side so you don't have to run your ground wires around to the other side of the panel.

As for your sub panel, you should get a 100 amp main breaker panel instead of a main lug only (MLO) panel. The reason is you need to have a main disconnect for the detached building and the main breaker serves that purpose. Also, you'll be able to get a full 32 space panel. All panels come with a main bonding jumper in the form of either a green screw or a copper bar or strap. You'll discard this as they are only to be installed if it's your main service panel.

You also mentioned that you have metal underground water pipes. You can actually use this for an additional grounding electrode but you still have to have the ground rods. Actually I think you only need one ground rod for an outbuilding but 2 is better. I always do two. Regardless of whether or not the water pipes are a viable grounding electrode, you must bond them to to grounding system in your garage. Any shared metal systems between the house and garage must be bonded. You can use #6 copper or #6 aluminum. The only ground wire that has to be copper is the wire running out to the ground rods. Your wires running to the ground rods and the metal water pipes can both terminate on the ground bar (s) in the panel.

I'm sure you'll have more questions and I encourage you to ask away. I hope this'll get you started though. Good luck! [emoji3]

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I wonder why NEC and CEC have different opinions on grounding? Everything in that nature in this area are only grounded and bonded at one location and everything including sub panels are only bonded from there with the bonding screw/strap removed at any sub panel. I can see how additional ground rods/ plates are beneficial but don’t understand why 2 similar neighbouring countries running the same/ similar equipment have so different rules around grounding?

 

2) Run 2 hots from the breaker, 1 neutral (4 gauge THNN), 1 ground (6 gauge solid),

If I were you, I would use aluminum conductors such as THHN or XHHW. Those sizes (#4 with #6 ground) are good for 65A. That means you can plan to have 65A of loads. They don't sell 65A breakers so you use 70A. That is not permission to intentionally load the wires to 70A.

If you mean copper, then use aluminum (the subpanel lugs will be aluminum so you're not avoiding any dissimilar metal problems, much the opposite actually). And then use the money you saved to buy a panel with more spaces. The #1 problem people run into with subpanels is running out of spaces. You go through them much faster than you'd imagine. You should be able to give every 240V machine tool its own breaker if you want to, particularly if some are 20A and some are 30A because that's mandatory - you can run 15A tools on 20A circuits, but you can't run 15A or 20A tools on 30A circuits.

If you want 90A, bump to the next size, #2 conductors yet still #6 ground (weirdly). Still aluminum. These wires are modestly priced so there's no reason not to "think big".

from the main in sched 80, 1.25" (above ground) PVC underground. run these wires the 30' in sched 40 (below ground), and back up in sched 80.

That's fine, but I hear you mentioning the conduit after the wires. If you are running conduit from panel to panel, you need to assemble the conduit complete, finish it, get it inspected and bury it BEFORE pulling any wires. Shoving a stick of conduit over wires is fine when it's just one stick to act as a damage shield in a tough spot, but actual end-to-end conduit needs to be built, inspected, buried, and tamped/anchored before any wires get pulled in. That "keeps you honest" as far as pulling access points, not an impossible number of bends, and not making conduit that is un-pullable.

1) is a 50 amp breaker the correct size based on the max I calculated from the data cards on my equipment? should it be 60?

The individual breakers on each appliance protect the appliances.

The breaker in the main panel protects the feeder. You select this breaker based on the maximum the feeder is allowed, e.g 65A for #4 aluminum, rounding up to the next available breaker size, 70A. You can always use a smaller breaker.

 

The individual breakers on each appliance protect the appliances.

The individual breakers on each circuit protect the wire that leads from the appliance to the panel. The appliances are supposed to protect themselves, but if they fail and draw excess current, the wire that runs through the walls needs to be protected from overheating.

 

The NEC only requires the rods to be 6 foot or more apart. The conductor to the first rod needs to be continuous. The conductor to the second rod is a jumper and con run rod to rod using a second clamp.

Pricing over the internet without seeing the actual conditions are meaningless. They also don't account for regional labor rates and other differences. Trenching at the beach is different than in granite.

 

The NEC only requires the rods to be 6 foot or more apart. The conductor to the first rod needs to be continuous. The conductor to the second rod is a jumper and con run rod to rod using a second clamp.

Pricing over the internet without seeing the actual conditions are meaningless. They also don't account for regional labor rates and other differences. Trenching at the beach is different than in granite.

That's the code minimum spacing. The further apart the better. In practice, we use the length of a ground rod (8 ft) to space them so that's why many just say 8 ft.

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Thank you all for your very detailed feedback… this is more than enough info to get this job done. Much appreciated. One last item. The quite for $2400 did not include getting a permit, and I wasn’t planning on it. That being said, i noticed all of your responses included getting a permit…. Can you give me your reasons why? Or related thoughts?
Thanks
J

 

Permitting a job makes sure it is done to local codes and ordinances. It also ensures the job is compliant for insurance reasons. You don't want an unpermitted job going up in flames as they may not pay for it. Resale. Any future buyer will want the comfort in knowing the work was done properly, which the permit will help with.

 

Also, our GEC only needs to be "electrically continuous". No need for irreversible splices.

 

It has to be physically continuous (without a splice or joint). Read 250.64(c) more closely.

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@seharper my comment was related to how the geology could affect pricing and how internet prices were irrelevant. Similar to real estate prices between California and Maryland.

 

It could be explained away as the NEC doing overkill for grounding. Across the country we have sandy soil, pure hard clay, loose loamy soil, so it could be to ensure there is enough resistance in the rod(s), and by adding a rod they make sure of it. In our location as long as there is a UFER in the concrete pad, we can install a single rod.

 

The Ufer is a standalone ground. No supplemental electrode required.

 

No supplemental electrode required.

I think our inspector just covers his butt. No big deal to driving a rod to keep him happy.

 

The reason for additional electrodes at outbuildings is simple. To create a low impedance path to ground to dissipate transient currents. Without the local electrode, the transient currents have to travel the entire length of the equipment ground (which could become compromised as EGCs have less strict termination requirements) and to ground. I'm pretty sure this is sound reasoning from an engineering standpoint. I don't know why this is so hotly debated. Even if the improvement in the earthing system is marginal, why not do it? Why not make an electrical system as safe as possible? Why are people so resistant to these safety improvements? They are bare minimum requirements in my opinion.

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The GEC can be joined by irreversible crimps or a Cadweld type process.

 

Yes in places the storms hit often an harshly like here in the southeast you really need more lightning protection...a strike just burnt a neighbors home up an zapped my outside light..
Nothing is 100% but be as secure as you can to the next strike !
Location can factor inspection an code strickness.

 

Mike Holt has an interesting video that shows more electrodes could allow the surges into your wiring since they create entry points.

 

That may be why we've never adopted rods at out buildings.

 

Some jurisdictions (not the NEC) require "single point grounding." Think: maximum distance between ground rods. Typical construction taking this into account is having the equipment grounding conductor for a TV antenna brought to the ground rods near the panel instead of having a ground rod directly under the antenna. No additional wire runs are involved since multiple ground rods about a building need to be bonded (with #6 copper).

If there is a water pipe that qualifies as a grounding electrode then one such must be included in the grounding electrode system even if it exits underground at the opposite end of the house from the panel..

 

The reason for bonding is to maintain equipotential. If different metal systems or systems that require earth grounding for transient current protection are not bonded, potential differences can occur between those systems and cause electric shock.

Water mains may be a viable grounding electrode at the time of installation, but that cannot be guaranteed in the future as it is a common practice for water utilities to install a dielectric union in water mains in an attempt to limit electrical noise on municipal water mains.

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Just to clarify, is the OP in Canada or US?

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OP in the US

 

Then why are we discussing the CEC. So confused [emoji848]

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You asked in post #10. And then didn't read post #34 I guess.......

 

For what its worth, I did the same job myself for my shed, just learned it all by asking and Googling. I went by all the local codes which meant sticking two 6 feet grounding rods into hard soil, a royal pita.

I thought a permit would have the inspector look at all my work done and help with any improvements. He just looked at my panel and said "good". Well, 3 years later its still running top notch. It was $120 for 5 minutes of no help but at least I can add it if I ever sell the house.

 

The inspector wasn't there to "help" you out. He was there to inspect your job. His "good" comment should have sent chills down your spine. Quite often they will make a list of deficiencies, red tag the job and let you stew until you correct the mistakes and pay again for another inspection.

 

The inspector wasn't there to "help" you out. He was there to inspect your job. His "good" comment should have sent chills down your spine. Quite often they will make a list of deficiencies, red tag the job and let you stew until you correct the mistakes and pay again for another inspection.

My experiences have varied. I've had nightmares inspectors and also a couple that were really like mentors to me. One is now my instructor for me CEUs.

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And they'll make you pull a permit for the demo, too.

 

The cover wasn't supposed to be in place for an inspection. If he OK'd it and signed off on it, you have to assume it was good.