# Electrical plan review - detached garage subpanel

Going to run entirely new power to a detached 2-car garage. I have bolded concrete questions, but appreciate review/feedback on the entire plan. I will have this inspected by my city who uses NEC 2017 edition, so that is my minimum; beyond that, I want this to be as safe as it can be, because I live here.

This will be a workshop so I need to be able to run a few different power tools, lighting, and other basic outdoor power needs like weedwhacker, stereo system, etc. No current plans for an electric vehicle but would like to be ready for that in the future.

Given this I am looking at a 60A subpanel. Planning to go underground in PVC conduit. The route from my main panel at the house to the garage is approximately 68 feet, I'm doing calculations at 90 feet just in case I need to re-route.

Using this Voltage Drop Calculator, I have determined that I can use 2AWG Aluminum for 60A over 90ft. What wire type should I use for this application (e.g THWN, USE-2, etc)?

Using this Conduit Fill Table, I have determined that I can put 4x2AWG THWN/THHN Aluminum conductors in 1 1/4" Schedule 40 OR 80 PVC. I know I will have to use schedule 80 where the conduit is above ground between the buildings and the dirt. I will have pull points outside both the house and garage where the conduit comes up from the ground, because the underground run will have a total of 4 90 degree angles (2 vertical to horizontal below the entry points to the ground, and 2 90s to clear obstacles in the yard).

I have a Eaton BR series main panel, so only for consistencies sake I am looking at an Eaton BR for the subpanel as well. Will choose one with between 16-20 spaces to ensure that future expansions do not run out of spaces, even though I only need perhaps 4-5 spaces right now. Any problems with Eaton BR series which make it a poor choice?

The main panel will have a BR260 to feed the subpanel. Based on the Eaton product page, this model accepts #8-1/0 AWG, so I can land 2 AWG on it. Is this advisable, or should I put a small section of a smaller gauge that is spliced to the 2 AWG? Based on NEC 310.15(b)(16), it looks like I can use as small as 6 AWG Cu or 4 AWG Al. I have not worked with 2 AWG before, it seems like it will be large and perhaps difficult to land on the breaker.

Inside the garage, I will use 1/2" EMT to run all branch circuits, and pull 12 AWG Cu stranded THHN. I am choosing EMT, even though exposed NM-B would probably be acceptable for most of it, for added protection from rodents, and I also just want to learn how to bend EMT. Should I prefer set-screw or compression fittings for the indoor connections? The building has a good roof, but is not conditioned space, so can become quite humid.

I am planning to use 4x4 metal boxes for several outlets around the walls. Each box will have 2 duplex receptacles on separate 20A GFCI circuits, so that motor devices can be easily separated onto separate circuits (and these two receptacle circuits will also be on separate legs of the incoming service). At least one exterior wall receptacle on a separate GFCI circuit in a weather resistant box.

I will have a separate lighting circuit for overhead lighting inside, exterior lighting above the doors, both of which will be separately switched with 3-way switches located in between the two garage doors and on the wall next to the spot for a future planned man-door.

Grounding: my understanding is that 2, 8ft ground rods, a minimum of 6ft apart, are required. Are copper-cladded 5/8" diameter rods a good choice? And what is the best way to get a conductor from the rods to the panel, and what conductor should be used? I am assuming that the exposed parts of the conductor will need to be in conduit, can I just use a bare stranded 8 AWG copper wire running from one rod to the other, connected to the rods with direct burial rated clamps, and have it enter the PVC conduit a few inches underground, and then run the conduit inside and into the panel?

In subpanel, I will make sure that the grounding and neutral bars are isolated by either removing screw, or adding grounding bar, depending on model. Grounding will be provided to devices by the EMT, with devices being connected to their metal device boxes by a pigtail. What is the best way to test for grounding continuity at all device boxes?

• Two many questions for a simple garage. Search other questions on the site as this has been answered many times. If you even consider a RV charger 100 amp panel would the minimum size to consider. Any listed rod is fine as are driven pieces of galvanized pipe. Unless you purchase a 4 point probe for measuring resistance of the ground you are wasting your time and so is a 4 point probe. The rest of the questions are opinion based and as such are off topic. Commented Jun 20, 2021 at 20:04
• Ed, I have done much of my planning research on this site and others, but hoping to fill in a few gaps in what I have been able to find. It looks like other plan-review questions have been considered on topic here. However, I can break out some of my more concrete questions into their own questions, that will probably help others more than this big one. Commented Jun 20, 2021 at 20:15
• Ivan that will be a much better way and other than opinion questions like problems with Eaton, open question, I could say yes I have indeed had some problems , but in truth Eaton, square D, cutler hammer are all good options but at times I have seen problems with each one (minimal over many years of professional work). Ground rods , any listed method or even driven 3/4” galvanized pipe (way expensive today) the conductor to the panel #6 or larger copper solid, stranded, insulated or bare all work from the rods. Commented Jun 20, 2021 at 20:53

#2Al is fine for 90A at the distance you plan. Feel free to breaker it at 60A, the breaker will be cheaper if you do.

No need to pigtail #2Al.

I prefer compression fittings all around. (Pun intended lol). Not a fan of setscrew type.

Any box in which you might put GFCI receptacles, use 4-11/16" (120mm) boxes instead of 4”. They make all the difference in the world with regards to box cram.

With multiple circuits in 1 conduit, you are required to distinguish which neutral is matched to which hot.

You don't need to run a ground pigtail to devices in metal boxes with metal covers, if they will have hard flush clean metal-metal contact between the receptacle yoke and the box or lid.

That only fails if the receps are held proud of the box by drywall ears, or have crud in there (including those little paper "screw keeper" squares). But even those problems are cured if the receptacle is marked "self-grounding".

Domed covers that connect the plain receptacle ONLY by the screw in between the two oval openings are not good enough. Those need to either use the yoke screws, or be pigtailed to the metal box.

You can test for ground connectivity by using a plug-in GFCI tester and hitting "test". Those rely on safety ground to create the simulated (well, actual) ground fault.