Garage Build - Electrical
 

Starting to get more into the fun stuff now to make this place actually useful.

Submitted a separate permit for electrical and was approved end of last year. Im doing a bare minimum approach on this permit - typical wall outlets, a handful of ceiling outlets for temporary overhead lighting, and outlets for the wall mount garage door openers. Feed wiring and box size will easily support future upgrades as it expands down the road.

First big piece showed up - 1000 foot spool of 3/0 Al THWN2:
https://cimg3.ibsrv.net/gimg/monteca...82e3b1c307.jpg

Total run building to building is about 200 feet, so it's oversized a tad to keep voltage loss in spec. Unfortunately I have to run it on a complicated path to avoid our spectic system area, so I'm going to have to put in a pull box / handhole midway through due to the number of turns. Planning to hide it behind the shed to keep it out of sight.


Not much to look at, but I got the first strand of wire pulled. It's a good motivator to keep pushing.
https://cimg4.ibsrv.net/gimg/monteca...1e6aec7924.jpg


Also got the ground rods driven - that was sure brutal. Id bought a 'hard soil water probe' to try to make this easier - it's a hollow steel tube with a spiked end where you hook up a garden hose to help soften / blast the dirt out of the way. Worked great for about 4 feet... then the dirt got so hard that the water wasnt able to push it out of the way anymore / kept clogging it.

As the rods need all 8 feet underground, I swapped to the sledge hammer. That lasted about 3 minutes before I gave up. It's impossible to do solo with so much sticking out of the ground (as it wobbles a ton after each hit) and Im afraid to hit it hard with someone else holding it as Im probably 50/50 on actually hitting it.

Ended up going down to home depot and rented a 27 lb rotary / demo hammer. I wish I wouldve done that as step 1 - the rod sunk into the ground like butter. No force at all (other than the weight of the tool) and the knurled face gripped onto the rod to keep it from slipping off.

Got both rods in and a shallow trench between them for the wire. Just need to drill through the stucco / lath to finish it up.


https://cimg9.ibsrv.net/gimg/monteca...23fbfb6a76.jpg
(pic looks flush, but it's sitting in a ~12" crater Id shoveled out to make sure it's well subsurface in the end)

It's so good that Im a bit embarassed I wasted even one minute trying any other avenue, much less the hour+ I actually spent.

I figured when I found a ground rod driver bit in stock for them locally, that this must be the normal way to go (granted the driver bit they stock is SDS plus and all of their rental hammers are SDS MAX only - but they had plenty of various SDS MAX bits to find something suitable enough.

That's certainly the longer term plan. Problem at the moment is budget constraints - so Im sizing the feed wire + panel to allow for plenty of future expansion, but only installing the bare minimum branch circuits to start to make the garage usable.

I think Im going to ultimately end up with 4x 220 circuits on the back wall:
-2x 3 ton mini splits
-1x shared for the lifts (long term plan Id like 2 four post lifts in the back left bays to double stack cars - and 220v lifts seem vastly more common locally than 110v units).
-1x shared circuit in the back right (welder, compressor, milling machine, etc - as Ill never be running more than one at a time being a solo garage).

Nice work!

Are you required to have two grounding rods? In my situation, my main panel has two rods, but since the subpanel was ALSO being grounded to the main panel, I was only required one grounding rod.

That first strand you ran, what size wire? I think most manufactures use yellow for 12/2 with ground (except I found 12/3 with ground for multi-switch outlets, a vendor went from yellow to purple).

Technically no. There is an exception if you can show the resistance value under a certain number with 1 rod, then they'll allow it. But I've never heard of anyone out here actually meeting it with 1 (most not even meeting the value with 2 rods if they do measure, but luckily they dont make you keep adding more and more). It's a city specific (although probably copied from other local cities) code modification since our ground is so dry / poor at conducting. Personally I didnt even bother to measure; its only like $40 to add the second one / remove any risk of failing. It's all sub grade anyways, so once this passes and I refill the dirt, no one will ever see any of it.

But that's why I was really hoping to get away with the ufer ground in the driveway - avoids this whole mess. But that didnt work out. Most builds out here seem to be doing ufer instead anyways as theyre almost all slab on grade- but normal house contstruction doesnt have a vapor barrier under the slab like I do.

This stuff / brand follows the same color codes you mentioned. This is orange 10/2.

The overall run length is so long that voltage drop calculations show more voltage drop than reccomended when running this close to capacity. So I oversized the feed and am oversizing all branches that will have heavy load potential (basically anything but the lights and garage door openers) to keep voltage drop within the suggested limits.

10/2! WOW! That is definitely upping the project cost. At least you know it will handle what you want. Are you using a 20amp breaker since you mentioned concern with voltage drops on heavy load?

Unfortunately unavoidable to stay within the NEC reccomendations for voltage drop. They suggest no more than 5% total - 2% feed + 3% branch. Sized off rated ampacity alone, 12 gauge on this circuit, with a 20 amp draw at the furthest outlet which will ultimately be in the work bench area (a bit over 100 feet away as it runs along the walls to hit all of the other outlets along the way) comes out to over 7% drop on this branch and nearing 10% overall.

As a result 10 was about the smallest wire feasible. I still end up a little high on branch drop, but I oversized the feed wire to help across the board, so it put me right about the max reccomended (at least rounds to the suggested max). TBH 8 wouldve been a better fit (and is the max wire size for my 20A breaker) but its a lot tougher to get locally.

Honestly 12 to 10 wasnt really a huge cost delta in terms of the overall electrical project. It was a tiny drop in the bucket compared to the upsized feed wire. That stuff is wicked expensice per foot, especially for that long of a run.

Yep. I really dont want to go any lower on wall outlets as its not unusual for me to use all of the capacity of that circuit.

It's not really the amperage that's the issue, but more the long run length. Ignoring the vertical parts of the run, Im about 200 ft panel to panel and in the case of the wall outlets, Im over 100 sub panel to furthest outlet. Even reduced to 15 amp, I still wouldnt have been ok with 12 gauge as thats nearly 4.5% drop alone just on the branch circuit.

Making little bits of progress here and there.

Wiring inside the garage is done up through rough in. Wrapped up the subpanel wiring tonight for the branch circuits. Next up is running the ground and feed wires into the panel / to the house.


https://cimg4.ibsrv.net/gimg/monteca...89afaf31cd.jpg

Time for some trenching!

Got everything dug as far as I could with the machine. Still need to open up all of the bends (as it fills the first one with loose dirt when cutting the 2nd one), finish out the ends to the buildings (house will be the hardest as Ive got about 3-4 feet to hand dig since this crosses over both a branch circuit and the main house feed), and dig out the mid way hand hole / pull box.


https://cimg9.ibsrv.net/gimg/monteca...41375602c2.jpg

Looking at the pic of the machine you have, that looks way better than the one I attempted to rent.
I hope this goes smoothly!