Wiring a garage with a tall ceiling

[Innovate1]

Thinking about the upcoming wiring for my 30 x 40 detached garage with 14' ceiling.

As currently planned the panel will be about midway in one of the 40' walls - I could move it closer to the 30' wall away from the big doors which is also near the furnace/AC. The big doors are in a 30' wall. Wondering if it would be worth it to put a conduit (or a couple) straight across to the other 40' wall to keep from having to run all the circuits up and through the attic or around the end.

I could put a large box on the end of the conduit and run the circuits for that side from there. I suppose I could even put a small subpanel there - overkill but they are cheap so would likely pay off in less work running wire.

I plan to have a couple 30A, 240V circuits on the far side as well as several 120V standard outlet circuits.

 

[Norcal]

Add a sub panel near where you plan for a large number of circuits, 16-20 spaces would allow for changes in the future.

 

[Bert_]

At only 30x40 I wouldn't worry about a sub panel. None of your runs will be that long.

 

[sberry]

Also get a grip on "several" circuits for a side. 99% of the time you will use 1. The other 2. This place isn't so big that a cord cant be used once in a while. I got a neighbor, 3 circuits for 120V, one is for lights. NEVER needs more. Has a welder circuit and 1 for air comp.

 

[6768rogues]

I have receptacles every 8 feet down each side of my 36x48 building. There are two circuits for each side, so the plugs are on circuit 1, circuit 2, circuit 1, and so on. Then a fifth circuit does the plugs along the back wall. That made for 5 home runs, but two are on the side with the panel. If I need two things plugged in close to each other, they are on different circuits. Not worth a subpanel.

 

[Farmallboy15]

Buy or rent 2 sections of 6' roll around scaffolding for work high on the walls and ceiling. This is what I did for my 14' ceiling. One section and a short step ladder would also work but not be as safe. Much easier and safer than a 8' step ladder... https://www.sunbeltrentals.com/equipment/detail/1338/2000910/multi-purpose-unit-baker-2-high-128in/


I liked running surface mounted conduit for my circuits. I ran probably way more circuits than I need but I never want / plan to mess with it again... I would try to place your main panel in the highest circuit density area if possible. I don't think a sub panel would be necessary.

 

[tfi racing]

At only 30x40 I wouldn't worry about a sub panel. None of your runs will be that long.

Yep, not long enough or enough of them to warrant a sub panel. People on this forum love to grossly overspend other people's money...

 

[nahansmsu]

+1 for Scaffolding.....I went ahead and just bought it. You'll need it in the future without doubt!

 

[Innovate1]

Definitely will get some scaffolding when I get started on this.

I am planning to flush mount the panel and put wiring in the walls. But also want to plan ahead for future wiring. In the house I ran a conduit from the panel through the top plate into the attic but that is pretty high and hard to get to in the shop. Any tips for allowing for future wiring additions both low voltage and 120/240? I could just run to a large box above the panel and then add an extension and surface mount conduit for future use.

Low voltage will come into a flush mount large box and then fan out from there. Same issues with it.

I may run empty conduits from the panel to a box on each wall (in addition to the things I know of now - that would allow me to run whatever power is needed later.

 

[sberry]

I have a sub on every wall and for air comps. But,,, my buiding is 80 wide and tall, would start out a couple of them 120 ft from outlet. I got a lot of **** and it allowed wire as I went. It cost me a few extra breakers to separate some recepts but same amount of wire. In the grand scheme another 6/8 breakers or so I could have shared, maybe 10 but it's easy and simple.
In a smaller building it's not such an issue. Just talked a customer in to doing this in a 60 wide tall burger where he wants air on far side. My storage is wide too, ran a couple 10 to the far side, it was a toss but didnt need welding or air there. I way over wired it in the end.

 

[alfredeneuman]

Keep in mind that any more than 3 current carrying wires in a conduit will cause the wire to be derated to 80% of it's original amp rating @ 90 degrees, and 7-9 wires have be derated to 70%.

 

[dscheidt]

Keep in mind that any more than 3 current carrying wires in a conduit will cause the wire to be derated to 80% of it's original amp rating @ 90 degrees, and 7-9 wires have be derated to 70%.

But, keep in mind, that for derating purposes, THHN 12 AWG has an ampacity of 30 A. 30 A * .8 = 24 A;, 30A * .7 = 21, so either way, still 20A. 14 AWG is 25 A, so it's good for 15A under either derating. It can be a problem with bigger wires, which do not have as generous margins in the ratings.

 

[dcg9381]

I have a 40x60 shop with 16' eves.
When I had it built, I dropped in 3/4" conduit through the slab in a couple of places - the idea was for air and perhaps electrical. I haven't used the thru-slab runs.

What I did do, is from the main panel in the shop, I took 1.25" conduit to the ceiling and across the side to another sub panel. 60A on the sub-panel.

I rented a scissor lift for a weekend, which makes the job 1000% easier. You can drive the thing by joystick when working at the ceiling.

Just having panels on both sides of the building makes things much easier.. Much less labor than having to run branch circuits to the other side. I tend to use exterior-grade panels that are built for RV usage - they're $130 and include 50A, 30A, and 20A GFCI breakers, all 3 plugs, and have room for 4 more breakers. I think they are Siemens Talon...

 

[sberry]

The benefit of a sub is in larger buildings it shortens the branches and allows for local disconnect of special equipment, can save fussing around with extra equipment In a tall 40 wide building it starts to become a wash depending on layout. In a small building all the hi draw stuff might be able to be down one side, even fairly close to the panel. Even side or end where heavy circuits don't even need to go overhead. Lots of places could make it with 1 general down a far side.