I'm looking for insights and guidance.
Context.
My 3-bay garage is being used for a 1-bay garage and 2-bay woodworking shop, but I don;t yet have the shop set up. All of my existing tools are currently 110/120v. I anticipate getting a "new to me" table saw with 220v ([possibly 3-phase),
STOP. Don't touch 3-phase
with a 10 foot pole unless you know *exactly* what you are doing.
Craigslist is flush with ads for "3-phase tool for $<1/3 of market>. Worked when I bought it. Cannot show since do not have 3-phase power here". They figured they'd get the tool and cross the 3-phase bridge later and found it was a bridge to nowhere.
but everything else will remain 110/120v - 14-inch bandsaw, 17-inch drill press, multiple routers & sanders, wood lathe, 12-inch planer, 6-inch joiner, portable air compressor, smaller hand tools, etc. I will virtually always be the only person working with tools in the shop, but there could be some rare occasions when one of my sons may be there working with me. That said, about the majority of times when multiple outlets will be runnings is for the lights and my dust collection/filtration systems in conjunction with one of the primary tools like table saw, band saw, joiner, planer, etc.
You are correct about not needing to provision the planer *and* table saw to run at the same time, and correct to consider the dust collector (which so many people overlook).
Current electrical supply.
The garage was built with the house 15 years ago with two garage door opener outlets in the 11' high ceiling, and a single outlet on the wall shared with the home. To supply my shop, I've had a licensed electrician install a 100 amp subpanel for me which is fed from my main house 200 amp panel (the extra cost was minimal to go with 100 amps as opposed to 60 amps). The new sub has either 12 or 20 slots, so I have ample room for what I need to run. The sub is also wired to supply either 110v or 220v for my new circuits.
Well done, except if you start getting into 240V (single phase) tools, and there's no reason you shouldn't, you'll go through breaker spaces like lightning. I'm sure the electrician recommended a 12-space because most electricians figure for the same money, you'd rather have a 12-space
and a latté than a 20-space. I'm not a big fan of latté's myself.
THE GOAL:
I will be running individual 110v circuits for each of my primary tools (table saw, band saw, drill press, dust collector, portable air compressor, and wood lathe). I'll also run several additional circuits, some being dedicated to a single outlet, and most being run to several outlets per circuit plus a new lighting circuit for new overhead LED lighting strips.
A separate lighting circuit is super important so the saw doesn't knock the lights out with your fingers 3" from a spinning blade. (even if you have a SawStop, I'm not entirely sure the blade-catcher *works* when the power's out).
However, the bigger problem will be GFCI requirements. Every 120V circuit <30A needs to be GFCI. When your state adopts NEC 2020 (which for MA is already; for several other states is July 1), every circuit must be, which means every 240V breaker must be GFCI. You might've solved that by feeding the whole subpanel from a 50A GFCI breaker, but no such thing as a 100A GFCI breaker.
As such, the "separate circuit for everything" philosophy will have a cost in GFCI receps or breakers. As you said, it'll be rare to use 2 appliances at once. So 3-4 120V circuits may suffice.
CURRENT PLAN (pun NOT intended):
I'm considering using a self-built boxed in chase around the upper perimeter of the garage (there is no crown molding) for the bulk of the circuit distribution, and then have multiple low-profile drop chases down from the this ceiling elevation chase to reachable receptacle/switch boxes. I'm considering maxes the chases from wood (i.e. 1x4's or 1x6's and 1x2's) with removable front panels. I would even be willing to consider using strips of sheet plastic (HDPE, LDPE, Lexan, polycarbonate, etc.) for the fronts of the chases.
Question.... What do you guys think about my self-built chase concept? Suggestions? Code issues/solutions? Does the chase enclosure need to be vented at all for heat dissipation?
That sounds fine to me. Thermally, the rule to look at is 310.15(B)(3)(a) which calls out (to massively simplify it) 4 circuits per conduit/raceway before you have to care about thermal derating.
You could even have a hinged fascia on the chases so you can just flip it up and get access to it at relevant points
Do think about how you'll pull cables around corners. It's not a proper *raceway* so you can't do THHN individual wires, more's the pity.
Honestly I'm a conduit guy so my reaction is "Given your expandability/modifyability desires, for Pete's sake, do it in EMT conduit, because modification and customization is so very darned easy, especially with stranded wire. And when you sell, take it off the wall". You leave nothing but screw holes, a bit of spackle and
it was never there.
Every 4x4 box has 3 knockouts on each side, I'd run 3 conduits most of the way around the garage (no need to carry all 3 all the way to the end). Two 1/2" and one 3/4" conduit because that's what the knockouts are. A 4x4 box every 6-12 feet or so, whatever suits, with all 3 conduits going through each box. Then drop a 1/2" pipe down to wherever you want outlets. Then I'd cover up the conduits with a fascia of some kind. If I was *very* clever I might use translucent plastic, and put low voltage LED strips behind the plastic, so when people look at it, what they see is stylish, bespoke mood lighting instead of a conduit cover-up. Now the reason for 3 pipes is the 4-circuit-per-conduit rule. The 4x4 boxes would have 0 splices in them, so for cubic-inch purposes they'd be treated as conduit bodies not junction boxes. (so 27 wires passing thru them won't be a cubic-inch problem).
I would let the next homeowner keep the fascia and conduits behind it, and then, remove the drop-downs at house sale time.
