[F250]

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), 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.

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.

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.

I do not want to run a bunch of PVC or metal conduit for each of these runs throughout the garage. Getting inside the walls is not going to happen, either, so everything will be surface mount. I want the appearance to be neat, tidy, accessible for expansion/modification, easy to keep clean (no dust collection), and have the overall look be something which would not detract from home resale (it is a higher end home in a very nice neighborhood).

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?

Thanks ahead of time for sharing your thoughts and ideas.

 

[HotRodx10]

If it was me, I'd be running a big conduit around, with junction boxes along it, where required, and from the junction boxes drop armored cable to the outlets.

I wouldn't want to figure out how to make the chase system code complaint, wouldn't want to build it, and my guess is it would cost more. If that's the look you want, though, I'm sure some of the more knowledgeable electrical people will be along shortly to help you with all the ins and outs.

 

[seharper]

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.

 

[seharper]

a big conduit

Everybody thinks that

Then you get nailed by 310.15(B)(3)(A), coarsely "4 circuits per conduit". For 5-10 circuits, every wire in the pipe needs a wire size bump. Above 10 you may need another.

That's why you see people running many small conduits instead of one big.

 

[HotRodx10]

Then you get nailed by 310.15(B)(3)(A), coarsely "4 circuits per conduit".

I didn't know about that. Thanks for setting us straight. In that case your 3 conduits is a much better plan.



Just out of curiosity, is the "4 circuits" limit because there's 4 standard colors for hot wires, and you're supposed to use those different colors to make tracing the circuits easier?

 

[F250]

Thanks for that, HotRodx10. I can easily build the wooden chase enclosure for much less than even "cheap" gray plastic conduit, especially once all the fittings and connectors are included.

The other thing I really don't like about the conduit approach is the fact that the top of it is going to be a dust collection/accumulation point, and I don't want to have to be cleaning it off at 11' from the ground every month or so just to keep tramp airborne dust from getting into a high end finish on a piece of custom furniture/project (I don't have a permanent or filtered spray booth for controlling potential dust contamination, so the shop proper has to stay rather clean).

I guess I could encase the conduit inside a boxed structure, but then I'm doing twice the work for my power cable enclosure (and at least twice the cost).

 

[jreagan]

Everybody thinks that

Then you get nailed by 310.15(B)(3)(A), coarsely "4 circuits per conduit".

For this, does a MWBC count as 1 or 2 circuits?

 

[F250]

Thanks for the thorough review of my situation, seharper!

I've just checked out the EMT, and it may actually end up being as inexpensive as my "wooden box" chase. I need to develop and vet the parts list, though, to make sure.

As for the 3-phase stuff... I've already been investigating that for a while, and if my table saw comes with the converter, all's good. If I end up having to provide my own converter, I'll be using a reputable and responsibly sized VFD, and will have the engineers where I work evaluate the application before I even purchase the VFD. (Our paper mill's Process Controls department reports directly to me, and I also have trusted resources in both our Maintenance and Engineering departments as well).

 

[seharper]

Yeah, EMT is stupid cheap when you get into it. Check with a real electrical supply too; they are much more reasonable on some boxes (notably, 4-11/16" square).

Yes, a VFD completely moots the 3-phase issue. Nice when you can do it!

 

[F250]

At the moment, I finally have most of my "new to me" cabinets in place, but still have to do some counter top work and get the rest of my boxes unpacked into the cabinet storage space. Once that is done, I'll have physical room to start running wire.

Once all of that is finished, I'll be shopping around for another "new to me" item which is the replacement table saw, and that's where the potential 3-phase/VFD opportunity may come to fruition. I'm hoping I can secure a single phase 3-5 hp unit setup. If, however, it comes with a 3-phase motor, the VFD cost will be roughly equivalent to the cost of a replacement single phase motor and I'll just keep the 3-phase config at that point. Ideally, the saw would come with 3-phase AND a converter, but those seem to be less commonly available in the used table saw market.

 

[Measure twice]

I'm new to the party and late to the thread, but Pete, I think your shop idea sounds great and I'm a bit envious. Cars fill up my garage, but I've thought about doing what you are doing since my current shop is in the attic and unbearable in the summer (I'm just down the road from you in Cary).

I wouldn't worry about resale stuff, as I expect your Realtor would tell you to take down all of the improvements.

I like the idea of a proper chase, with sheetrock and painting so that it blends in. And it should reduce the dust as you mentioned.

My table saw is an old craftsman belt driver, 110V and it's perfectly adequate for nearly everything I do. Only when I am cutting some huge hardwood does it strain.

 

[seharper]

Sorry for ghosting on these questions...

Just out of curiosity, is the "4 circuits" limit because there's 4 standard colors for hot wires, and you're supposed to use those different colors to make tracing the circuits easier?

That's not it, and in fact there are no color coding requirements except the usual. But of course you do have to identify/group your wires/circuits... There are 8 "common, any competent electrical supply house stocks it" hot colors and 2 common neutral colors before you get into striped-wire weirdness, and then the sky's the limit lol.

The 4-circuit limit is an extreme simplification of the actual rules when applied to split-phase (120/240V) systems. The actual rules are a big gory mess:

- The same wire has different ampacity rating (310.15(B)(16)) based on the survival temperature of insulation and the terminations (lugs/screws).
- The 60 degree C rating is *about* 30% lower than the 90C rating.
- 240.4(D) forces use of the 60C rating for small appliance branch circuits up to #10 wire.
- 310.15(B)(3)(a) covers thermal derate in grouped conductors. It does NOT count safety ground, and in a split-phase 120/240V circuit, does NOT count neutral (since it only carries differential current).
- Therefore, any possible circuit in a 120/240V system has 2 wires that count.
- Thermal derate comes off the highest temperature the insulation can withstand, so THHN gets to derate off of the 90C number. Remember point 2.
- The thermal derate for 7-9 wires is 30%. Well heck, we're already there. So this has no effect on us.
- The thermal derate for 10-20 wires is 50% (holy smoke Andy!!!) This derate is quite punishing, and effectively requires you to bump a wire size.

But if you work out all the angles and dangles, you can see where yeah, for 15-30A circuits, this adds up to "4 circuits per conduit".

For this, does a MWBC count as 1 or 2 circuits?

Happily, it counts as 1 circuit.

And that's the power of this rule, suppose you are CostCo and you want to power half your ceiling. You use 277V circuits. 3-phase MWBCs (3 hots per neutral). 3 such circuits (9 wires = 30% derate which has no effect on #12 wire). So boom, in one 3/4" conduit you have 277 x 16 x 9 = 39,888 watts of lighting. That's a lot of light for one little conduit!

 

[HotRodx10]

Thanks, seharper. I sorta, kinda, almost followed that. I knew the electrical code was convoluted, but I didn't know it was that bad. I also didn't know there were 8 wire colors for hot wires; I've only seen black, red, yellow and blue, except in low voltage automotive wiring.

 

[Terabitdan]

A couple ideas for you to consider. First, designate an outlet at every box for a vacuum circuit. Using a relay or any of the commonly available automatic switches to turn on dust collection whenever something in that receptacle is turned on. I did separate boxes for it, but that was only because I didn’t think of it until too late.

Second, I like your idea of a chase, but I’d use either 4x4x4” square boxes or 4 1/16 with extenders around the top of the wall to allow you to tap into any circuit in any box. Leave a loop to allow you to tap into each circuit. I really like using Wago lever wire nuts since it’s so easy to add another drop compared to standard wire nuts. Then a single 1/2” or 3/4” conduit run down to the outlet boxes inside your chase.


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