The important consideration is how many devices will be in use at the same time. If it's a one-man shop, it's unlikely that you'll have more than a shop-vac and a single power tool (and perhaps a dust cleaner) energized at the same time.
Or even AWG 10 for the 20A circuits if the run is long enough.
Many businesses are wired that way and strictly have receptacle panels and outlet panels. I would love to do that to my home but too much involved with rewiring everything.
There isn't a code for it, but electricians will tell you to keep it around those numbers.
A rule of thumb is to assign a maximum draw of 1.5 amps to each receptacle.
20/1.5 = 13.315/1.5 = 10
But they lower those numbers to allow start up on accessories that may have motors or high peak start ups.
Lighting can be on 20 amp or 15 amp circuits, it doesn't mater. What matters is the wire size. Code requires 12 gauge for 20 and 14 gauge for 15.
hmmm..."receptacles panels" and "outlet panels"?
Just curious, what length (in feet) would justify that?
Surprisingly short if use full current ratings -- 20A @ 120V is 2% drop at 36 ft for #12, 57 ft for #10. For 240V, double the distance (altho rounding the numbers in the table are 71/113 instead of 72/114).
Rarely if ever is the full amp rating of the circuit called for for single machine, so actual will be proportionally less based on actual current draw of the machine.
But, if have larger planer or TS and a DC or similar, having 30A service is protection in my case -- I never did actually measure out the distances from the panel to the area in the barn I set the shop up in--let's see from across the driveway to the far end corner would be
12 + 18-6 + 30 ==> ~54. The run back up the far wall would add another 20-8 to the farthest or ~68 ft altogether. All the stationary machines and the small DC and compressor are 240V except the PM180 planer that's 240V/3PH. It's on the phase converter and back in the other corner of the barn. I've not yet got around to hooking up the 3PH DC for it...couldn't decide how wanted to arrange the duct work for permanent as it's too tall for inside the barn on first floor and been too lazy to get it up in and rearrange stuff in the loft to put it up there...but that's a pain for collection/emptying even if convenient to have out of the way otherwise...
That is, of course, the current is proportionally less than the rated value by the actual draw of the load(s); the 2% drop distance then is proportionally longer...
I found one calculator that said use 10 AWG at 16' for full 20 amps at 120V, 1% drop.
What I don't like is that many of the calculators are strictly formula based and don't factor in "code" in any way. Shorten the length enough and you can use 14 AWG for a 20 amp draw. You'd think they'd include an "IF" clause that didn't allow the calculator to go below the minimum gauge allowed based on the amperage entered.
Not an electrician and do not play one on TV. The possible flaw in your argument re 14ga/20amp is (right or wrong, willing to learn) is what happens if a future homeowner decides to extend that circuit w/add'l outlets/load. Does that affect the safety of the installation? TIA...
I'm not sure what you mean by "your argument re 14ga/20Amp".
I'd *never* argue for or even suggest using 14 AWG for a 20 amp circuit. Nowhere in the NEC is that allowed.
I was pointing a *flaw* in some of the calculator that I tried. They appear to ignore code and return 14 AWG for a "short" run even if the user entered 20 amp as the maximum draw. I'm saying that the calculators should include limits and never return a result that would violate code.
Understood, sorry for any misunderstanding... Thanks
It really depends on what you're calculating. If you're calculating
6" pigtails for an internal connection, 14 may be fine.
This site calculates 14 AWG for a 20 amp circuit up to 56', allowing up to
3% voltage drop.The description says "Our calculator yields results that are within code in most locations however we advise you to check your local electrical code."
Am I wrong that the NEC requires 12 AWG for all circuits protected by a
20 AMP breaker, which I would assume would be the case if you expected a maximum draw of 20 amps?
Thermal effects (wire expanding and contracting) would be higher meaning you would check the connections and wires might be lose. That can cause arcing which causes fires.
You would not be wrong.
The calculator is used for a lot more than residential/commercial/institutional wiring - a lot of applications where "code" is totally irellevent
"The" calculator? What is "the" calculator that you are referring to?
I linked to a site that specifically says that their results "are within code in most locations".
It also says that a 56' 120V, 20 amp circuit can be run with 14 AWG. Based on their "within code" statement, can you explain why 14 AWG would be a valid result?
Oops....my brain obviously needs to be rewired also.
Receptacle panels and lighting panels.
For sure you want your air compressor and dust collection on separate circuits. Rare a home shop runs two large tools at once, but, it's common to run dust collector and a large tool together, and, if your air compressor happens to kick on you could easily trip the breaker. Of course lights should be separate as well, preferably two different circuits.
I have 8 large tools on one 20 amp circuit and never once had a problem. Air compressor, Dust collection and Planer are on separate circuits. Planer is 240 otherwise it would be 9th on my list. Naturally this would not be cool in a multi-user commercial shop.
On 8/20/2020 8:09 AM, Jack wrote: ...
Surely all (or almost all) of those "large tools" are dual-voltage motors. Why wouldn't you switch them all over to 240V?
My key item for stationary tools is they all be on magnetic starters so won't restart if for any reason there is a power interruption.
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