GFCI circuit breaker or receptacle?

Factual Questions
1

I’m trying to plan the wiring for a basement shop.

For a particular circuit, I want to have one set of fluorescent lights and a power strip on one 20-Amp circuit. It’s my understanding that I need to protect the outlets with a GFCI mechanism, either a GFCI receptacle before the power strip or with a GFCI breaker.

Other than cost, placement, and wiring (which in this instance favour using a circuit breaker), am I correct in understanding that a protected breaker and a protected receptacle are indistinguishable to the rest of the line? Given the application/environment, is there any reason to favour using a receptacle to protect the power strip? Is the fluorescent fixture likely to cause problems (I’ve read about a lot of issues, but have not been able to discern a pattern)?

Note that the panel is located within ten feet of the power strip—there is no added convenience to locating the reset switch close to the power strip.

2

You should not put lights and receptacles on the same circuit.
While it’s not legally against code in most areas, it is “discouraged”.

A couple of the reasons for this:

  • most often, it’s a plug-in device that blows a circuit breaker. If when that happens, it also blows the lights and leaves you in the dark, that’s more dangerous.
  • lighting circuits don’t need a whole lot of power (and even less lately as CFL’s & LED’s replace incandescent bulbs), while outlet circuits commonly need more. Combined circuits are often higher amperage than fixture wiring can handle. For example, the internal wiring in your fluorescent fixture is not going to be #12 (20 Amp) wire. Yet the breaker won’t blow until it is overloaded to that point. So it’s safer to keep lighting circuits separate.
3

it is good to have lights on a separate circuit from appliances and receptacles.

if you don’t put the lighting on a separate circuit then you could put lighting in the circuit before the GFCI receptacle, so if that trips without tripping the breaker then you would still have lights.

4

Yes.

5

Thanks. The basement is already lit on another circuit (but not well enough to work on a project), so a tripped shop-breaker wouldn’t darken the entire basement. Also, there are only four slots left in the sub-panel and I’ll be adding at least one more circuit to the shop for machinery; hence my stinginess with circuits. Therefore, since I’ve so adroitly handled all concerns raised I’m going to interpret your answers as validation for my original question and do whatever the hell I want anyway. That’s how GQ is supposed to work, right?

Then again … since I’m not a complete idiot, the lighting fixture will be taken out of consideration. A few follow-up questions then:

Can I consider the GFI breaker and receptacle to be substitutes—given that all I’ll have is the one power strip, the cost difference and lack of additional wiring are good trade-offs, and the panel is just a few paces from the workbench? [edit: sorry, I had started this reply earlier and ended up distracted–hence I didn’t see Chefguy’s reply before hitting submit]

Can I make one-to-one replacements of the light fixtures on the current circuit? The current fixtures are designed to take 60-watt incandescent bulbs (the house is ten years old). The fixtures I have take two T8 fluorescent bulbs at 32 watts each (i.e. a total of 64 watts). I’d take out one fixture, add a box to extend the wire (with similar 15-amp NM), then add the fixture about fifteen feet away.

If this is permissible (to code and common-sense), is the math linear in that if I swap out ten incandescent fixtures for ten fluorescent fixtures I’d only be adding 40 watts to the overall circuit?

Further, since all of the bulbs have been changed to CFL or LED bulbs, does the wattage difference allow me to *add * fixtures? That is, if the 15-amp circuit had 10 60-watt fixtures for a total of 600 watts, but I now have ten 13-watt bulbs in there, does that give me 470 watts of additional capacity? Does that mean that mathematically speaking, I can add up to seven of the same fluorescent fixtures without increasing the original circuit’s planned load? (This assumes I can permanently label the old fixtures as taking 13-watt bulbs maximum, and I guess assumes I want to blind people who enter the basement).
[also ETA: well that’s weird. My car hit 160,000 miles this week, my van hit 150,000 yesterday, and I just noticed this is my 11,000[sup]th[/sup] post. Neat!]

6

One exception to sharing circuits with outlets and lights:

It is a good idea to put devices you normally ignore, but want to work continuously on the same circuit as heavily used lights. Examples would be smoke detectors or other alarm systems, refrigerators, freezers. This way you are likely to notice a problem with the circuit sooner than you would otherwise.

7

I don’t think this is really an issue, as long as you don’t try to draw 20 amps (that’s a LOT of light!) from the fixture; a short will trip the breaker whether it is #22 or #12 wire. Note also that 20 amps for #12 wire is ridiculously conservative (see this table; I know from experience that even the rating for chassis wiring can be exceeded by a factor of several times without burning the insulation off, like when I use a length of wire (hung in free air, and much more current if in water or oil and magnet wire with its insignificant insulation; or the thickness of the leads on a 100 amp transistor) as a makeshift load resistor, of course, not good for long-term reliability) and is based more on voltage drop than current capacity (heating).

8

A 15 amp circuit is fine up to about 1500W, though there’s probably some recommendation to keep a lighting circuit a bit lower. 600W is nothing, though, and yes, total wattage (well, amperage, but the relationship is linear) is all that matters. If you have 10 60W incandescents, feel free to put in 40 15W CFLs. Somebody will bring up inrush current, but at 600W total you’re not going to have issues. Just don’t put in 40 fixtures and then stick 100W bulbs in all of them and expect it to work, cuz that’s 33 amps.

9

It’s okay to over-think, right?

Built in 2002-3, the house has no AFCI protections.

It’s my understanding that:[ul][li]AFCI protection is generally required in places where GFCI isn’t (e.g. AFCI in a bedroom; GFCI in a kitchen). [/li][li]The two protections are completely different—AFCI offers (some) protection against** fire**, while GFCI offers (some) protection against** shock**. [/li][li] *Not *requiring both is largely a trade-off for cost and practicality reasons; the requirements are geared towards the more likely hazard. [/li][li]Having both protections (AFCI breaker and a GFCI receptacle as first in line) may be beyond what is strictly required, but is permissible and unlikely to cause problems. [/ul][/li]
In other words, taking the lighting completely out of the picture, I’m back to thinking of adding a GFCI receptacle before the power strip and connecting to the panel via an AFCI breaker.

Since I’ll be in the panel anyway, does it make sense to swap out other ‘normal’ breakers with AFCI breakers? I’m fairly risk-averse and the few hundred dollars in breakers and time is a minor factor if it adds more than nominal protection. Are there any circumstances/circuits where I wouldn’t want to add a AFCI breaker?

10

This is going into a shop. Motors in tools and such have brushes in them, which arc. This will trip your AFCI.

ETA: For other circuits in the panel that don’t have tools and arcing things normally attached to them, AFCI breakers are a good idea.

11

So if I add them to a bedroom circuit, any time I use a motor with a brush in it (vacuum?) the AFCI breaker will trip?

12

There was one protecting our living room circuit for some stupid reason. The vacuum tripped the bloody thing constantly. I replaced it with a standard breaker.

13

Yes, it’s conservative. But it’s what code requires for NM cable run inside houses. And it’s my house, and the lives of me & my dependents that is being conserved! And the extra cost to go to #12 instead of #14 for a 15 foot run is really minor.

Also, what’s the need for the power strip?
it’s quite easy to put in several boxes with receptacles when you are doing the wiring, and that’s usually preferable to having power strips hanging around. And the cost is negligible. Unless you need to turn them all on & off at once with the power strip switch.

14

Oops. Not that kind of power strip, one that has to be hard-wired into the circuit. I built an eight-foot bench and this will be centred on the front beneath/recessed from the lip (somewhat like this, but again a hard-wired strip without a cord).

Safety-wise, as soon as the cable leaves the ceiling joists it’s going into a junction box where it changes over to bare wire (well, not bare per se, but not sheathed in the yellow romex jacket. What’s the right term?). I got listed wire rather than simply stripping off the romex jacket because the wires inside the romex had no printing—and hence I (or an inspector) couldn’t tell if they were listed for such use). The bare wire will travel through 1/2-inch EM metal conduit through to the GFCI receptacle box and then to the power strip.

Speaking of conduit, how the $#@% does the math work on a conduit bender? All I can find is information for making offsets to go over/around a substantial object, not the little jog to get into a junction box. Pre-fab offsets are good for when the box and conduit are flat against the wall, but not when the conduit is on the same stud as the box sticking out. I got good at making offsets by practising and eventually figured out that 6” at 22 degrees would get me where I want, but I never found a basic guide for beginners.

And continuing to speak of conduit, is there any place I can find rules for attaching it to the wall? The best place to run it vertically is about six to eight inches from either ceiling joist where the junction box will go. The conduit will be secured to the wall along the way up, but can I make the short horizontal turn without strapping it down? It will be held in place via connection clamps to the top of the conduit and the side of the box—is that enough?

15

There are videos on the internet which will explain it best, search “star point conduit bender” but basically your bender will have a Star, on most this you can use this to align the back of your 90’ bend.

I am not an electrician but for a shop I prefer to have a GFCI receptacle because it is closer to reset.

If it is on a string of outlets I prefer to have it at the breaker box, only because the next person who owns your house won’t know exactly how the string is wired and will walk straight to the breaker box if they aren’t plugging directly into a GFCI outlet.

Edited to add a link to a very useful PDF from Ilein Tools

http://www.kleintools.com/sites/kleintools/files/instructions/Conduit%20Bending%20Basics_Iron.pdf

16

That’s a great PDF, thanks!

The sub-panel will be two feet around the corner from the bench, so fortunately both the panel and an added receptacle will be convenient.

17

Note that I was referring to the wire used in the lighting fixtures (from the post I was replying to; “For example, the internal wiring [emphasis mine] in your fluorescent fixture is not going to be #12 (20 Amp) wire. Yet the breaker won’t blow until it is overloaded to that point.”), which will be thinner due to the low currents; there is no need for it to have to handle 20 amps if the lights don’t draw that much current and if a short occurs the breaker will trip before the wire even gets warm (unless it was very thin, far thinner than anything you’d see). Similar to using an appliance with a #18 cord on a 20 amp circuit (#12); the cord is perfectly fine if the equipment doesn’t draw more than 10 amps (a typical rating for a #18 cord if they have an amp rating on them).

18

OK – that’s just the kind of thing I was going to suggest.

Don’t know. I always cheat by using flexible metal conduit for complicated little sections like this.

Generally, EMT must be strapped to a wall within 18 inches of a junction box. If 2 boxes are closer than that, you don’t need any extra straps. If it is strapped along the vertical run, then make sure one of those straps is high up, within 18 inches of the horizontal junction box.

In practice, most inspectors use the sophisticated grab-and-shake test – if it wobbles when they shake it, they insist on more strapping. So try that test yourself before calling the inspector. Sometimes you will have to install a short piece of 2x4 between studs to provide a place for a strap.