Very Basic Elec. Question

[Michael O'Sullivan]

Is there a reason not to run 20 amp circuits (as opposed to 15, all at 110v) in the shop (or elsewhere for that matter) other than the need for lower gauge wire? Is there a risk of burning out the motors?

[Luciano Burtini]

A larger circuit than needed is always beneficial and will never present a problem to the tool/motor. The breaker and appropriate sized wire are maximum and you can run any smaller tool with no concern.

Remember that the breaker protects the wire, not the motor. If you want to protect the motor, use one with internal thermal breakers, or use an appropriate starter (manual or magnetic) with appropriately sized heaters.

One last comment. If you go to 20 amp circuits, use appropriate 20 amp receptacles as well. For a 20 amp 120 volt circuit, use Nema 5-20R
http://www.nuttyb.com/receptacle.jpg

[Michael O'Sullivan]

Thanks -- that's what I thought

[Greg Peterson]

I'm wiring my shop and everything going in is at least 12/2 AWG, 20 amp breakers and 20 amp outlets and switches. Peace of mind at the least. for the relatively small difference in cost between 14/2 and 12/2, it just doesn't make any sense to install a circuit that one day may not be able to provide sufficient capacity.

[Rob Will]

Perhaps placing every-other outlet on a different circuit would be a good move. That way you always know that any two adjacent receptacles are on different circuits. I think this is better than running all the receptacles on one side of the room on the same circuit.

The 20A receptacles are definitely the way to go in a shop. Pay special attention to the way the wires hook up to the receptacles. The back wire style with built in clamps is good. Lowe's sells one for about $3.00 ea.

Personally, I don't like 14 ga wire on receptacles of any type.
(just a personal preference)

Rob

[Todd Burch]

I prefer 12 wire as well, and that's how I wired my shop.

I didn't mess with alternating lines in boxes or even adjacent boxes for that matter. I did put in mostly quad boxes. In my typical home shop, if I ever find I am tripping a breaker (and I have a few times), I turn 90 degrees or 180 degrees and find another outlet, and since it's on a different wall, it's a different circuit - problem is solved.

One thing I did do was flip one receptable upside down in my quad boxes. That way, if it's empty or even has one cord plugged in, I have a 100% chance of grabbing and stabbing the plug correctly the first time. :)

Todd

[David G Baker]

Perhaps placing every-other outlet on a different circuit would be a good move. That way you always know that any two adjacent receptacles are on different circuits. I think this is better than running all the receptacles on one side of the room on the same circuit.

The 20A receptacles are definitely the way to go in a shop. Pay special attention to the way the wires hook up to the receptacles. The back wire style with built in clamps is good. Lowe's sells one for about $3.00 ea.

Personally, I don't like 14 ga wire on receptacles of any type.
(just a personal preference)

Rob
Rob,
The Lowe's 20 amp receptacles with the back wiring with screw tightening clamps are great. They speed up the wiring time and in my opinion are much safer. Most wiring for plugs are done with #12 wire and most receptacles are 15 amp, the 15 amp plugs are much more difficult to wire with #12 wire.
The 20 amp plugs cost more but are more than worth the extra money. Try wiring a 4 plug input using #12 wire and 15 amp receptacles. I have done it many times but it was always a pain. I can do the 20 amp back torque receptacles in a couple of minutes. Love them.
David B

[Garay Holland]

In most cases 12AWG is good insurance for supply line to shop or home outlets. However, I continue to fine wiring where voltage drop is not taken into consideration in choosing wire size. If you are wiring a group of outlets that happen to be a good distance from your service entrance (I see this in cases of rural area outbuildings-shops, AND in homes with long footprints where cable runs from entrance box to outlets can easily exceed 80-90 feet. In these cases, a heavier gauge wire is called for (10 or 8 AWG) to provide connection between service box and an area junction box from which 12AWG can be used to the outlets. I try to maintain a maximum of 1.5volts of drop between service entrance and any outlet. If not taken into cosideration, voltage drop (created by higher resistance of smaller gauge wire where voltage=current x resistance) can affect motor operation and/or cause damage. But more improtant is over the long term you are paying for power that your wire is consuming instead of you equipment. For comparison: 90ft of 12AWG @ 20 amps = 2.86 volts vs 75 ft of 8AWG +15 ft of 12AWG = 1.42 volts. "Why do the lights all go dim when Ma plugs in her iron". :D

[Todd Burch]

Garay, good point - hadn't ever thought of that. (voltage drop & what goes through the meter versus what gets supplied to an appliance)

Could you put this in pespective please? I pay by watts. What would this mean over a year in your example above? (assume 8 hours a day use).

Todd

[Al Willits]

""""""
One thing I did do was flip one receptacle upside down in my quad boxes
""""""""
Had a electrician once tell me the grounding plug should whenever possible be at the bottom, something about safety or code, can't remember, anybody??

I'm in the 20 and 12 camp, everything with a receptacle is 20/12 except for the lights, all them plug into a recpt, but there on dedicated circuits and no more than 2 or 3 fixtures per circuit, they use 14ga.

All my runs are short enough that 12ga takes care of them.
The 110v extension cord for the saw is 10ga though and the 220 extension cord I think is 8ga.

When I bought the house the previous owner had run 6ga aluminum wire out to the garage, didn't catch that as he had the connections taped up, but did discover it when after running the stick welder for a while, I had a line of melting snow from the garage to the house....replaced that with 6ga copper after that...:)

Al

[Alan Tolchinsky]

Hi All, I would think that all these outlets are GFI protected. In a lot of areas it's code and just for the safety aspect of I' d put them in my shop. Think about it: You're usually standing on bare concrete when using electrical tools. And that's a perfect path to ground.

[Todd Burch]

Yes, I have these everywhere, and 20amp GFIs are not cheap.

Todd

[Steve Kohn]

I was not thinking when I had my shop wired. Everything was done in 12 AWG, outlets were 50 inches above the floor, and every other outlet was wired to the alternating circuits in the box. I have 4 circuits total servicing the wall outlets. Other circuits service the lights, door opener, and drop down power cords.

However, I wish I had "homerun" wired every outlet in the shop. That way, with a simple breaker and outlet change, any outlet could have been converted to a 220V, 20A outlet.

I would also suggest a 4 way box behind any workbench. I am always fumbling around unplugging one charger for another.

[Rob Russell]

One last comment. If you go to 20 amp circuits, use appropriate 20 amp receptacles as well. For a 20 amp 120 volt circuit, use Nema 5-20R.


Luciano,

I don't know if you're implying this, but it is not an NEC requirement that one use 20 amp receptacles on 20 amp circuits, provided there is more than one receptacle on the circuit. It is perfectly OK to use 15 amp receptacles on a 20 amp circuit, as long as you have more than 2 receptacles. Remember that a typical receptacle is a duplex, so what we consider to be a normal 15 amp receptacle actually counts as (2) receptacles. Refer to NEC article 210.21(B)(3)Receptacle Ratings for the verbiage behind all this.

Rob

[Mike Henderson]

Garay, good point - hadn't ever thought of that. (voltage drop & what goes through the meter versus what gets supplied to an appliance)

Could you put this in pespective please? I pay by watts. What would this mean over a year in your example above? (assume 8 hours a day use).

Todd
To get you a number requires making some assumptions. Let's assume the 2.86 volt drop as mentioned by Garay for 90 feet of 12 gauge wire. I assume that drop is at maximum current draw of 20 amps for the 12 gauge wire. Since R=E/I, the resistance of the wire is 0.143 Ohms for 90 feet. But let's assume that you are not drawing 20 amps all the time. Althought this is much higher than reality, let's assume 10 amps constant draw. Watts = I(squared) * R so your watts lost in the wire is 14.3. You pay for power in kilowatt hours so we have to multiply by the hours and divide by 1,000. For 8 hours per day, 365 days per year, you will lose 41.76 KWh. If power is $0.15 per KWh, your cost for the losses will be about $6.26 per year.

But you can't save all that because whatever wire you use will have some loses in it. If you put in larger wire that reduces your losses in half, your savings in electricity will be about $3 per year.

In reality, this is significantly overstated because you won't be drawing an average of 10 amps every day, eight hours per day. Your actual draw will likely be much lower so your economic savings will probably be much less.

Mike
[an added note: Since watts are equal to I(squared) *R, the watts go up (and down) by the square of the average current draw. So if you did draw 20 amps eight hours per day, every day, the economic loss would be about $25 per year. In other words, if you double the average amps, the cost goes up a lot. If you halve the average current draw, the cost goes down a lot.]

[Todd Burch]

Thanks Mike!

Todd

[Kent Fitzgerald]

I was not thinking when I had my shop wired.
Sounds to me like you have a very thorough wiring plan.

IMHO, a home run for each receptacle is way overkill (and would make for a very full panel). If/when you need to add a circuit, that's what conduit is for.

[Kent Fitzgerald]

Had a electrician once tell me the grounding plug should whenever possible be at the bottom, something about safety or code, can't remember, anybody??

The NEC doesn't care either way. Some people prefer to put the ground pin on top (more commonly seen in commercial jobs). The argument is that it's safer; if the plug is partly pulled out, a metal object (say, a wire coat hanger) that falls on the plug will hit the ground pin first.

[Garay Holland]

Todd,
Mike is right, it is all relative - to look at cost you must take in cosideration no. of circuits, avg. load, and in the end cost of larger wire vs cost of kwh. If you are only talking about one circuit, with low no. of outlets, low to med usage it may be hard to justify increasing wire gauge. My input was for consideration where a whole shop/house is being wired with a multitude of circuits - i.e. Our shop has 7 dedicated 220v circuits and 12 20A 120v circuits and is very near the service entrance so I use 10AWG for all of the 220v circuits and 12AWG for 120v. But, the house we are building is 120 ft long with 400A service, lot of cable runs over 80 wire ft, 25 220v curcuits, 42 120v curcuits and here it really was important to size the system well for balance, service and cost. I was just pointing out one area that I see often under considered.

We are also now living in a very rural area of Arkansas where there is basicly NO code and a real lack of understanding of basic electricity EVEN BY THOSE PROVIDING SERVICE and a lot of DIY home wiring. When in doubt, hiring a QUALIFIED electrician is money well spent.

[Mike Henderson]

I absolutely agree with Garay. When in doubt, hire someone who knows what they are doing.

I do my own wiring but I always over spec everything. Code is the MINIMUM acceptable - not necessarly the best you can do. It's my house and I want to make sure that there's essentially no chance I'm going to burn it down or kill myself. A few dollars extra in the wiring (or whatever) is peanuts compared to dealing with a disaster.

Mike

[John Terefenko]

Yes, I have these everywhere, and 20amp GFIs are not cheap.

Todd

You do not need each recepticle to be a GFCI. If you have a circuit with so many outlets on it just make the first outlet GFCI and all down stream will be protected providing you wire them on the load side of the GFCI. You can also buy GFI breakers and it will protect the whole circuit. Do not use 15 amp receptacles in a shop. Use the 20 amp rated receptacles.

[Todd Burch]

I know. I only use the GFCI as the first in each string.

And they are still not cheap.

Todd

[Travis Lavallee]

Al, you stated that you were using an 8 ga. wire for 220V, and 10 ga. for 110v. Your wire should be sized based upon current draw, and not voltage requirements. The insullation on a wire is based upon voltage. Actually a device would draw half as much current running on 220 as it would on 110 and would allow you to get by with a smaller cord.