What 20a backwired outlet

[djjsr]

I have at least 15, maybe 20 circuits in my shop that are 120 volt, 20A breakers, 12 gauge wire and 20A receptacles. Unless you're really pinching pennies, use 20A.

It gives you good flexibility for moving things around if you use space heaters, big power tools or maybe a 120V welder. If you'll never use that kind of equipment, then you don't need 20A circuits.

jmo

[djjsr]

Originally Posted by Norcal

15A receptacles are rated 20A feed through, unless someone gets a good deal on 20A there is no reason to use them, unless you have extra money to squander.

Ok, I think it's wrong, so once again I'll ask.

If 15A receptacles will do everything a 20A receptacle will do, then why do they bother selling 20A receptacles?

I have a space heater that's 120V and it has a 20A plug that will not plug into a 15A outlet.

There's a reason these exist ..........

[Stuart in MN]

Originally Posted by djjsr

I have a space heater that's 120V and it has a 20A plug that will not plug into a 15A outlet.

Well, that's one example of where you need a 20 amp receptacle, but appliances like that aren't very common.

As mentioned, the vast majority of 120vac consumer devices use a 15 amp plug, so they only need a 15 amp receptacle. Putting those 15 amp receptacles on a 20 amp circuit provides a little more capacity, if there are several devices plugged into the same circuit, and helps avoid having nuisance trips.

20 amp circuits aren't necessary by any means, but in a place like a garage or workshop where people are more likely to be using power tools that need more amps they're not a bad idea.

[FakeName]

Thanks for all the info here- much appreciated.

So- is it a good idea to run 20 amp receptacle circuits with one 20amp outlet and the rest 15? This would allow the occasional 20 amp device and one could be sure to unplug anything else on that circuit for the duration of the 20 amp device's use?

[cyamaha2007]

As far as my lighting goes i will have 35 8ft t8 fixtures for 2000sqft. 14 will be on each circuit. Each fixture has a .98a draw. As far as a 20a outlets go my portable plasma, mag drill,spot welder, belt sander, hydraulic accessory pack have a 20a male plug so im stuck with using 20 a receptacles i guess. Thanks for the info. I had no idea you could use a 15a outlet on a 20a circuit. One more question can you use a 15a switch for a 20a circuit? Or is that a no no. My electrical training was 2 years trade school. So im no pro thats for sure.

[soj]

One more reason for 20A rec. is a 10G extension cord. I have one with a 20A male plug, so with 20A rec. I can use it anywhere, esp on the outside rec. which is where I usually use the 100' 10G cord anyway.

[ishiboo]

Originally Posted by djjsr

Ok, I think it's wrong, so once again I'll ask.

If 15A receptacles will do everything a 20A receptacle will do, then why do they bother selling 20A receptacles?

Originally, they were designed so that you wouldn't accidentally plug a 20a device into a 15a circuit, which best case scenario would blow the breaker/fuse/etc. In addition, back when there were fuses, if people kept blowing a fuse many would just put a bigger fuse in instead - bad idea! In addition, a breaker will pass overcurrent for a period of time. It also prevents you from putting a 20a space heater on a 100' 16-gauge extension cord, since no <12ga extension cord would have that plug.

For the shop, it's good to wire with #12 and breaker for 20a as you often run larger tools which often consume the power. A few devices also require 20a still - 120v welders at full output, for example.

I've never owned a piece of equipment with a 20amp plug, but when I wire a 20a receptacle circuit I almost always use 20a receptacles. Reason being, it is much easier to not accidentally buy the lowest-quality receptacles at the stores when you go up to 20a... and the price difference is slim to none between the two. 20a gets you a quality back-wired screw receptacle.

IEC connectors (the plugs that computer power supplies, LCD/Plasma TVs, etc. typically use) also come in 15a and 20a variants which are very different, and a 15a plug cannot go into a 20a receptacle. What sucked though is that they are used for both 120v and 240v in US datacenters, so power supplies which are not auto-switching go up in smoke if you accidentally plug one in to 240v with the switch set to 120. Ask me how I know

[djjsr]

Does the NEC require or recommend that a 20A receptacle be used on a 20A circuit?

[Charles (in GA)]

Originally Posted by djjsr

Does the NEC require or recommend that a 20A receptacle be used on a 20A circuit?

20 amp receptacle is required if there is only one receptacle, that means a single receptacle, on the circuit. If there is a duplex receptacle, or more than one in any way, then 15 amp receptacles are OK.

NEC 210.21

(B) Receptacles.
(1) Single Receptacle on an Individual Branch Circuit.
A single receptacle installed on an individual branch circuit
shall have an ampere rating not less than that of the branch
circuit.

(2) Total Cord-and-Plug-Connected Load. Where connected
to a branch circuit supplying two or more receptacles
or outlets, a receptacle shall not supply a total cord-and-plugconnected
load in excess of the maximum specified in Table
210.21(B)(2).

(3) Receptacle Ratings. Where connected to a branch circuit
supplying two or more receptacles or outlets, receptacle
ratings shall conform to the values listed in Table
210.21(B)(3), or, where rated higher than 50 amperes, the
receptacle rating shall not be less than the branch-circuit
rating.

Table 210.21(B)(2) Maximum Cord-and-Plug-Connected
Load to Receptacle
Circuit Rating (Amperes) - Receptacle Rating (Amperes) - Maximum Load (Amperes)
15 or 20 - 15 - 12
20 - 20 - 16
30 - 30 - 24

[djjsr]

Thanks Charles.

[automobiliben]

Well I learned something tonight! Guess I will go and return those 20A outlets that I bought.

The cost difference is pretty significant, like 3Xs the price for the bulk boxes...

[Speedy Petey]

Originally Posted by automobiliben

The cost difference is pretty significant, like 3Xs the price for the bulk boxes...

Make sure you still get spec-grade receptacles. The cheap <$1 ones are not worth it.

[automobiliben]

Originally Posted by Speedy Petey

Make sure you still get spec-grade receptacles. The cheap <$1 ones are not worth it.

Which ones would you recommend?

Just an aside, my last shop was wired with the El cheapo ones and I never had an issue. But I don't mind spending a bit more to get a better outlet.

This is what I bought:

http://www.lowes.com/pd_61241-334-BR...AID=1368030917

IIRC, they didn't have any mid grade 15A receptacles.

[Speedy Petey]

Originally Posted by automobiliben

Which ones would you recommend?

Just an aside, my last shop was wired with the El cheapo ones and I never had an issue. But I don't mind spending a bit more to get a better outlet.

This is what I bought:

http://www.lowes.com/pd_61241-334-BR...AID=1368030917

IIRC, they didn't have any mid grade 15A receptacles.

I just ask for CR15's at the supply house.

Most manufacturers use this designation: https://www.google.com/search?q=cr15...w=1680&bih=912

[automobiliben]

Originally Posted by Speedy Petey

I just ask for CR15's at the supply house.

Most manufacturers use this designation: https://www.google.com/search?q=cr15...w=1680&bih=912

I returned what I had bought and picked some of these up. They are $16 for a box of 10 at Home Depot.

[green.bubbly]

Originally Posted by ForceFed70

In my neck of the woods, feed-thru is not allowed. You must pigtail. It's one of the 1st things the inspector looks at as part of your rough-in inspection.

I'm thinking there must be a reason why they've adapted this rule, but damned if I could tell you what it is.

I just want to make sure I follow this right because I always did it the way it is done in the second pic.

So if I understand correctly, the first pic is the way it should be done and the second pic is not recommended???

[ishiboo]

Originally Posted by automobiliben

Which ones would you recommend?

Just an aside, my last shop was wired with the El cheapo ones and I never had an issue. But I don't mind spending a bit more to get a better outlet.

This is what I bought:

http://www.lowes.com/pd_61241-334-BR...AID=1368030917

IIRC, they didn't have any mid grade 15A receptacles.

Those are acceptable... that's what I use. You're usually safe with any of the backwire receptacles.

[Charles (in GA)]

There are tens of thousands of housed wired like that in the second pic. I'm not a real fan of it, because of the hassle of installation, you are trying to hook up four wires at once and its much stiffer to push back into the box (even after forming a Z in the wires). The pigtails mean much less effort to push back into the box, easier to replace in the future, but a little more box fill.

Charles

[green.bubbly]

Thanks Charles. I am thinking that with #12 wire, using the pigtail would be easier. Is there any thing code wise wrong with doing it the way shown in the second pic? Is that what forcedfed referred to as feed through?

[sberry]

Even a 120V welder has a 15A plug, about the only place I can remember running across any 20A was floor cleaning equipment. I got to agree with Norcal, that was simple,,, you don't need it. I cant think of a single thing I own that has a 20A plug.