Putting a 15 amp receptacle on a 20 amp breaker

[txgp17]

Gentlemen,
It has become common place in the electrical industry to offer receptacles that will accept both 15 and 20 amp blade plugs, like the one pictured below. NEMA 5-15P & 5-20P


Assuming all my extension cord is 12/3 or greater.... *IF* it is acceptable to power 15 amp blade plugs through 20 amp breakers, is there any reason why it would not be acceptable to power 15 amp twist lock plugs through 20 amp breakers?

Say I place this unit on a 20 amp breaker, rather than a 15.


Your thoughts?

[Acklan]

Assuming all my extension cord is 12/3 or greater.... *IF* it is acceptable to power 15 amp blade plugs through 20 amp breakers, is there any reason why it would not be acceptable to power 15 amp twist lock plugs through 20 amp breakers?

Say I place this unit on a 20 amp breaker, rather than a 15.

Your thoughts?

Bad idea. In the case of the traditional 120 volt receptacle you are talking about running less than the rated amperage, 15 amp on a 20 amp breaker. With the twist lock you are suggesting increasing the load by 33%, 20 amp load on a plug that is rated for 15 amp. You may never have a problem, but would it not just be simpler to buy the proper receptacle\plug?
Remember the more amperage you flow the high the heat you will generate. That is why the more amps the large the wire you will need.

[FIREMECH1]

There is an inherent difference between a 15-20 amp wall socket compared to the 15 and 20 amp twist lock sockets. (notice the single and plural)

Wall sockets of the 15-20 are heavier duty compared to the standard 15 amp receptacle, and can do both jobs easily, and handle the extra heat of any loads put on it. As well, the breaker will be rated at 20 amps.

On the twist lock sockets, if you install a 15 on a 20 amp breaker, you can trip the breaker because of the load and resistance. 15 amp sockets are smaller internally, and build up resistance and heat. This has no effect per say, on the wire you are using. The problem is built into the socket.

Question... is this for your home, or for an apparatus with a gen-set???

FM1

[txgp17]

would it not just be simpler to buy the proper receptacle\plug?

No, as we'd have to switch out almost 1,000 connectors on 40+ apparatus to keep things consistent.

The problem is built into the socket.

Ahh, I didn't consider the wiring inside the receptacle. I was only considering the practice of running a 15 amp load on a 20 breaker. The pitfall is running 20 amps through a 15 amp plug.

Question... is this for your home, or for an apparatus with a gen-set???FM1

Writing specs on an Akron Junction Box. It would be supplied by 200' of 10/4 through a L14-30R receptacle. The junction box would send one hot wire to each side of the box, supplying two L5-15R duplex receptacles, with individual breakers for each. The box would have a total of eight 15 amp twist-lock receptacles.

This gives four times the available wattage at the end of the cord over a single 10/3 cord on a 15 amp breaker. Plus if you remove the junction box, you have a 120/240 volt receptacle, which opens the door for 240 equipment, like some of the larger electric PPV fans making their way onto the market.

[RoofTopTrucky]

was told this by an electrical inspector and wasa able to verrify with electrical device mfg rep i spoke with about this same thing about 2 years ago... Believe it or not, the only major difference between a 15 and 20 amp receptical is the face cover, the "guts" of the 2 are exactly the same, this is done for no more than ease of production. The guts themselves are not actualy wires, but copper bars and clips bent and twisted and fused togther so that it works. Now if you go to your lowes or home depot, you'll see regular household recepticals, and "heavy duty" or Commercial Grade. These do have a little thicker bars used for the guts and a heaver duty housing. so, in theroy there is no difference between the 2, BUT, if you use a 15 in place of a 20 and something go's wrong, and when the lawyer from Duie ****em and Howe finds out what you did.... your toast.
Bottom line, if you plan on useing 20 amps, use the right device, now, it dosent hurt to increase wire size one gauge at times, For exsample, we have 200' electric reels on our rigs and they are wired with 10/3 wire, and are wired into a 20 amp breaking. We do this to help compensate for voltage loss (friction loss).

[FD1976]

according to the NEC

The technical answer is that if there is only one receptacle on the circuit, it MUST be rated for the breaker size. ex: 20 amp breaker must have a 20 amp receptacle, such as for an A/C or clothes washer.

If there are more than one receptacle on the circuit, they may be rated 15 or 20 amp each on a 20 amp breaker. Such as a kitchen or garage circuit.

NEC doesn't care if its in a structure or on 4 wheels.

Hope this clarifies a bit.

[FIREMECH1]

RoofTopTrucky is right about the receptacles that mount on a wall with 2 outlets. But not true for the twist lock connectors.

FM1

[RFDACM02]

Bear with me as I'm somewhat ignorant too most electrical things. But wouldn't running an anticipated 15 amp load on a 20 amp circuit defeat the purpose of the breaker or at least diminish it's capacity to work properly? I'm picturing someone damaging equipment when it fails to kick off when the tool is drawing too much? Otherwise wouldn't we all just install 30 amp breakers throughout? NEC be damned of course?

[fireinfo10]

Call Weldon engineer. They will be able to answer with expert knowledge of code, design, and practice. And it's free.

http://www.weldoninc.com/pages/contacts.aspx

[avalanchex88]

So in theory you are intending to power 4 15amp TL connectors off of each leg of your cord reel. Given your 200+ feet of cable and appropriate volt drop, i don't see a problem powering them off of a 20a breaker. Another option which may be cheaper than replacing 8 receptacles per box, is to replace the breakers feeding the reel with 15a models. A third option would be to add circuit protection at the junction box itself at a 15a while keeping 20a breakers in the panel.

[mrpita]

Bear with me as I'm somewhat ignorant too most electrical things. But wouldn't running an anticipated 15 amp load on a 20 amp circuit defeat the purpose of the breaker or at least diminish it's capacity to work properly? I'm picturing someone damaging equipment when it fails to kick off when the tool is drawing too much? Otherwise wouldn't we all just install 30 amp breakers throughout? NEC be damned of course?

Not an electrician/engineer, nor do I play one on TV... YMMV, call an electrical pro and all the standard disclaimers apply if you zap yourself.

You generally want your breakers sized the "next up" from your load(s). I seem to recall some sizing element to a circuit where the anticipated load(s) of a circuit should be only 80% of that circuit's protection.

As for why not the 30A circuits all over, as memory serves,
15A = 14 ga wiring minimum
20A = 12 ga min
30A = 10 ga min

I can get 100' of 14, 12, or 10 ga Romex at about $30, $50, or $90 respectively. So from an economic standpoint it's $3x more to have a 30A circuit, just in wiring. Generally the hardware (breakers/outlets) cost more also.

Not to mention NEMA standards holds a 30A outlet to look (and FIT) different than what your standard 15A plug will fit - a GOOD thing... Also prevents 250V stuff from connecting to 125V, or vice-versa.

See attached for the most common household configurations of straight blade plugs/receptacles. First line is the old 2 prongs. Then the "standard" plug on line 2, progressing toward heavier equipment. Next is "250V only" stuff like a window AC, heavier power tools, etc. Finally the 125V/250V combo stuff like old ranges and dryers - these are now obsolete, but common in older (pre-1996) homes. Note it does not have the "new" (since NEC 1996) 4 prong outlets/plugs for 125V/250V like your electric stoves and dryers with electronic controls.

[RFDACM02]

Thanks Mrpita, that all makes sense.

[txgp17]

Followup from a long way off.....

NFPA 70, the National Electrical Code, in section 210.21 (B) describes the requirements of single and multiple receptacles on a circuit. Part of the UL listing for the 15 amp receptacles is that they are capable of feeding through the 20 amp circuit, the primary difference between 15 and 20 amp receptacles being the faceplate configuration.

The use of multiple 15 amp receptacles on a 20 amp circuit is permitted. A duplex receptacle is considered as multiple receptacles and is therefore permissible to use as the single, or one of several, multiple type receptacles on the circuit.