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240 V plugs, receptacles - basic Qs

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Forum topic by unclearthur posted 12-08-2017 04:37 AM 1341 views 0 times favorited 13 replies Add to Favorites Watch
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unclearthur

182 posts in 1870 days


12-08-2017 04:37 AM

I apologize for this being mostly non-woodworking, but it does related to my dust collector. Anyways, not so long ago I had an electrician install some 240 V circuits in my garage and am confused by the different types of plugs / receptacles.

On the first one the breakers look like this:

20 Amp circuit, correct?
The corresponding plug (the only one on the circuit) looks like:

.. which is a 240 V 15 A plug correct?

Is there a reason why he would put a 15 A plug on a 20 A circuit?

Though my dust collector is only 9 A (240 V) and has a 15 A plug, the remote control I bought for it has a 20 A plug (NEMA 6-20) and won’t fit into the 15A plug. I assume I can either swap out the receptacle for a 20A receptacle or replace the 20A plug with a 15A plug on the remote switch ….. correct?

Then on the second 240 V circuit, the breaker looks like this:

.... which is a 15 A circuit, right?

and the (only) plug on the circuit looks like this:

... which is a 240 V , 20 A plug right?

Is it safe / code to have 20 A plugs on 15A circuits?

Has he just messed things up or am I confused?

Thanks for any input


13 replies so far

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msinc

480 posts in 586 days


#1 posted 12-08-2017 07:55 AM

Well, what we really need to know is which gauge wire he ran to these plugs. The breaker trips at the given amperage, but it’s really the wire that carries the load. This maybe a bad way of explaining it. Code requires the breaker, wire size and outlet to all match. Plus, I cant really see the outlet type in the second photo…it appears all black on my computer.
15 amp should be 14 gauge {14awg} wire. 20 amp should be 12 gauge {12awg} wire. You want to match the machines load to the wire and breaker, but not go over. Where you get into trouble is when you run, for example 14 gauge wire to a 30 amp breaker and outlet. Yep, there are people that do this…and it might even run okay. The real problem happens when you have an overload or short. It wont pop the breaker until it has probably already caused an electrical fire if it even pops then.
The outlet in the second photo is a 15/20 amp outlet depending on how it’s wired and or which plug you use. It will take either. Both horizontal blades is a 15 amp. One vertical and one horizontal is a 20 amp. When you get to the 30 amp it has blades set in a round or circle configuration unless it is like a big range or dryer plug. The outlet you have in the second picture can be used for either 15 or 20 amp. It is not really a big deal if you have a 15 amp rated device plugged into a 20 amp circuit but if you plug in a 20 into a 15 you may or may not have trouble. Most devices don’t hardly ever pull the amps they are rated for, but it could and when it does it will pop the breaker. Again, the main thing is that the wire is sized right…too small a gauge wire and it will get hot during use and that is never good.

Edit: okay, I can see that second photo now, don’t know why it looked all black at first. That is a 15 amp outlet {both horizontal blades}. Are you sure he doesn’t have the 15 amp breaker feeding that one? If he doesn’t then you might want to get him back there and swap the breakers so they are feeding the proper rated circuits, assuming he has the correct wire{?} Could just be a simple mistake. Also, I failed to answer one of your questions…you can swap out the outlet to fit your remote to a 20 amp type as long as the wire run to it is 12 gauge. If 14 gauge wire then no the wire has to match the breaker as well as the plug and outlet. So, no, you should not install a 15 amp plug on a device{your remote} that is rated for 20 amps just so you can plug it in and use it. Again, it will probably turn on and probably run, it’s when a problem comes up that you could have smoke and blue sparks….never good. I should also add that while things swapped around, but not necessarily matching the rated amps might run okay and never cause any problems…if you ever do have a fire your insurance company is going to send out an inspector, when he finds 15 amp plugs on 20 amp machines your insurance company will deny the claim, even if the fire is totally unrelated. Not worth taking the chance.

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unclearthur

182 posts in 1870 days


#2 posted 12-08-2017 08:32 AM

@msinc – thanks very much for your answer, learning something here.

He definitely has the 15 A breaker feeding the dual 15/20 amp outlets (2nd set of photos) and the 20A breakers feeding the single 15 A outlet (1st set of photos). Triple checked it.

Two questions:
1. The DC plugs into the remote switch which in turn plugs into the wall. The DC itself runs at around 9 A and has only a 15A plug, so as long as I’m only plugging that DC into the remote switch, I assume its OK to change the plug on the remote switch to a 15 A plug (so it will fit into the outlet), as nothing is pulling more than 15 A through it anyways?

2. Any simple way to I tell if they used 12 awg vs 14 awg wire? I assumed it must be 12 gauge as it is going into a 20 Amp breaker …... major code violation otherwise, isn’t it?

3. Is having the 15/20 plug on a 15 amp circuit to code? The breaker protects the wire, so worst case is just unwanted trips if you plug something with to high an amperage in – correct?

View Fred Hargis's profile

Fred Hargis

5034 posts in 2576 days


#3 posted 12-08-2017 11:58 AM

1) you will be good to go changing that plug.
2) you might be able to look at the wire itself and tell what size it is but the easiest is to just look at the jacket on the wire where it’s printed. There’s a noticeable difference between the 2 sizes, if you have a small piece of one or the other (or both) to compare to the wires at the outlets you may be able to discern what size it is. Any chance your electrician just got his outlets switched when he installed them? That would be a big problem, not only relative to the code but for safety in general.
3) there shouldn’t be a 20 amp outlet on a 15 amp circuit….but you are correct, the breaker should protect in case of an overload.

-- Our village hasn't lost it's idiot, he was elected to congress.

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jonah

1820 posts in 3381 days


#4 posted 12-08-2017 12:22 PM

You can absolutely over-rate an outlet. The breaker protects the wire. It’s fine to use a 20A rated outlet on a 15A circuit. It’s not fine to use the reverse, a 15A outlet on a 20A circuit.

If the plug doesn’t match the remote switch, replace the plug, not the receptacle.

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msinc

480 posts in 586 days


#5 posted 12-08-2017 01:23 PM

I will answer your questions in order:

1. I have to ask a question first; is the plug on that remote the one it came with from the factory?? Or does it appear that maybe someone has already changed it to a 20 amp when it was likely a 15 amp when new?? If so than change it back, if not, then I would not put on a lower rated amp plug on any device. If it is a 20 amp remote as rated from the factory then it needs to stay that way for general safety, NEC code and insurance reasons. Better to change and match the outlet to it.

Edit: I should add that just because this remote is operating a lower amp rated device doesn’t mean you can go ahead and degrade the plug to a lesser rated one. Remember that the remote itself is using some power to operate, I don’t know what type of remote this thing is, but if it uses a magnetic type contactor 20 amp rating might be correct for both the device and remote.

2. As above, the best way is to look at the printed jacket, it should say 12awg for 20 amp 14awg for 15, etc. Typically, the 20 amp 12awg has a yellow colored plastic jacket and the 14awg will be white, but they could both be white depending on the brand of wire and/or how old it is. Best to either pull the cover off the breaker panel or pull the cover off the outlet, but it is usually easier to see in the breaker panel. Also, it is printed on the individual wires too, so if, as typical the wire has had the outer jacket skinned off you can still see the 12/14 awg markings on the wires in the breaker panel going to the breaker.

3. Well, not really. Worse case is a fire. When it comes to wiring any device, you really need to match the breaker, the wire and the outlet. Again, as posted by others too , the problem comes in when you plug in a device rated for higher than the wire is rated. This could lead to wire getting hot and that starts a bad thing that gets worse…as a conductor heats up {wire gets hot} the resistance across it becomes greater, causing more of a drain {higher amps} to get through. The more amps the more the heat builds, kind of a loop until either the breaker pops or a fire gets started. Because breakers are not exactly fool proof and can “stick” this scenario is never recommended.
All that said, we get to the combo outlet 15/20 amp type…..they should always be wired with 12awg 20 amp wire and put on a 20 amp breaker. I know this is contradictory to what I have said in general already, but this way there wont be any 20 amp devices plugged into a 15 amp circuit that is being mistook for a 20 amp. It is usually not a big deal to have a 15 amp device plugged into a circuit rated 5 amps higher. The breaker should still pop before that 12awg wire gets hot enough to cause a problem.

If I were arriving at your shop today to have a look I would first verify the wire sizes and then go in the panel and either flip flop the two breakers or wire permitting make them both 20 amp circuits. Then change out the one outlet so your remote would plug in. That all sounds simple…the old “all ya’ gotta do”, but it gets a little more complicated if the wire sizes are not 12awg.

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jonah

1820 posts in 3381 days


#6 posted 12-08-2017 03:50 PM

Just to correct a common misconception: Circuit breakers protect wire.

Devices have thermal overload protection to protect themselves. They do not depend on the circuit breaker for protection, nor should they.

Receptacles and plugs should be rated equal to or greater than the breaker they’re attached to, obviously with appropriately sized wire.

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WhyMe

1034 posts in 1644 days


#7 posted 12-08-2017 04:51 PM

Short answer is both receptacles are wrong if the circuits are wired correctly as 20A and 15A respectively. The single 15A receptacle on the 20A circuit needs to be a 20A, and the duplex 15/20 on the 15A circuit needs to be a 15A only. You can change that single 15A receptacle to a duplex 15/20A since it is a 20A circuit.

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MrRon

4917 posts in 3326 days


#8 posted 12-08-2017 05:27 PM

Not knowing when you hired that electrician, but unless I’m wrong, he installed those receptacles upside down. The latest electrical code has the receptacles with the grounding pin on top, not on the bottom.

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msinc

480 posts in 586 days


#9 posted 12-08-2017 06:12 PM

Just to correct a common misconception…circuit breakers prevent an electrical fire.

Not all “devices” have overload protection. Those that don’t absolutely do depend on the breaker in the panel.

One out of three is not bad, I can do the word play game and split hairs with the best of them.

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jonah

1820 posts in 3381 days


#10 posted 12-08-2017 06:22 PM



Just to correct a common misconception…circuit breakers prevent an electrical fire.

Not all “devices” have overload protection. Those that don t absolutely do depend on the breaker in the panel.

One out of three is not bad, I can do the word play game and split hairs with the best of them.

- msinc


Your 5V USB phone charger or 18V laptop adapter could catch on fire by drawing fractions of an amp of power from the panel and without coming close to tripping the breaker. Circuit breakers prevent electrical fires caused by one particular thing (current overload or a short circuit at 120/240VAC). They are designed to protect the wires in the wall, not the thing you plug into them.

View unclearthur's profile

unclearthur

182 posts in 1870 days


#11 posted 12-08-2017 11:34 PM

Thanks for everyone’s comments.
I did check and the sheathing on the cable going into both outlets is yellow and the wires seem a bit thicker than the wires going into my 110 V outlets (which has white sheathing). Though I couldn’t read any markings on the sheathing or the wires, it seems like its probably 12 gauge wire.

So on the first 240V circuit I have 20 Amp breakers, 12 gauge wire and a single 15 A outlet.

And on the second 240 V circuit I have 15 A breakers, 12 gauge wire and a double 15/20 A outlet.

Anyone know if either of these are code violations in Canada?

The best long term resolution to me seems to be to put a 20 A outlet on the first circuit and 20 A breakers on the 2nd circuit.

View Fred Hargis's profile

Fred Hargis

5034 posts in 2576 days


#12 posted 12-09-2017 12:01 PM

No knowledge of Canadian requirements, but if it is #12 on both circuits I would think you have nothing to do…you’re good to go.

-- Our village hasn't lost it's idiot, he was elected to congress.

View jonah's profile

jonah

1820 posts in 3381 days


#13 posted 12-09-2017 01:06 PM

If the first outlet is really only rated for 15A I would replace it with a 20A. Same with the second if you replace that breaker.

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