Somethings buggin me and I need help, input or clarification please:
As I understand, NEC requires that the receptacles on a circuit match the rating of the circuit – i.e., a 20-amp breaker at the panel, wired with 12-ga wire, requires a 20-amp rated outlet at the wall.
Right??
So how come I have YET to see this in practice in the field?? Every home I’ve been called into to do wiring, I find 15A outlets on 20A circuits. Especially in the Kitchen (which is the most obvious place that I always check first).
Is this just a technical rule commonly flaunted? Or do I fault both the building electrician and the inspector (seems unlikely they’d ALL be at fault, which is why I think my understanding of the Code might be incorrect!)
On a related note (and maybe my answer to the question above) – why are 20A outlets so darn expensive. My clients mostly want Decora style, and I can get 15A from my suppliers for about a buck, while 20A costs closer to ten! What gives?
Thanks for any comments – it’ll help me sleep at night ;o)
Cheers,
Jcd
Replies
"As I understand, NEC requires that the receptacles on a circuit match the rating of the circuit - i.e., a 20-amp breaker at the panel, wired with 12-ga wire, requires a 20-amp rated outlet at the wall."
Not exactly.
On 20 amp circuits you can have either 15 or 20 amp receptacles as long as you have more than ONE. If you only have one receptacle it has to be a 20 amp receptacle.
Note - the common duplex receptacle counts as TWO receptacles.
"On a related note (and maybe my answer to the question above) - why are 20A outlets so darn expensive. My clients mostly want Decora style, and I can get 15A from my suppliers for about a buck, while 20A costs closer to ten! What gives?"
They aren't. They are about the same cost for the SAME QUALITY. I have not looked at the decor lines. But in the regular lines the 39cent builder specials are only available in 15 amp versions.
But if you go to the spec grade (commercial grade) they cost about the same.
Looking at Lowes web site they have the 15 amp CR15V-Sp for $1.63 and the 20 amp equivalent, CR20V-SP for $1.95.
Bill,
Nice explanation. I'll save your post and share it with my Habitat volunteers who ask the question (and most do).
About 20A receptacles--I once helped an owner-builder wire his house. He wanted me to do the panel, generator transfer switch, etc. He said he'd take care of the simple stuff, and also he'd provide the materials. He'd insisted on all 20A branch circuits, and because he was too proud to ask, he went out and bought all 20A receptacles outlets (the only ones he could get were expensive--$5-6 per). And he installed them. One day his wife was complaining about how weird the T-shaped slots looked, and I explained to the two of them that 15 amp receptacles would have been more than adequate. She was still lettin' him have it as I left.
Cliff
Thanks for the comment.
As a sidenote: many dedicated 20A circuits with accompanying receptacles are colored orange i.e. the receptacle, indicating this is a dedicated circuit. I've got two of my own; one for an iron receptacle in a laundry area which I didn't bother to buy color coated (however the receptacle configuration is an obvious giveaway), and one in an office/computer area which I bought color coated in grey after I looked at the cost of the orange-colored ones!
only thing the orange isolated recp, is it lets you add a extra ground for protection.
That (color) does not have anything to do with it being used for a dedicated ground.
That means that it has an isolated ground.
The grounding pin on the receptacle is isolated from the metal mounting strap. The metal mounting strap and metal box are grounded through witth the building grounding system often conduit.
The isolated ground wire is run for the ground connection on the receptacles.
Edited 7/25/2004 10:46 am ET by Bill Hartmann
What in the world does...." That does not have do with it be used for a dedicated ground " .... Swahili maybe?
Bill, if you would, work me through this; was is the difference between an "isolated ground" (receptacle) and grounded receptacle which is required on a single-receptacle 20A circuit. Thanks for the help.
The single receptacle used on a dedicated circuit is basically just 1/2 of the common duplex receptacle. The metal mounting strip, ther ground contact hole and the ground screw are all connected together and when installed are also connected to the metal box and conduit or BX if used.
All of the metal acts as an antenna.
An isolated ground system is used for "sensitive" (female <G>) electronics in electrically noise areas. There is not practical reason for them in a home.
The isolated ground receptacle the ground contact is connected to the grounding screw terminal. The metal strap (and screw for the coverplate) don't connect to anything else. AFAIK (but I have never worked with one) they are only to be installed in metal boxes. That ground the strap through the box and conduit/bx.
The equipment that is plugged in connects to the grounding contact and through the ground terminal to a separate ground wire that is run back to the main grounding bus bar or some other electrically quiet place.
http://www.hubbell-bryant.com/training_files/ig.asp
Not too many years ago Isolated Ground, IG, receptacles were all the rage. Install a circuit for electronic cash registers and the company specing out the installation insists on IG receptacles. A major PITA if they also spec that the power comes from a sub-panel. Or, worse, a series of sub-panels.
As you know to get the full benefit and meet the spec the IG has to be run back to the first point of disconnect. Feeding the #12 conductor through endless conduits while everything is live can be quite entertaining.
Never mind that engineers and experts on the subject assert that the IG system is worthless on most single phase systems and of little benefit for well maintained three-phase systems depending on what loads are present. A lot of this is simply from the KYA school of construction specification.
Once went on a job that the consultant claimed that the repeated glitches on the networked computers would only be eliminated with a full installation of IG receptacles on everything. We were looking at a pretty big project time wise. We dug around a bit and solved 95% of the problem by tightening and cleaning ground and neutral connections. Basic electrical maintenence techneques. Little more than a screwdriver needed. A multi-thousand dollar project reduced to an afternoons work.
When absolutely necessary IG receptacles are grand. In new construction they can be sometimes justified by the possible advantages in relation to the slightly higher cost of the installation. As an upgrade they are often a waste and almost conpletely useless on single phase systems where a dedicated circuit will do as well at less cost.
"Once went on a job that the consultant claimed that the repeated glitches on the networked computers would only be eliminated with a full installation of IG receptacles on everything. We were looking at a pretty big project time wise. We dug around a bit and solved 95% of the problem by tightening and cleaning ground and neutral connections. Basic electrical maintenence techneques. Little more than a screwdriver needed. A multi-thousand dollar project reduced to an afternoons work."
My background is an an electrical engineer, but for a long time I am done mainly software for embedded microprocessors. Anything over 5 volts is "high voltage".
The way that I work varies depending on the client. For this job I sketched out a rough circuit showing the processor, menory, and interface. My client, designed all of the interface details, power supplies, packaging and manufactured the equipment. It was in turn a sub-contract from a company that makes damppening systems for printing presses.
So I am usually out of the electrical problems, but often get called in to solve problems such as verifying stored data on a low voltage shut down or sampling a signal several times to filter out noise.
In this system we had a local control pannel on each press position on a news paper presses and it connected to the spray bar on that press position. Each press tower would have several of these system and ther would be a string of several press towers.
There was a single central control pannel that connected to all of the local control pannels with a twisted pair, differential signaling systme. They where daisy chained from one unit to the next one.
The system worked fine until the presses started up. Then the central pannel would not talk to any of the other ones. But all of the local pannels worked normally.
Well they claimed that it was an electrical noise problem. Tried all kiinds of things. Brought in electricans, changed out power supplies, check all of the press motors, etc, etc.
For some reason I just stuck in go up to look at it although as I said electricions are not by specialty anymore.
I put a scope on the signal lines. Looked great until the presses started. Yes, there was noise, but it did not look like any electrical noise that I was familar with.
Started dividing up the daisy chain and it started working. Connected that leg back and it stopped. Keep trying it at different places until I found the unit that was causing the problem.
The ELECTRICAL NOISE was caused by a few strands of wires that not under the connector scew and when the presses ran they viberated and touched the case.
My view is that in electrical work most problems, even the ghosty ones, are solved by paying attention to the basics. Cover the bases and most problems disappear.
Bill and 4LORN, thanks for the input and clarification.
I guess my finally question is, can the isolated ground receptacles be used in a more standardized application of a dedicated 20 A circuit? Again, thinking for the reason of using them (say in a double gang box) to indentify a dedicated circuit on a wall where perhaps there are other receptacles (15 A or otherwise)?
Functionaly or safety wise there is nothing wrong with doing that.
I would have to read the code, but I suspect that it is not legal unless you run the separate ground wire. IE, it is not used as intended.
BTW, there are a number of othe colors that you can get to ID a special purpose receptacle. Black and gray come to mind, but I think that you can get them in yellow and red also.
For some reason I thought the orange ones were the ticket; obviously not. ;-) I ended up going with grey like I outlined above because the orange (isolated grounds) were too expensive!
I'd have to read code too, and don't think on my final inspection anyone would have caught the misuse of the isolated ground receptacles.
>> BTW, there are a number of other colors that you can get to ID a special purpose receptacle.
Could you point me to a source for these? I've gotten no useful results at all Googling for colored receptacles.
http://www.hubbellcatalog.com/wiring/
or
http://www.hubbell.com/
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming.... WOW!!! What a Ride!
Thank you kindly.
And thanks to Bill Hartmann, too.
Cooper has some.
There web sit is a little hard to use because you keep drilling down and select options. If you go far enough you can download a PDF catalog, but I haven't found it this time.
http://www.cooperwiringdevices.com/catalog/SubCategory_line_item.cfm?Sub_Category_id=1095&SubCat_Parent_id=1055&type=child&Category_id=1050&Product=Y
Any way in the commericial series ($2.00) they have
BR15A 15 Amps Almond 5-15R 125
BR15BK 15 Amps Black 5-15R 125
BR15B 15 Amps Brown 5-15R 125
BR15GY 15 Amps Gray 5-15R 125
BR15V 15 Amps Ivory 5-15R 125
BR15LA 15 Amps Light Almond 5-15R 125
BR15W 15 Amps White 5-15R 125
BR20A 20 Amps Almond 5-20R 125
BR20BK 20 Amps Black 5-20R 125
BR20B 20 Amps Brown 5-20R 125
BR20GY 20 Amps Gray 5-20R 125
BR20V 20 Amps Ivory 5-20R 125
BR20LA 20 Amps Light Almond 5-20R 125
BR20W 20 Amps White
And in their commerical ($4.00) series they add red
http://www.cooperwiringdevices.com/catalog/SubCategory_line_item.cfm?Sub_Category_id=1076&SubCat_Parent_id=1075&type=child&Category_id=1050&Product=Y
Orange and green also..
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming.... WOW!!! What a Ride!
Isolated ground receptacles can be used for every day use. I think that Bill is right, sounds right but I haven't searched the code for an official answer, that they have to be installed with a real isolated ground.
My question is: Why?
I have never seen a residential situation where there was any benefit to having an isolated ground. A simple dedicated circuit for the computers and attached equipment accomplishes the same thing, at least if it is in a 120/240v single-phase residential system where the dedicated circuit is run off of the main panel, at substantially less cost.
I think the only place where isolated grounds are really important is medical equipment, and then generally the equipment has an external ground connection to a "patient grounding bus".
Note also the 15A and 20A receptacles have the same internal construction, and can both pass 20A from one set of terminals to the other (i.e., wired in series). It's just that the 20A receptacles will accept 20A plugs.
The ony 15A's this may not be true for are the really cheap ones that will only accept 14AWG wires on stab-in connectors (no screw terminals), whic can't be installed on 20A circuits since they don't accept 12AWG wire.
The reason 15 amp outlets are allowed on 20 amp circuits is not all that strange when you think about it. No appliance that draws more than 15 amps can be plugged into a 15 amp outlet because the plug won't fit due to the different configuration. So, you can't, for example, plug in a 17 amp load which would exceed the rating of the outlet yet not trip the breaker.
Thanks Guys... this is good feedback and makes me feel better.
My current client had some troubles with the wallplates literally having burn marks and starting to melt (she had a 1200W portable heater plugged in) and I wanted to blame the receptacle. My reasoning was that the receptacle was the "weakest link" because it was only 15A - when otherwise the receptacle would have held its own and caused the breaker to trip (versus burn marks).
So it sounds like in this case it was really just a matter of a cheapo plastic wallplate - she has little ones so it was one of those Safety 1st deals with the built-in sliding shutter to cover the slots. But it was very thin plastic and maybe one a little less flimsy would've held up better. No matter - anything leaving burn marks or melted plastic is BAD to me no matter what the cause.
Thanks for clarifying the code on this one... I'll go back and re-read that section just to reinforce it in my head. I should've known that it couldn't possibly have been everyone else was wrong and I was right (I try to save that for only special occasions! ;o)
Cheers,
Jcd
Plastic cover plates, even the cheap ones, should not melt. If they do something is definitely getting too hot. Most likely the cause of the excess heat is a worn or defective receptacle. With time the receptacles will no longer firmly grip the plug. In extreme cases you see plugs falling out on their own or not working unless you wiggle them a bit.
This loose connection can easily cause enough heat to melt any plastic close to it. While tinkering with the plug or receptacle can often squeeze another days service out of the situation it isn't safe. Replacing the receptacle is the best solution.
One or more defective connections going to the receptacle could also cause excessive heating. Redo the connections after eliminating any damaged insulation will correct this. If the receptacle only has push-in connections replace it with one with screws or clamping devices that uses a screw.
The heaters plug could also be defective. Commonly the wires break internally within or behind the plug itself. Installing a replacement cord-cap of the same type will get things working.
I prefer Bakelite cover plates. They won't melt even if the receptacle goes completely ballistic. They are also a bit stiffer and so often seal tighter to most walls. Their weakness is that they crack if hit or over tightened. Better to eliminate the source of abuse but plates that get beat can be replaced with nylon plates. More flexible they often fit less tightly, sometimes leaving unsightly gaps, and in extreme situations they might melt but they absolutely won't crack.