How to Wire a 220v Outlet.
posted March 31, 2008 - 1:29pmHow to Wire a 220v Outlet.
Electrical wiring can be a real challenge, especially if you know nothing about how it all works. One weekend I got to learn first hand how to set up and connect a 220v outlet for use
with my brand new air compressor. Here is my story.
I was already pretty familiar with normal 110v wiring and have completed several installations. However, my first attempt at wiring 220v yielded some shocking results.
Lesson 1 - DO NOT Connect the red and black 110v wires together, that will not create 220v. What it will do is pop your circuit breaker.
When wiring 220v there are two possible ways to wire up your receptacles. One way is with 4 wires and the other is with 3 wires. For my application I wassetting up an outlet for general use with my 220v air compressor. This compressor required wiring 220v on at least a 15amp circuit. The compressor did not come with a plug end wired to it,and it had only 3 wires running from the motor.
In my garage I already had an existing 4 wires that were connected to a 15amp "ganged" double pole circuit breaker and routed along the garage door header and over to the corner, where they were left just hanging down the wall about 2 feet from the ceiling. Personally I really didn't like this unfinished circuit that the previous owners had left, but I didn't know how 220 worked and I didn't have anything to wire into it either. So I left it all as I had found it, until I acquired a new air compressor and now had a reason to learn how to wire a 220v outlet.
Pictured below is my service panel and a second picture of my panel with the service cover removed. The double breaker I used for this installation is the one on the upper left, the black wire goes to one terminal and the red wire to the other. Ground and common go to the bus bar (upper right in the second picture).
Garage Breaker Panel
Garage Breaker Panel (Service Access)
NOTE: When connecting wires of different colors (e.g. in the picture above a blue wire was used for a ground, see how it has been marked with green electrical tape to avoid confusion.) be sure to mark wire substitutions appropriately with electrical tape in the colors they should represent. In the case of my panel shown above, everything is as I found it when I bought the house. So, it may or may not be correct. One thing for sure, see the wires coming into the box at the lower right corner? They should be secured, not just running through a hole in the box. But that is another story.
In order to make this work for my application I needed to extend the wires further down the garage wall and then attach and wire in a box and receptacle. I also would need to install a plug end on the compressor's 10’ cord. So, off to the local hardware store where I bought some grey pvc conduit, a 90 degree bend, a 90 degree splicing box, a receptacle box, a cover plate, and a 250v 3 wire receptacle, 4' of red wire & plug end.
There are several styles of 220v receptacles available depending on what you are going to run with it. I chose one that was the size of a standard outlet with 3 prongs. 1 for ground, 1 oriented vertical , and 1 oriented horizontal. This way it will prevent anyone from accidently plugging in a standard 3 prong 110v plug end.
It is important to note that your wires should be no smaller than 12 gauge. I used 10 gauge wire for this application.
A QUICK NOTE ON WIRE GAUGE: 10 gauge wire is heavier than 12 gauge wire, 8 gauge is heavier than 10 gauge and so on
How 220v works with 4 wires: (one wire to each)
1 Black wire carries 110v
1 Red wire carries 110v
1 White wire acts as a common
1 Green wire acts as a ground
1 Black wire carries 110v
1 Red wire carries 110v
1 White wire acts as a common
1 Green wire acts as a ground
How 220v works with a 3 wires:
1 Black wire carries 110v
1 Red/White wire carries 110v (if you use white flag it with red electrical tape)
1 Green wire acts as a ground/common
1 Black wire carries 110v
1 Red/White wire carries 110v (if you use white flag it with red electrical tape)
1 Green wire acts as a ground/common
(If you have 4 wires in the wall, but you are wiring them to a 3 prong receptacle, connect the green wire to the green "ground" screw on the receptacle or if no ground screw is present, attach this wire to one of the receptacle mounting screws. That way if the common fails, you still have the added protection of a ground)
Because I already had 4 wires coming from the panel I extended them as follows: I attached green to green (ground), black to black (110v), red to red (110v) and white to white (common)Then attached them to the receptacle. My receptacle did not have a ground screw so, I attached green to the mounting screw between the receptacle and the plastic box.
Once the wiring was complete, a volt meter was used to test the voltage at the receptacle. Mine read in at 239v, which would be considered normal. So with the receptacle installation complete, that only left the plug end to be installed on the compressor’s cord. Which was a very straight forward process of connecting 3 wires to 3 terminals in the plug end. Once complete all worked beautifully.
IMPORTANT NOTE: It is my opinion that you should avoid running romex wire through electrical conduits. Due to it’s potential to overheat, melt, and possibly cause a short or a fire! Not even through just a few feet of PVC conduit. I have found it in my own garage and it can be a real danger. I have pulled apart 3-4' lengths of PVC conduit and found half melted romex right near the breaker box. If you are running conduit, use individual wires.
220v Receptacle in Box
Pictured above is the finished installed outlet . . . not much to look at, but I'm proud of it.
DISCLAIMER: IF YOU ARE NOT COMFORTABLE WITH ATTEMPTING TO WIRE 220v CIRCUITS DO NOT HESITATE TO CALL IN A PROFESSIONAL, OR SOMEONE WHO IS VERY FAMILIAR WITH THIS PROCESS. MISTAKES WITH ELECTRICITY CAN CAUSE SEVERE INJURY AND SOMETIMES DEATH. FOLLOW MY ADVICE AT YOUR OWN RISK.
FC4J
Last Updated: 12/7/2009 to address best practices and comments as seen below.
Author:
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Comments
Volt Meter
First get a volt meter and check the power at the 60 amp double pole. If it is good there. Check it coming into the box that houses the 15 amp breaker.
If it is good coming into that box, check the 15amp breaker and it's connections.
If it is dead coming into the box where the 15amp breaker is. Consider replacing the wire, as it is likely broken, or shorted, etc...
can anyone help me here
I was going to install a 15amp double pole breaker for a 220 outlet for air compressor. When I open my breaker box in the garage I found that the black side is dead no power, there are 2 breakers in this box they both run of the red side. I checked and replaced the 60amp double pole breaker that sends power to my garage thinking the breaker was bad on one side, but no luck still no power to the black side of the breaker box any suggestions.
you make me nervous
Never assume anything about electricity. I am NOT a certified, registered, licensed, electrician for residential by any means. However, I am an industrial electec and have been for 40 + years, military and civilian. I've dug into a panel box or two. If you have any doubt, call a pro. BBB and Chamber of Commerce can help. It could mean your house, life or family.
power cord to connect 220V out from a generator to well pump
I need to connect the 4 prong 220V output from a generator to a 3 prong well pump plug in. How do I know what wire goes to each contact on each end? The plug in for the 220V looks like this: Ground(D-shaped opening) is at the top. Lower left is a slot running vertical and the lower right is a vertical slot with a horizontal slot off to the right.
You make me Nervous!
The outlet you have pictured is a 125V 18amp outlet. On a 220V outlet the right prong is horizontal.
So Much Wrong....
Ok,
Stranded wire - What I used appeared to match what was run, but maybe what was run was wrong to begin with.
Spliced Ground - Maybe, I have no idea if the ground was spliced or not, as the box pictured represents the wiring as I found it when I opened it.
Unsecured entering wires - Yep. Left it as I found it, until I made time to reconnect it with a box-clamp a few months down the road.
No GFCI breakers - were in the box, so I did wire in GFCI outlets on most frequently used circuits at my make shift workbench.
Inappropriate Receptacle - The receptacle used in the application was rated for 220v.
Future Home inspections - Home inspectors are not going to site lack of GFCI in a circuit depending on the year the structure was built. Other than that, they should have something to say about unsecured wires entering a box. (wonder why mine didn't)
A couple of hundred dollars for a competent electrician - Yes. When I wrote this article I did not have a couple hundred dollars for an electrician, nor did I have an extra $4 for a couple more feet of wire. There are those that live paycheck to paycheck and have literally no means to afford a professional. I acquired the compressor as a gift.... installing it was up to me. I am better off now, but that is a whole series of other events....
So, what else can I say. I guess if anything people who read this article can do 2 things. 1) Learn from my mistakes and 2) Truly assess if you would like to try to tackle this type of project. If you could afford a pro, I am sure you would not be trying to look up how to do it yourself.
Use my advice at your own risk.
FC4J
there is so much wrong with some of the info here, stunning
Please don't follow these techniques. There are some REALLY bad practices here.
just a few:
reusing the stranded wire from the compressor cord to extend the circuit (was $4 too much to spend on wire?)
what looks like (but I hope isn't) a splice to extend the ground in the breaker panel
code violations in the panel itself (multiple entries, not secured)
no GFCI breakers (hard to believe NONE of the outlets require them)
Inappropriate receptacle (what do you think will happen to your (or the next owner's)) lawn trimmer when you plug it into that 220v?
this "homeowner style" of electrical should raise a HUGE red flag with any competent home inspector and make the sale of this home unnecessarily difficult
BUT MOST OF ALL, bad electrical can burn this structure down, putting your home and your NEIGHBORS' homes at risk.
It should only cost a couple of hundred dollars to have an electrician add a receptacle where you already have the capacity on the panel. PLEASE call one.
Safe Advice Is Not So "Bad Advice"
Hi All,
I suppose a bit of a response is in order here.
To answer your first question "KingD" my qualifications in electrical are that of a DIY novice. I have lots of experience in running 110v circuits, switches, doing fan installations, and running boxes, outlets, etc.
As I clearly stated in my article this was my first attempt at wiring 220v.
Now on to the more important question of Derating and running romex through conduits.
My statement that says it is "just plain wrong" is not entirely accurate and deserves further explanation.
Since this is written by a novice and generally for use by a novice I guess we had better start with a basic definition of "Derating". After all, I had to look it up in-order to intelligently respond to your comment.
Derating - Is a specified reduction in the output power at elevated temperatures to improve reliability.
Now in order to address the issues of heat inside of a conduit when running romex through it. One would need to consider the diameter of the conduit. The number of lines being run through it and the loads of the circuits on said lines. You must factor in the potential for overload, and when your romex is running an electrical outlet, there is nothing you can do to guarantee that the outlet will not be misuesed and overloaded. A general consensus in electrical forums is that there is no regulation for running 3 conductors through a conduit, I can not confirm if that is absolutely true.
Rather than try to address the various aspects and methods of safely running romex through a conduit, although possible and not necessarily against code, I still feel it is a much safer practice to just not do it.
Thank you for helping me to bring additional value and accuracy to my article's content.
If anyone else cares to comment with additional helpful information please feel free to do so! :)
FC4J
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bad advice
What are your qualifications in electrical? You have no idea what your talking about. You indeed can put romex in Conduit wether in the outer jacket is stripped off or not. If you choose to leave the outer jacket, you must derate the wire.
No, I did not give bad advice.
The advice I have dispensed is sound and has likely helped a few thousand people get the job done.
It is possible the picture is not a 220v receptacle. But it is a dead on accurate depiction of the plug configuration that I installed on my compressor and on my wall.
So please, when you are throwing stones, throw them gently.
FC4J
FreeCracker4Jack Join the ranks of starving amateur writers competing for your attention and praises! SIGN UP HERE
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