Wiring for AC window unit

Reply

  #1  
Old 06-17-01, 09:23 AM
Visiting Guest
Posts: n/a
Question

Wiring 24,500 BTU AC.(230volts) 3 prong plug (ground prong and two horizontal prongs) I have a 10/3 wire running from outlet box to panel box-4 wires (black, red, white, green) What amp outlet and what amp double breaker do I use? I have a receptacle that matches the plug but it is 20 amps and I think I need a 30 amp double breaker. Can this be done or must I try to find a 30 receptacle? Or can I use 20 amps for both?
An electrician told me that the two hot wires go into the breaker (black and red) and the green goes to the bus bar and forget about the white wire altogether. I read the same thing in another post explaining that no 120 is going to the ACondit so the neutral is not needed.

[Edited by brockb on 06-17-01 at 07:43]
 
Sponsored Links
  #2  
Old 06-17-01, 01:40 PM
Visiting Guest
Posts: n/a
Always match the recptacle to the cord plug and never tamper with the cord plug.If the rating of the receptacle that accomodates the cord plug is 20 amps it's adequate.You can use a 30 amp breaker with #10 branch-circuit wire.You mention "10/2" and "black","red" "white" "green"-3 current-conductors and an insulated ground.What exactly is the type of cable your using.Check the cable jacket for identification.
 
  #3  
Old 06-17-01, 04:39 PM
Visiting Guest
Posts: n/a
Oops! It is a Romex 10/3 with ground...not 10/2. With a 10/3 coming from a 30 amp circuit breaker shouldn't I have a 30 amp receptacle so that I do not have to pigtail the wires at the receptacle? The AC unit is 11.3 amps so I should have to have a 30 amp circuit--right?
 
  #4  
Old 06-18-01, 08:08 AM
Visiting Guest
Posts: n/a
Match the recptacle to the cord plug,not the branch-circuit conductors.Connect the red,black, and green to the terminals and tape around the recectacle to insulate the terminals.The terminals will accept #10 wire.You were astute in determining the full-load current=11amps which means the wires will conduct only 1/3 of their ampacity.I advise a 20-amp CB but a 30 would not be a code violation.There is an over-current device in the unit that will open the circuit if a mal-function causes excessive current-this protects the AC, not the branch-circuit CB.
 
  #5  
Old 06-18-01, 02:52 PM
Wgoodrich
Visiting Guest
Posts: n/a
You will have to install 12 ga pigtails on that 10 ga. wire reducing it to the wire size approved by UL to attach to a 220 volt 20 amp receptacle that is matching your A/C unit. Do not install a 30 amp breaker on that 10 ga. wire. The receptacle must be rated to match that A/C unit. Then the breaker must match that receptacle's ampacity rating if that receptacle is a single outlet.

The requirements in the NEC are as follow;

210-21-B-1 minimum single receptacle rating related to a branch circuit am rating. Check with UL or your manufacturer's instructions as required in 110-3-B considering using larger that 12 ga on a 20 amp rated receptacle. The breaker must have an ampacity not exceeding the device it serves 210-20-D.

Hope this helps

Wg
 
  #6  
Old 06-18-01, 03:10 PM
Visiting Guest
Posts: n/a
Ok, I have several differences of opinion from a lot of sources. I now have a 20 amp double pole breaker and a 20 amp receptacle that matches the plug on the air conditioner. I can either leave the 10/3 wire or replace it with 12/3. Replacing the wire is not difficult at this point. I have been told that I do not have to pigtail it and that I do. Those who say I do not have to pigtail it think that a 10/3 wire is not excessive. What is the purpose of the pigtailing if the 20 amp receptacle can take two hot wires and one ground?
I am so confused! LOL
 
  #7  
Old 06-18-01, 03:44 PM
Wgoodrich
Visiting Guest
Posts: n/a
You said;
Ok, I have several differences of opinion from a lot of sources. I now have a 20 amp double pole breaker and a 20 amp receptacle that matches the plug on the air conditioner.

Reply;

Your right so far.

You said;
I can either leave the 10/3 wire or replace it with 12/3.
Replacing the wire is not difficult at this point.

Reply;
You will not be using the white wire of the 10/3 that would contain a black, red, white, and bare wire in that cable. If you install a 12 ga wire then you would most likely install 12/2wGrnd. Again your A/C unit will not be using a neutral conductor.

You said;
I have been told that I do not have to pigtail it and that I do. Those who say I do not have to pigtail it think that a 10/3 wire is not excessive.

Reply;
Try emailing Underwriters labrotory. They will adamantly tell you that connecting a 10 ga wire to a 20 amp receptacle is a violation of both the UL rating, the manufacturer's recommendations, and the NEC. 110-3-B. You should also look at the brand name of your receptacle and type in http://www.enter the brand name and then add .com. Find the email sections for questions and email them for confirmation of this requirement also if you like. Or you should find it on the manufacturer's recommendations that are listed for that receptacle.

You said;
What is the purpose of the pigtailing if the 20 amp receptacle can take two hot wires and one ground?

Reply;
The 10 ga wire is much stiffer than the 12 ga wire. The size of circumference of the wire is larger than the screws are designed to receive. If you install the 10 ga to screws approved only to accept 12 ga which your 20 amp receptacle is listed for you stand a good chance of a loose connection causing heating problems or fire hazard. When you shove that receptacle into the box you will be shoving on those lighter designed screws causing damage or the connections to loosen. If you do not install the reduction in wire size down to the size the device is designed to take and this starts a fire that cause damage to your house your insurance most likely will not pay for your damages due to your violating the UL listing of that device, the NEC requirements, and the Manufacturer's recommendations.




Table 210-24. Summary of Branch-Circuit Requirements

Circuit Rating 15 A 20 A 30 A 40 A 50 A
Conductors (min. size):
Circuit wires 1 14 12 10 8 6
Taps 14 14 14 12 12
Fixture wires and cords See Section 240-4
Overcurrent
Protection 15 A 20 A 30 A 40 A 50 A
Outlet Devices:
Lampholders permitted Any type Any type Heavy duty Heavy duty Heavy duty
Receptacle rating 2 15 max. A 15 or 20 A 30 A 40 or 50 A 50 A
Maximum Load 15 A 20 A 30 A 40 A 50 A
Permissible load See Section 210-23(a) See Section 210-23(a) See Section 210-23(b) See Section 210-23(c) See Section 210-23(c)



Your free white and 21. I gave you the rules that apply, and the locations or contacts to confirm what I am saying, its up to you. If you opt to ignore that advise, you will have to be knowledgable and strong enough to know the gamble you take and accept the losses if you loose that gamble. Remeber, your family's lives may be a part of your gamble.

My advise would be contact those people that I listed. UL, the manufacturer, or the copy of the Code above that I supplied. Be careful with that above chart. The numbers may shift when posted. If that happens, then ask someone to look it up in the NEC.

Your choice.

Hope this helps

Wg
 
  #8  
Old 06-18-01, 03:54 PM
Visiting Guest
Posts: n/a
I stand corrected in stating that a 30amp CB would not be a violation-this is a single-outlet circiut,so use a 20amp CB. As to the termination a 10-12 wire spade crimp lug might be used to avoid a pig tail.The lug can acccept a #10 wire and the lug connection to the terminal would be the same as if the lug was crimped to a #12.
 
  #9  
Old 06-18-01, 04:24 PM
Wgoodrich
Visiting Guest
Posts: n/a
Switchman, I disagree with your suggestion to connect a 10 ga wire to a receptacle designed and approved to accept a 12 ga. wire. The strength of the bending resistance of that conductor is stronger that the screws on the 20 amp receptacle is designed and approved to hold when installing that receptacle into its box.

Can you show me a manufacturer's recommendation to install 10 ga wire to a 20 amp receptacle device? Curious on that but don't know of one myself.

Maybe some others that normally reply in this forum will issue their input. Hope we can get an agreement between our two views then.

Till then

Wg
 
  #10  
Old 06-18-01, 07:06 PM
Visiting Guest
Posts: n/a
Wgoodrich: Your explanation of why I must pigtail or use 12 guage wire makes sense. It is always better when one know WHY something must be done. I think I will just replace the 10/3 with 12/2wgrnd. I am only going 4 feet down through the floor and 9 feet over and down to the panel box.
Normally I do not play by the rules but neither do I play with fire (or electricity)! LOL Thanks for your help and the great explanation. I will take your word for it since you obviously know the rules and what you say makes good sense.
Thanks!
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes