Replies

1. 
   oldsub86 | Feb 21, 2007 08:30am | #1

   I think we need more information to be of much help. Generally, #8 wire is good for 40 amps. #10 is good for 30 amps. #12 is good for 20 amps etc. 220V may or may not need 3 conductor wire. 100 feet is quite a long run. You should probably get some "expert" advice from your local electrical inspector or a qualified electrician based upon what sort of an air conditioner you propose to use and what load you can expect it to draw.

   Randy

2. 
   jeff100 | Feb 21, 2007 10:56am | #2

   Here's my advise. I do a lot of 'backyard' wiring, my dad was an electrician and taught me when I was a kid. I know enough to handle most jobs in a residential home and don't think twice about doing my own work. To date I've hooked up one residential service, and installed two sub panels in two different shops I built for myself. But here's my advise...

   No matter who does the work, get a permit, and have the work inspected. Anything I do I have inspected, and since I'm NOT licensed, I can only work on my own home, and I respect that restriction.

   Permits are relatively cheap in my state (Washington). Homeowners can legally do their own work although inspectors don't like it and frown on it, and man do they look at your work closely, but in my mind, that's a good thing to have happen. By getting a permit and getting the work inspected, you will absolve yourself of any liability if God forbid anything goes wrong and the house burns down AFTER YOU SELL IT. If you don't, and things go wrong, it can really come back on you.

   Be safe....Jeff

3. 
   bill5335 | Feb 21, 2007 09:01pm | #3

   I would pull a permit and then talk to the inspector before I bought the wire. One resource might be to call your State Board of Electricity. 

   Since you are going 100 feet you will see a voltage drop due to the length of the wire.  For example, a 10 gauge wire 100 feet long will have a voltage drop (at 10 amps) of 2 volts.

   I think FWW had a chart with wire gauge and lengths.  (It was probably 15 years ago.)

   You will need three conductors, 2 hot, 1 ground.  220 is nothing more than 2 - 120's added together.   

1. 
   Rich14 | Feb 21, 2007 10:29pm | #4

   bill,

   Technically, 2 hots and a ground is not 3 conductors, it's 2 conductors and a ground. The ground is not an insulated wire and is not intended to conduct current. If it ever does conduct current, there is something wrong.

   A 220 volt circuit can consist of 2 conductors (black and red) plus a ground. Another option is to pull 3 actual conductors (black, red and white) plus a gound. The white conductor is connected to the neutral bus at the breaker box and conducts current when the circuit is between itself and either of the black or red conductors. Such a circuit is 110 volts and is useful when the 220 volt device requires 110 volt control circuitry (such as a stove or dryer). The gound is always used in such wiring. Again, the ground wire is not a current conductor.

   Rich

1. 
   cscwem | Feb 22, 2007 12:08am | #6

   you beat me to it....but exactly right

   I would just add that sizing circuits and distribution should be based on the draw of the device.  until you know that  there is no point doing anything.  Once you know that just about any decent book on wiring will tell you what size wire you need to run over a given distance.

4. 
   DaveRicheson | Feb 21, 2007 11:43pm | #5

   Need to know what the listed amp rating is for the a/c unit. As a general rule 100' is the limit for voltage drop for any specific guage wire. After that you need to calculate voltage drop and adjust the wire size accordingly.

   Is this a window unit or split system. Other code things come into play if it is a split system.

   BTW, I'm a licensed Master Electrician in KY.

    

   Dave

    

5. 
   dukeone | Feb 22, 2007 01:44am | #7

   Steve: The nameplate on the a/c unit calls out the load and also the circuit ampacity. The name plate is law in a way as the NEC says you must provide the circuit it calls for. It may even specify fuses or circuit breaker and to be totally legit you must do what it says. If it is a split unit you will need a 3/R (raintight) disconnect at the condensing unit (the outside part). The other advice is good: get a permit and ask the inspector all the questions you come up with, then if you decide it is over your ability level get professional help.

   Duke

   Support the Troops, Support your Country

   Support Western Civilization:

   Fight Islamofascism

1. 
   DaveRicheson | Feb 22, 2007 01:12pm | #8

   Depending on loacl code, he may also need a 120v outlet within 6' if an outside condenser unit, for a split system.

   Asking an inspector what they want is ok onlView Imagey up to a certin point. After that, most of them figure you don't know enough to be doing your own work, or you are trying to use them instead of hiring an electrician.

    

   Dave

    

1. 
   dukeone | Feb 22, 2007 06:14pm | #9

   Dave: You are right, I forgot the one about the convenience outlet for the servicing of the unit.

   DukeSupport the Troops, Support your Country

   Support Western Civilization:

   Fight Islamofascism

6. 
   jeanlou | Feb 22, 2007 06:30pm | #10

   "This is a serious matter, please don’t lead me wrong."

   So far you have received honest feedback, but your finishing statement tells me that you do not necessarily trust the information you will be receiving...so I ask myself why do you want to ask this question to a bunch of Knotheads?

   My suggestion to you is, if you really want to do the work yourself, to pay a local master electrician for a consult. He will meet with you, tell you everything you need to know, and then you pull the permit, do the work and have it inspected...and you will sleep like a baby instead of tossing and turning as you wonder if the information you were given is according to the rules and regulations of the jurisdiction you live in.  JL

1. 
   Joe Sullivan | Feb 22, 2007 07:11pm | #11

   Good advice from Jeanlou.I had a rather more involved wiring project to do. I got quite a bit of advice, especially over on on the Breaktime forum that you can get to by clicking on the name at the top of the Taunton banner. There are a half-dozen electricians over there. I used this (excellent) advice when noodling through my project, BUT I still consulted a Master Electrician before actually laying it our and starting work.I was in the electricl supply business for a long time and am not a novice. Still, the more I learn about electricity, the more I realize I don't know. And, what you don't know can do real harm.

1. 
   jeanlou | Feb 22, 2007 07:24pm | #12

   Joe

   I appreciate your story, because I have also done similar things in the past. Where electrical work is concerned, I am extremely cautious, because I can honestly say that a raging fire is one of the things I do not want to have to deal with.  JL