12-2 vs 12-3


  #1  
Old 03-06-05, 04:58 PM
Mangi
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12-2 vs 12-3

I am renovating my basement and have run most of the wiring for lights, outlets and an electric heater (not purchased yet). My question is, can all of these fixtures run on 12-2 wire? I plan on putting separate 15 or 20 amp breakers for each of the three. Or can 12-2 only handle 15 amp breakers?
Home Depot told me to re-run the line for the electric heater with 12-3 bec. it is for 20 amp and thats the minimum I can use.
I would also love any advise on whether I'm better off hooking up an electric Modine heater instead of electric baseboard. It's for my garage workroom and I would imagine the modine would heat it up a lot faster. Any suggestions welcom.
Mangi
 
  #2  
Old 03-06-05, 05:13 PM
R
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12-2 cable is three wire cable, all 12 gauge. One conductor is black, one white, and one is bare (no insulation). Except for a switch loop, the black is used for the hot wire and the white is used for the neutral. The bare wire is always a ground.

12-3 cable is four wire cable, all 12 gauge. One conductor is black, one is white, one is red. and one is bare (no insulation). Except for a switch loop, the black and red are used for hot wires and the white is used for the neutral. The bare wire is always a ground.

If you are running 12 gauge wire for your lights and receptacles, you can use 20 amp circuit breakers. You can also use 15 amp circuit breakers, but I would not unless a 15 amp breaker was explicitly called for.

"Home Depot told me to re-run the line for the electric heater with 12-3 bec. it is for 20 amp and thats the minimum I can use." This statement does not make sense. Ignore it. The advice you get from any of those stores is not always correct. 12-3 and 12-2 are both for 20 amps.

However, you MAY have the wrong wire for your heater, or you may have it connected improperly. What is the voltage and current requirement for this heater? Is it a 120 volt or 240 volt heater?

If it is a 120 volt heater you will need x-2 wire. The "x" will be determined by the current requirements of the heater, and you will need an appropriate 120 volt circuit breaker.

If it is 240 volt heater, you will most likely need x-2 wire. There is a slight possibility you will need x-3 wire (if the heater needs a neutral). A standard baseboard heater needs only two conductors (plus ground). Again, the "x" and the breaker rating will be determined by the current requirements of the heater. However, in this case you will need a 240 volt breaker.
 

Last edited by racraft; 03-06-05 at 05:57 PM.
  #3  
Old 03-06-05, 08:12 PM
Mangi
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Thanks Bob. I haven't purchased a heater yet so I will probably buy a 240 volt as I hear they are more energy efficient. Should I re-run the line for the heater or can I get buy with the independent 12-2 I already ran?
Also, I plan on having three switches for 3 separate light runs. Do I need to run an independent power feed for each switch to the panel or would a 12-3 handle two of those power feeds. I'm trying to reduce the amount of wire run through the joists...
THanks,
John
 
  #4  
Old 03-07-05, 04:27 AM
R
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Mangi,

Reread my descriptions of 12-2 and 12-3. I'm not sure you are following the difference. There is no need for you to use 12-3 at all unless you plan on 3 way switches or need to have switched and unswitched power in the same cable.

If all three sets of lights are on the same circuit breaker then you only need one power run from the panel.

Don't buy or install cable for your heater until you have bought the heater and know it's requirements. 12-2 may be appropriate for it. However, it is possible that you need 10-2.

May I make one other suggestion. It sounds like you are very new to this. Please purchase two or three books on home wiring and read them. There are many little things that you need to know for a job like this. If you have already run cable you may have made a mistake or two.

When working with electricity you don;t want to make mistakes. Mistakes can cause death or fire. Neither of those are pleasant.
 
  #5  
Old 03-07-05, 09:55 AM
Mangi
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THanks again Bob. I appreciate your advise and you are correct that I am very new to this. I am planning on hiring an electrician to hook all of my wiring up at the end. I'm pretty sure that I'm following code thus far.
John
 
 

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