Replies

1. 
   Peter36 | Dec 19, 2004 12:05am | #1

   I would wonder if it was the panel or the cord. You could try plugging something other than the cord in to see which one it was.

2. 
   bones | Dec 19, 2004 12:30am | #2

   I would suspect a dead short. Throw that breaker. Use a multimeter. If you do not have one, big boxes have them. Get one that can check both voltage and continuity.  I would first (with the breaker off!) check to make sure that the two hots and the ground are still open. By selecting the Ohms on the multimeter, you can see if the circuit is open or closed. Generally on the meter you will see a 1 and when you touch the two probes together, the reading will go to 0, indicating a closed loop. If you plug the probes in and get a 0 (assuming this is a dedicated circuit and no other outlets in between) you have a short somewhere. You will need to track it down.  Check each leg and the neutral. If no short is present, check voltage.  Check each leg for 120. Put the positive probe in one of the hots, and with the negative touch the ground. You should see 120 (or close). Repeat with the other hot. Finally put the probes in the two hots and make sure you have 240. If that appears ok, then check your breaker box.  Good luck. 

3. 
   budreaux | Dec 19, 2004 07:40pm | #3

   Where is your neutral return?  220 volt circuits should be 3 conductors plus ground.  Ground and neutral are not the same.  120v + 120v + Neutral + Ground. Each 120v leg must come from a different phase as well, otherwise you just get 120v. You cannot use 120v 20 amp plugs and receptacles either. If you were using 220 v plugs and receptacles you would have an empty lug the way you have described hooking this up.   You should get a volt meter and verify readings prior to plugging anything in.

   Your ext. cord should be 12/3 + ground.

   
   

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   Edited 12/19/2004 11:42 am ET by treefreak

1. 
   Peter36 | Dec 19, 2004 08:01pm | #4

   Residential 220 volt wiring has 3 wires. 2 hots 110volts each and a neutral. Neutrals and grounds all go to the same place. A ground is there to ground the box.

2. 
   jako17 | Dec 20, 2004 06:32am | #10

   Just a couple of observations,the 240 v residential supply is single phase.Secondly you don't need a neutral (take a look at 240 v baseboard circuits).You are assuming that ALL 240 v is wired as a dryer circuit which as stated by others contains control circuits operating at 120v which need a return.

   Edited 12/19/2004 10:42 pm ET by jako

4. 
   Stuart | Dec 19, 2004 08:01pm | #5

   It isn't totally clear what the situation is...I take it that you have a 240 receptacle that you knew was okay, but then you built a 240 extension cord, plugged it in the 240 receptacle and that popped the circuit breaker.  Without being able to see things with my own eyes all I can imagine is you got a couple wires crossed when you built the cord, or it has some bare insulation someplace allowing the wires to touch each other.

   In general terms a 240 volt device only requires the two hot leads and a ground.  If that device also uses 120 volts (an electric kitchen stove is a good example, it has 240v heating elements along with 120v controls), then a neutral wire is also required.  As was pointed out by someone else, make sure the ground and neutral connections aren't mixed up.   Also make sure to use plugs and receptacles designed for 240 volts, so someone doesn't accidentally try to plug a 120 volt device into it.

5. 
   SawdustSteve | Dec 19, 2004 08:24pm | #6

   Check that you did not cross the White (second leg) and the Green (ground) wire. It's a common mistake when rushing to do this kind of job. You can easily check it out with a continuity tester (ohm-meter)
   SawdustSteve

6. 
   Peter36 | Dec 19, 2004 10:47pm | #7

   As a relevant example- if you run your table saw on 220 you only have 3 wires coming from it. You cut your neutral from the supply and cap it and connect the green ground from your saw to the copper ground of the supply.

1. 
   MikeMD | Dec 20, 2004 01:03am | #8

   I'm wondering if in the extension cord it's possible to "cross" the wires, is there a left and a right to an extension cord? I checked the grounds they were correct, but the white and black could they potentially cross?  Since white is hot and black is hot do they have respective sides?

1. 
   budreaux | Dec 20, 2004 02:02am | #9

   Doesn't matter.  Make sure you didn't get a strand that went stray.  Sometimes one of the strands can stick out and cross over to another lug.  If you have a meter you can check this by checking for a short between wires.  What are you hooking to the ext cord?

7. 
   JohnWW | Dec 20, 2004 07:15am | #11

   A few questions:

   1. If you plug a tool directly into the wall outlet does the tool run properly when you turn it on?

   2. If you plug the new cord you made into the the same wall outlet used for question #1, with nothing plugged into the other end of the cord, do you get a short circuit?

   3. If you didn't get a short circuit with the cord alone (as in question #2) do you get a short circuit when you plug the tool from question #1 into the cord and then plug the cord into the wall?

   4. Did the problem disappear after the first time you plugged the cord in, so that the cord works properly now with a tool connected to it?

   Depending on the answer to these four questions it should be possible to determine the cause of your problem.

   John W.