Circuit to nowhere

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  #1  
Old 09-18-06, 06:27 AM
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Circuit to nowhere

I have a home in Austin, TX which was built in 1986. It has a main breaker panel on the outside of the house with a sub-panel in the garage. I need to run a 220, 30 amp circuit to the garage for a welder. The sub-panel is most convenient, but I think it only supports 110v. There is a tandem, 220, 50 amp breaker in the main panel which seems to go nowhere. When I turn it off, I can find nothing that looses power. I've accounted for all the usual 220 equipment: AC, range, sub-panel, dryer, etc.

So my question is: Could it have been common practice to install a spare, unused circuit for future use? If so, where would the cable be routed to? Any suggestions for how to find it? All wiring is in the attic (no basement).

Thanks
 
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  #2  
Old 09-18-06, 06:51 AM
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Is this garage attached or detached?

If thye agrage id detached, then you can't run another circuit to it. You could replace the existing circuit, but not run a second circuit.

I find it unlikely that a 120 volt sub panel would have been run. Why do you think the panel in the garage is only 120 volts?

When you say a 50 asmp tandem breaker, what do you mean?

If you feel comfortable doing this, open the panel, see if wires are attached to the 50 amp breaker, then follow them as best you can. Any wire connected to a 50 amp breaker SHOULD be much thicker than wires attached to regular 15 and 20 amp breakers. It should not be too hard to find this wire in the attic and follow it.
 
  #3  
Old 09-18-06, 07:05 AM
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Another good reason for panel schedules. Always mark the breakers as to their use when you install them.
Do you have Grinder Pump sewage systems in Austin? If so, you will have a sewer pump located in a tank somewhere on your property. This could be a use for the 50A circuit.
If the 50A breaker has wires attached to it, it was put there for a reason, you need to find out why before you convert it to some other use.
steve
 
  #4  
Old 09-18-06, 11:37 AM
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OK I'm using the wrong terminology. When I said "tandem", I should have said 2-pole. It is a 2-pole, 50A breaker, and the wires are large and stranded. Upon further checking, I found that the circuit is for a furnace, but I have a gas-fired furnace. I could use the circuit for my welder, but as it turns out, don't need to. Read on.

The garage is attached. But I was wrong about the sub-panel, it is a 120/240V, 125A sub-panel. I see now that by proper placement of a 2-pole breaker, both high sides can be picked up, and it will support a 30 amp breaker, even though they are all 20's now. I have exactly 2 open slots, but I'll have to move one of the breakers to allow for the 2-pole breaker to be mounted where it will pick up both high sides. As for running the extra wires, I think I can:

1. Disconnect power to the sub-panel at the main panel
2. Remove the 4 screws holding the panel to the wall studs
3. Pull the panel out enough to fish the new wires from the top wall plate and through one of the openings in the top of the panel.
4. Install the new 2-pole breaker.

Does this sound about right?

Final question: For a 30 amp circuit run of about 45 ft., can I use 10 guage?

Thanks for your help!

Tall Texan
 
  #5  
Old 09-18-06, 11:55 AM
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What you are stating now makes perfect sense.

Yes, a 30 amp circuit can be 10 gage wire for a distance of 45 feet.

However, make certain that 30 amps is the correct value for the circuit. You might also want to consider a larger size wire, to allow for a larger welder in the future.
 
  #6  
Old 09-19-06, 05:00 AM
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On that 1 pole breaker that you're going to move.....follow the wires back to where they enter the panel and make sure that it is a 2 wire circuit (black and white wire). If there is a (red?) third wire (3 total plus ground) in this circuit, it may be a connected as a multi-wire circuit. If it is, then you must be careful as to where you place that breaker on the buss.
post back.
You're correct in this point....TURN THE POWER OFF before removing the cover and doing any work! ELECTRICITY CAN KILL!
steve
 
  #7  
Old 09-25-06, 06:49 AM
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steve,

Thanks for the post. Yes, the breaker I'm planning to move is a two wire circuit which supplies only the refrigerator.

I'm an electrical engineer and I worked many years with and around electricity before retiring, so I know the dangers. But so many novice DIYers don't know the hazards, so your warning was appropriate and much appreciated.

Thanks

talltexan
 
  #8  
Old 09-25-06, 07:32 PM
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Why would you need to dismount the panel?
 
  #9  
Old 09-26-06, 09:11 AM
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I have to pull a pair of wires through the top stud plate and into the panel. I don't know how to fish them through both the stud plate hole and the panel opening without having access to the top of the panel. Is there a way to do it without pulling the panel?
 
  #10  
Old 09-26-06, 09:48 AM
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Originally Posted by talltexan
I have to pull a pair of wires through the top stud plate and into the panel. I don't know how to fish them through both the stud plate hole and the panel opening without having access to the top of the panel. Is there a way to do it without pulling the panel?
Yes. First thing to consider is that there is not likely to be alot of slack in those wires when you pull the panel you could be causing damage.

You can drill a hole down from the top hoping that you don't nick a wire, then drop a string and chain down to the panel. Use a scrap bit of wire with a hook on the end to catch the string. Then tie the new wire to the string and pull in. This is much easier with two people.
Last use a snap in romex connector to hold the cable in place.
 
  #11  
Old 09-26-06, 01:43 PM
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Complicating things is the fact that it is an insulated wall with insulation batting. I have a standard electrical fish, which is fairly stiff, but going through insulation, it is hard to predict where it goes, and it is hard to fish out with insulation in the way. I've always been working through a standard outlet box hole, and that can be difficult enough, but through a romex hole will be challenging. Since it is a garage wall, I may just cut an access hole in the sheetrock above the panel, and make a screw-on cover for the hole. I think I can cut off a scroll saw blade for my power scroll saw to limit the blade travel to the wallboard thickness to minimize damage to the wires. Any better idea for how to cut the opening?

Thanks
 
  #12  
Old 10-02-06, 02:40 PM
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Success! I decided to avoid the problem by putting the outlet below the panel and between the same studs as the panel. That way, I didn't have to penetrate any studs or plates. I also took the recommendation to upgrade the circuit for future needs and so used a 40A, 2-pole breaker and AWG 8 for the short 5' run. With a 35', 10 guage extension, I will be able to reach any point in my garage with the welder, which BTW only requires 230V/20A, so I should be fine with the 10 guage.

And yes hillbilly ace, I disconnected power to the sub-panel at the main before doing any work!

Thanks to all who offered advice.
 
  #13  
Old 10-02-06, 07:51 PM
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Cool

TEX, I'm glad it all worked out.
However, Contrary to popular beleive. Sometimes a hammer is the best "cutting" tool. Done correctly, it will never nick a wire.

And the hole has always been patched. Without a trace.
 
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