Garage subpanel

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  #1  
Old 09-19-05, 04:37 PM
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Question Garage subpanel

Just need some help interpreting a subpanel in my garage. I can comprehend 120, but I am unsure if there are different rules for 240.

The subpanel has three wires coming into it: black, white, and bare copper. The voltage across the white and black is 240. The black is attached to one side of the subpanel, white to the other, and the copper to the grounding bar of the box.

On the subpanel are two 30 A breakers. One controls a 240 V heater and one controls this wire with electrical tape over the end that is just dangling in a cabinet. I checked and this dangling wire carries 120 V. The white neutral from the 120 is attached to the grounding bar of the subpanel. There is no neutral back to the main service panel.

Is this allowed? If not, is there a way to use this existing setup to get 120? (Short of running a new wire?)

Thanks!
 

Last edited by Gizzorge; 09-19-05 at 06:31 PM.
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  #2  
Old 09-19-05, 05:31 PM
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No its an installation that shoud be replaced ASAP, if you want power to the location.You can use the same wire for 120v but you must change the 2 pole breaker to a 1 pole breaker at the main panel from where this circuit is fed.The black wire is terminated at the new 1 pole breaker & the white wire must be terminated on the neutral bar { with the other white wires in the panel}.One very important thing is that the breaker you use must be the right type for the panel & be of the right size for the gauge wire you have {i.e 15 amp breaker for 14 AWG, 20 amp breaker for 12 AWG}.If you are at all uncertain with what to do then I would call a pro.The sub-panel can be done away with & receptacles &/or lighting put in.
 
  #3  
Old 09-19-05, 06:36 PM
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Hi,

I edited my post to make it a little bit more clear on what was where. This garage subpanel is actually fed off the AC compressor circuit from my main service panel, so I can't really switch wires around. It was wired (I think) for the heater in the garage. The compressor breaker in the main panel is a 40 A double-pole.

The other circuits in my garage that control the lights and outlets are branch circuits fed from the main panel.

Also, I reread your post, and I gotcha now. If I remove the dangling wire that carries 120 V, is the subpanel correctly wired for 240?

My main reason for investigating this is to see if I really need this subpanel in the garage. I plan on installing a 120 or 240 V heater and need the power supply, but I just don't know if I need a small subpanel for just the heater!

Any thoughts would be appreciated!
 
  #4  
Old 09-19-05, 11:20 PM
elect_fireman
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Smile Sub-Panel

The way you have described the wiring in the garage is kind of scary. If you really want to have that kind of power in your garage I would suggest that you remove the wire coming from the compressor and run a new feed to the sub-panel. If you are adding to the exsiting load you might want to consider increasing the size of wire. I would suggest a #8/3 wire. It has three wires inside it. (a black, red, and white) The bare wire is not counted when ordering wire. When you hook it up to a double pole 40A breaker, the black and red wires go to the breaker and the white goes to the neutral buss (along with the others white ones). The bare (or ground) wire connects to the body of the panel. You will get 240V between the black and red wires and 120V between either the black/white or red/white wires.

Hope this helps
 
  #5  
Old 09-20-05, 02:37 AM
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Question Sub-panel

Originally Posted by elect_fireman
The way you have described the wiring in the garage is kind of scary.
You're not the first person to say this. This garage was added on after the house was built, and it's pretty obvious that no one inspected it. I had a mixture of 12 and 14 gauge wire, hot neutral and ground wires purposely wired that way, wires supporting hanging light fixtures, and the list goes on. I'm taking care of what I can and learning about stuff so I can get it taken care of later.

That's why I want to investigate this subpanel. The wire used for the 40 A, 240 V circuit from the main panel is 12/2 throughout, and the wire on the subpanel 30 A breakers is also 12/2. I am surprised this place is still standing after 20 years of bad wiring...
 
  #6  
Old 09-20-05, 04:38 AM
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Is this a detached garage or an attached garage?

If this is an attached garage then you must replace the wire from the main panel to this sub panel. The sub panel, to be correct, requires four wires from the main panel to the sub panel so that a separate neutral and ground can be provided.

If this is a detached garage then you need to move all the lights, receptacles and such to the sub panel and then correctly wire the sub panel, which would be best fed with a four wire circuit.

Either way, the setup needs attention.

As far as the other things you mentioned are concerned, they need attention as well. The circuits that are 12 gage wire with larger than a 20 amp breaker need to be redone. With 12 gage wire the largest breaker you can have is 20 amp.

I recommend that you immediately turn off power to the sub panel until you fix it properly, including getting it inspected, and that you turn off any improperly wired circuits from the main panel until they are repaired as well.
 
  #7  
Old 09-20-05, 07:39 AM
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Originally Posted by Gizzorge
The wire used for the 40 A, 240 V circuit from the main panel is 12/2 throughout, and the wire on the subpanel 30 A breakers is also 12/2. I am surprised this place is still standing after 20 years of bad wiring...
You absolutely need to tear that stuff out and replace it; there is no other option with the number of problems with your subpanel feeder. I recommend you cease to use it and disconnect it now.
 
  #8  
Old 09-20-05, 08:16 AM
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Originally Posted by racraft
Is this a detached garage or an attached garage?
It's an attached garage.

As for turning off the circuits, the circuits that power the receptacles and lights have been off. I have also turned off all the breakers on the subpanel already, too. I don't like to take chances.

I can't turn off the feed to the subpanel from the main service panel because the breaker also serves my AC compressor, and it's in the low 90's right now. Does an AC compressor need a dedicated circuit, or can I get a subpanel off of this that just runs the garage heat in the winter? Thanks for the help, folks.
 
  #9  
Old 09-20-05, 08:26 AM
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Originally Posted by Gizzorge
Does an AC compressor need a dedicated circuit, or can I get a subpanel off of this that just runs the garage heat in the winter?
The A/C needs a dedicated circuit seperate from the subpanel feeder that is sized properly just for the A/C compressor motor. Putting a heater on this circuit is not possible.

You should turn off the A/C for an hour or two and disconnect the subpanel feeder from the A/C circuit. You have safety hazards which need to be addressed ASAP in my opinion.
 
  #10  
Old 09-20-05, 09:28 AM
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Smile Thanks!

I will try to find where they made the connection and disconnect it. I really don't need the subpanel in there anyway.

Thanks for the help, everyone! I greatly appreciate it. For all I know, your advice could have saved my life or house!
 
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