Garage Sub Panel Problem

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  #1  
Old 10-14-13, 02:44 PM
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Garage Sub Panel Problem

My garage sub panel has wiring for 240 volts coming off a 40 amp breaker at the house. The old sub panel was a very old 70 amp that I replaced with a 100 amp sub panel.

I was wiring an outlet and I accidentally put the breaker in a slot that wasn't knocked out. I didn't feel like knocking another panel out in order to keep it looking clean, but what I didn't realize is that it would deliver 240 to that outlet now. So, the outlet popped and I hit all the breakers to see what I did wrong. I turned the known good breakers on one at a time and checked the voltage and they appeared fine reading ~120 volts. The one that I just wired now read ~240 so I immediately shut it off and moved it 1 slot down and checked the voltage which was now at about 120.

Everything seemed to be okay, except I decided to shut the breaker off and check the voltage with my multi-meter and it reads about 90 volts with the breaker shut off. This concerned me so I started to work backwards towards the house, first hitting the main breaker in the sub panel which didn't eliminate the 90 volts but hitting the breaker at the house does kill it.

I've spent some time reading over forums about what could be wrong, and it seems that it could be faulty grounding or something was damaged when I put 240 to that outlet. There is a ground for the sub panel that was used for the previous sub panel but I don't know how far underground it goes or if it's attached to anything. When I plug a battery backup into an outlet it displays a wiring fault, which according to the owners manual, indicates there is no ground.

The other thing that I checked with a multi-meter is the power coming into the garage. I placed the tips on each of the screws of the 100 amp breaker and I'm only reading 120 volts which makes me think something was damaged further up along the line, unless I'm not checking it correctly.

Sorry for the wall of text. I have pictures of everything that I can post, including the wiring from the house if needed also. Any help/comments are appreciated, even if it is to call an electrician ha!
 
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  #2  
Old 10-14-13, 03:03 PM
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A single pole breaker can not give 240 volts regardless of where it is plugged in. Please post the pictures. http://www.doityourself.com/forum/li...-pictures.html
 

Last edited by Tolyn Ironhand; 10-14-13 at 05:20 PM. Reason: fixed typo
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Old 10-14-13, 03:09 PM
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Here is a picture of the sub panel. Originally, I had the bottom right breaker up one more slot and that's when the outlet popped. I've been going slow trying to make sure I'm doing everything right so if there are things that look bad please tell me.
 

Last edited by McMania; 10-14-13 at 04:16 PM.
  #4  
Old 10-14-13, 04:25 PM
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I went out and checked the voltage at the sub panel from the house and this is what I am seeing. Reading the black and white gives 120 volts, reading black and blue gives me 120 volts and reading blue and white is giving me 240 volts.

This makes me think that the colors aren't correct from the house. That would also explain how I was able to send 220 to that outlet as well. Unless I'm thinking about this wrong, shouldn't reading black and blue give me 240?
 
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Old 10-14-13, 04:48 PM
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Makes sense. You need to open the house panel. There should be a black and blue on the breaker.
 
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Old 10-14-13, 05:25 PM
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Ray is correct. Black and blue should be connected to the breaker that is feeding the subpanel. The white should be connected to the neutral bar.

I doubt you damaged the receptacle in any way by putting 240 volts to it unless it is a GFCI device.

You have a few other issues. You can not just have wires running through a hole into a panel like that. With individual wires you are required to install them in conduit, and the conduit needs to be continuous. I think I can see flex conduit in the hole but you need a connector.
 
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Old 10-14-13, 06:15 PM
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That appears to be a Siemens copper bus main lug only panel with a backfed 100 amp main breaker, but I don't see any main lugs. Did the panel come with the 100 amp breaker factory installed? If you added the 100 amp breaker, it needs to have a main breaker hold down kit installed. The Square D Homeline breaker (top right) shouldn't be used in that panel.

I didn't feel like knocking another panel out in order to keep it looking clean, but what I didn't realize is that it would deliver 240 to that outlet now
I don't see how that would be possible unless you were using a 2 pole breaker. What kind of meter are you using to check votage?
 
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Old 10-14-13, 07:32 PM
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Tolyn Ironhand-
I replaced the outlet that breaker was on, it was the only thing wired. The sub panel is on a hollow cinder block wall that had a hole punched out for the wiring to go through the wall. So what you're seeing is part of the cinder block wall and part of the wood it is mounted on. The outside has conduit feeding up to this hole, but the hole doesn't have anything. I have posted a picture of the outside portion.

CasualJoe-
You're correct with the panel, it was factory installed too. The hold down piece I broke today trying to get it out so I will need to replace it. I'll yank the Square D breaker as well, didn't occur to me that different brands would cause an issue although it does make sense now. I'm using a fluke multi-meter if I remember correctly. What I think is happening is that the wires coming into the garage from the house are not color coded correctly and I assumed they were. I think that the blue and white are wired hot and the black is neutral. That would explain why I'm reading 240 between the blue and white and only 120 between the black and blue.

I'm going to pull the panel at the house off tomorrow and see what's going on. If the wires aren't color coded to being black/blue hot and white neutral I might have an electrician fish me new wire from the house.

Thanks for all the responses, I want to do this correctly but it's like trying to drink from a fire hydrant!

The wiring is coming in from the left of the door.
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  #9  
Old 10-15-13, 12:07 PM
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Pulled the panel off at the house and it seems that I was right about the colors being weird. At the house, the black is the neutral with blue and white being hot. I don't know why it was wired like this but it was my fault for assuming the wires were correct. Whoever wired it originally tried to color on the wires at the house, but didn't mark them at the garage.

As of right now, I'm thinking of having new wiring fished to the garage which is color coded correctly. Thanks for all the input and help.
 
  #10  
Old 10-15-13, 01:02 PM
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By code blue and black are acceptable as the ungrounded conductors (hots). Is there any writing on the wires that tells you the type and size of wire? What size breaker in the main panel? Can you give us a close up of where the conduit enters the building?

You can probably use the existing wire and panel with the addition of a ground rod to the subpanel.
 
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