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Old 04-01-2010, 12:54 AM   #1
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Question about a 20amp popping on me.


Replacing/repairing electrical supply at my detached garage. We recently had a powerful snow storm that damaged the two black load and ground wires going into the garage (above ground).

Prior to the damage this was the set up and everything has been working fine (prior to the storm): From the house the Main has the garage on a double 50 Amp pole breaker; with two copper #4 black and copper #4 neutral that feed up to the service above my house (this is new wiring installed about three years ago by our electrician). From here it ties into #4 (I presume it to be something close to #4; the black and neutral wire is 16 gauge/7 strand bundle...it's the original wiring that travels from the house to the detached garage (about 150 feet) that was installed in the 70's) aluminum two black and one neutral. The aluminum (two black wires) were tied into a 16 guage/7 bundle (black) copper feed that feed into the box in the garage along with the aluminum neutral. The box in the garage just has a 20Amp and a 15amp breaker only. The 20 Amp breaker has two 12/2 attached. One of the 12/2 goes to 4 receptacles (nothing plugged into them) and the other feeds the garage door, two outside lights, a security light and three receptacles (nothing plugged into them). The 15Amp goes to two banks of lights (4 florescent bulbs) only.

I have recently repaired the storm damage with new copper #4 tied into the existing overhead aluminum wiring (as it is coming from the Main to the overhead). The box in the garage now has two black #4 and the neutral aluminum replaced with #4 copper. When I turned on the power at the Main and flipped the switches on, the 15 Amp had no problems, but the 20 Amp keeps popping as if it is overloaded. Just to be sure I didn't have an electrical issue with the 12/2 wiring I switched out each one to the 15 Amp breaker and everything worked. Could the 20 amp breaker be damaged? Or did changing the 16 gauge/7 bundle to modern #4 overloaded the 20 amp breaker? At any rate, would I be OK if I just put the existing 2 12/2 on separate 15 Amp breakers or do I need to split the two lines exiting from the 20 amp breaker into two separate 20 amp breakers?

Any help/suggestions would be appreciated.


Last edited by AlDaja; 04-01-2010 at 12:59 AM.
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Old 04-01-2010, 01:01 AM   #2
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Question about a 20amp popping on me.


sounds like it's most likely the breaker....or somehow the load has changed. You can most definately install two new 15a breakers and tie one wire into each of them. You can install two 20's as well. Either way is legal.

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Old 04-01-2010, 01:04 AM   #3
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Question about a 20amp popping on me.


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sounds like it's most likely the breaker....or somehow the load has changed. You can most definately install two new 15a breakers and tie one wire into each of them. You can install two 20's as well. Either way is legal.
Ok, so probably a breaker...would stepping down to the 15 Amp have any issues when I run my table saw or compressor...I usually don't have more than one item running at a time.
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Old 04-01-2010, 01:05 AM   #4
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Question about a 20amp popping on me.


i should probably point out though that there's certain measures that need to be taken when connecting aluminum with copper. Also you could have ran 6's instead of fours for the copper lines. Oversized wires never hurt anyone though .
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Old 04-01-2010, 01:08 AM   #5
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Question about a 20amp popping on me.


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Ok, so probably a breaker...would stepping down to the 15 Amp have any issues when I run my table saw or compressor...I usually don't have more than one item running at a time.
you'll have to physically check the draw of each motor. There should be a silver plate on the motors that will tell you the amperage of them. most table saws are under 12A...the compressors probably got about a 3/4 HP motor on it so that would be fine too....but as i said double check the plates to make sure what each motor draws.
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Old 04-01-2010, 01:12 AM   #6
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Question about a 20amp popping on me.


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i should probably point out though that there's certain measures that need to be taken when connecting aluminum with copper. Also you could have ran 6's instead of fours for the copper lines. Oversized wires never hurt anyone though .
I mimicked how the electrician tied into the existing aluminum, so I hope my install will fare well (any pointers/cautions I should be aware of, please let me know). I just used #4, cause that was what the electrician at HomeDepot suggested.

Yeah, I did check the motor plates and the table saw was 12 amps...the compressor I couldn't read it (worn off) but it is very small and only goes up to about 50-60 psi.
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Old 04-01-2010, 01:13 AM   #7
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Question about a 20amp popping on me.


How exactly is it connected?
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Old 04-01-2010, 01:18 AM   #8
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Question about a 20amp popping on me.


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How exactly is it connected?
From overhead the aluminum to copper is using a splicer (coaxial is striped and the bare ends go into either side and the screw tightens, holding them the ends in place, then wrapped with rubber tape and then electrical tape over it).

I should add, that I tried to be sure that neither metal touches...the splicer I used has a semi divider in the center to keep the two wires separate to avoid corrosion.

Last edited by AlDaja; 04-01-2010 at 01:25 AM.
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Old 04-01-2010, 01:28 AM   #9
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Question about a 20amp popping on me.


not sure what code is on that....always thought it had to be in a junctionbox but my residential knowledge on code isn't the best...there's others that can answer better probably.
My main concern is that any time you splice aluminum with copper you have to use and approved device to do so and generally you need to give it a good coating of nolux as well if any part of the copper actually touches the aluminum. The reason for this is that the connection will oxidize and fail over time. Aluminum and copper don't agree with each other. If the splice is legal in the way it's done and i'm asuming it is because an electrician did the job then once those steps are taken to protect the different wire types the rubber tape is a good idea with the electricl tape...for my own personal preference i would have put a chunk of shrink wrap over top of the whole thing as well just for some piece of mind.
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Old 04-01-2010, 01:34 AM   #10
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Question about a 20amp popping on me.


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not sure what code is on that....always thought it had to be in a junctionbox but my residential knowledge on code isn't the best...there's others that can answer better probably.
My main concern is that any time you splice aluminum with copper you have to use and approved device to do so and generally you need to give it a good coating of nolux as well if any part of the copper actually touches the aluminum. The reason for this is that the connection will oxidize and fail over time. Aluminum and copper don't agree with each other. If the splice is legal in the way it's done and i'm asuming it is because an electrician did the job then once those steps are taken to protect the different wire types the rubber tape is a good idea with the electricl tape...for my own personal preference i would have put a chunk of shrink wrap over top of the whole thing as well just for some piece of mind.

Yeah, I didn't use nolux...but I'll have to keep an eye on it. Like I said, it's above ground (30') so If I start seeing scorching on the electrical tape around the splice then I'll know I'll need to replace it with something specific for the job; if it's going to oxidize, I'd rather have it do it up in the air than in my box on either end and burn the building to the ground. I'm hoping it will last me for awhile. The splice put in three years ago seems to be ok...I'm more concerned with why the 20 amp breaker was snapping when it wasn't having issues before.

I do appreciate you addressing my question. I ran my table saw and miter saw on the outlet that feeds from the side of my house and it's on a screwy 15Amp set up and nothing seemed to happen, so I think tomorrow I'll go and purchase a couple of 15Amps and just split the draw.

Last edited by AlDaja; 04-01-2010 at 01:48 AM.
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Old 04-01-2010, 01:43 AM   #11
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Question about a 20amp popping on me.


there wasn't a problem before because it was aluminum on aluminum wiring.....you have to use an approved copper to aluminum splice or else if the connections fails and bad things happen your insurance in null and void. It could fail fairly quick or it could last forever...depends on how much air can get at it.
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Old 04-01-2010, 02:00 AM   #12
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Question about a 20amp popping on me.


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there wasn't a problem before because it was aluminum on aluminum wiring
Nope, to clarify, I replaced older spliced copper to aluminum (have no idea how long it was like that, at least three years, which is when I bought my home) with my own copper to aluminum. The only constant was the aluminum neutral to the garage (which I have since replaced), but now the only aluminum is up in the air between both entry caps. From the splices, all copper feeds into the Main at the house and the box in the garage.

...At some point when I get a moment, I need to just replace that 150' with copper and be done with it. I'm at the moment just trying to get service back to my garage. I'm hoping putting two new 15amp breakers in tomorrow will solve my 'popping' problem. I'm no electrician, but I'm guessing as you suggested that the load changed somehow. I know that aluminum wiring needs more area to pass current than copper...I'd assume that #4 being such a larger feed would compensate. Could that be the reason that 20 Amp circuit was popping? More current than the original splice allowed? I noticed the #4 copper has a smaller gauge but a larger bundle than the 16 gauge/7 wire bundle copper that was originally spliced. I should note that the current aluminum line is also like the original copper wire with 16 gauge/7 bundle.

Last edited by AlDaja; 04-01-2010 at 02:26 AM.
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Old 04-01-2010, 07:45 AM   #13
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Question about a 20amp popping on me.


Andrew, I think the OP has the splice at the overhead triplex. What concerns me is whether this is now an unmetered service and the OP talks about some #16 ga. wiring.

The barrel splicer may have been filled with a compound from the factory. I don't normally use that style so I don't know for sure. Just basing that on the Polaris style connectors.
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Old 04-01-2010, 10:22 AM   #14
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Andrew, I think the OP has the splice at the overhead triplex. What concerns me is whether this is now an unmetered service and the OP talks about some #16 ga. wiring.

The barrel splicer may have been filled with a compound from the factory. I don't normally use that style so I don't know for sure. Just basing that on the Polaris style connectors.
The meter is at the Main. It is also as I stated a overhead service (not underground). City code for my area allows for either under or overhead to detached garage/out buildings. The original wiring that was used was a 16 guage - 7 strands of it in a coaxial. Apparently, they no longer sell this. So I spliced with a #4 from overhead to the garage, as the original electrician did from my Main (at the house) to the overhead.
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Old 04-01-2010, 10:41 AM   #15
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Question about a 20amp popping on me.


If one breaker in the barn works, and the other does not work, it has to be a bad breaker or a shorted load on that breaker.
Nothing you did feeding the barn will cause a downstream breaker to trip.
You need to disconnect the wire on the breaker and start looking for the short.

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