electriction advice/education for needed detached garage


Hi all,
I have a detached garage that the former owner built and wired. He ran 12 gauge (it might be 10) romex 2 conductor + ground through a pvp pipe underground (about 60 feet) to the garage. At the source it's double lugged to a 220 60 amp breaker (servicing the dryer) with the bare ground wire acting as neutral, at the garage it's split (using wire nuts) into two 120 circuits in a junction box at the garage.
I since added a panel at the garage end, back feeding the input line to a 30 amp double pole breaker then distributed to four 120 v garage circuits (2 for outlets and 2 for lights) via 15 amp breakers.
The service (source) end junction box I'm talking about only handles 220. There are six 60 amp breakers in this box, servicing the dryer, a/c, heater, stove, water heater, and the house panel.
In the house the neutral and ground are connected via a metal bar.
When adding the junction box in the garage, as I untangled the 'rats nest' that was his original connections, I saw that he had twisted together all the ground wires from the receptacles and lights but they did not actually connect to anything except each other.
Wanting the ground plug to be connected to a ground, I did some research and found that normally a 4th ground wire would be run from the service panel to the remote building, but I had only three wires, two hot and one neutral. Research revealed that if the remote building had no other metallic connection to the main site, that is no phone, water, cable, nothing, then it was acceptable to drive a ground rod at the remote building and to bind the netural and the ground (assuming local code required ground and netural bond).
My detached garage meets this requirement, so I dorve an 8 foot ground rod and attached it with heavy gauge copper wire to the netural of the incoming feed at the panel in the garage.
Now when I put a 12 amp load on the garage circuit (a window a/c unit + lights) I measure 3 amps at the ground rod.
So 3 amps of the 12 amps (25%) is returning to ground through the ground rod instead of the neutral wire.
My question is this:
Why am I seeing current at the ground rod?
How concerned should I be?
Keep in mind this circuit operation for 15 years with no problems before I installed the panel or the ground rod.
Is the reason because the neutral wire is not of sufficient gauge to carry the current back the 60 feet to the main panel and back to the neutral coming from the electric company?
This made me think further about the ground rod of the house. Forget the garage, in a normal home wiring setup when electric code mandates the ground and neutral be bond at the service panel, I would expect to see current flowing through the ground rod as well. My reasoning is that the current has to return through the neutral (assuming no fault in the circuit) and when it arrives at the service panel it has a choice of returning through the electric company neutral or the ground. Electricity will flow through the path of least resistance, and logically I think the ground rod would offer the least resistance - the wire length is shorter to the ground rod than to the transformer on the pole.
However when I measure the current on the house ground rod it is zero.
Why is this? How is it that all the house current will flow to the pole neutral and none to the ground?
Could someone please educate me on what I am missing here?
I know the ground rod is a safety backup for the electric company neutral, and ideally would not carry any current, but I don't understand why, when they are bound at the service panel, the ground rod would not have at least some current like I'm seeing in my garage setup.
Thanks.
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It sounds as though your wiring is in complete violation of the National Electrical Code. #12 wire is rated for 20 amps and should have a 20 amp circuit breaker protecting it. The three wire plus a ground rod set up for a detached building is no longer permissible under the 2008 code. You need the four wires. Using the bare wire in the cable as a neutral is not allowed. You are seeing current on the ground rod because you do not have a good neutral connection. The ground and neutral must be separate at a subpanel. That connection together is only made at the main panel or the meter. Romex is not approved to be used underground even though it is in a pipe. You need to use conductors such as THWN or type UF cable in your PVC pipe. You are not seeing any current on the ground rod connected to your main panel (Assuming it is connected properly) because you have a low resistance neutral conductor to carry the current back to the transformer.
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Well, yes. That all sounds correct. Thanks.
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So if one has an older detached garage with only 3 wires running is it safe? It has been this way since 1942....
I wanted to replace the fuse panel with a breaker box and was going to add a ground wire near the garage - I guess this is not good to do.
kpg wrote:

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The dude wrote:

Any time you update pretty much anything in a structure, you're required to update all affected systems to the latest code requirements. Whether you can get away with replacing a fuse panel without replacing the wiring is a question for the guy who will do the inspection. You do know you'll have to have an inspection, don't you? Few areas let you get away with wiring changes on your own any more.
Call the permit office in your town, and ask them what they require.
--
Steve Bell
New Life Home Improvement
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SteveBell wrote:

I will have to see, I am not in town. I am in a rural area.
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The dude wrote:

Well, you might be one of the exceptions. :) Call the county.
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The dude wrote: ...

We're outside the City "3-mile limit" so no permits. County would "like" them, but no legal requirement. No inspections either way. YMMV, of course.
3-wire feed was Code-compliant until relatively recently so I personally wouldn't worry about the panel switch out--I've done some of the farm outbuildings for the purpose of adding an additional circuit or three from the one or two that were run originally and where there was no expansion room, either in the original box.
--


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So 3 wire is no longer code, it must be 4. So what about in my case where the line is run from the main panel (the meter and a bunch of 220 breakers) and no ground is present here. The ground is in the house 'sub' panel.
How would I run 4 wires from this panel????
(I guess I could be wrong about no ground being at the meter, but my memory is that there is none. I'll check aging later when I get home.)
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*The same way the three wires are run. Pull out the existing from the conduit and pull in new wires. If the conduit is a complete run from box to box, I suggest that you just pull in individual conductors instead of a cable. It will be easier and you can pull larger wires.
What size is the conduit?

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In the land of the unfree, and the home of the brave. How'd we let ourselves get so regulated?
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