Adding ground to 2-wire house


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Old 05-03-09, 11:25 AM
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Adding ground to 2-wire house

I have installed a new 3-prong outlet and run the proper AWG romex back to the house breaker box. I have not installed the new breaker yet. Here is my question. The house is all 2-wire. Should I sink a new ground rod and install a ground bus in this box for the one new grounded outlet, and if I do that do I also bond the ground plane to the neutral bus inside the breaker box like I would in a new installation?

Thanks!
 
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Old 05-03-09, 04:19 PM
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Missing something here. You mention breakers, which suggests a breaker panel, not fuses, which implies that sometime ago, the panel was updated??? It should be grounded, unless the panel was installed in the 'way back' days. If it is not grounded, it should be, with a ground rod connected to the ground buss, which connects to the neutral buss in the main panel. Sub panels require the neutral and ground buss be separated.

You cannot install grounded outlets(3 prong) to a circuit with no grounding conductor.
 
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Old 05-03-09, 04:23 PM
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Is this the first disconnect in the house? Do you have a main breaker or disconnect on the outside of the house? Only bond the neutral and ground if this is the first disconnect point.
 
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Old 05-03-09, 04:57 PM
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Yes, this is the only breaker panel in the house. It is an old Federal Pacific breaker box that looks to be from the 50's that does not have any ground in it at all, and the house does not have a grounding rod that I can locate. The panel (100 amp service, it seems) is immediately downstream from the main disconnect and power meter. I just wanted to make sure it was kosher to drive a ground rod and add a ground plane to do a "upgrade" on the system and that I do not have to completely replace the box with a modern one - although that might be the better ultimate solution.
 
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Old 05-03-09, 06:39 PM
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The panel (100 amp service, it seems) is immediately downstream from the main disconnect and power meter.
Then it is a sub-panel and does not require a ground. The ground should be at the disconnect assuming it is a breaker or fuses.
 
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Old 05-04-09, 04:45 AM
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Ray is correct, except the panel Does require a ground, just not a ground rod. Drive the ground rod, better yet drive 2 about 6 feet apart and connect both of them together and to the grounding bus in the main disconnect. Then run a properly sized ground wire from the main disconnect to the load center inside and connect this to the ground bus that you will add. Only hook ground wires to this bus, and make sure that the existing neutral bus in this panel is NOT bonded to the case or any other equipment ground. Sometimes neutrals in older panels can not be isolated and panel replacement is necessary, check this before you start.
 
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Old 05-04-09, 06:18 AM
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Thank you both, that is exactly the information I needed. BTW the main disconnect is a fused knife switch.
 
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Old 05-04-09, 08:59 AM
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Just to correct my own post I meant ground rod not ground.
 
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Old 05-04-09, 02:50 PM
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You cannot use a Ground-rod to Ground the Equiptment Grounding Conductor (EGC ) of a cable. If the cable extends from the enclosure that contains the Service Dis-Connect , than the cable EGC connects to the Neutral.

If the cable extends from a panel that is supplied from conductors that "link" that panel to the Service , then the "Wiring Method" that is used to route the conductors between the Service and the "sub panel" must include an EGC. Arnored Metallic Cable , and Non-Metallic cable, are two approved types of "Wiring Methods."

You need to provide an exact description of the type of "Feeder" cable between the Service and the panel to be positively sure that the cable includes an EGC. It's most probable that it's a cable with three insulated conductors , and either Metallic , or Non-Metallic.

The relevant Code Articles --- 250.134 250.118
 
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Old 05-09-09, 08:57 AM
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UPDATE: the job is finished. The neutral in the sub panel was isolated from the metal case, so I installed a new ground bus in this panel and ran a new 8AWG copper conductor back through the metal conduit to the main disconnect panel and connected that to the existing ground. I was wrong the house does have two ground rods already, connected to the disconnect panel. I then wired my new circuit in the sub panel and all is well. Thank you all for the assistance.
 
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Old 05-09-09, 09:14 AM
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Originally Posted by DRY_CA View Post
The neutral in the sub panel was isolated from the metal case, so I installed a new ground bus in this panel and ran a new 8AWG copper conductor back through the metal conduit to the main disconnect panel and connected that to the existing ground.
I underlined a key part of info. Not saying you wasted your time but the metal conduit was your ground all along. It never hurts to have a redundant ground though.
 
 

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