Service Disconnect Wiring

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  #1  
Old 02-26-11, 10:42 PM
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Service Disconnect Wiring

Hi all! I recently had a service disconnect installed in my home and would like to know if it has been wired correctly. The electrician I hired seemed like he didn't know what he was doing and my lights now dim when the furnace kicks on...they didn't do this before! I'm thinking it might be a grounding issue. The service disconnect is directly below the meter outside the house which is grounded with the existing ground rod. Inside the house, the service panel was grounded to the city water pipe.
The electrician used 4/0-3 aluminum SEU to run from the disconnect to the main service panel inside. I'm pretty sure the bonding is correct in the disconnect (neutral to ground), but should there be an extra ground introduced in the service panel? He ran a 4AWG solid copper line from the inside service panel to the water line which wasn't there before. [IMG][/IMG]
 
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Old 02-26-11, 11:17 PM
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Dimming lights is not related to grounding. Some dimming is normal, but excessive dimming can have numerous causes. The most common is a loose connection, which can happen after service work. A call back to the electrician to retorque the lugs on the new panel may be necessary. It could also just be that the electrician reordered some of your breakers and now the furnace is on the same leg as the lighting which amplified the normal dimming effect.

The picture of how the panels are grounded you posted is pretty close to consistent with National Electric Code. The slight variation may be part of your local code or power company's policy. I don't see any obvious problems there. The ground to the water line should have been there all along, he was right to add it. The slight variation is whether the ground to the water line comes from the first panel or the second, but I honestly don't think it matters. I would need to review the code book to see if the way he did it was exactly right, but it is very close to how it should be.
 
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Old 02-27-11, 06:12 AM
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everything's right. 19 20 21 22 23 24 25
 
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Old 02-27-11, 08:48 AM
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The water line ground should have come from the service disconnect.
 

Last edited by pcboss; 02-27-11 at 09:51 AM. Reason: corrected bonding note
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Old 02-27-11, 12:59 PM
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Originally Posted by pcboss View Post
The water line ground should have come from the service disconnect.
I agree. Also, he should have run 4/0 SER between the disconnect and the service panel which is now a subpanel, not SEU.

The electrician used 4/0-3 aluminum SEU to run from the disconnect to the main service panel inside.
These are technicalities and shouldn't keep the service from operating. but in my area it wouldn't have passed inspection. Regardless, the local AHJ has the final say on these issues, many jurisdictions do things slightly differently so the way it was installed may be what the local AHJ wants.
 
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Old 02-27-11, 01:29 PM
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In another forum the Op corrected their post to read SER, not SEU.
 
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Old 02-27-11, 05:54 PM
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I thought that that would count as the ge system for the sub.
 
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Old 02-27-11, 06:52 PM
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All grounds must originate at the first source of OCP.
 
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Old 02-27-11, 07:13 PM
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Doesnt each subpanel also require its own add'l ges? I thought it did.
 
  #10  
Old 02-28-11, 04:32 AM
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Each sub-panel requires an equipment grounding conductor but not a grounding electrode conductor unless it's in a detached building from the service.
 
  #11  
Old 02-28-11, 09:57 AM
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I actually think the way he did it may be okay. The GEC is allowed to be spliced using bus bars, so the ground between the main disconnect and panel may be legal as a dual purpose equipment ground and grounding electrode conductor. I can certainly see it being an approved installation. Even if it's not I see no functional or safety deficiency.
 
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Old 02-28-11, 10:04 AM
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I agree with Ben. It is a little unorthodox but it does meet Code.
 
  #13  
Old 02-28-11, 02:37 PM
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Art 250.24 , (A) , Service Grounding Connections , (1) reads -----

"The Grounding Electrode Conductor connection shall be made ( at any accessible point on the Service drop ) , including the terminal or bus to to which the Grounded Service Conductor is connected at the Service Cisconnecting Means."

Art 250.142 (B) reads ---- " ---- A Grounded Conductor shall not be used for Grounding on the Load side of the Service Disconnecting Means."

My understanding is that the Service Disconnect is connected to the Load terminals of the meter.
 
  #14  
Old 02-28-11, 11:59 PM
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Grounding and ground loops

When member ElectricJoe stated in the thread below: "All grounds must originate at the first source of OCP." My understanding is this requirement basically ensures that all grounding is a star configuration so that stray currents and ground faults always return to one point. That point should be the grounding electrode.

However, it appears that some daisy chaining of ground points in equipment is allowed in NEC 2008, Art. 250 but that bothers me. Here's why: I know that in electronics or automotive electrical systems the engineers always bring each ground to land on a central, common star ground point and each wire is an insulated home-run to that star grounding point. To do otherwise can create ground loops , hum and harmonic distortion in connected electronics due to accumulated series/parallel resistance and resultant voltage drops developed across those inherent minor series/parallel resistances. The home run grounding design concept is pretty close to NEC requirements for neutrals that need to be isolated and always return to the service entrance. Any comments would be appreciated.
 
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