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Old 09-22-2008, 12:04 PM   #1
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Grounding for two service entrances to same house.


I live on a farmstead. Power comes in to a a box about 20' high on an overhead pole by the drive. The pole has a meter and shutoff lever about 5' high that connects to the overhead box. Four runs of SE cable in conduit come down the pole and then feed underground. Two go to a couple outbuildings and two go to my house.

One of those going to my house is a typical 100 amp service feed with a standard 100 amp breaker panel. This panel appears to be wired to current codes and supplies all the electricity I currently use in the house. The second service to my house is a 200 amp service that use to supply dedicated power to an electric furnace in the house. I replaced the furnace with a gas furnace some time ago so the 200 amp box is currently not used.

I'm adding on to my house and would like to utilize this 200 amp service entrance. I opened it up this weekend to see what it looked like inside. It had the typical two hot leads to the double pole breaker and a neutral to the neutral bar but there was no ground wire anywhere to be found. (Is this normal for a service entrance dedicated to an electric furnace??)

In order to use this service entrance I will need replace the panel with a new panel and add appropriate grounding. That would be pretty straightforward for me if it was the only service entrance to the house but the presence of two service entrances gives me a few questions:
1. Can I use the existing ground rod for both service entrances?
2. Will bonding the ground wires from both service entrances to the water lines cause a probelm?
3. Should there be any special bonding of the grounds between the service entrances and, if so, how should this be done?
4. Are there any other special issues that come up when a hosue is served by two service entrances?

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Old 09-22-2008, 01:49 PM   #2
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Grounding for two service entrances to same house.


You say there are 4 runs of SE cable that run down the pole. Is this from the disconnect to the 4 panels in your yard? (house 1, house furnace panel, 2 outbuildings) Simply put, does shutting off the one disconnect at the pole kill power to all locations on your property? It sounds like the wire fed underground was improperly run. Since there is a main disconnect, there should be a 4 wire service to each panel beyond the main disconnect, not 3; this would have given you the proper ground at the panel in question.

I don't know about the grounding of both services to the water pipe, but I would probably look at driving at least one ground rod for each panel as a minimum. I believe new NEC code requires 2 8ft ground rods now, though it depends on what code revision your area is on.

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Old 09-22-2008, 02:42 PM   #3
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Grounding for two service entrances to same house.


The disconnect at the pole shuts off all power to all buildings. There are not 4 panels at the pole. Just one big metal box at the top from which all the lines come. To my knowledge this box at the top serves only as a disconnect for the entire farmstead and for the meter feed. The meter is not your typical residential one - it is mounted down below and is wired by lighter gauge wire to the rest of the device in the box above. All building feeds from the pole are 3 wire (2 hots and 1 neutral) and each building has it's own ground rod and the ground and neutral bars are bonded in each panel (except the one which has no ground). So the building panels are not set up as subpanels - they are setup as main panels.

I'm pretty sure all farmsteads have a similar distribution setup around here. I'm also pretty sure that the box, shutoff and meter belong to the power company as they paid for repairs to it after a storm. Basically it's the pocos way of putting in one meter for all the buildings on the farm.
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Old 09-22-2008, 03:46 PM   #4
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Grounding for two service entrances to same house.


The disconnect on the pole is stated as being 20 feet up in the air. That would not be considered the main service disconnect.
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Old 09-22-2008, 04:21 PM   #5
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Grounding for two service entrances to same house.


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The disconnect on the pole is stated as being 20 feet up in the air. That would not be considered the main service disconnect.
I think you are right. Each service panel is located right where the power comes into each building and has it's own main breaker that I believe is considered the main service disconnect for that building. I look at it as several buildings each with it's own underground feed and main service panel but all are monitored by a common meter.

Just for clarity there is a lever at meter level (5') that can mechanically throw the switch that is on the box at the top of the pole to disconnect power to the whole farmstead. There is no fuse/breaker that I know of in the box at the top of the pole.
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Old 09-22-2008, 04:43 PM   #6
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Grounding for two service entrances to same house.


The box at the top of the pole is like you say. It is a disconnect and CT metering setup. It is common in my area for services on farms over 200 amps, but could serve a smaller service as well.

Since this is not disconnect for the owner side, and does not contain overcurrent protection, all of your sets of cables are technically services. If you read NEC 230.2 You will see that a building is allowed to have only one service. There are exceptions, this not being one of them. (Even if some guys call those "feeders" [which is incorrect] it doesn't matter, you can only have one feeder too...) I would say that it is illegal to have more than one set of service conductors feeding your house. I will ask, will the 200 amp service handle everything in your house that you plan to add? If it does, I would get rid of the 100 amp line and either get rid of the box altogether or convert it into a subpanel if it means moving a ton of circuits. If the 200 amp panel is small in the number of breaker spaces, you could replace it with a new 200 amp 40 space panel.

Last edited by junkcollector; 09-22-2008 at 04:46 PM. Reason: add
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Old 09-22-2008, 05:01 PM   #7
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Grounding for two service entrances to same house.


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Originally Posted by junkcollector View Post
If you read NEC 230.2 You will see that a building is allowed to have only one service. There are exceptions, this not being one of them. (Even if some guys call those "feeders" [which is incorrect] it doesn't matter, you can only have one feeder too...) I would say that it is illegal to have more than one set of service conductors feeding your house. .
I agree, but i'm more worried about the SE cable underground.
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Old 09-22-2008, 05:29 PM   #8
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Grounding for two service entrances to same house.


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I agree, but i'm more worried about the SE cable underground.
I may have called it the wrong thing. I'm pretty sure the wiring is rated for buried use and same as I've seen on other homes with underground feeds.
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Old 09-22-2008, 05:36 PM   #9
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Grounding for two service entrances to same house.


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I may have called it the wrong thing. I'm pretty sure the wiring is rated for buried use and same as I've seen on other homes with underground feeds.

Is it a cable or individual conductors?
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Old 09-22-2008, 05:48 PM   #10
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Grounding for two service entrances to same house.


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Is it a cable or individual conductors?
Individual conductors. They are aluminum strand (rough guess maybe 5/8" diameter not counting insulation) with a thick black plastic/rubber-like insulation.
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Old 09-22-2008, 06:13 PM   #11
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Grounding for two service entrances to same house.


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Originally Posted by junkcollector View Post
If you read NEC 230.2 You will see that a building is allowed to have only one service. There are exceptions, this not being one of them. (Even if some guys call those "feeders" [which is incorrect] it doesn't matter, you can only have one feeder too...) I would say that it is illegal to have more than one set of service conductors feeding your house. I will ask, will the 200 amp service handle everything in your house that you plan to add? If it does, I would get rid of the 100 amp line and either get rid of the box altogether or convert it into a subpanel if it means moving a ton of circuits. If the 200 amp panel is small in the number of breaker spaces, you could replace it with a new 200 amp 40 space panel.
Well, not what I really wanted to hear but better to know now. I probably don't need more than 200 amps (though going all electric was a possibility) and the two boxes are side by side in the basement so I could either transfer everything over to a new 200 amp box with more spaces or make the current 100 amp panel a subpanel (remove the bond between the ground and neutral and feed from a 100 amp breaker in the 200 amp box.

But either way the difficult part would be dealing with disconnecting and removal of the extra underground feed. The house has had these two services since it was built in 1976 and would have been subject to a state electrical inspection at that time. If the two services were not forbidden by local requirements when it was built I'm not convinced that it must be removed now.
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Old 09-22-2008, 09:34 PM   #12
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Grounding for two service entrances to same house.


Quote:
Originally Posted by jogr View Post
I live on a farmstead. Power comes in to a a box about 20' high on an overhead pole by the drive. The pole has a meter and shutoff lever about 5' high that connects to the overhead box. Four runs of SE cable in conduit come down the pole and then feed underground. Two go to a couple outbuildings and two go to my house.
Is the disconnect "lever" at the 5ft height or is it higher up at the 20ft height? Do you see 4 runs of conduit going up to 5ft high, or do they run all the way up to the 20ft high box? From the sounds of it, the disconnect switch is 5ft high, and if that is the case this would serve as your service disconnect. Some pictures would help greatly.

Personally, i'd remove the 100amp service and panel to your house and move everything into a single 200 amp 42 space panel. Eliminate the guess work, and keep it simple. Maybe you have another outbuilding you could run this service to instead? (though might be a lot of work to re-run this service underground)
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Old 09-23-2008, 10:51 AM   #13
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Grounding for two service entrances to same house.


I looked over the pole again and I saw that my memory was faulty.

The conductors that run underground to my house to serve both the 100 amp panel and the 200 amp panel are attached to the lines coming out of the power company's disconnect box that sits at the top of the 20' pole. All 6 conductors that feed the 100 amp and 200 amp panel run into one weatherhead at the top of one 4" conduit that runs from near the top of the pole (just below the power companies disconnect box) to underground. I cannot see underground but I assume that all 6 run together underground to my house and are separated just before entering my house. The three supplying the 100 amp panel come out of the ground through one conduit that goes through the wall directly into the 100 amp panel. The three supplying the 200 amp come out of the ground 2' over through a conduit that goes through the wall directly into the 200 amp panel that is next to the 100 amp panel.

The power company's box at the top of the pole provides two hots and one neutral to the farmstead. The two neutrals from my weatherhead are connected to the power company neutral. Two "hot" conductors (one for the 100 amp panel and one for the 200 amp panel) from the weatherhead are connected to one of the power companys hots and the other two "hot" conductors from the weatherhead are connected to the other power company hot.

I believe that according to the definitions for 230.2 this is considered one service and therefore the house is in compliance with 230.2.

BTW the lever which actuates the power companies disconnect is located about 5' high and connects to a long rod that triggers the disconnect in the power company's box that is at the top of the pole.
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Old 09-23-2008, 12:25 PM   #14
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Grounding for two service entrances to same house.


I found a related issue on an inspection forum that distinguished between a service drop and service riser. The service drop is apparently considered a "service" as per 230.2 and there can be only one for single family dwelling. Service Risers are apparently not limited in number.
https://www.nachi.org/forum/f19/over...ce-drops-6560/

In the case in the link above the house had multiple service drops. But in my case I have only one service drop from the pocos disconnect/meter box. I also have only one riser but the 6 conductors from that riser do split to enter two different side by side panels at the house. I can't find any NEC reference prohibiting this.

Speedy Petey posted on the above link and sometimes does post here so maybe he'll chime in as to whether I'm interpreting this correctly.

If this is considered one service, and it looks like it is, I'm still back to the questions regarding appropriate grounding between the two panels. I'm assuming that I want some form of bonding between the grounds for both panels and it seems that could occur by bonding both to common ground rods as well as the water pipe. Should I also run a ground wire between the two panel's ground bars?
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Old 09-23-2008, 01:01 PM   #15
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Grounding for two service entrances to same house.


Quote:
BTW the lever which actuates the power companies disconnect is located about 5' high and connects to a long rod that triggers the disconnect in the power company's box that is at the top of the pole.
What you have is a site isolation device which is covered in NEC 547, specifically 547.2 and 547.9 and related sections. The pole is your distribution point and is commonly called a farm yard pole. This belongs to you not the power company.
It is not your service disconnecting means these are located at each structure and panel ..gec systems installed at each structure. It is one service as you suspect. Grounding and bonding is in accordance with 250.32. In your situation an equipment grounding conductor was not run with the service entrance and that is fine as long as neutral to ground bonding occurs at the service equipment enclosures with the grounded conductor and no other metallic paths exist. A gec is also required at the pole.

The 200 amp panel used for the dedicated electric furnace was allowed under different application or uses from the yard pole.

Your problem is you want to use the second 200 amp panel for your dwellings addition and as such it is served by service conductors not a special application. You cannot have two services to a single family dwelling... at least not in your situation. And I don't think the poco will welcome hanging another meter on the pole. If the pole was set up for feeders with disconnecting means (service equipment) located at the pole you could do what you want. this would be no different than a 400 amp service to a dwelling where two sets of service entrance conductors are ran from the meter to the 'service equipment' and then to two panels in the home.

Since your service equipment is not located on the pole I don't believe you will be allowed to use the 200 amp panel as you described. You could however use it if you disconnect the service to the 100 amp panel and run a sub feeder from the new 200 amp panel to the 100 amp panel or use a feed thru lug panel for your 200 amp arrangement. all this subject of course to the local jurisdiction.

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Last edited by Stubbie; 09-23-2008 at 02:13 PM.
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