Cold Water Bonding

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  #1  
Old 07-19-11, 04:36 PM
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Cold Water Bonding

I'm upgrading my main service panel to 200A (Located on back of Garage). I'm adding a 100A breaker to feed a subpanel located in my house (about 100 ft away). I will feed the subpanel with 3 x #2 THHN cable plus a #6 Bare Ground, all in 2" Conduit to make the pull easier. My Water Main (Galvanized) enters the house about 10 ft from where the new subpanel will be located.

Can I bond the Water Main to the Ground Bar on this new subpanel, or do I have to run it all the way back to the main service panel? I'm installing 2 new grounding rods near the new main service panel.

I'm located in Long Beach, CA.

Any thoughts would be greatly appreciated.

Thanks
 
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  #2  
Old 07-19-11, 05:50 PM
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Since the house is a separate building you not only can bond the water pipe to the equipment grounding bus but must do so IN ADDITION to having at least one ground rod for the sub-panel. The Service panel (in the garage) MUST have at least one ground rod and if any underground metallic piping systems are available that too must be bonded to the service panel NEUTRAL connection which MUST be bonded to the panel enclosure.

At the house the neutral bus MUST NOT be bonded to the equipment enclosure nor are the ground rod, water pipe or equipment grounding conductor from the Service panel (in the garage) to be bonded to the Neutral bus.
 
  #3  
Old 07-19-11, 06:39 PM
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It is unclear to me if the garage is attached to the house or not. You say the 100 amp panel is 100' away but you did not state if it is attached. If it is detached, then follow Furd's advice.

If the garage is attached then yes, you need to run the water pipe bonding to the new 200 amp panel only. Follow Furd's advice about separating the neutrals and grounds.
 
  #4  
Old 07-20-11, 09:27 AM
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Thanks for the Quick response

Here is a little more detail, to clear up my installation

The house was built in the 1960s and we’ve lived here about 2 years. We are getting ready for our first major project (Complete Basement Remodel, adding Central A/C) that requires a major electrical upgrade

The current electrical system is as follows

1. The Main Service Panel/Meter is a flush mounted exterior panel on the back of the detached 2 car garage.

2. The Main Panel has the following Circuit Breakers
1 x 30A for an Electric Dryer
2 x 15A for Garage/Outdoor Lighting
2 x 20A for Garage/Outdoor Outlets
1 x 90A Sub Panel Feed

3. The Subpanel is a flush mounted exterior panel on the back of the house

4. The Subpanel is fed via 3 x #2 TW wire in metallic conduit that is buried beneath the concrete slab of the garage. There is no ground wire, just 2 hots and 1 neutral. I have no idea how deep it is buried, or the actual path it takes to the subpanel.

5. There doesn’t appear to be any ground rods near the main panel.

6. Each circuit fed from the house subpanel is wired with 1 Hot, 1 Neutral in Flexible metal conduit.

7. There is no Ground bus in the subpanel. All grounding is done via the conduit/metal boxes. The Neutral is NOT bonded to the box.

8. The house subpanel is pretty full (2 empty slots) and serves my entire house (2800 sqft)

As part of my basement remodel, I’ve demoed the walls/ceilings down to the studs/joists. My intent is redo all the basement wiring and move these circuits to a new / additional subpanel.

Here is the proposed electrical system:
1. In order to upgrade to a 200A service, the power company is requiring that I move my meter/panel location to another wall of my garage because of clearance issues with my neighbor’s property line.

2. Install new 200A meter/main panel with the following circuits
1 x 30A for an Electric Dryer
2 x 15A for Garage/Outdoor Lighting
2 x 20A for Garage/Outdoor Outlets
1 x 90A Subpanel Feed (existing)
1 x 100A Subpanel Feed (for new basement subpanel)

3. Neutral and Ground are bonded on new 200A meter/main

4. Install 2 new grounding rods below the new 200A meter/main and at least 6 ft apart. Interconnected (Panel to Rod1 to Rod2)

5. Bond any exposed underground metal piping to these ground rods

6. Run 2” conduit from new 200A meter/main to existing main to pickup existing circuits and existing Sub Panel Feed. This will be run on the inside of my garage, exposed on a finished wall.


Question #1: Since there is no existing ground conductor between the existing main/sub, how to I pick up this connection to the NEW main? I’m not sure its possible to run a new ground conductor all the way to the existing sub panel. There is room in the existing conduit, but its also been in the ground for 50 years or so. Can I put a Ground clamp on the conduit and run a ground wire from the new 200A main to the clamp?

7. Run another 2” conduit from the new 200A meter/main to the new basement subpanel. Again this conduit will be run on the inside of my garage, exposed on the finished wall. From there it will punch through the exterior wall and continue along a cinder block wall and the exterior back wall of my house, before punching through the wall into the basement ceiling joist cavity and finally to the basement subpanel location.

Question #2: Since the house is detached, do I need to additional ground rods for the NEW subpanel? What about the existing subpanel?

For the new subpanel, would something like this work?
From the new basement subpanel
- Run Bare Armored Ground to the Cold Water Main
- Install 2 new ground rods, (>6ft apart) near the Cold Water Main
- Interconnect (Cold Water Main to Rod 3 and Rod 4)

Thanks

Cory
 
  #5  
Old 07-20-11, 09:59 AM
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Originally Posted by cwagon View Post
Since the house is detached
I want to clarify these points first before continuing as all of the other issues depend on this one.

The house and garage are separate buildings with separate foundations?

The existing service entrance is at the garage and the proposed new service is at the garage?

Has it been evaluated to install the new 200A service to the house instead of the garage?
 
  #6  
Old 07-20-11, 10:20 AM
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BTW - What year code are you on? 2008?

Originally Posted by cwagon View Post
4. The Subpanel is fed via 3 x #2 TW wire in metallic conduit that is buried beneath the concrete slab of the garage. There is no ground wire, just 2 hots and 1 neutral. I have no idea how deep it is buried, or the actual path it takes to the subpanel.
Your metallic conduit is your ground
Originally Posted by cwagon View Post
5. There doesn’t appear to be any ground rods near the main panel.
Not surprising, Ground rods are a fairly new thing (30years?)
Originally Posted by cwagon View Post
7. There is no Ground bus in the subpanel. All grounding is done via the conduit/metal boxes. The Neutral is NOT bonded to the box.
Ground bar can be added very easily, if needed.
Originally Posted by cwagon View Post
As part of my basement remodel, I’ve demoed the walls/ceilings down to the studs/joists. My intent is redo all the basement wiring and move these circuits to a new / additional subpanel.
Sounds like a good plan.
Originally Posted by cwagon View Post
2. Install new 200A meter/main panel with the following circuits
1 x 30A for an Electric Dryer
2 x 15A for Garage/Outdoor Lighting
2 x 20A for Garage/Outdoor Outlets
1 x 90A Subpanel Feed (existing)
1 x 100A Subpanel Feed (for new basement subpanel)

6. Run 2” conduit from new 200A meter/main to existing main to pickup existing circuits and existing Sub Panel Feed. This will be run on the inside of my garage, exposed on a finished wall.
If it was me I would leave the existing circuits in the old main panel and make that a sub panel. Just feed it off the new 200 main with a 100 amp breaker.
Originally Posted by cwagon View Post
Question #1: Since there is no existing ground conductor between the existing main/sub, how to I pick up this connection to the NEW main? I’m not sure its possible to run a new ground conductor all the way to the existing sub panel. There is room in the existing conduit, but its also been in the ground for 50 years or so. Can I put a Ground clamp on the conduit and run a ground wire from the new 200A main to the clamp?
As I said above, you have metallic conduit. This should be your grounding path. However, it has been in the ground for a long time. Is it Rigid or IMC or just EMT?
Originally Posted by cwagon View Post
7. Run another 2” conduit from the new 200A meter/main to the new basement subpanel. Again this conduit will be run on the inside of my garage, exposed on the finished wall. From there it will punch through the exterior wall and continue along a cinder block wall and the exterior back wall of my house, before punching through the wall into the basement ceiling joist cavity and finally to the basement subpanel location.
2" is a little large for 100 amps. 1 1/4" or 1 1/2" would likely be just fine.
Originally Posted by cwagon View Post
Question #2: Since the house is detached, do I need to additional ground rods for the NEW subpanel? What about the existing subpanel?

For the new subpanel, would something like this work?
From the new basement subpanel
- Run Bare Armored Ground to the Cold Water Main
- Install 2 new ground rods, (>6ft apart) near the Cold Water Main
- Interconnect (Cold Water Main to Rod 3 and Rod 4)
I would think you just need to bond one sub panel to the water pipe and install a ground rod to one of the sub panels. You do not interconnect the water pipe to the ground rod. They would be interconnected already in the main panel. You also do not need armored ground wire. Bare is fine.


I see Ben and I have the same thought:
Another option: How about changing your existing exterior sub panel on the house and making that your new 200 amp main panel? You would then just re-feed the existing main with a 90 amp breaker. Your basement would come out of the new 200 amp main on the house. This would be easier and cheaper as well.
 
  #7  
Old 07-20-11, 10:51 AM
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The biggest problem I see is that generally you may NOT have two circuits (feeders) serving the same building. This would rule out the second feeder between the garage and the house for the proposed new 100 ampere sub-panel in the basement.

Sometimes the AHJ (Authority Having Jurisdiction) will give special permission to allow multiple feeders but it is in no way guaranteed. Before you proceed any further I strongly suggest that you get permission IN WRITING from your local building department to have two feeders.

The alternative is to have the Service at the house as others have advised OR to run a 200 ampere feeder from the garage to the house to a new 200 ampere panel and then take a 90 (or 100) ampere feeder from this new panel to the original house panel. In this second option you would then abandon the existing 90 ampere feeder to the original house panel.
 
  #8  
Old 07-20-11, 12:20 PM
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@ipbooks:

The house and Garage are indeed separate buildings with separate foundations.

Both the existing and new service entrance will be on the garage. The problem is that my property (as with all the property in the neighborhood) is long and narrow (25' wide by 125' long).
rage
The current service entrance is on the back of the garage which sits directly on my proptery line (125' side). In order to access the main panel, I currently have to stand in my neighbors driveway. The power company won't upgrade my service unless I move it to around the corner to the 25' side of my garage. This gives me the required 36" clearance in front of the panel located on my property.

I looked into bringing the service into the exisiting subpanel on the back of the house, but I ran into the same problem. I only have 24" of clearance from the subpanel to my neighbor's property line. This is a farily congested city block with maybe 5ft between houses. The only real clearance I have is on the narrow sides of my property.

@Tolyn
Long Beach has adopted NEC 2008

I don't know what type of metal conduit is buried in the ground. I'm assuming the worst, so I'll say EMT.

I thought about turning the existing main into a sub, but I still run into clearance issues with the neighbors

I've had the power company come out and do a meter spot for the new service and I've had three reputable companies come out to give me quotes, and they all agreed the proposed scenario.

I am a little worried that no one mentioned a problem with 2 subpanel feeds to the house.
 
  #9  
Old 07-20-11, 12:37 PM
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Yikes that's a lot of constraints to work around. I suppose in that case what I would do is drop the new 200A service to a meter/main panel on the back of the garage. Convert your old garage panel to a big junction box and extend the garage circuits to the new service panel, or just rewire them if it's more convenient. You might have to flip the panel around so it opens into the garage instead of into your neighbor's drive. Put in a 1-1/2" conduit from the new service panel to a new 150A main-breaker subpanel on the house. Install a 150A feeder through the conduit. Feed your existing 90A panel from this one and install your new circuits to this one. There seems to be no justification for full 200A at the house, but you could upsize everything if you want it just in case.

My jurisdiction definitely would not allow two feeders to the house in a case like this; maybe yours would, but I suspect somebody didn't look at the big picture and notice that issue.
 
  #10  
Old 07-20-11, 02:59 PM
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Is there a specific section on the NEC that prohibits two feeders? I apologize for my ignorance. I would just like a reference when I ask the question to the electical contractors.

Thanks
 
  #11  
Old 07-20-11, 03:15 PM
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230.2 Number of Services. A building or other structure served shall be supplied by only one service unless permitted in 230.2(A) through (D).

The noted exceptions A - D cover pretty unusual situations that do not apply to a normal residential house such as emergency fire pumps, backup power for medical facilities, certain types of apartments/condos, enormous power equipment, etc.
 
  #12  
Old 07-20-11, 03:44 PM
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Something similar occurs in houses here. Here though I suppose you could say semi-detached garage. There is an open breezeway between them, really just a roof and all the circuits for the house run through the attic of the breezeway. Cwagon do you have a breezeway?
 
  #13  
Old 07-20-11, 06:31 PM
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Ben, that isn't quite the proper citation as it pertains to SERVICES. I don't know about the latest code but in the 2002 code it is 225.30. The wording and exceptions are the same as 230.2
 
  #14  
Old 07-21-11, 10:01 AM
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You're right, 225.30 does apply much more directly in this case.

225.30 Number of Supplies. Where more than one building
or other structure is on the same property and under
single management, each additional building or other structure
that is served by a branch circuit or feeder on the load
side of the service disconnecting means shall be supplied
by only one feeder or branch circuit unless permitted in
225.30(A) through (E). For the purpose of this section, a
multiwire branch circuit shall be considered a single circuit.


Again the noted exceptions do not apply to your case.
 
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