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Converting 100 amp main panel to sub panel, adding 200 amp panel...

Converting 100 amp main panel to sub panel, adding 200 amp panel...

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  #1  
Old 09-13-14, 06:19 AM
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Converting 100 amp main panel to sub panel, adding 200 amp panel...

Hi,
This is in USA / Massachusetts.

First time poster.

The main house has 100amp panel. We added detached garage and living space that is connect to the house via an upper bridge! (SO not really detached?)

Anyways, the meter socket is being moved to the new structure and a 200 amp panel is installed. I'm going to use the existing 100amp panel as a sub panel.

Local Elec. inspector was already out for the rough and didn't comment on grounding yet.

I have the following questions:

1.) I have added a grounding rod to the near the new meter socket. Based off the fact that we have no city water, I should add a 2nd ground rod more than 6' apart as we don't have the equipment to measure for 25 ohms?

2.) There is an existing ground rod for the 100amp panel (that has to be removed) ? All grounding should be brought back to new 200amp panel?

3.) I will convert the 100amp panel to a sub by separating the neutrals and grounds.

4.) Do I have to bond the cold water pipes in the existing structure? There are no cold water pipes in the new structure, if so, can I tap of the grounding bar of the 100amp now sub panel?

We could ask him, but wanted to fetch some advise first, then run it by him

Thanks!
 
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  #2  
Old 09-13-14, 07:42 AM
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The new 200 amp service will need a grounding system. Depending on whether your inspector considers the old house attached or detached will determine if the original ground rod will be needed.

I understand that Mass. is a fairly regulated state as far as electrical work. Can you do this or do you need to hire it out?
 
  #3  
Old 09-13-14, 08:31 AM
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4.) Do I have to bond the cold water pipes in the existing structure? There are no cold water pipes in the new structure, if so, can I tap of the grounding bar of the 100amp now sub panel?
My thoughts are that the new building will be considered as attached and that you'll need to run a #4 copper or #2 aluminum ground from the new 200 amp panel's neutral bus to where the metallic water service piping enters the original house.

I also agree with PCboss, you need to know the inspector's decision on whether the new building is considered as attached or detached.
 
  #4  
Old 09-13-14, 12:37 PM
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Yes I already pulled the permit with local town. There is no water coming in from the street. The house has it's own well. If structure is considered "attached" then do I need to connect the water pipes from the 200 amp new service with #4? Or can I use the grounding of sub panel to connect to the water pipes (which I think might actually be connected already, I'll have to check).

Thanks!
 
  #5  
Old 09-13-14, 07:55 PM
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There is no water coming in from the street. The house has it's own well. If structure is considered "attached" then do I need to connect the water pipes from the 200 amp new service with #4?
Is the water line from the well plastic or metal? If metallic with at least 10 feet of metallic line buried, treat it as if it was water coming from the city supply and run the #4 copper (or #2 aluminum) from within 10 feet of the water service entry to the house to the neutral bus of the main panel. If it is a plastic water service line, any metallic piping in the house likely to become energized should be bonded back to the main panel. This is all asuming the buildings are considered attached.
 
  #6  
Old 09-16-14, 06:15 AM
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Talked to the inspector today.

The well is pvc coming into the house, converts to copper after the water filter system.

Inspector said "bond the cold water line, you can use the sub panel to do so".

Now, I thought this wasn't good, my understanding was that the cold water pipe had to be bonding to the main panel not a sub, given the fact that this is considered an "attached" structure. He also said the reason was because we don't have a kitchen or bath in the new structure.

It's fine with me, but I just wanted to be safe. I'll put a new #4 copper on the grounding bar (of the sub) to the copper cold water line right after the water filter.

Oh one last thing, what do we do with the existing ground rod attached to the now sub panel? My understanding was that this was to be disconnected but now I have no idea!

Thanks,
Joe Q.
 
  #7  
Old 09-16-14, 09:25 AM
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what do we do with the existing ground rod attached to the now sub panel? My understanding was that this was to be disconnected but now I have no idea!
I would disconnect and remove the original GEC and drive the ground rod down under the surface to keep from hitting it with your lawn mower.
 
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