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Inactive, Master Electrician
Category: Electrical
Satisfied Customers: 4772
Experience:  Electrical Contractor
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Replacing A 200 Amp Meter Base With A 400 Amp Meter Base.

Resolved Question:

I need to replace a 200 amp meter base with a 400 amp base, splitting off 200 amps to my house and 200 amps to a new shop. I will need the local power company to upgrade the drop to 320 amps.

My question is: what meter base will be appropriate for this change and are there any other issues I need to be concerned about to comply with codes? The existing lines enter the base from the top through a mast and exits through the bottom into the house. The conduit to the new shop is underground so it needs to enter the new base panel through the bottom also.

Submitted: 8 years ago.
Category: Electrical
Expert:  Inactive replied 8 years ago.

Thank you for your question

What you need to do is go to your local electrical supply house and ask for a 400amp meter main. This will have the meter on one side with spaces for breakers on the other. This will allow you to feed your home, and the garage.

What you will have to do with this setup is change the wiring from the panel to the inside of your home, and change the wiring going to your garage. The wiring will need to be 4 conductor.

Now question for you - how far from the home to the garage?

Customer: replied 8 years ago.
It is about 100'. The wire (copper 0000) has already been pulled. I am using 3 wires because the garge has a separate ground
Expert:  Inactive replied 8 years ago.

Ok the wiring to your garage is going to be a problem. It needs to be 4 wire. You will need to pull an additional grounding wire #4 copper and then install a grounding bar kit in the panel. Then you need to be sure you isolate the neutral and grounds in that panel and bond the grounding bar to 2 separate grounding rods spaced at least 6' apart.

Here is how you do this:
Now at the new service you need to get the 400amp meter main like I stated before and run 4" conduit up the mast to the weather head using (2) 500mcm cables and (1) 250mcm for the neutral.

Again you will need to ground all of this like I show here:
Just keep in mind that if you don't have a metallic water meter, you will need to drive 2 grounding rods spaced 6' apart.

Now onto the house panel, the new cable from the meter main to the house panel will need to be 4/0 aluminum SER cable. And it will need to be installed like this:

Just be sure to get the proper electrical permits and inspections co-ordinated when you do this. In this way you can get this inspected and re-energized the same day.

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