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Adding a new 200amp Main


psherrill
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I need to add a 200a Main Disconnect at the MC. The existing load lines proceed unfused to the MDP.

1. At the MC, can I disconnect the existing load side hots and and land new conductors in the new Main Disconnect on the line side without bringing over a neutral to the MD?

2. Can I then bring the load side of the new disconnect back into the MC (separate conduit) and polaris tap the existing load conductors?

3. There is a separate ground wire from the MC to the existing MDP. Is it sufficient to connect a ground wire from the MC to the new MD (still unbroken segments)?

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Originally posted by psherrill

I need to add a 200a Main Disconnect at the MC.

Why?

The existing load lines proceed unfused to the MDP.

1. At the MC, can I disconnect the existing load side hots and and land new conductors in the new Main Disconnect on the line side without bringing over a neutral to the MD?

No. All of the conductors must travel together. Besides, from the new disconnect on, you're going to need separate grounding and neutral conductors.

2. Can I then bring the load side of the new disconnect back into the MC (separate conduit) and polaris tap the existing load conductors?

Huh? Wouldn't the existing load conductors be disconnected at the other end? I'd think that you'd run the new feeders from the new disconnect to the existing panel and discard the old conductors.

3. There is a separate ground wire from the MC to the existing MDP. Is it sufficient to connect a ground wire from the MC to the new MD (still unbroken segments)?

It depends on what, exactly, it is that you're calling a "ground wire." You'll have to establish a connection to a grounding electrode at the new main disconnect, run four wires to the old panel, reconfigure the old panel to separate the neutral & ground wires and adhere to a bunch of rather specific rules for each of these tasks.

What you're proposing doing is a rather serious electrical upgrade. Based on the content of your post, I think that you have just enough knowlege to be a danger to yourself and your house.

Please call an electrician.

- Jim Katen, Oregon

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Jim, thanks for your answer.

The AHJ is requiring the installation of a Main Disconnect near the Meter.

We added a Service Entrance Rated ATS near the Main Distribution Panel that also has a main disconnect (in the garage 35 feet from the existing meter). So we essentially had a change of service from the existing MDP to the new ATS (less than 2 feet apart). We had a custom fabricated pull box to make the transition from the existing rigid conduit inside an interior garage wall to the new surface mounted ATS. The pull box introduced unfused conductors in the building (inside garage), thereby requiring the new disconnect. I have already separated the equipment grounds and neutrals in the existing distribution panel and will remove the bonding screw when the new disconnect is installed and existing Main becomes a sub-panel.

There are four wires coming from the existing meter can (2 primaries, 1 neutral and a ground) to the existing MDP.

I was looking for input from an inspector's perspective on what I had hoped would be a simple way of installing the new disconnect.

I had planned to:

1. Set the new disconnect next to the existing meter can joined by two 2 inch nipples.

2. Disconnect the load lines in the existing meter can and land new conductors through one of the 2 inch pipes to the line side of the new disconnect.

3. Attach new conductors on the load side of the new disconnect and feed them through the remaining 2 inch pipe and polaris tap them to the existing load lines that were disconnected from the load side of the meter in step 2.

4. Based upon Jim's answer, it's obvious I also need to bring the Neutral into and out of the new disconnect box as well as bonding it to the new box and appropriate grounding to the GEC.

If the above seems reasonable, since a ground wire already runs unbroken from the meter can to the equipment ground bus on what will become a sub-panel, would a wire from a ground lug in the new disconnect run to a ground lug in the existing meter can be sufficient for the system?

I will now go quietly into the night.

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Originally posted by psherrill

. . . I had planned to:

1. Set the new disconnect next to the existing meter can joined by two 2 inch nipples.

2. Disconnect the load lines in the existing meter can and land new conductors through one of the 2 inch pipes to the line side of the new disconnect.

3. Attach new conductors on the load side of the new disconnect and feed them through the remaining 2 inch pipe and polaris tap them to the existing load lines that were disconnected from the load side of the meter in step 2.

4. Based upon Jim's answer, it's obvious I also need to bring the Neutral into and out of the new disconnect box as well as bonding it to the new box and appropriate grounding to the GEC.

If the above seems reasonable, since a ground wire already runs unbroken from the meter can to the equipment ground bus on what will become a sub-panel, would a wire from a ground lug in the new disconnect run to a ground lug in the existing meter can be sufficient for the system?

I will now go quietly into the night.

What you're proposing seems reasonable, though a bit awkward. The grounding electrode conductor doesn't need to terminate in the main disconnect. It can stay where it is in the meter can.

Have you considered discarding the existing meter can and installing a meter main? It wouldn't be any more trouble that what you're proposing but it would result in a much cleaner product.

Howcome you were able to install the ATS without upgrading your main disconnect first?

Why did the original installer provide a four wire feed from the meter can to the main panel when he didn't need to?

- Jim Katen, Oregon

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Originally posted by Jeff Remas

Are you installing a standby generator? What size is the ATS?

200a SE Rated w/Load Shedding (20kw Genset).

Sounds like you have a plan and since it is getting inspected I'm sure everything will be done correctly.

Just soliciting opinions to get it right before the final.
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Have you considered discarding the existing meter can and installing a meter main? It wouldn't be any more trouble that what you're proposing but it would result in a much cleaner product.

Agreed. Homeowner wouldn't pony up and we have several new 200a disconnects in stock (we are a commercial/residential generator installer, but do not normally wire branch circuits or service drops. This allows us to work with several ECs without conflict).

I'll reconsider a meter main. It is the more elegant solution. Just trying to minimize excessive cash outlay.

Howcome you were able to install the ATS without upgrading your main disconnect first?

The inspector recognized the installation was not unsafe, just not code perfect (~30" of unbroken/unfused feeder in a pull box in a garage) and gave us a couple of weeks to correct.

In this jurisdiction, no plan review is required for this type of permit.

Why did the original installer provide a four wire feed from the meter can to the main panel when he didn't need to?

- Jim Katen, Oregon

Good question, because they didn't separate the neutrals in the panel (arrgh!). It looks like an afterthought as they ran a separate conduit from the can through the attic to the panel (maybe AHJ leaned on them inappropriately).

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