Meter Move and wire choices

[sodaparis]

I a moving our meter and going from overhead to underground. The new meter main will be on the side of our detached garage. The old meter base (no disconnect) is on the side of the house. I have a 200 amp breaker that will feed the 200 amp panel at the house downstream of the old meter base. My question is aluminum wire size. My current thinking is 250 mcm aluminum for the 2 hots and 1 neutral and 2 awg aluminum for the equipment ground. I think 4/0 may be allowed but am not sure since its not rated for the full 200 amps. The new meter main will also feed some circuits in the garage.
I have pulled the permit and what I have installed so far is 2“ schedule 40 conduit through the garage and secured under a ground level deck between the garage and the house. I have also installed the meter main. If I go with the (3) 250 MCM and (1) 2 AWG I’m coming up with a 36% fill on the 2” conduit.
Thanks in advance for advice on this installation.

Meter Main: Siemens MC4040S1200S
SubPanel: Siemens PN4040B1200C

 

[dcg9381]

(3) x 250 MCM and a 2 AWG through 2" conduit? Maybe...

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[sodaparis]

(3) x 250 MCM and a 2 AWG through 2" conduit? Maybe...

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Thanks, yes the installed 2” is not ideal, I installed it thinking (3) x 4/0 and a 4 AWG which would have been closer to 29%, but now questioning that size wire, Would the 250 MCM and 2 AWG be the better option for our 200 amp sub?

 

[wyliesdiesels]

Have you checked to make sure that you can convert the current main in your house to a subpanel? ie removing the bond on the neutral bar? adding ground bars as well?

 

[dscheidt]

The other question is does the house really need 200A, since the garage is getting service from the meter main, and the house won't have an electric car charger or your shop equipment? Assuming your existing main panel can be converted to a sub (need to separate the neutral from the ground at it, and make sure the grounds are on their own ground bars), there's no reason it has to be fed from a 200A breaker. Overcurrent protection on subpanels is provided by the feeding panel, not the main breaker in the sub, that just serves as a disconnect. you could run smaller wire, using a suitable smaller breaker in the meter main. that will save some money, and make the wire pulling easier.

 

[sodaparis]

Have you checked to make sure that you can convert the current main in your house to a subpanel? ie removing the bond on the neutral bar? adding ground bars as well?

Thank you, the next upgrade is to install the outdoor load center listed in my first post, but I won’t be ready for that at meter swap. The existing 200 amp panel is bonded. I found the ground bars I need for it that are listed on the old panel sticker as new old stock. I plan to separate the neutrals and grounds, the panel has an isolated neutral bar with neutrals and grounds landed on it and it is bonded to enclosure. I also added a second ground rod 10 feet from the original and connected it to the existing rod.

 

[sodaparis]

The other question is does the house really need 200A, since the garage is getting service from the meter main, and the house won't have an electric car charger or your shop equipment? Assuming your existing main panel can be converted to a sub (need to separate the neutral from the ground at it, and make sure the grounds are on their own ground bars), there's no reason it has to be fed from a 200A breaker. Overcurrent protection on subpanels is provided by the feeding panel, not the main breaker in the sub, that just serves as a disconnect. you could run smaller wire, using a suitable smaller breaker in the meter main. that will save some money, and make the wire pulling easier.

Thank you, I’ve gone back and fourth, and I think this is the correct way to go, anything added in the future will likely be added to the combo and not the house sub. I think the best way to go is 3 x 4/0 and 4 awg ground. Would still like to confirm the 4 awg is correct for the ground coming from the main to the house sub. Is this correct? Any reason for it to be larger?

 

[Norcal]

If the calculated load is 180A or under, 4/0 would be fine using the next size up rule, since there is no 180A breaker, it's allowed to use the next size up, 200A.

 

[sodaparis]

If the calculated load is 180A or under, 4/0 would be fine using the next size up rule, since there is no 180A breaker, it's allowed to use the next size up, 200A.

Thanks, I haven’t done a load calculation. Even if the 200 amp branch circuit breaker or panel breaker was called out I could downsize to 175.

 

[Bert_]

You are allowed 4/0 for a 200a residential service. Doesn't directly apply to a feeder but the feeder conductors aren't required to be lager than the service.

 

[sodaparis]

You are allowed 4/0 for a 200a residential service. Doesn't directly apply to a feeder but the feeder conductors aren't required to be lager than the service.

Thanks Bert, is there a majority preference in the field for insulation types, xhhw etc.? Or is it typically cost and what’s readily available?

 

[sodaparis]

One clarification on ground wire. Will it need be sized based on the breaker I end up using (200 amp breaker and 2 awg) or would it fall under the next size up exception also.

 

[sparky 1971]

One clarification on ground wire. Will it need be sized based on the breaker I end up using (200 amp breaker and 2 awg) or would it fall under the next size up exception also.

You only need a #6 copper or #4 aluminum for the feeder. It's an equipment ground, not a GEC (grounding electrode conductor) which would be #2 aluminum or #4 copper.

Table 250.122 in the code book.

 

[sodaparis]

You only need a #6 copper or #4 aluminum for the feeder. It's an equipment ground, not a GEC (grounding electrode conductor) which would be #2 aluminum or #4 copper.

Table 250.122 in the code book.

Thanks sparky, the GEC is installed at the new meter location and I did use #4 copper.