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I have a 200amp service meter wired to a 200 amp outdoor breaker panel which has lugs feeding my 200amp breaker box in the house. I'm adding a garage 30 feet away.

Can I put another set of lugs in the outdoor breaker panel and run 200amp to the garage, or do I have to downsize the amps and if so what is the largest amps I can run?

double lug main panel

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  • Are you wanting to "add lugs" before or after the main breaker in the existing panel? Is there a main breaker?
    – JPhi1618
    Sep 1 '21 at 18:33
  • Not worried about cost. the new 1200sq foot garage will have a 3ton heatpump. occasionally running an arc welder and I plan on purchasing the new f150 lightning which requires and 80 amp breaker for the charging. Sep 1 '21 at 19:18
  • I'm wanting to add the lugs after the 200 amp breaker in the outdoor panel. it already has lugs for the house so I'm not sure if it can be done or would even meet code. Sep 1 '21 at 19:19
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You need 3/0 not 2/0 for running this in copper

Since this is a garage you're feeding and not a house, you can't use the "83% rule" (aka Table 310.12 in the current Code), as that rerate only applies to feeders or services serving entire dwelling units. As a result of that, and the fact that a 2/0 copper wire is rated for 175A (a standard breaker size) at 75°C, you're stuck upsizing this feeder to 3/0 copper hots and a 1/0 neutral, or chasing down a 175A circuit breaker for your panel if you can't enlarge the feeder wires.

The good news: the parts you need aren't that bad

The easiest way to do this is to use a subfeed lug kit to tap the busses on your panel. For your panel (Square D HomeLine), the correct kit is a HOML2225; this includes both the subfeed lug block itself and a neutral chair lug that adapts your fat 1/0 neutral to the panel's busses.

The bad news: you might want to rethink your choice of panel

The bad news is that you have a Square D HomeLine panel. While normally a reasonable choice, your complaints about salt air and aluminum are a problem for this panel, as it has busses made from tinned aluminum. If you want a copper bus option, the Siemens PNW0816B1200TC is reasonably priced but'd require you to get a different breaker and lug block, while the Square D QO1816M200FTRB is somewhat more expensive, and also requires different parts, but might be easier to mate to the existing conduits.

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Yes, that's fine. If the panel manufacturer supports double-lugs for the output lugs you could use those. Otherwise, use 3-port Polaris splices to fork the wires. Note this all needs to happen inside the enclosure, and the enclosure needs to be big enough.

You would need 4/0 Al wire for the feeder. (Normally you would need 250 kcmil, the next size up; however your service is 200A and serves a residence, so a downsize is allowed.)

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  • I have 2/0 and 1/0 neutral copper wire as the feed wire. from the Meter to the panel. planning on using the same wire to the garage. plenty of room in the enclosure. will run 35 feet of wire from the outdoor panel to the garage panel. Sep 1 '21 at 20:26
  • @RandyEbner sure, 2/0 copper is allowed... if cost is no object. But there's no reason to use Cu. AL is fine for this type of duty. The only reason to consider Cu is if conduit size or lug size is an limitation that would cost more than the wire to resolve. Sep 1 '21 at 21:33
  • @Harper yes id love to use cheaper aluminum but I live on the coast and the salty air does nasty things to aluminum wire. Also thanks for the response. Sep 1 '21 at 21:39
  • Not saying you're wrong, @RandyEbner, but an honest question: Does the salty air quickly form a layer of AL oxide on the wire, then all is good, or does it actually completely destroy the wire? Usually, AL gets an oxide layer on it that protects it from further degradation, unlike iron which oxidizes, then the layer flakes off exposing new fresh iron to be quickly oxidized, lather, rinse repeat.
    – FreeMan
    Sep 2 '21 at 12:12
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I realize this doesn't directly answer your question, but I'd consider swapping your meter base to a class 320 service. That way you can run 2 200 amp panels at full capacity. Class 320 meter bases aren't cheap, but since you said you weren't worried about cost, that would give you the most robust solution. You'll need to involve the power company to make sure the feed and transformer is up to feeding a class 320 service. The POCO is always the long pole in the tent!

Since the new garage is only 30' away, wire cost wouldn't be a major consideration. You'll have 2 "main panels", one in the house, the other in the new garage. Not only that, you wouldn't have to mess much with the existing setup because all the new stuff will be "before" your outside breaker panel.

Heat pump, EV charging, arc welder....hmmmm, those aren't light loads.

So in summary, my suggestion is, even if not fully responsive to your question is: Swap the meter base (If supported by the POCO), to a class 320, run your 4/0 and 2/0 to the garage (in conduit of course) to the new 200 amp panel in the garage and you're done.

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  • thanks the electric company wont support the upgraded meter. so I'm trying to get the most out of what I have. hoping when the loads are high in the garage they are low in the house and vise versa. that way I have fewer and hopefully no tripped breakers. Sep 1 '21 at 20:16
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    The PoCo is going to turn down the opportunity to jack your bill up? What weird alternate universe do you live in???
    – FreeMan
    Sep 1 '21 at 20:26
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    @FreeMan Yeah, go figure. Sometimes, the PoCo's transformers are maxed out, serving too many houses and they don't want to upgrade. That or the cabling (wires?) coming to the house aren't large enough to handle a class 320 service. I went thru that helping wire my son's new build and feed a large, existing shop. The class 320 worked out great. Sep 1 '21 at 20:56
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    @FreeMan Can depend on how the lines are run. Overhead wires are relatively cheap and easy to upgrade if need be. Buried lines, not so much. I could see a utility balking at having to dig new lines in.
    – Machavity
    Sep 2 '21 at 13:17
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    Fair enough @Machavity. However, don't they usually charge the customer for that work? Therefore, they don't care, they just pass the cost along (plus markup for profit). Anyway... </OT conversation>
    – FreeMan
    Sep 2 '21 at 13:20

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