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First of all is a 100 amp panel sufficient? Will only be lighting and general outlets because it is going to be a horse barn. No heavy equipment

Secondly just want to make sure my math is correct. I believe I can use 1/0 copper in an 1.5 inch schedule 40 pvc

Well pump will be 240 Located in south Florida

Hugh Von Minden
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    Unless it is a short distance, using aluminum will be cheaper. Will need a load calculation before adding that much extra use. – crip659 Oct 05 '23 at 16:16
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    One catch is if there will be any sort of heaters keeping the water tank/buckets/trough from freezing - those can eat a lot of power on livestcock facility "general outlets" come freezing weather. If you're just dumping the ice and drawing fresh water often enough, little power use. – Ecnerwal Oct 05 '23 at 16:22
  • Your 40 amp well pump... is that 120v or 240v? – Machavity Oct 05 '23 at 16:24
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    Even South Florida gets freezing weather and you'll be busy buying & plugging in heaters when that happens. Also, nobody but you can determine if 100A is going to be sufficient for whatever future growth might happen. The general advice is to buy the biggest panel you can get your hands on now. The bigger the Amp rating of the panel, the more spaces it will come with (in general). The more spaces you have, the less likely you are to have to branch to another sub panel in the future (or replace this one), saving time, frustration and money in the future. – FreeMan Oct 05 '23 at 16:38
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    a 40A 120V pump is highly unlikely @Machavity 1/2-3/4 HP is about as big as 120V pump motors get before defaulting to 240V – Ecnerwal Oct 05 '23 at 16:38
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    What is the length of the run? – NoSparksPlease Oct 05 '23 at 16:49
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    If you're planning for a 20-30 year time horizon, think about capacity for a vehicle charger at the barn so you can charge your electric pickup truck without disconnecting the horse trailer from it. – MTA Oct 05 '23 at 16:58
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    If your load calc results don't allow the capacity you desire you can certainly still provide for the future by installing larger wire and panel fed by smaller breaker that you can change out later when you improve your service. Inspector may be suspicious but that's not grounds for denying approval. – NoSparksPlease Oct 06 '23 at 01:53

3 Answers3

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Your copper is likely significantly overkill unless you're running this a very, very long distance. For reasonable distances 1/0 THWN will be good for at least 150A. Do consider using what is known as 'mobile home feeder'. It's aluminum, much cheaper per foot, can be direct buried in some circumstances, and widely available for a fraction of the cost per foot of copper cable. If you end up only needing 90A you can probably use 2-2-4-6 which is so widely used that it's downright cheap in most places, the cost of a single strand of #1 THWN. Even 2-0/2-0/2-0/1 comes in at less per foot than two strands of the #1 THWN you need to run the same current.

As to 100A being sufficient, the only way to answer that is with a load calculation. We don't have sufficient information to help there, as we don't know your loads. My 'gut check' says a barn fed with 100A should be fine because I've seen plenty of them fed with 40A and working just fine, but that doesn't actually help if you have specific plans that need more current.

KMJ
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  • Aluminum wire - no reason whatsoever for copper when it comes to feeders.
  • As noted in another answer, 2 AWG (2/2/24) aluminum is often priced very competitively, and that is enough for up to 90A.
  • BIG panel. The panel has to be rated at least as high as the feed breaker. Beyond that, there is no particular requirement. So a 90A feed (or even a 60A feed) is perfectly fine with a 100A panel. But you do not need to stop there. A 200A "main" panel is perfectly fine, and in fact often a 200A panel that comes with free "bonus breakers" can be about the same price as a much smaller 100A subpanel.
  • There are two key differences between a "main" panel and a "sub" panel: Main breaker and grounding. A "main" breaker is not required, per se, in a subpanel. However, when that subpanel is in a separate building from the main panel, it needs a disconnect. A "main" breaker works perfectly fine as a disconnect and saves having to add another box just to have a disconnect. As far as grounding: many, but not all, "main" panels do not include a ground bar, so you may need to add one, and you need to make sure that neutral is not bonded to ground. Other than that, a "main" panel is 100% fine as a subpanel.
  • 200A panels tend to be larger than 100A panels. Larger panels have the advantage of lots of breaker spaces. You probably only need ~ 4 breaker spaces now. But someday if you decide to do more things in the barn you might need many more. Empty spaces cost very little. Replacing a panel costs in time and materials.
  • Load Calculation - With your current (pun intended) plans, I'm not worried about a Load Calculation for the barn feed breaker. But I am concerned about your overall service. You should do an NEC Load Calculation to make sure you can spare 40A+ from your service/main panel. If your service doesn't have the capacity then you either need a heavy-up or some changes to other loads or load shedding.
manassehkatz-Moving 2 Codidact
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First of all is a 100 amp panel sufficient?

Usually fine, yes.

Will only be lighting and general outlets because it is going to be a horse barn.

Assuming LED lights, 20 amps would suffice in all honesty.

No heavy equipment.

You could comfortably run most power tools and a shop-vac simultaneously without tripping a 20 amp breaker. I do it all the time with my miter saw + show-vac or table saw + show-vac.

Secondly just want to make sure my math is correct. I believe I can use 1/0 copper in an 1.5 inch schedule 40 pvc.

I don't know electrical math once you get into those sizes.

Consider aluminum like the other posts suggested and consider running a 200 amp wire instead just in case you find that a 100 amp panel is insufficient in the future.

Well pump will be 240 Located in south Florida

These usually require 240v, so you lied about "lighting and general outlets"?

You'd want at minimum whatever the well pump draws plus 20 amps.

MonkeyZeus
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  • If you stick with 1/0 THWN then 3@1/0 + #6 ground (since 1/0 is 150A wire) will result in 29.11% fill, so would be permitted. – NoSparksPlease Oct 06 '23 at 00:35
  • @NoSparksPlease Thank you for the math =) I wonder if OP's PVC is already buried or if 1.5" is the existing plan. Hopefully they bury something larger. – MonkeyZeus Oct 06 '23 at 12:57