200 AMP Service - Feeding 3 Sub-Panels - Wire Size and Set Up Help Needed

Question

We are installing a 200 amp outdoor service panel (specifically, this one) and want to run 3 subpanels (1x100amp for the pole barn/workshop and 2x60amp for other locations on the farm). I was planning on running 2-2-2-4 Dyke Quadruplex Aluminum Conductor 600V URD wire as the main feed for each of these sub-panels because I found a great deal on it. Each run to the sub-panel will be directly buried to each of the 3 different locations (see attached sat image)

My Questions:

• Is this wire sufficient to power each of these sub-panels using separate breakers (no feed-thru)?
• Is this wire overkill for what I am trying to accomplish?
• How should I go about hooking larger wire to breakers in the main box, or will this 2-2-2-4 wire fit into 100 or 60amp breakers without modification or tap lugs?
• Am I missing anything?

Any help or advice would be massively appreciated.

Answer 1

Stop. You're making the classic novice mistake.

I'm referring to sizing the subpanels.

Ever bought tires? They come in different speed ratings. Have you ever gone "My truck has never gone faster than 85 mph, therefore I can't use an HR rated tire"? Of course not. The fact that it's good for 112 mph, you see that as safety margin. Am I right?

Well, panels work exactly the same way. Even if you never plan to pull more than 60A, a 100A panel is better, and a 200A panel is better still.

Remember. The size of the subpanel does not decide the load. That's decided by the feed breaker in the main panel. The "main breaker" in the subpanel is nothing but a disconnect switch.

Your actual main panel has a 60A breaker feeding a 2-2-2-4. This goes to a 200A subpanel. Legit? YES. The subpanel has its own "main" breaker of 200A. Legit? YES. That breaker is nothing but a local disconnect switch. What is the rating of the subpanel? 60A. Because that's decided by the feed breaker. Is the panel running at redline? No, not nearly, it's well in its safety zone. And that's good, because it's outdoors.

Some people want the subpanel's local main breaker to be same size as the feed breaker. Their dream is that this local breaker will trip first, and save them a walk. Nope! That trick never works! But I'll come back to that.

And don't be chintzing out on panels anyway.

This one person thought the $20 6-space panel was a great bargain. #1 guess what, you need a main disconnect. Boom 2 spaces gone that the person did not expect to lose. Just for one each 120V and 240V utility sockets, the person now has 1 space left. They wanted a hot tub, well that takes 2 spaces, and they're out of space. Can't use double-stuffs because 2020 NEC pretty much outlaws them. That person is painted into a corner and must now install an 8-space, and will need to go 12-space for the next thing. How many times are you going to replace panels?

I put the person into a 24-space panel with a main breaker and with $20 worth of bonus breakers, for $70. So $30 more (net) and a vastly superior panel with plenty of expansion room. $30? That's a takeout pizza.

Spaces are cheap. Redoing work is expensive. Everytime you change a panel you risk damaging wire - and then you're really in trouble.

If it was hundreds of dollars of wire, sure. But c'mon. A pizza? Skip it and enjoy an installation with expansion room. You'll thank yourself later.

If I were paying for the panels - and I do pay for most of the panels I install - I would use a 12-space main-lug at the remote sites and a 30-space at the shop. Space not circuit... circuits mean nothing anymore.

The wire size

The 2-2-2-4 Al is a perfectly fine wire size for the runs you have "60A". Feel free to breaker those at 80A at the main, since that is allowed on 2-2-2-4 of any length (unless the length carries it into Canada, then no). "Nanny breakers" (downbreakering to a 60A to protect yourself from "voltage drop" ooga-booga) are not required in the USA or El NEC countries.

For the 100A run, you can't breaker the 2-2-2-4 at 100A, I'm sorry. You need to use at least #1 aluminum. Now, if you actually needed 100A, you'd be required to breaker for 125% of that, or 125A obviously. But let's say you actually need 80A, so you breaker for 100A.

Never calculate voltage drop on breaker trip. Either calculate it on expected load, or on 80% of breaker trip since that is the max you're allowed to plan to load. So that means we're calculating your workshop run at 80A.

• #1 wire gives 4.44% drop at 80A
• 1/0 wire gives 3.82% drop
• 2/0 wire gives 2.98% drop

So pick your poison.

You do need a "main breaker" (well, disconnect switch) at EACH subpanel

"6-space guy" got blindsided by needing a "main" breaker as a disconnect switch. In a 6-space panel, "main breakers" are placed in regular breaker positions and backfeed. Suddenly 2 of 6 spaces are gone - whoops!

However, you can use that same backfeeding trick (hopefully with a larger panel, say a 12-space) -- fit a plain common breaker at the top left, label it "Main Disconnect", apply a Tie-Down Kit, and feed the panel there.

This means you're using the same kind of branch circuit breaker that is supplying the panel at the other end. So that makes "trips locally first" at least a 50/50 proposition. (if the other one always trips first, swap them; that's just manufacturing tolerances.) You can help that even further by making the local breaker smaller. Say you use an 80A feed breaker at the main panel, and a 60A or even 30A "main breaker" in the sub. It's a "nanny breaker", sure, but it's helping you save a long walk.

Answer 2

Why not run conduit?

I noticed first that you seem to be wanting to direct bury your electrical cables; this is a massive mistake upfront, as renting a trencher to rerun cable costs a lot compared to the cost of throwing Schedule 40, or even Schedule 80, PVC in the ground vs. simply slapping a direct bury cable in there. I would run 2" PVC conduit (Schedule 40 underground, Schedule 80 at stub-ups) instead to the shop and 1.5" conduits to the other locations, and then pull the 2-2-2-4 URD/USE cables through the conduits; this gives you up to 90A at the polebarn and the two subsidiary locations, with the capacity to change the wires out for fatter ones, enabling you to run a 200A feeder to the polebarn and 125A feeders to the subsidiary locations at a later point in time, without the terrible expense of retrenching.

As to panel selection...

One of the other major mistakes most folks make when wiring buildings is to skimp on panel spaces. While your meter-main has a reasonable amount of capacity on that front (even if it's constrained by stab ampacity limits and such), chintzing on the subpanels is a poor plan. I would put a 40-space or 42-space, 200A, main breaker panel in at the pole barn, with the main breaker as the disconnect, and get some 125A, 24 space, NEMA 3R, main breaker panels for the various subsidiary locations. Getting a panel for the pole barn's outbuilding might be wise at this point in time, for that matter -- another one of these 24-space, 125A, main breaker panels will do quite nicely there, even. Don't worry about the oversized main breakers in these panels, by the way; they're simply there as cheap ways to get big disconnect switches to provide the Code-required local disconnect at each structure or fed point.

Note that with all these panels you're putting in, you'll need to get the appropriate ground bar kits for them and fit them to the panel if they aren't already factory fitted, as well as omitting the bonding screw that would be used to connect neutral-to-ground at a service entrance location, as all of these are subpanels (remote distribution panels), powered by feeders from the meter-loadcenter combo mounted on the pole. You'll also need grounding electrodes at the pole and at the remote sites; 2 8' ground rods driven 8' apart and connected to each other and the panel at the location in question with 6AWG bare copper will get the job done at all locations involved.

(P.S. if you were wishing to stay in Square D Homeline, the required parts would be a HOM4080M200PC, a trio of HOM2448M125PCs, and 4-5 PK23GTA ground bars, to go with a large coil of 6AWG bare copper and 8 8' ground rods.)

You don't have to do anything funny to make this wire fit the breakers, at least...

You won't have to do anything funny or special to make your wire of choice fit on the breakers, either. Homeline breakers from 35A through 90A (and beyond, but that doesn't matter here) all will accept 2AWG wire without issue. Furthermore, the main breaker and neutral lugs on most subpanels will have no trouble with this either, nor will any of the grounding bar connections as just about all equipment grounding bars will accept 4AWG wires.

However, there is one problem with wire sizing here, and that's the neutral bar on the meter-main you picked accepts a maximum of 4AWG for the neutral wire, save for the two large neutral lugs it provides. Fixing this will require at least one add-a-lug kit; the LK100AN is readily available and will get the job done.

TORQUE ALL LUGS TO SPEC (so you don't come out looking like a loose lugnut, or worse)

The one other downside with cheap URD cable, such as the stuff you found in the discount bin, is that much of it is made from AA-1350 (EC) aluminum, also known as the same stuff that had a hand in the Great Aluminum Wiring Debacle. While by no means categorically unsafe, AA-1350 wire is somewhat less forgiving to terminate than either copper or AA-8000 series alloy wires, so it's critically important you use proper termination procedures. A proper joint (anti-oxidant) compound should be used, and more importantly, you must use an inch-pound torque wrench or torque screwdriver (depending on how much torque you need to apply) to tighten all breaker and loadcenter lugs that you are using to their labeled specification torques. This is not only a new Code requirement as of 2017 (see NEC 110.14(D) for details), but is a very good idea anyway, as most of the issues aluminum wiring ever had had to do with bad terminations at devices, something that proper lug torquing helps prevent!

Answer 3

Direct burial is a very expensive way to be cheap. Which you won't discover until the second time you have to dig the trench. Once you have paid (whether in money or time) to open the trench, laying conduit is cheap insurance to never have to do that again.

Choosing wire size "because I got a great deal on it" rather than "because it's the right size" is only good when the wire is also larger than the right size, which this is quite arguably not. Likely just adequate for the 60A sub-panels, quite dubious for the 100A "workshop" since that seems likely to use much of its rated capacity at times (welders, power tools, etc. just based on typical farm workshops since you provide no load details.)

Answer 4

The number 2 wire at those distances for anything more than a 60 amp load, will have a large voltage drop. The 300’ and 275’ 60 amp will work with the voltage drop being 4.4% this will work , it is above the recommended 3% but also at full load for those distances. Number 2 aluminum is two small for a 100 amp service. You will need to bump up to 1/0 aluminum for that or drop to a 75 amp feeder breaker you will have a 5.04% drop at full load there with number 2.