Pole barn electrical wiring runs from the house panel to the last outlet in the barn. A typical setup is a 100 amp subpanel in the barn, fed by a four-wire aluminium cable buried between the two buildings. Here is how to handle wiring a pole barn, in five steps:

1. List every load and size the subpanel.

2. Pick a feeder cable rated for the barn breaker, such as 1/0 aluminum URD quadruplex for a 100A subpanel.

3. Check the voltage drop along the actual run and upsize the cable if needed.

4. Bury the feeder at least 24 in deep for direct burial cable, or 18 in deep in PVC conduit. An overhead feeder needs 12 ft of clearance over yards and driveways.

5. Wire the barn interior for its conditions: UF-B or conduit in damp barns, PVC conduit where livestock are housed, and NM-B only in dry, finished spaces.

This guide covers feeder cable sizes, voltage drop, burial depth, a pole barn wiring diagram, interior wiring methods, and layout ideas.

Plan the load before you buy  pole barn wire

Check your home's electrical capacity. A 200A service must supply both the house and the barn. Calculate their combined electrical load to make sure it stays within the service rating. If the load exceeds 200A, you may need a service upgrade. A 200A barn subpanel is still possible, provided the total calculated load stays within the available capacity.

Choose the feeder cable for your pole barn

A pole barn feeder needs four conductors: two hots, a neutral, and an equipment grounding conductor. NEC 250.32(B)(1) requires the separate ground for any feeder to a detached building. Here are the types of cable s used:

• Mobile home feeder (MHF): A practical choice for underground power to a pole barn subpanel. It bundles two hot conductors, a neutral, and a ground in one aluminum cable. Direct-burial-rated MHF can be buried without continuous conduit.

• THHN/THWN-2 or XHHW-2 in conduit: Four individual conductors pulled through underground PVC conduit. THHN/THWN-2 is commonly used for copper wiring, while XHHW-2 is a popular choice for larger aluminum feeders. Both are suitable for wet locations when properly rated, and conduit makes future wire replacement easier.

• UF-B: A direct-burial copper cable for a small pole barn that only needs one circuit for lights and a few outlets. It can eliminate the need for a subpanel but isn't suitable for supplying a full workshop with multiple circuits.

Pole barn feeder sizes by breaker

The sizes below come from NEC Table 310.16, 75°C column, which applies when the breaker and panel lugs carry a 75°C rating. 

Important: Mobile home feeder (MHF) cable contains two hot conductors, a neutral, and an equipment grounding conductor. Although designed for manufactured homes, suitably listed MHF cable can also serve an underground feeder to a detached pole barn. Verify direct-burial and building-entry ratings before installation.

The linked MHF assemblies use larger conductors than the minimum sizes in some rows. For 200A, use individual 250 kcmil aluminum conductors with an appropriately sized neutral and equipment ground in conduit. Standard 4/0 aluminum MHF is rated 180A at 75°C under NEC 310.16; its 200A dwelling-feeder rating does not automatically apply to a pole barn.

The 2-2-2-4 constructions are the cables pole barn owners ask about most, and many sources call them 100 amp cable. That rating comes from NEC 310.12, which allows smaller conductors only for the main service or feeder that carries the entire load of a dwelling. A pole barn subpanel does not carry the whole house load, so 310.12 does not apply. Under Table 310.16, 2 AWG aluminum carries 90A, so it pairs with a 90A breaker. Step up to 1/0 aluminum for a full 100A.

Check Voltage Drop on Long Runs

A wire can have enough ampacity for the barn's breaker but still be too small for a long feeder run. NEC 210.19 and 215.2 provide informational guidance recommending no more than 3% voltage drop on a feeder and 5% combined across the feeder and branch circuit.

Excessive voltage drop can reduce welder performance and make compressor motors harder to start.

Voltage drop (%) = (2 × L × R × I × 100) / (1,000 × V)

Here, L is the one-way run length in feet, R is the conductor resistance in ohms per 1,000 feet from NEC Chapter 9, Table 8, I is the load in amps, and V is the supply voltage (240V in this example).

Voltage Drop at an 80A Load, 240V

These estimates use conductor resistance at 75°C and an 80A load at 240V. Actual voltage drop depends on the equipment operating at the same time. Lighter loads produce less voltage drop, while 120V circuits and motor starting conditions require separate consideration.

At 80A and 240V, 2 AWG aluminum reaches approximately 3% voltage drop at 140 feet, 1/0 aluminum at 225 feet, 2/0 aluminum at 280 feet, and 4/0 aluminum at 450 feet. These distances indicate voltage-drop performance, not breaker compatibility. The conductor must also have sufficient ampacity for the feeder.

Burial depth for an underground feeder

NEC Table 300.5 sets the minimum cover, measured from the top of the cable or conduit to finished grade.

NEC 300.5(D)(1) requires conduit where a direct buried cable rises out of the ground, from the minimum depth up to 8 feet above grade or into the panel. Backfill the first layer with sand or clean soil, since 300.5(F) prohibits rock that can damage the cable. A warning tape about 12 inches above the cable costs little and protects the next person who digs.

Overhead clearances

An overhead feeder needs a cable rated for the span and these clearances from NEC 225.18 for 120/240V systems:

• 10 ft above areas reached by pedestrians only

• 12 ft above residential driveways and yards

• 18 ft above public roads and areas with truck traffic

Farm equipment usually decides the real height. Measure the tallest machine that passes under the span before you settle on overhead.

Pole barn wiring diagram

The diagram shows the standard pole barn electrical wiring layout: one feeder from the house, one subpanel, and a separate grounding system at the barn.

pole barn wiring diagram · house panel to subpanel, ground rods, branch circuits

1. Feeder breaker at the house: A 2-pole breaker in the main panel, sized to the feeder conductors.

2. Four-wire feeder: Two hots, a neutral, and a ground run together to the barn, in conduit where the cable leaves the ground at each end (NEC 300.5(D)).

3. Barn disconnect: NEC 225.31 and 225.32 require a disconnect at the barn, nearest the point where the feeder enters. A subpanel with a main breaker serves as that disconnect.

4. Neutral and ground kept separate: The neutral lands on an isolated bar. The ground lands on a bar bonded to the enclosure. Remove the bonding screw or strap that ships with most panels.

5. Ground rods: NEC 250.32(A) requires a grounding electrode at the barn. A single rod must test at 25 ohms or less under 250.53(A)(2), so most installers drive two rods at least 6 ft apart.

6. Branch circuits: Lights run on their own circuit with a switch at the door. One GFCI receptacle protects the outlets downstream of it. The 240V welder receptacle takes two hots and a ground, with no neutral.

Wire the inside of the pole barn

The right wiring method depends on how the pole barn is used. In a dry, enclosed workshop, NM-B cable is suitable for wiring inside finished walls where permitted. For an open barn exposed to moisture, use UF-B cable or THWN-2 wires in conduit. Barns that house livestock may also fall under NEC Article 547, which has additional requirements for wiring in damp and corrosive environments.

Pole barns have girts and posts instead of studs, so cable often runs exposed across the girts. Many inspectors treat cable within reach of a tractor or a stack of lumber as subject to physical damage and want it in conduit or behind a liner panel. Mount boxes on blocking between posts, not on steel siding.

Livestock Barns and Article 547

NEC Article 547 covers agricultural buildings exposed to excessive dust, moisture, or corrosive conditions from animal waste. Ordinary NM-B cable (Romex) is not permitted in these areas because it is designed for dry indoor locations.

NEC 547.20 allows more suitable wiring methods, including UF-B cable, moisture- and corrosion-resistant NMC cable, and appropriately rated jacketed MC cable. Another option is THWN-2 wires in PVC conduit, with Schedule 80 PVC or other suitable protection where livestock or equipment could damage the wiring.

NEC 547.44 also requires special electrical bonding in certain livestock areas with concrete floors. A metal grid in or beneath the floor is connected to nearby metal equipment and the grounding system. This helps prevent electric shocks when an animal stands on the concrete and touches a metal water trough, fence, or other equipment.

Pole Barn Electrical Layout and Planning Tips

Lighting

• Put lights on their own circuit, so a tripped welder breaker does not leave you in the dark.

• Add a 3-way or 4-way switch at every walk door, so you never cross a dark barn to reach a switch.

• Hang LED high-bay or strip fixtures above the travel height of the tallest machine.

• Wire a dusk-to-dawn or motion fixture over each large door on a separate circuit.

Receptacles

• Mount receptacles about 48 in above the floor, above workbench height and clear of stored equipment.

• Space duplex or quad boxes every 6 to 8 ft along the bench wall.

• Add a ceiling receptacle for a cord reel and another for each garage door opener.

• Place the 240V welder receptacle near the main door, where long stock and trailers come in.

GFCI protection

NEC 210.8(A) requires GFCI protection for 125V through 250V receptacles in accessory buildings at dwellings. Under the 2023 NEC, that includes a 240V welder receptacle. Barns on commercial or farm property fall under 210.8(B). Water trough heaters and outdoor receptacles need GFCI protection in both cases.

Future-proofing

• Buy a subpanel with at least twice the breaker spaces you need on day one.

• Lay a 2 in conduit in the trench even when you bury URD, for a future upgrade or a second feeder.

• Run a separate conduit for ethernet or fiber in the same trench, so cameras and Wi-Fi reach the barn.

• Add a generator inlet with an interlock at the barn panel if livestock water or heat depends on power.

• Install a surge protective device at the barn panel. A long feeder picks up lightning surges that a house panel never sees.

Pole barn electrical wiring FAQ

These are real questions pole barn owners sent to the Nassau National Cable team.

Is 2-2-2-4 aluminum enough for a 100 amp pole barn subpanel?

Not at a full 100A. 2 AWG aluminum carries 90A under NEC Table 310.16, and the 310.12 dwelling allowance does not cover a barn subpanel. Use a 90A breaker, or move up to 1/0-1/0-1/0-2 Notre Dame URD for 100A.

Will 1/0 aluminum quadruplex feed a 100 amp subpanel 170 feet away?

Yes. 1/0 aluminum carries 120A, and an 80A load over 170 feet drops about 2.3%, inside the 3% target.

What wire runs a 125 amp subpanel about 120 feet to a pole barn?

2/0 aluminum, rated 135A, with a 4 AWG aluminum ground. 2/0-2/0-2/0-1 Syracuse URD fits, and a full 100A load over 120 feet drops about 1.6%.

Can 4/0-4/0-4/0-2/0 URD run 200 amp service 220 feet to a pole barn?

Yes, with one condition. 4/0 aluminum carries 180A, and NEC 240.4(B) allows a 200A breaker only when the calculated load stays at or below 180A. At a 160A load, 220 feet of 4/0 Wake Forest URD drops about 2.9%.

Does a pole barn need four wires from the house?

Yes. NEC 250.32(B)(1) requires two hots, a neutral, and a separate ground to a detached building. The neutral stays isolated from the ground at the barn panel, and the barn gets its own ground rods.

Can I run Romex from the house to the pole barn?

No. NM-B cannot be buried or used in wet or damp locations under NEC 334.12. Use URD or MHF for the feeder, and UF-B for a single small circuit. NM-B works only in dry, finished areas inside the barn.

Copper or aluminum for a pole barn feeder?

Both meet code when sized correctly. A 100A copper feeder in conduit uses 2 AWG THWN-2 for the hots and neutral and an 8 AWG copper ground. Aluminum costs less per amp and makes more sense on long runs.

What feeds a pole barn with a welder and an air compressor 150 feet away?

A 100A subpanel on 1/0 aluminum covers both. At an 80A load, 1/0 drops about 2.0% over 150 feet, while 2 AWG drops about 3.2%.

Get the right cable for your pole barn

Pole barn electrical wiring comes down to three numbers: the barn breaker, the one-way distance, and the load you expect on a busy day. Those three numbers pick the feeder, and the NEC sections above tell you how to install it.

Nassau National Cable stocks URD quadruplex, mobile home feeder, and UF-B in cut lengths and full reels, shipped from four U.S. warehouses. Send us your breaker size and run length, and our team will confirm the cable before you dig.