NEC 310.16 Feeder Sizing
What Size Wire for a 60 Amp Sub-Panel?
The feeder conductor, equipment ground, breaker, conduit, and voltage drop for a 60 amp sub-panel, plus the 4-wire feeder and neutral-isolation rules that pass inspection. Pick your material and run length below.
Sub-Panel Wire Size Chart (Copper & Aluminum)
| Sub-panel | Copper feeder | Cu ground | Aluminum feeder | Al ground | Breaker |
|---|---|---|---|---|---|
| 60 A | 6 Cu | 10 | 4 Al | 8 | 60 A |
| 100 A | 3 Cu | 8 | 1 Al | 6 | 100 A |
| 125 A | 1 Cu | 6 | 2/0 Al | 4 | 125 A |
| 150 A | 1/0 Cu | 6 | 3/0 Al | 4 | 150 A |
| 200 A | 3/0 Cu | 6 | 250 Al | 4 | 200 A |
Conductors at the 75°C column of Table 310.16 (feeder lugs are 75°C-rated, NEC 110.14(C)). Aluminum is one to two sizes larger than copper for the same rating. The equipment grounding conductor is sized from Table 250.122 by the breaker, not by the feeder size.
How to Wire a 60 Amp Sub-Panel: Isolate the Neutral
The single most-failed sub-panel detail is the neutral bond. A sub-panel is on the load side of the service, so the neutral and ground are separated here and bonded only back at the main panel.
A sub-panel feeder carries four conductors: two ungrounded (hot) legs, a grounded (neutral) conductor, and a separate equipment grounding conductor. The neutral and the ground are separate conductors all the way to the sub-panel - never a shared 3-wire feed.
In the sub-panel the grounded (neutral) bus and the equipment-ground bus must be kept separate. Remove the main bonding jumper - the green bonding screw or strap that ties the neutral bar to the metal can. Bonding neutral to ground here would put normal neutral current onto the ground path and every metal enclosure downstream.
The one place the neutral and ground are bonded is the service disconnect (the main panel), via the main bonding jumper. The grounded conductor cannot be reconnected to ground on the load side of that service disconnect, which is exactly what a sub-panel is.
A sub-panel in a separate building or structure still gets a 4-wire feeder with the neutral isolated, plus its own grounding electrode (a ground rod or rods) connected to the sub-panel's ground bar. New feeders to a separate structure must include an equipment grounding conductor - the old 3-wire feed is allowed only on existing installations.
Frequently Asked Questions
What size wire do I need for a 60 amp sub-panel?
A 60 amp sub-panel feeder uses 6 copper or 4 aluminum ungrounded (hot) and neutral conductors, sized from NEC Table 310.16 at the 75°C column. Run a 10 copper (or 8 aluminum) equipment grounding conductor with them per Table 250.122, protected by a 60 amp feeder breaker (NEC 240.6). This is a 4-wire feeder: two hots, a neutral, and a separate ground.
Is #4 copper enough for a 100 amp sub-panel?
Only when the feeder carries the entire dwelling load. NEC 310.12 permits a reduced conductor (#4 copper at 100 A) for the service or the main feeder that supplies an entire one-family dwelling. A sub-panel that feeds only part of the home does not qualify, so it is sized from Table 310.16 instead - #3 copper for 100 A. Using the 310.12 number on a partial-load sub-panel is the most common sizing mistake.
Do you bond the neutral and ground in a 60 amp sub-panel?
No. The neutral (grounded) bar and the ground (equipment grounding) bar must be kept separate in any sub-panel. Remove the main bonding jumper - the green bonding screw or strap. The neutral-to-ground bond is made only at the service disconnect (NEC 250.24, 408.40). Bonding them in the sub-panel puts normal neutral current on the ground path and every metal enclosure downstream, which is a shock hazard and a failed inspection.
What size equipment ground for a 60 amp sub-panel?
10 copper or 8 aluminum. The equipment grounding conductor is sized from NEC Table 250.122 by the feeder breaker rating (60 A), not from the size of the feeder conductors and not from Table 250.66 (that is the grounding electrode conductor, a service conductor). If the feeder is upsized for voltage drop, the EGC is upsized proportionally per 250.122(B).
Does a detached-garage sub-panel need a ground rod?
Yes. A sub-panel in a separate building or structure gets its own grounding electrode (a ground rod or rods, or other electrode present) connected to the sub-panel ground bar, plus the 4-wire feeder with the neutral still isolated (NEC 250.32(B)). New feeders to a separate structure must include an equipment grounding conductor; the old 3-wire feed is allowed only on existing installations.
Other Sub-Panel Sizes
100 Amp Sub-Panel
3 Cu feeder, 8 ground, 100 A breaker.
125 Amp Sub-Panel
1 Cu feeder, 6 ground, 125 A breaker.
150 Amp Sub-Panel
1/0 Cu feeder, 6 ground, 150 A breaker.
200 Amp Sub-Panel
3/0 Cu feeder, 6 ground, 200 A breaker.
Wire Size Calculator
Size any conductor for ampacity, derating, and voltage drop.
Feeder sized. Will the main panel carry it?
A 60 A sub-panel adds load to the service. Check whether the main panel has the headroom before you tap it.