WireGaugeCalc Free calculator · NEC cited · works offline
Ground Conductor Size For Parallel Feeders
Ground conductor size for parallel feeders is quick with WireGaugeCalc, since the tool sizes the equipment grounding conductor from the breaker rating using NEC 250.122.
You enter the overcurrent device size and the conductor material, so each raceway gets the right grounding conductor.
The payoff is a correctly sized ground for every parallel run, ready for inspection.
Open the calculatorSmallest conductor whose ampacity meets the load, NEC Table 310.16. Field aid only, verify against the current NEC and your local authority having jurisdiction.
Grounding Each Parallel Raceway
The equipment grounding conductor is sized from the overcurrent device per NEC 250.122, so a larger breaker calls for a larger ground.
When feeders run in parallel through separate raceways, each raceway needs a full-size grounding conductor, not a split share.
Switching the material updates the size, since aluminum grounding conductors are larger than copper for the same rating.
What Sets The Grounding Conductor Size
The parallel feeder ground depends on:
- The overcurrent device rating per NEC 250.122
- One full-size grounding conductor in each parallel raceway
- Conductor material, copper or aluminum
- Any upsizing when the ungrounded conductors are increased
- The 1/0 minimum that allows conductors to be paralleled
One app for every NEC calculation
WireGaugeCalc keeps the calculations you reach for most in one place:
- Voltage drop and wire sizing for any run
- Conduit fill for EMT, PVC, and RMC
- Box fill and junction box sizing
- Ampacity and temperature derating
- Motor circuit and load calculations
- Conduit bend offsets and saddles
Built for the field, works offline
The whole app runs on your phone, so it keeps working in a basement, an attic, or a job site with no signal.
There is no account to create and nothing to load. Open it, run the number, and get back to work.
- No signup and no signal needed
- Answers in a tap, not a spreadsheet
- Same tool on phone, tablet, and desktop
Every result cites the NEC article
Each answer shows the table or formula it came from, so you can check the method and learn the code as you go.
That makes the app useful on the job and during exam prep, since the reasoning is right next to the number.
Switch the code year your job runs on
Jurisdictions adopt the NEC at different times, so you can match the calculation to the code in force:
- NEC 2017, 2020, and 2023 tables
- Copper and aluminum conductors
- 60, 75, and 90 degree C terminations
- Single-phase and three-phase systems
Run the number, then get back to work
Stop flipping through a paper book or hopping between calculator sites. Enter your values, read the code-cited answer, and move on. Free to use, no signup.
Open the calculatorFrequently asked questions
Does each parallel raceway need its own ground?
Yes, NEC 250.122 requires a full-size equipment grounding conductor in each raceway of a parallel run. You cannot divide one grounding conductor across the parallel sets. Verify against the current NEC and your local authority having jurisdiction.
How is the parallel feeder ground sized?
It is sized from the rating of the overcurrent device protecting the feeder using NEC 250.122. The ground does not scale with the number of parallel conductors, only with the breaker size.
Do I upsize the ground if I upsize the phase conductors?
Yes, if you increase the ungrounded conductors for voltage drop, NEC 250.122(B) requires the grounding conductor to be increased proportionally. The calculator reflects that adjustment.
Is WireGaugeCalc free to use?
Yes. Every calculator is free to run with no signup. A paid tier adds saved projects, PDF reports, and extra code years, but the core math stays free.
Does it work without internet?
Yes. The app runs on your device, so it keeps working with no signal on a job site, in a basement, or in an attic.
Are the results code accurate?
Results follow published NEC tables and standard formulas, and each answer shows the article it came from. It is a field aid, not a stamp of approval, so verify against the current code and your local authority before you wire anything.
Which NEC code year does it use?
You can switch between NEC 2017, 2020, and 2023, since jurisdictions adopt the code at different times. Pick the year your job runs on.