Takeoff & Estimating — Electrical & Low-Voltage

Branch Wiring

The final circuit wiring from a panel breaker out to the outlets.

Quick Answer

Branch wiring is the circuit conductors between the final overcurrent device in a panel and the outlets they serve, such as receptacles, lights and equipment connections. In a takeoff it is measured in linear feet of conductor, cable or conduit, plus counts of boxes and devices.

The Full Picture

The key idea is where branch wiring starts and stops. Under the OSHA electrical definitions, a branch circuit is the conductors between the final overcurrent device and the outlets. Anything upstream of that breaker, between the service and the panel, is a feeder. Branch wiring is the largest wiring quantity on most buildings, since every receptacle, light and small piece of equipment needs a circuit, but each run is short and repetitive.

Branch wiring shows up on the lighting plans, power plans, panel schedules and equipment connection schedules. Home runs are the lines or arrows drawn from the first device toward the panel, with hash marks that show the number of conductors and a circuit number such as LP-12. Panel schedules list the circuits each breaker serves and the load. Specifications set the wiring method, whether metal-clad cable, nonmetallic cable where permitted, or conductors pulled in conduit, and any minimum conductor size.

Estimators usually measure branch wiring as linear feet of the wiring method, then multiply by the conductor count for pulled wire. Device and box counts are taken separately in EA, because the device is where the plan symbol sits. Vertical drops from the ceiling or into walls are rarely drawn, so estimators add a drop for each device from the floor-to-ceiling and mounting heights, and add slack at each box for making up the connection. Allowances for waste and slack are an assumption each estimator sets, not a code value.

The recurring mistakes are leaving out vertical drops, counting the homerun length once for a multi-circuit home run that shares a raceway, and missing the conductor count in a home run drawn with hash marks. Dedicated circuits, such as kitchen equipment or mechanical connections, are easy to omit because they appear in equipment schedules, not on the lighting plan.

Real Examples

→Worked takeoff: one receptacle circuit in conduit: A circuit serves 8 receptacles. The home run from the panel to the first box is 40 LF, and the 7 spans between boxes are 12 LF each, so raceway is 40 + (7 x 12) = 124 LF. With a hot, neutral and ground conductor, wire is 124 x 3 = 372 LF. Add an assumed 2 ft of tail per conductor at each of the 8 boxes: 8 x 3 x 2 = 48 LF. Total conductor is 372 + 48 = 420 LF, with 8 boxes and 8 devices counted EA.

→Dedicated circuits: The mechanical schedule shows four unit heaters with a circuit each. None appear on the power plan as receptacles, so the estimator adds four home runs and four disconnect or connection points from the equipment schedule.

→Drops to devices: Wall receptacles mount at a standard height and the ceiling is 10 ft. A drop of the difference is added from the ceiling junction to each device, and the estimator multiplies it by the device count so the vertical wiring is not lost between plan views.

Common Misconceptions

People assume: Branch wiring and feeder wiring are the same thing.

Actually: They are separated by the last overcurrent device. The OSHA definitions put the feeder upstream of the final branch-circuit breaker and the branch circuit downstream, and the two are usually priced as separate lines.

People assume: Measuring the plan length of a run gives the full wire quantity.

Actually: Plan length misses vertical drops, slack at boxes and the conductor count. A run measured once in LF is multiplied by the number of conductors, then adjusted for drops and slack.

Does MeltPlan Solve This?

Partially — adjacent

Branch wiring lengths, device counts and circuit runs are measured from electrical plans, and MeltPlan's takeoff service covers that measuring: AI pulls quantities from the plans, and US-based experienced estimators review and adjust them. The wiring method, drop and slack allowances, and labor assumptions stay with your estimator.

Get circuit runs and device counts measured from plans →

Frequently Asked Questions

What is branch wiring?

Branch wiring is the wiring between the final overcurrent device and the outlets. It is the last part of the circuit and carries power to receptacles, lights and connected equipment.

How is branch wiring measured in a takeoff?

Estimators measure the run in linear feet from the plan, multiply by the number of conductors for pulled wire, and add drops and slack. Boxes and devices are counted separately in EA.

What is a home run?

A home run is the circuit's run from the first device or fixture back to the panel. On plans it is drawn as a line with hash marks that give the conductor count, and it is often the longest piece of the circuit.

How is branch wiring different from a feeder?

A feeder carries power from the service or a source to a panel. Branch wiring begins at the breaker in that panel and ends at the outlet. The two are priced separately.