Conduit, Pull-Box, and Voltage-Drop Questions
Quick answers about the calculator, its planning assumptions, and the information shown in its reports.
What fill percentage should I use for low-voltage cable?
The calculator defaults to a 40% low-voltage planning fill. Project specifications, adopted codes, manufacturer guidance, pulling conditions, or design standards may require a lower value.
Can the calculator recommend more than one conduit?
Yes. When the cable load exceeds one raceway, the calculator can recommend a multi-conduit capacity plan and distribute the entered cables across the selected conduits.
Which conduit types are included?
The current library includes EMT, IMC, RMC, PVC Schedule 40, and PVC Schedule 80. Available trade sizes depend on the selected conduit family.
Can I enter a cable that is not in the library?
Yes. In any cable category, select Custom / user-entered under Manufacturer or Custom round cable under Cable product, then enter the outside diameter. You may also add a custom name and description for reports.
Does the calculator account for conduit bends?
Yes. Bend information and pathway warnings are tracked independently from fill. The default NEC fill method applies no automatic bend-based reduction, including for electrical conductors. Optional manufacturer/project planning allowances can reduce capacity per 90-degree equivalent or use a project-approved adjusted fill percentage. These optional allowances are not NEC fill rules and do not replace pulling-tension, sidewall-pressure, bend-radius, or cable-jamming analysis.
Can the Pull Box Size Calculator handle multiple conduits?
Yes. Add a paired run for each conduit path and select the entry and exit walls. The calculator automatically includes the conduit openings entered on each wall and evaluates straight, angle, U-pull, and paired-entry-spacing requirements together.
Why does the Pull Box Size Calculator not calculate depth?
The straight, angle, and U-pull multipliers establish plan-view length and width clearances, but they do not establish one universal enclosure depth. Enter the proposed usable inside depth and verify conductor bending space, splices, hubs, covers, and enclosure construction for the project.
What does the Branch Circuit Wire Size Calculator cover?
It coordinates the site's 2023 NEC ampacity, voltage-drop, and wire-type equipment-grounding workflows for common DC, single-phase, and balanced three-phase circuits using one non-parallel conductor per phase. The user must confirm the protective device and current-carrying-conductor count. It does not model neutrals, motors, HVAC, welders, EV-specific rules, taps, dwelling allowances, hazardous locations, or complete code compliance.
Does the Voltage Drop Calculator size conductor ampacity?
No. Its recommendation is the smallest modeled conductor that meets the selected voltage-drop target. Verify ampacity, continuous-load sizing, correction and adjustment factors, terminal ratings, overcurrent protection, fault current, and applicable requirements separately.
What does the Wire Ampacity Calculator cover?
It models a common 2023 NEC Table 310.16 workflow: table ampacity, ambient-temperature correction, current-carrying-conductor adjustment, a user-confirmed terminal-temperature limitation, continuous-load treatment, and the general small-conductor overcurrent-protection cap. It does not determine neutral counting, exceptions, equipment listing compatibility, special equipment rules, rooftop conditions, parallel conductors, or complete code compliance.
What does the Equipment Grounding Conductor Calculator cover?
It models a narrow 2023 NEC Table 250.122 wire-type EGC workflow through 600 A and proportionally increases circular-mil area when the installed phase conductor is larger than the entered minimum phase conductor. It excludes parallel raceways, raceway-as-EGC determinations, fault-current-path verification, motors, taps, special equipment rules, and complete code compliance.
What does the Electrical Box Fill Calculator cover?
It adds the six 2023 NEC 314.16(B) allowance categories for 18 AWG through 6 AWG conductors in one undivided outlet, device, or junction-box space. It covers counted conductors, ordinary internal clamps, luminaire studs and hickeys, device yokes, entering equipment grounding conductors, and terminal-block assemblies. It excludes barrier-separated volume, special integral clamp assemblies, conduit-body sizing, 4 AWG and larger conductors, and complete code compliance.
Do internal pigtails count in electrical box fill?
A conductor that remains entirely inside the box is not entered as a separate conductor allowance in this calculator. Count only equipment grounding conductors that enter the box; an equipment bonding jumper that begins and ends within the box is not included. Device yokes, terminal blocks, clamps, and support fittings may still require their own allowances.
What circuit length should I enter for voltage drop?
Enter the one-way source-to-load distance. The calculator applies the return-path factor for DC two-wire and single-phase systems or the square-root-of-three factor for balanced three-phase systems.
Can voltage drop include both a feeder and branch circuit?
Yes. Choose the feeder-plus-branch layout and enter each segment's one-way length and conductor. The result separates the segment drops and compares their combined drop with the selected target.
How are watts and kVA converted to current?
Real power in watts or kilowatts uses voltage, phase, and AC power factor. Apparent power in VA or kVA uses voltage and phase without applying power factor a second time. The calculated amperes are displayed before the voltage-drop result.
Are the results a final engineering design?
No. Results are planning calculations. Verify the adopted code, project specifications, exact manufacturer data, installation conditions, and authority-having-jurisdiction requirements before use.
Does cable tray fill account for imperfect cable packing?
Only when the user selects an installation allowance. The default is 0%; presets include 10%, a recommended 20% typical-field allowance, 30%, and a custom value. The allowance adjusts planning demand but is not presented as a code requirement.
Does the Cable Tray Fill Calculator include manufacturers?
Yes. The manufacturer library includes published tray dimensions for Eaton B-Line, Legrand Cablofil, nVent HOFFMAN, Hubbell, and Snake Tray products, while generic custom dimensions remain available. Confirm the exact catalog number and usable dimensions before specifying equipment.
Does cable tray fill verify structural loading?
No. Fill and cable weight are not substitutes for tray load class and support-span verification. Confirm the selected product, supports, fittings, grounding, separation, and governing installation requirements.
What does the Conduit Jam Ratio Calculator verify?
It divides conduit inside diameter by the outside diameter of one identical round cable and classifies the published jamming-risk range for three or more cables. Cable quantity does not change that diameter ratio, so the calculator separately checks quantity-sensitive conduit fill and maximum identical-cable capacity. It does not verify pulling tension, sidewall pressure, bend radius, lubricant, or cable pulling limits.
Does the Conduit Offset and Rolling Offset Calculator provide exact bender marks?
It provides planning marks from the published common shrink factor and ideal travel, plus standard and rolling-offset geometry. Exact field marks can vary with bender take-up, shoe radius, gain or deduct method, springback, conduit material, and manufacturer instructions, so those items must still be verified.
Does a ground wire count in conduit fill?
Yes. A wire-type equipment grounding conductor occupies physical space and is included in conduit fill, even though it is not normally counted as a current-carrying conductor for ampacity adjustment. Conduit Fill and Conduit Size can optionally calculate and add one supported EGC for an electrical-only, single-circuit, non-parallel raceway workflow.
How does the conduit calculator choose ground wire size?
It uses the confirmed breaker or fuse rating, copper or aluminum EGC material, and minimum versus installed phase-conductor sizes through the existing supported 2023 NEC Table 250.122 workflow. It does not guess ground wire size from the phase conductor alone, and an exact insulated product must be selected for verified outside diameter.
Which conduit bending calculator should I use?
Use Conduit Offset and Rolling Offset to change elevation or direction, 3-Point Saddle Bend for a narrow obstruction, 4-Point Saddle Bend for a wider obstruction, and 90° Conduit Stub-Up for a finished rise.
Are the saddle and stub-up marks exact for every bender?
No. The calculators use published field tables or centerline geometry. Confirm the actual bender symbols, take-up, shoe radius, compatible conduit, springback, and obstruction clearance before bending.