Temporary Power Cord Screening Tool
Screen temporary power cord current and voltage drop using cord data, jobsite allowable current, circuit phase, and a user-entered voltage-drop target.
Cord and load details
Enter the distance from source to load; the calculation accounts for the return path or balanced three-phase factor.
Use manufacturer data for the actual cord and expected temperature.
Enter the applicable allowable current after cord, temperature, grouping, and jobsite conditions are considered.
Enter the project or equipment criterion; this is not a universal code limit.
Estimated load voltage
About this screen
Enter the circuit configuration, load, one-way cord length, cord conductor resistance, allowable current for the actual setup, and a voltage-drop target. The screen reports current and voltage-drop checks separately.
Use it as a preliminary jobsite check. It does not select a cord or verify the temporary wiring installation.
Method and assumptions
Voltage drop is estimated from circuit current, one-way length, one-conductor resistance per 1,000 feet, and a path factor of 2 for single-phase or the square root of 3 for balanced three-phase. The maximum one-way length uses the same entered target and conditions.
The allowable current and voltage-drop target are user inputs. Use values that account for the exact cord construction, temperature, connectors, load, protection, and jobsite environment.
Interpret the result
The current result compares load current with the allowable value you entered. The voltage-drop result compares estimated drop with your entered target. Both checks must be reviewed with the actual temporary power plan and jobsite requirements.
FAQs
Which current rating should I enter?
Enter the allowable current for the exact cord and installation after the applicable cord rating, temperature, grouping, protection, and jobsite conditions are reviewed. Do not use the result to choose an extension cord.
How should I enter cord length and resistance?
Enter one-way distance from source to load and the manufacturer’s resistance for one conductor per 1,000 feet. The estimator accounts for the return path in single-phase circuits.
Does a passing screen approve temporary wiring?
No. Verify cord type, connectors, overcurrent protection, grounding, GFCI, wet or damp exposure, physical protection, inspection, and applicable OSHA, code, and site requirements.
Sources
- Use the cord manufacturer’s data sheet for conductor resistance, cord construction, and product rating.
- Use the jobsite temporary power plan, applicable safety rules, and authority requirements to establish allowable current and the voltage-drop target.