Load Entry Form
Formula Used
Lighting load = floor area × lighting VA rate.
Small appliance load = number of small appliance circuits × 1500 VA.
Laundry load = number of laundry circuits × 1500 VA.
Connected load = general 120V load + specific 120V load + 240V load + continuous load + largest motor load.
Demand load = non-continuous load × demand factor + continuous load × 125% + largest motor load × 125%.
Service current = total demand VA ÷ 240V ÷ power factor.
Neutral current = absolute difference between Leg A 120V VA and Leg B 120V VA ÷ 120V.
Target service current = service current × spare capacity multiplier.
How to Use This Calculator
Enter all known construction loads in volt-amperes. Use watts when the power factor is near one. Add floor area for lighting estimates. Enter 120V loads by leg when known. Add 240V appliances as total connected VA. Set the demand factor based on your design method. Press the calculate button. Review service amps, leg balance, neutral current, and recommended service size.
Example Data Table
| Load Item | Example Value | Notes |
|---|---|---|
| Floor area | 1,200 sq ft | Used for lighting load. |
| Lighting rate | 3 VA per sq ft | Creates 3,600 VA. |
| Small appliance circuits | 2 | Creates 3,000 VA. |
| Range load | 8,000 VA | Shared across both legs. |
| Continuous load | 1,200 VA | Calculated at 125%. |
Construction Load Planning Guide
Why Single Phase Load Checks Matter
A 120/240 single phase service is common in houses, shops, garages, and light construction projects. It has two ungrounded legs and one grounded neutral. Loads at 240 volts use both legs. Loads at 120 volts use one leg and the neutral. Good planning keeps the service practical, safe, and easier to inspect.
Connected Load Review
The first step is to list every expected load. Lighting, receptacles, appliance circuits, heating, cooling, tools, water heaters, ranges, and dryers should be included. Some values come from nameplates. Some values come from design assumptions. This calculator keeps each value visible, so the estimate is easy to review.
Demand Load Method
Connected load is not always the same as service demand. A demand factor can reduce loads that are unlikely to operate together. Continuous loads need special care because they can run for long periods. This tool applies a 125 percent multiplier to continuous load. It also adds 125 percent for the largest motor load.
Leg Balance
Balancing Leg A and Leg B improves panel performance. A large difference can increase neutral current. It can also show that branch circuits should be rearranged. The calculator estimates line current and imbalance, then displays neutral current from the unequal 120 volt load.
Service Size Choice
The recommended service rating is based on calculated demand current plus spare capacity. Spare capacity helps future additions. It also reduces redesign risk during construction. The result should still be checked against local rules, conductor ratings, breaker ratings, temperature limits, and authority requirements.
Practical Use
Use the tool during early planning, panel scheduling, bid review, and load documentation. Keep one report with the drawings. Export the CSV file for spreadsheets. Export the PDF file for records. Update the inputs when appliance selections change. A clean load summary helps avoid undersized feeders, crowded panels, and unclear field decisions.
FAQs
What is a 120/240 single phase system?
It is a common split single phase service. It provides 120 volts from either leg to neutral and 240 volts between both legs.
Does this calculator replace code review?
No. It gives planning results. Always compare results with local electrical rules, approved drawings, equipment ratings, and inspector requirements.
Why are 240V loads split between both legs?
A 240V load connects across both ungrounded conductors. It draws equal current from each leg and normally does not add neutral current.
How is neutral current estimated?
The tool compares the entered 120V load on Leg A and Leg B. The difference is divided by 120 volts.
Why is continuous load multiplied by 125 percent?
Continuous loads can run for long periods. The multiplier gives a conservative service and feeder planning value.
What does demand factor mean?
Demand factor reduces selected connected loads when full simultaneous operation is unlikely. Enter 100 percent when no reduction is desired.
Why add spare capacity?
Spare capacity gives room for future loads and design changes. It can reduce panel replacement risk during construction.
Can I use watts instead of volt-amperes?
Yes, when the load power factor is near one. For motor or reactive loads, volt-amperes give a better design value.