Dryer Load Input Form
Formula Used
Unit watts from kilowatts: W = kW × 1000.
Unit watts from single phase amps: W = V × A × PF.
Unit watts from three phase amps: W = √3 × V × A × PF.
Connected load: connected W = unit W × quantity.
Duty adjusted base: base W = connected W × duty factor.
Diversified demand: demand W = electric base × demand factor + gas base.
Design volt amperes: design VA = demand VA × continuous multiplier × spare multiplier.
Feeder current: single phase A = VA ÷ V. Three phase A = VA ÷ (√3 × V).
Voltage drop estimate: single phase VD = 2KIL ÷ CM. Three phase VD = √3KIL ÷ CM.
How To Use This Calculator
- Enter the main feeder voltage, phase, and power factor.
- Select a demand method matching the project basis.
- Add each matching dryer group with quantity and nameplate value.
- Choose the input unit shown on the equipment schedule.
- Apply the minimum load rule required by the design basis.
- Add spare capacity, continuous percentage, and panel data.
- Press calculate and review the result above the form.
- Download the CSV or use the print button for records.
Example Data Table
| Input | Example value | Reason |
|---|---|---|
| Main voltage | 240 V | Common single phase laundry feeder. |
| Standard dryers | 4 units at 5 kW | Base appliance group. |
| Large dryers | 2 units at 6.2 kW | Higher capacity machines. |
| Demand method | Household table | Shows diversity for multiple dryers. |
| Spare capacity | 20% | Allows future load changes. |
Dryer Load Planning Guide
Multiple dryer rooms need careful electrical planning. Each dryer adds heat, motor current, controls, and branch circuit demand. A simple total can overstate the feeder. A weak diversity assumption can understate it. Good construction estimates sit between those risks. They show connected load, diversified load, design current, and spare allowance.
Why Dryer Groups Need Diversity
Dryers rarely heat at the same exact moment. Thermostats cycle elements during normal work. Users also load machines at different times. That creates diversity. Codes may allow demand factors for certain dwelling dryers. Commercial laundries may need stricter values. This calculator lets you compare both approaches. You can use full load, a household demand table, or a custom factor.
Key Inputs To Check
Start with nameplate power for each dryer group. Use watts, kilowatts, volt amps, or amperes. Enter the quantity for matching units. Add the voltage and phase used by that group. Use a power factor near one for resistance dryers. Lower values may suit mixed motor loads. Gas dryers often need only controls, motors, and igniters. Electric dryers usually carry the major heating load.
Design Margin Matters
The calculated demand is not always the final feeder basis. Some projects add spare capacity for future machines. Some laundry rooms need continuous load treatment. Long feeders may also need voltage drop review. This page provides demand current and a suggested standard breaker size. It does not replace drawings, field data, or local inspection rules.
Construction Use
Use the result during early design, bid review, or plan checking. Compare the demand with panel space, feeder rating, and service capacity. Share the summary with the electrical designer before ordering equipment. Keep dryer cut sheets with the calculation. Update the inputs when the appliance schedule changes. A small nameplate change can affect feeder size and panel balance.
Practical Review Notes
Check exhaust routing, room heat, and makeup air. Electrical load is only one part of dryer planning. Confirm receptacle type, branch circuit size, disconnect access, and equipment grounding. Balance single phase dryers across panels where possible. For three phase systems, verify line voltage and phase loading. Clear notes reduce surprises during rough in work.
Review manufacturer instructions before issue. Record assumptions so future changes remain easy to audit during inspections, bidding, commissioning, and maintenance.
FAQs
What is multiple dryer load calculation?
It estimates the electrical demand for several dryers. It combines nameplate loads, quantities, demand factors, power factor, and design margins for feeder planning.
Should every dryer be counted at full load?
Full load is safest for conservative checks. Demand factors may be allowed for some dwelling dryer groups. Commercial laundry projects often need stricter review.
Why is a 5000 watt minimum included?
Many household dryer calculations use a minimum load per electric dryer. The calculator lets you keep it, remove it, or enter a custom minimum.
Can this calculator handle gas dryers?
Yes. Choose gas heat controls only. Enter the electric motor, control, and igniter load. Gas heating fuel load is not added to electrical demand.
What does duty factor mean?
Duty factor reduces a group load when operation is intermittent. Use one hundred percent when the design basis requires full simultaneous operation.
How is three phase current calculated?
The calculator divides volt amperes by square root three times voltage. This estimates line current for balanced three phase service planning.
What is spare capacity?
Spare capacity is an added allowance above calculated demand. It helps cover future dryers, equipment changes, and small design adjustments.
Does this replace an electrical engineer?
No. It supports early planning and checking. Final feeders, breakers, conductors, and code decisions should be verified by qualified professionals.
Can I use amperes instead of watts?
Yes. Select amps as the input unit. The calculator converts amperes using row voltage, phase, and power factor.
Why include voltage drop?
Long feeders can lose voltage under load. The estimate helps flag conductors or distances that may need closer design review.
When should I update the calculation?
Document assumptions and update calculations whenever dryer schedules change.