Calculator Inputs
Formula Used
Cooling BTU/h = Tons × 12,000
Cooling watts = Tons × 3,516.852842
Input watts by EER or SEER = Cooling BTU/h ÷ Efficiency value
Input watts by COP = Cooling watts ÷ COP
Input watts by kW per ton = Tons × kW per ton × 1,000
Single phase amps = Watts ÷ (Voltage × Power factor)
Three phase amps = Watts ÷ (√3 × Voltage × Power factor)
Design amps = Running amps × Safety factor
How to Use This Calculator
- Enter the cooling tons for one unit.
- Add the number of identical units.
- Select EER, SEER, COP, or kW per ton.
- Enter voltage, phase, and power factor.
- Adjust load percentage for part load operation.
- Keep the safety factor at 125 percent for conservative planning.
- Press Calculate Amps to view the result above the form.
- Use CSV or PDF buttons to download the result.
Example Data Table
| Tons | Method | Voltage | Phase | Power Factor | Input kW | Running Amps |
|---|---|---|---|---|---|---|
| 1 | EER 10 | 120 | Single | 0.95 | 1.20 | 10.53 |
| 3 | SEER 14 | 240 | Single | 0.95 | 2.57 | 11.28 |
| 5 | EER 11 | 240 | Single | 0.95 | 5.45 | 23.92 |
| 10 | COP 3.4 | 480 | Three | 0.90 | 10.34 | 13.82 |
| 20 | 0.90 kW/ton | 480 | Three | 0.92 | 18.00 | 23.53 |
Understanding Tons to Amps
A ton is a cooling capacity unit. It is common in air conditioning work. One standard refrigeration ton equals 12,000 BTU per hour. That value describes heat removal, not electrical draw. An amp value depends on the power needed to create that cooling. This calculator connects those two ideas with voltage, phase, power factor, and efficiency.
Why Efficiency Matters
Two systems with the same tonnage can use different current. A high efficiency unit needs fewer watts for each ton. EER and SEER compare BTU per hour against watt hours. COP compares cooling watts against input watts. The kW per ton method is also useful for chillers and larger plants. Pick the method that matches the data plate, design sheet, or energy report.
Single Phase and Three Phase Use
Voltage and phase change the amp result. A single phase load uses current through one alternating supply path. A three phase load spreads power over three supply paths. That is why the three phase formula includes the square root of three. Power factor also matters. Motors and compressors rarely convert every volt amp into real work. A lower power factor means more current for the same real power.
Load and Safety Settings
Real equipment does not always run at full capacity. The load percentage lets you estimate part load operation. The safety factor helps with planning margins. Many designers compare calculated current with code rules, manufacturer data, and breaker limits. Starting current can be much higher than running current. The start multiplier gives a rough view of that surge. It is not a replacement for locked rotor amp data.
Practical Electrical Planning
Use the result as an estimate first. Then check the equipment nameplate. Nameplates often show rated load amps, minimum circuit ampacity, and maximum overcurrent protection. Those values should control final wiring choices. This tool is helpful during early sizing, quote checks, energy comparisons, and concept design. It also helps explain why a larger unit does not always need a larger circuit. Efficiency, voltage, phase, and power factor can change the answer.
Example Workflow
Start by entering the cooling tons. Choose the efficiency method you know best. Enter the matching efficiency value. Add voltage, phase, and power factor. Set the number of units when several identical units are used. Change load percentage for partial operation. Keep the safety factor at 125 percent when you want a conservative planning estimate. Submit the form. The result area shows cooling load, input power, running amps, design amps, and estimated starting amps.
Limits of the Calculation
The calculator assumes steady operation. It does not model variable speed drives, defrost cycles, crankcase heaters, fan staging, wiring temperature, voltage drop, harmonics, or local electrical code limits. SEER is seasonal, so it may not match one hot hour. EER or measured kW per ton is usually better for peak current estimates. For final installation work, consult a licensed electrician and the manufacturer documentation. Good planning starts with math, but final safety depends on verified field data.
Keep records for each estimate. Save the CSV when comparing several units. Download the PDF when sharing a quick summary with a client, manager, or installer. Recheck every assumption before purchase. Small changes in voltage, power factor, or efficiency can move the amp result enough to affect panel planning, wire size, and operating cost during busy seasons.
FAQs
1. What does tons to amps mean?
It means estimating electrical current from cooling capacity. Tons measure cooling output. Amps measure electrical current. Efficiency, voltage, phase, and power factor connect both values.
2. Is one ton always the same amp value?
No. One ton can draw different amps on different systems. The answer changes with efficiency rating, voltage, phase, power factor, and operating load.
3. Why does the calculator use 12,000 BTU per hour?
One standard refrigeration ton equals 12,000 BTU per hour. HVAC cooling capacity is commonly rated with that relationship.
4. Which efficiency method should I choose?
Use the method shown on your equipment data. Use EER for peak performance, SEER for seasonal estimates, COP for thermodynamic efficiency, and kW per ton for chiller style data.
5. Is SEER exact for amp sizing?
SEER is a seasonal rating. It can estimate current, but it may not match peak operating current. EER or nameplate electrical data is better for final planning.
6. Why does three phase current look lower?
Three phase power spreads load across three supply paths. The formula includes the square root of three, so current is often lower for the same power and voltage.
7. What power factor should I use?
Use the equipment power factor when known. If unknown, values from 0.85 to 0.95 are common planning estimates for many motor driven systems.
8. What is the safety factor for?
The safety factor adds planning margin. A 125 percent setting is often used for conservative estimates, but final circuits must follow local code and equipment labels.
9. What is starting current?
Starting current is the short surge when a motor or compressor starts. It can be much higher than running current. Use nameplate locked rotor amps when available.
10. Can this size a breaker?
It can help with early planning. Do not use it as the only breaker sizing source. Check nameplate MCA, MOCP, manufacturer rules, and electrical code.
11. Can I calculate several units together?
Yes. Enter tons per unit and set the number of units. The calculator multiplies total cooling load before estimating watts and amps.
12. What does load percentage do?
Load percentage estimates part load operation. For example, 50 percent load uses half the selected total tons for the current estimate.
13. Why is my calculated value different from the nameplate?
Nameplates include real equipment design, motor behavior, controls, fans, compressor type, and safety rules. This calculator gives an estimate from selected assumptions.
14. Should I use this for final installation?
Use it for estimates and comparison. Final installation should be checked by a qualified professional using manufacturer documentation and applicable electrical standards.