Refrigeration Ton Converter (US RT vs Japanese/Korean RT)

Understanding the refrigeration ton converter — concept and principle

This converter changes cooling capacity between the US refrigeration ton (12,000 BTU/h), the Japanese refrigeration ton used in Korea (3,320 kcal/h), kilowatts, BTU per hour and kilocalories per hour. Use it to compare chillers, air-conditioners and heat pumps whose specification sheets use different "tons", or to check a design load against equipment capacity.

How it is calculated

result = value × (watts per "from" unit) ÷ (watts per "to" unit)

• 1 US RT = 12,000 BTU/h = 3.516852842 kW.
• 1 Japanese/Korean RT = 3,320 kcal/h = 3,320 × 1.163 W = 3.86116 kW.
• 1 BTU/h = 0.2930710702 W (International Table BTU); 1 kcal/h = 1.163 W.

The two tons differ by about 10%: 1 US RT = 0.9108 Japanese RT.

The principle

Both tons describe the cooling power of melting or freezing ice over one day. The US ton is the heat needed to melt one short ton (2,000 lb) of ice at 0 °C in 24 hours: 2,000 lb × 144 BTU/lb ÷ 24 h = 12,000 BTU/h. The Japanese ton is the heat removed to freeze one metric tonne (1,000 kg) of water at 0 °C into ice in 24 hours: 1,000 kg × 79.68 kcal/kg ÷ 24 h = 3,320 kcal/h. The metric tonne is heavier than the short ton, so the Japanese RT is the larger unit.

Worked example

Default inputs: 1 US refrigeration ton to kilowatts.

1. 1 US RT = 12,000 BTU/h.
2. 12,000 × 0.2930710702 W = 3,516.852842 W = 3.516852842 kW.
3. In kcal/h: 3,516.852842 ÷ 1.163 = 3,023.949133 kcal/h.
4. In Japanese RT: 3,023.949133 ÷ 3,320 = 0.9108280522 RT.

How to read the result

Capacity in RT or kW is heat removed, not electricity used. A chiller rated 100 US RT removes about 352 kW of heat; with a coefficient of performance (COP) of 5 it would draw roughly 70 kW of electricity. Small split air conditioners are often rated around 1–2 US RT (about 3.5–7 kW). Korean product literature and design documents may use either ton, so always check whether "RT" means 3,024 or 3,320 kcal/h before comparing quotes.

Common mistakes

• Comparing a US RT figure with a Japanese/Korean RT figure without converting; the difference is about 10%.
• Treating cooling capacity as electrical input power.
• Confusing a refrigeration ton with a ton of mass or a tonne of air.
• Using thermochemical calories (4.184 J) instead of IT calories (4,186.8 J per kcal).

Frequently asked questions

How many kW is 1 US refrigeration ton?

3.516852842 kW.

How many kW is 1 Korean (Japanese) RT?

About 3.861 kW.

How many BTU/h is 1 Japanese RT?

About 13,175 BTU/h (3,861.16 W ÷ 0.2930711).

Why is it called a ton?

It comes from the era of ice cooling, when capacity was compared with the melting of a ton of ice in a day.

Sources: ASHRAE Handbook, Fundamentals (refrigeration ton definition) · NIST Special Publication 811 (2008), Appendix B