Understanding Ton of Refrigeration (TR) and Watt (W)
The ton of refrigeration (symbol: TR) is a legacy unit that quantifies the rate of heat removal. Historically it represents the amount of heat required to melt one short ton (2000 lb) of ice at 0 °C in 24 hours, which is equivalent to 12,000 BTU/h. In the International System of Units (SI) this is expressed as power, and the exact conversion factor is:
\(1\ \text{TR}=3516.85\ \text{W}\)
The watt (symbol: W) is the SI unit of power, defined as one joule per second. It is the standard unit used in engineering for both electrical and thermal power calculations.
Practical Applications
HVAC system sizing – designers often specify cooling capacity in TR for commercial chillers and air‑conditioners.
Energy audits – converting TR to W allows direct comparison with electricity consumption and utility rates.
Thermal load calculations – using watts simplifies integration with other SI‑based calculations such as heat‑gain from equipment.
Because many manufacturers still quote equipment in TR, engineers must routinely convert between TR and W to perform accurate load analyses, select appropriate compressors, and estimate operating costs.
Ton of refrigeration to Watt Conversion Reference Table
Ton of refrigeration (TR)
Watt (W)
0.1
351.685
0.5
1758.425
1.0
3516.85
2.0
7033.7
5.0
17584.25
10.0
35168.5
20.0
70337
50.0
175842.5
100.0
351685
500.0
1.7584e+06
1000.0
3.5168e+06
Conversion Example: 10 TR to Watts
Follow these steps to convert 10 TR into watts.
Identify the conversion factor: \(1\ \text{TR}=3516.85\ \text{W}\).
Multiply the number of tons by the factor.
\[\begin{aligned}
10\ \text{TR} \times 3516.85\ \frac{\text{W}}{\text{TR}} &= 35168.5\ \text{W}
\end{aligned}\]
Result: 10 TR is equal to 35,168.5 W (≈35.17 kW).
TR remains common in the HVAC industry because legacy equipment specifications, standards, and contracts were established before the widespread adoption of SI units. Converting to watts is straightforward, so engineers keep using TR for familiarity while still being able to integrate with SI‑based calculations.
The factor 3516.85 W/TR is exact, derived from the definition of a ton of ice (12,000 BTU/h) and the conversion 1 BTU/h = 0.29307107 W. Multiplying 12,000 BTU/h by 0.29307107 W/BTU/h yields 3516.85284 W, which is rounded to 3516.85 W for practical use.
"On fait la science avec des faits, comme on fait une maison avec des pierres ; mais une accumulation de faits n'est pas plus une science qu'un tas de pierres n'est une maison." "Science is built up of facts, as a house is built of stones; but an accumulation of facts is no more a science than a heap of stones is a house." — Henri Poincaré (French Mathematician, Theoretical Physicist & Mining Engineer)