Ton of Refrigeration (TR)
A ton of refrigeration (TR) is the standard measure of cooling capacity — 1 TR equals 3,024 kcal/h, about 3.517 kW of heat removal — historically the rate needed to melt one ton of ice in 24 hours.
Why it matters on an MEPF project
TR is the currency of Indian HVAC: heat loads are computed in kW or kcal/h but plant is bought, quoted and billed in TR. Converting correctly (and knowing that "100 TR installed" says nothing about diversity, redundancy or actual delivered capacity at Indian ambient) is the difference between reading a quote and being read to.
Capacity also derates with conditions: a machine's nameplate TR at test conditions is not its delivery at a 46 °C Ludhiana afternoon. Selections must be made at design ambient, and efficiency compared honestly — kW of electricity per TR of cooling (or ISEER band for smaller machines) is the number the electricity bill will remember.
How it's specified in practice
| Parameter | Typical / working position | Governing reference |
|---|---|---|
| 1 TR | 3,024 kcal/h ≈ 3.517 kW ≈ 12,000 BTU/h | standard definition |
| Comfort sizing shorthand | Area-based first cuts, corrected by real heat-load calc | heat-load calculation governs |
| Efficiency metric | kW/TR for plant; ISEER for unitary machines | BEE / ECBC framing |
| Derate factor | Capacity falls at high ambient — select at design conditions | manufacturer performance tables |
Common mistakes
- Sizing by ₹/sq.ft folklore instead of a heat-load calculation.
- Comparing chillers by TR price while ignoring kW/TR running cost.
- Reading nameplate TR as delivered TR at 45 °C+ ambient.
- Adding machine TR without checking the electrical infrastructure behind it.
Related on this site
One of 68 working definitions in the MEPF & solar engineering glossary. The buying side of the same decisions is in the buyer's guides; the numbers are in the calculators.
Frequently asked
How many TR does my building need?
Whatever the room-wise heat-load calculation says — occupancy, glass, orientation, equipment and fresh air all move it. Our AC tonnage calculator gives a serious first cut; the design basis fixes the final number.
Is a lower kW/TR always better?
At the same reliability and price context, yes — it is the running-cost metric. But verify it at your operating conditions and part loads, where machines spend most of their lives.
Standards referenced: BEE labelling framework (reference) · ECBC 2017