Matching a European Chiller kW Rating to a US Tonnage Catalogue
The machine manual on your desk states a cooling requirement in kilowatts, because the press, the laser source or the spindle motor was designed in Europe or Japan. The chiller quotation in your inbox is written in tons, because the supplier sells into North America. Nothing about the two documents lines up until the duty is expressed in one currency, and getting that step wrong is how a process cell ends up with a chiller that cannot hold coolant temperature during a full production shift.
Why the Same Duty Wears Two Numbers
Machine manuals list a kilowatt duty
Chiller catalogues split by market
Coolant temperature moves the rating
Almost every process watt becomes heat
Turning a Process Cooling Duty Into a Chiller Order
Work machine by machine, then total the cell. Diversity between machines is real but modest on a production line where everything runs at once, so most process engineers add the duties in full and take their margin at the end.
Enter the heat rejection from the manual
Type the kW figure from the machine's technical data — 8, 22, 35, 90 — and the tonnage appears alongside it. A comma decimal separator works, and spaces in the number are ignored.
Add margin before you shop
Take the tonnage up by ten to twenty per cent for a glycol mix, a low set point, a warm plant room or the ambient the condenser really sees, then round up to the nearest catalogue size rather than down.
Send the quote back the other way
When the offer comes back as a 10-ton unit, press the swap arrow (↔) for TR → kW and check it against the duty you started from. Ten tons is 35.17 kW nominal — enough for a 30 kW cell, tight for a 35 kW one.
Copy the digits into the duty schedule
The copy button gives you the plain number with no unit and no thousands spacing, ready for the equipment schedule or the enquiry email. Ctrl + C inside a field does the same.
Process Cooling Duties in Kilowatts and Tons
Representative heat rejection figures for equipment that normally sits on a process chiller loop, with the tonnage each duty converts to and the coolant temperature the machine builder usually asks for.
| Process load | Cooling duty | Tonnage | Coolant supply |
|---|---|---|---|
| Machine-tool spindle and hydraulics, 5-axis machining centre | 8 kW | 2.27 TR | Held within ±1 K of shop ambient |
| Fibre laser resonator, 6 kW cutting head, two circuits | 20 kW | 5.69 TR | 22 °C resonator / 30 °C optics |
| Injection moulding machine, 150 t clamp, mould and oil cooling | 22 kW | 6.26 TR | 10–15 °C |
| Resistance welding guns, robot body-shop line | 30 kW | 8.53 TR | 25 °C, above dew point |
| MRI scanner, 3 T, magnet cold head and gradients | 35 kW | 9.95 TR | 7 °C chilled water |
| Blown-film extrusion line, screw barrels and air ring | 45 kW | 12.80 TR | 15 °C |
| Electroplating bath and rectifier | 60 kW | 17.06 TR | 18 °C, titanium coil in bath |
| Moulding cell, four machines plus hydraulic oil coolers | 90 kW | 25.59 TR | 12 °C, glycol loop |
Two patterns fall out of the coolant column. The tight-tolerance jobs at the top — spindles and laser optics — need modest tonnage but very stable temperature, which points at a small unit with an accurate controller rather than a big one. The plastics and plating duties lower down need real capacity at a genuinely cold supply, and it is those set points, not the tonnage figure alone, that decide whether a catalogue machine will actually do the work.
Working Across Two Catalogues at Once
One number in, both catalogues answered
The two fields are live and editable together, so a machine duty typed once reads immediately in the unit each supplier wants to talk in.
Reverse the arrow when the quote comes back in tons
Swapping to TR → kW puts a US-sized offer straight back into the units the machine manual used, which is where an undersized selection shows itself.
BTU/h and kcal/h for older machine manuals
The searchable dropdowns on both sides cover every power unit, including the kcal/h that Asian and legacy European documentation still prints cooling duties in.
Figures that paste into the duty schedule
Copy delivers the bare value with no unit or spacing, and the display carries up to eight decimals, so a schedule of machine loads stays consistent line by line.
Process Chiller Selection Questions
Is the kW on a chiller data sheet the cooling it makes or the electricity it draws?
On a European sheet the headline kW is cooling capacity, and the electrical demand is listed separately, often as absorbed power or nominal current. The two are far apart: a unit making 25 kW of cooling at a COP around 3 draws roughly 8.3 kW at the terminals. Only the cooling figure belongs in this conversion. Feed the electrical figure in by mistake and you will order a machine about a third of the size you need.
Does a glycol mixture change the tonnage a chiller can deliver?
Yes, on both sides of the exchanger. Glycol carries less heat per litre and is more viscous than water, so at a typical 30 per cent ethylene mix you lose a few per cent of capacity and need roughly ten per cent more flow to shift the same duty. The bigger effect is usually the set point that made the glycol necessary in the first place — every degree the leaving temperature comes down costs capacity again, and a −5 °C process loop may run a machine at little more than half its nominal tonnage.
Why does the same chiller lose capacity on a hot day?
An air-cooled condenser can only reject heat into the air it is given. As ambient rises, condensing pressure rises with it, the compression ratio grows and capacity falls — typically around ten per cent between a 35 °C rating point and 45 °C. Machines mounted on a roof or in a walled compound routinely see air several degrees above the weather station figure because of recirculation, so take the derate from the real inlet temperature, not the regional design ambient.
The catalogue says 10 tons — can I put a 35 kW process load on it?
On paper it fits exactly: 10 TR is 35.17 kW. In practice it will not, because nominal tonnage is quoted at the manufacturer's rating point, usually plain water leaving around 12 °C into a moderate ambient. Ask that machine for 8 °C glycol on a 40 °C afternoon and the same 10-ton unit may only make 28 to 30 kW. Always read the corrected capacity from the selection table at your own water and air temperatures before treating a nominal figure as available duty.
How much buffer volume does a process cooling loop need?
Enough that a sudden step in load does not swing the coolant temperature before the compressor can respond. Comfort duties get away with two or three litres of system volume per kW of cooling; process loops that need close control, or that see the on-off pattern of a moulding cycle or a laser cutting head, are commonly built with six to ten litres per kW. Pipework rarely supplies that on its own, so a buffer tank goes in the return line. Machines with variable-speed compressors need less, but they still need some.
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