An ice bath chiller designed for 45 °C summers, and hidden from the room

What tropicalised means on our datasheet

A chiller sold on the headline figure is rated at a mild ambient and a warm water temperature. An Indian terrace in May is neither. We design against a 45 °C ambient and a 4 °C water temperature, and the quote says so. That means a condenser sized with margin, a pump head that does not rob the cooling, controls that hold ±0.3 °C, and, on the coast, a protective coating on the coil against salt air. We state the net cooling figure at 4 °C water and 45 °C air on each unit's datasheet, which is lower than any headline, because it is the figure you will live with. The datasheet also shows how far capacity falls above that point, so that a consultant can read it against the 48.0 °C recorded at Palam in June 2019 (IMD).

Headline capacity and real capacity

Cooling capacity falls as the water gets colder and as the air gets hotter. A unit that delivers its rating at 15 °C water and 35 °C air delivers noticeably less at 4 °C and 45 °C. When two quotes differ by a third, check the conditions on the datasheet before comparing prices. A short list of what to ask any supplier:

1. Net cooling capacity in kW at 4 °C water and 45 °C ambient.
2. Electrical data: supply, running current and starting current.
3. Free-air requirement and the allowable recirculation.
4. Sound pressure at 1 m and at the property boundary.
5. Coil and casing protection for coastal air.
6. Water-side material, flow rate and pump head.
7. Service access, and what the warranty covers in a first monsoon.

Three tub chillers and the pool plants

For pools the plant is a different class. A round pool 2.0 m across and 1.0 m deep holds about 3,140 litres, past the 1,200 litres the 4 HP unit is rated for; its plant is specified from the volume, the ambient and the duty, and appears on the pool page as a plant room, not as a catalogue item.

Pull-down and hold are two different jobs

Pull-down is the first fill: 500 litres from 30 °C to 4 °C takes about 15 kWh out of the water. Hold is the daily job: the heat that gets in through the shell, the sun, the surrounding stone, the hoses and the bathers, taken out again. A chiller that holds beautifully in December can fail the pull-down in May, which is why we size the unit for the longer of the two and put the pull-down time in the commissioning log.

Where the machine lives

• Air. The condenser needs fresh air in and hot air out, with no short circuit between them; a niche with a louvre at both ends is better than a closed cupboard.
• Shade. Direct afternoon sun on the casing costs capacity. A shaded wall or a small roof is cheap.
• Sound. Face the exhaust away from bedrooms and from the pool deck; the datasheet gives the level at 1 m.
• Service. One metre of clear space on the service side, a drain for condensate, and a path wide enough to carry a compressor.
• Coast. In Mumbai, Alibaug and Goa, wash the coil at the start of the monsoon and after it ends.

Coastal specification

Salt-laden air can attack fins, fasteners and electrical terminals within a few seasons. For Mumbai, Alibaug and Goa we specify a protective coating on the condenser coil, 316 stainless on fixings and brackets, and a casing with drainage that does not hold monsoon rain. The coil is washed with fresh water at the start of the monsoon and again when it ends. A plant behind a wall is better than a plant on an open terrace, because the wall takes the spray.

Controls and alarms

• A set point of 3-5 °C with a hold within ±0.3 °C, shown at the pool or tub on a plain display.
• A high-temperature alarm and a flow alarm, so that a stuck pump is a message, not a warm pool.
• A restart delay after a power cut, to protect the compressor, with a log of the last faults for the service visit.
• A stand-by mode that holds a higher temperature during long absences and returns to the set point on a timer.