Controlling temperature

Helping other Marlborough businesses reach their best profit margins is a focus for Martella, an airconditioning, refrigeration and sheet metal fabrication company in Blenheim.

Last month the company installed two new chillers at Saint Clair Family Estate winery, at Riverlands on the outskirts of Blenheim.

Housed in two containers, the new chillers are fitted with 12 compressors circulating glycol refrigerants around the tank farm and barrels at the winery.

Wine inside the tanks needs to be kept at optimum temperatures, ranging from minus 4 degrees Celcius to 34C, depending on the stage of the production cycle the juice or wine is at.

Senior winemaker Hamish Clark says Saint Clair's former chiller was working at peak level during the previous vintages and the risks were too high that the quality of the wine would be affected if the system failed.

Rather than adding more capacity to the old system, they decided to install new units.

Different systems designed by two companies were investigated and Martella won the contract.

Martella services manager Glen Herkt says the new chillers have a higher output with more efficient energy use.

Compressors in the new chillers output about 500 kilowatts to 800kW of refrigerating power but, unlike the four compressors on the old chiller, not all of them always operate.

A programmable logic controller on the new system senses the volumes and temperature levels of the wine inside the tanks and ensures enough compressors are working to keep them at the required temperature.

The number of compressors working at any one time fluctuate, according to the fermentation levels in the tanks.

Glen wouldn't talk about the cost of the system, but said it was more efficient with electricity use than the old compressors. They will also be able to deal with more wine in the tanks.

Heat is a byproduct of all refrigeration systems. At Saint Clair, pipes are connected to a stainless steel plate evaporator which reticulates hot water in one direction and keeps 25,000 to 30,000 litres of cooling glycol circulating in another around the tank farm.

The "free hot water" from the chillers is used to warm grape juices during inoculation later in the year and warm the wine before bottling.

Glen says the chillers were built by Martella's refrigeration and sheet metal engineers at their workshop in two containers. The complete systems were then transported to the Saint Clair Estate plant.

During the early stages the engineers visit each day, monitoring the operation and making small adjustments. Eventually, the chiller pumps, filters and cooling tower will need to be checked only every six months, Glen says.