Greener machines
THE importance of getting greener if we are to survive on this planet is being pushed at us from all sides, and with just cause. Commercial dishwashers, making heavy use of water, energy and chemicals, are among the principal pieces of kitchen equipment that need to be made more environmentally friendly, and manufacturers have been taking steps for some time to make their machines greener.
"Water consumption is the major key," says David Copeman of Commercial Dishwashing Systems. "The less water used, the less energy is required for heating, and fewer chemicals are needed to achieve the required concentration."
John Nelson, managing director of Nelson Dishwashers, adds: "Most of the better manufacturers have been moving towards greener machines for some time. People have started to look at installing double filtration systems, which reduce the volume of water. We have moved to shallow wash tanks, which use one-third less water."
According to Derek Paterson, marketing manager for Falcon, the introduction of smaller wash tanks saves not only on water but on rinse aid and detergent too. "It is essential when buying a dishwasher to take into consideration not only the cost of the washer itself but also its running costs," he says. "Machines that on the surface may look like good value for money could in the long term prove very costly, particularly as water metering and other methods of monitoring are introduced."
Recycling
Recycling water is another obvious way of making savings, and has been introduced by many manufacturers. Both Winterhalter and Elmwood, for instance, use fresh water for every rinse and recycle it in the wash tank. On Winterhalter machines, a fresh rinse at 85ºC is used at the end of each wash cycle to sanitise the products. The rinse water replaces the soiled wash water, which means that wash water is constantly being replaced with clean rinse water. Elmwood claims that recycling means its machines now use only 1.5 to 2 litres of water per cycle.
Miele's latest models, recently introduced in Germany and which will be available in the UK later this year, also claim a 20-30% reduction in water use, achieved by a redesign of the internal supply pipework between the top and bottom spray arms.
Other features include free programming of both temperature and hold time, with temperature selection between 30ºC and 93ºC depending on the model, with thermo-stop of one to 10 minutes. This feature makes the machines "future-proof" with regard to any changes in thermal disinfection requirements or in the event of the introduction of low-temperature dishwash chemicals, says the manufacturer.
Of course, installing a dishwasher incorrectly can create environmental problems. Water can back-siphon into the mains water supply, contaminating clean water. In light of such possibilities, Water Research Council inspectors have legal powers to enter a kitchen and order that incorrectly installed equipment be closed down.
To combat this possible problem, both Electrolux and Hobart have fitted Class A air-breaks to a number of their machines that allow them to be installed on mains water, but eliminate the danger of back-siphoning. Break tanks can be added to systems, says Hobart, but they are about the size of a domestic water tank and therefore take up considerable space, and the installation cost is around £400.
"Actually, it is mandatory for every item of warewash equipment to be fitted with a break tank," says FMS partner Cliff Scott. "FMS machines are fitted with internal break tanks but, due to a combination of trade demand for low prices and enforced ignorance by suppliers, a recent survey shows that more than 50% of new machines sold in the UK do not comply with this requirement."
Basic design elements can affect a dishwasher's efficiency. "A simple thing often overlooked by caterers is the effect the humble dishrack can have on efficiency," says Roger Flanagan, managing director of HMI Group, which manufactures a number of brands. "A correctly designed rack can increase efficiency by up to 18%, and often can mean not having to buy a new machine."
double rinses
"Heat recirculation is also an option we offer on all our throughput models, in an effort to reduce cost and use of power," Flanagan adds. "And we are about to launch the LCM2 range of pass-through rack machines, incorporating, as standard, double rinse for water reduction and double skin for sound and heat insulation."
Automatic detergent and rinse-aid feeds are a way of cutting back on the amount of expensive and potentially water-polluting chemicals going into machines. Nelson uses a system that automatically registers the amount going in and only tops it up when necessary. Probes in the machines measure the alkaline or acidic content of the water and the machine is topped up accordingly. "Unfortunately, the quality of detergent varies a lot," says John Nelson, "so you can have all the features you like but, if you buy cheap detergent, while you'll save money up front, you'll end up having to use two to three times as much and throwing more chemicals into the environment."
Zanussi believes its duo-rinse system encourages a reduction in detergent consumption by using less water and consequently less detergent and rinse aid. The system, claims Zanussi, can pay for itself in a few months. Other manufacturers have similar systems. FMS machines, for instance, are fitted with electronic detergent controls, and the detergents supplied are said to be eco-friendly and rapidly biodegradable.
Meiko has developed a chemical saving system for its conveyor machines, which it says reduces energy and detergent usage and thereby creates lower chemical contamination of the water. The system also transfers half of the final rinse water to the pre-scrapping section, reducing the soilage load in the main wash tanks. Meiko's machines are also fitted with heat recovery units which extract heat from the exhausted hot air of the main wash section, which is then used in the pre-heating of incoming rinse water. Meiko adds that savings of 6kW can be made through efficient recycling of heat from waste water and waste vapour-bearing air.
Winterhalter machines are also fitted with systems to decrease rinse aid consumption and use less detergent. On its rack-type machines, the final rinse is split, resulting in still lower rinse aid and power consumption.
"It used to be believed that the bigger the pump, the cleaner the washed items would be," says Buttress managing director Steve Loughton. "This is a bit of a fallacy. Of course, there is an optimum, but to increase the size of the pump and element above the optimum serves no additional benefit. The leaning towards smaller wash tanks with better filtration systems means less water usage and less power requirement. A major innovation is the use of an Interlock system. If the machine is not used for some time, it reverts to an energy-saving mode. Instead of maintaining the rinse water at 85ºC, it will automatically hold the temperature at 65ºC. When the machine is started, it will automatically wash until the correct rinse temperature is reached, and there is no chance of giving a cold rinse."
Reduced components
Dawson's Comenda range of machines have had all their electrical components reduced and, on certain machines, by including a dual rinse section, electrical loading and rinse aid have also been reduced, says the company's product market manager, Robin McKnight.
Supplier Ray Butler of Macdonalds Catering Equipment says the use of double-skinned machines is now a major factor in reducing energy consumption, and new buyers should look for this feature. And Elmwood says that, because its machines work from a cold water supply, water is only heated on demand. This means that the water is heated to the optimum temperature, ensuring that starch in the food products does not bake on to the plates, giving a better wash first time.
Falcon machines feature improved rinse heaters to speed the heat-up times, allow rapid recovery and increase throughput, all of which lead to increased energy efficiency, the company says.
"Things have changed considerably over the past 15 years," says FMS's Scott. "It was not unusual to have wash tanks of 60-70 litres and rinse demands of 80-100 litres an hour. Today, in our current range, an equivalent machine holds 25 litres of water with rinse demands of 30 litres an hour. All our machines, and many others, are double-skinned and insulated, which keeps the dishwash area both quiet and cool; and heating elements are automatically switched to standby to conserve energy when the machine is not being used.
"With less water being used, fewer chemicals are injected and built-in controls make chemical use very accurate." n
