Cabinet efficiency and maintenance
According to the Carbon Trust, refrigeration represents a significant and growing electrical load, currently accounting for 14% of the total electrical energy consumed in the UK. With energy prices increasing at rates not seen for decades, ‘efficiency’ is therefore a word much used, and abused, especially in retail refrigeration.
Many factors should be taken into account when measuring the efficiency of an open-chill refrigerated cabinet including design; compressor and fan efficiency and their ability to meet load and application requirements; location within the store environment; reliability and longevity; and maintenance and serviceability.
The choice of refrigerant is also important. Many of today’s cabinets, including those in Verco’s ranges, are not only designed for use with standard refrigerants but also with hydrocarbon gas, which not only produce zero ODP (ozone depletion) and minimal GWP (global warming), but can also help to significantly reduce energy consumption.
Further savings of up to 13% per year can also be achieved using the latest energy efficient fans, which not only use less energy in operation but also reduce the amount of heat being transferred to the refrigerated space.
Shelving is a key design factor in ensuring a cabinet’s performance and reliability. It plays an important role in stabilising the air curtain. Cold air is kept within the cabinet by an air curtain, which flows from the honeycomb at the top of the cabinet to the air return grille at the lower front. Without shelving the air curtain would simply collapse to the rear of the cabinet.
|Grille Clear - The air return grille should always be kept clear of products to ensure that cold air is recirculated|
Although a sloping shelf can improve merchandising, it has a detrimental effect on airflow, raising shelf temperatures and in turn increasing energy consumption. Sloping shelves with acrylic shelf risers and indeed merchandise that protrude into the air curtain can further reduce cabinet performance.
When a cabinet is delivered to site, shelving should therefore be positioned to achieve optimum performance, with horizontal, evenly spaced shelves. If sloping shelves are a merchandising requirement, fitting smaller shelves that stay within the air curtain can restore some of the lost performance.
The location of refrigerated cabinets is one of the most important factors affecting energy efficiency and should be given a great deal of thought when planning the store environment. For example, and from the point of view of cabinet efficiency, the worst position is immediately opposite the store entrance, which exposes the cabinet to drafts, dust and litter, fluctuations in temperature and humidity, and radiant heat.
Open-chill cabinets are particularly vulnerable to drafts. The EU standard specifies that cabinets are subject to a cross draft of between 0.1 to 0.2m/sec (i.e. 1m of air movement in 6.6sec). This is obviously very low and means that if a draft can be felt in the region of a cabinet, it is too much!
Cabinets are typically tested in ISO 3 conditions, which defines the maximum ambient temperature near the top of the cabinet as 25°C. A lower ambient temperature will result in lower shelf temperatures and therefore lower running costs. Conversely an increase in ambient temperature will result in higher temperatures and increased running costs.
High ambient air humidity is also a hidden load on the cooling system because any moisture entering the cabinet will initially condense as water before forming frost on the cooling coil. The energy used in forming the condensate is therefore no longer available for cooling the display. ISO 3 conditions specify that the ambient air humidity should be a maximum of 60%.
Unlike many glass-door cabinets that are fitted with UV-resistant glass, radiant heat from the sun and other light sources such as spotlights, passes unhindered through the air curtain of an open-chill cabinet and impacts directly on the merchandise. Cabinets should therefore be sited away from direct sunlight and where possible, in environments that do not use spotlights.
Regular servicing and maintenance is essential to maintain optimum operating efficiencies and ensure long-term reliability.
A condenser obstructed by dirt and litter has to work much harder to remove heat from the cabinet, which means it is uses more electricity. Frequent cleaning of the condenser – which is normally located just behind the grille at the base of a cabinet – can easily be carried out by the end-user and is important to ensure it is free from obstruction and working efficiently.
With properly managed maintenance a cabinet should give excellent service for years. In fact, Verco has recently exchanged two cabinets that are over 25 years old and still in good working order.
With immediate effect, Verco is now able to offer its customers an optional one-year labour warranty, which is available on all open-chill and glass-door cabinets in the Verco range including the new-generation Cambridge and recently launched Inline Merchandiser.
The optional labour warranty, which is being offered for a nominal charge, has been introduced in addition to the company’s existing parts cover to offer peace of mind to our customers in the event of a breakdown.