Here is the complete 4-article series we posted on our LinkedIn page, looking at key elements within a beverage cooler and bring to light areas that the consumer should consider when making their selection. Follow our page on LinkedIn for more helpful information.
We understand that beverage coolers and other items of refrigeration are not normally items that the general public have a huge amount of knowledge on, other than they should make things cold… how they do this, how well they do it, and for how long they can do it for is something that we will provide some practical advice and guidance on in these articles.
In a global marketplace where product choice is vast, knowing what it is that you are looking for can be very helpful in making the right choice for your requirements.
Part 1 – The Refrigeration System
Almost all beverage coolers have a compressor at the heart of the machine. The compressor is what you need to move your refrigerant around the system to allow the unit to cool. Think of a compressor as the engine in a car. They come in many shapes and sizes, but ultimately you want one that is suited to the fridge, size is an important consideration. Too small and you will be unable to maintain temperature in your unit and likely shorten the lifespan of the compressor through overworking. Too big will result in a high price point and you will start to pay the price of inefficiency in electrical bills. An optimised system will balance performance and efficiency. Advancements such as variable speed compressors offer new possibilities in terms of performance, both with regards to power and efficiency. Yet these currently add a lot of cost and complexity to a relatively simple system requirement.
Any refrigeration system works by removing heat (you cannot add “cold” to something). In order to remove heat, you require a method of transferring the heat from the air inside the cooler to outside of the cabinet. This is where you need heat exchangers and in our field, they are referred to as the evaporator and the condenser; The condenser outside of the unit and the evaporator inside the unit. These combine with the compressor and a throttling device (more about that later) to make the basic refrigeration system. This element, the evaporator and condenser, of the refrigeration system is where the mantra “size matters” is generally true – the larger (surface area) your evaporator and condenser are, the better they will be at exchanging heat. Materials used in their construction are also important for both durability as well as performance reasons. A copper and aluminium heat exchanger (referred to a fin on tube construction) offers a great mixture of performance (copper and aluminium are great conductors of heat) as well as reliability (both metals are very resistant to rust). Domestic and other units with a low performance requirement often make use of a simple pipe (referred to as a wire on tube construction) for their condensers as they are much less expensive. However, due to the materials often used in their manufacture, they are often more susceptible to rusting over time.
Pressure regulator or throttling device
As the refrigerant gas moves around the refrigeration cycle, a throttling device is needed to release the gas into the evaporator at the correct pressure. There are two ways of doing this, either by a static capillary tube, or by a variable expansion valve. The capillary tube (generally made using copper) solution is perfect for requirements where a steady, constant temperature is required. As there are no moving parts in a capillary system, the chances of breakdowns are almost nil. They are also durable and easy to replicate on a mass scale. Expansion valves are used in systems where variable or strictly controlled temperatures are required, or a speedy pull-down is paramount. Expansion valves are a more expensive way of doing things and because there are moving parts in the valves, susceptibility to failure is much higher.
The entire system will always need a controlling device to regulate the temperature – i.e. tell the system when and how much to cool. These devices are referred to as Thermostats. Thermostats come in either a mechanical form or electrical form. Both operate by monitoring the temperature inside the unit and at pre-set temperature points either turn on or off the compressor. Electronic thermostats are much more accurate than a mechanical thermostat. Electronic thermostats are often combined/included with an Energy Management Device. This not only controls the temperature but also improves efficiency by controlling the fans and lights of the units by pre-set parameters.
Part 2 – The Construction of the cabinet
Cabinet walls and structure
The skeleton of the cabinet needs to be rigid, durable and tough in order to meet the day to day, and year to year demands of use. Using rust resistant materials is a must – Chromadek is the ideal material for construction for this reason. Some units in the trade are constructed by using a corrugated plastic panels on some exterior faces, this saves cost, but those panels are more susceptible to gouging or attack from rodents. Internally some units have moulded plastic walls, again better for costs, but less durable than Chromadek when it comes to cracking and impact. Rigidity is gained by the insulation foam and doing this in one complete “tub” gives far superior rigidity compared to assembling using pre-foamed panels.
Polyurethane insulation foam is standard in the market. Some manufacturers will use Polystyrene in certain places, but this is not recommended as the polystyrene is not a closed cell structure which means that it will absorb water over time which will cause bacteria growth as well as loss of insulation properties. A 40-millimetre-thick Polyurethane wall has the same insulation efficiency of 3.35-meter-thick concrete wall! Polyurethane foam is made by combining two chemicals together. One of the chemicals is known as the blowing agent. Cyclopentane is popular blowing agent in the market, although Cyclopentane is flammable and has a high contribution to global warming (GWP). Ecomate or Methyl Formate is a more environmentally friendly option as it has zero Ozone Depletion Potential (ODP) and zero GWP and is included on the US EPA SNAP program.
Glass in general is not a very good insulator. In a normal beverage cooler, the glass door is responsible for ~80% of the heat ingress into the cabinet. There are a few things that can be done to reduce this problem. Multiple pane technology – making a sandwich of up to three panes of glass with a gas filling helps to reduce the transfer of heat into the unit. You can also apply a coating to the glass which still allows light to pass through, but reflects away much of the heat trying to get into the cabinet – this coating is referred to as Low-E glass. A double pane door with a Low-E coating is as effective as a triple pane door, but has much less weight, reducing the burden on the door hinges. Another benefit of Low-E is that during the reflection process, some of the heat is retained in the outer pane of glass meaning that it is much less prone to condensation build up in areas with high humidity. Safety is always a consideration where glass is concerned and ensuring that all the panes of glass on your door utilise tempered (safety) glass would be highly advisable and more often than not a requirement of local standards agencies.
All beverage coolers require some form of shelving. The ability to adjust the height of shelving makes for a more versatile cabinet, and the load baring properties of shelves should also be taken into consideration – in a normal beverage cooler, a shelf double stacked with cans would be under a load of up to 50kgs. The coating of the shelf is also important especially when the shelves are metal – using an epoxy coating allows for a certain amount of flexibility and resistance to cold, whereas a painted shelf will be prone to cracks and flaking.
Doors on a beverage cooler need to be able to take a lot of abuse, be it a trolley bumping into them, the weight of the glass within the frame, etc. A metal or aluminium frame on the door will be much more robust than a plastic or thermoformed door frame and ensures a long lifespan.
Part 3 – Electrical components
In almost all high-performance beverage coolers, electric fans are used to circulate the air inside of the unit as well as draw air over the condenser to ensure an efficient refrigeration system – this is known as forced air cooling. From a reliability point of view, using a tried and tested brand is a must, as a failed fan motor will contribute hugely to further (and more costly) failures in the refrigeration system. The use of EC or electronically commutated fans as opposed to normal shaded pole fans can also save you as much as 40% on your units overall electricity costs.
Units that don’t use a mechanical thermostat to control the temperature (see part 1) will more that likely utilise a digital Energy Management Device (EMD). These devices not only control the temperature of the unit, but also all other electrical elements within the unit such as the lights, fan motors, solenoid valves, etc. as well as monitor behavior such as door openings, shop opening and closing times etc. EMD’s can also allow you to automatically monitor the life signs of the unit through monitoring critical control points such as condenser temperature, incoming voltage levels and door status to protect the unit from misuse/damage.
Over recent years the development of LED technology and the resultant lower of pricing has led to the phasing out of fluorescent tube lighting. LED’s offer great reliability/durability, quality of light and lower energy consumption so a win, win all round. It is important to make sure that the drivers of an LED light are of good quality and are spec’d accordingly otherwise failures may occur.
The global electrical safety standard that beverage coolers should adhere to is the IEC 60335. In South Africa in order to apply for a Letter of Authority (LoA) from the National Regulator for Compulsory Specifications (NRCS) to sell the products you manufacture or import, your product must be certified to IEC (or other globally recognised safety institution) standards.
Part 4 – Design Features
Although beverage coolers are mostly described as plug-and-go units, a certain amount of housekeeping/general maintenance is required in order to keep the units running and performing at optimum efficiency and capability. Apart from day to day cleaning, a regular clean of the condenser is required to ensure that airflow and heat transfer is maintained. Depending on the location the cooler is in (dusty/kitchen/air conditioned/humid) will determine the frequency of such cleaning. Having easy access to the condenser makes this job a lot less time consuming, especially if no tools are required to gain access. Having good access to critical components of the unit also makes the work of a service engineer a lot easier and practical, especially if they are able to access everything without having to move the unit out of its location to perform work.
All refrigeration units require ventilation for the cooling process to be effective. Air needs to flow into and over the condenser and then exit the unit efficiently, and the design and orientation of the condenser in the unit influences this substantially. A condenser mounted in a left to right configuration will mean that the air can only exit at the back of the cabinet, meaning that a certain amount of space or ventilation is required there also. A condenser mounted front to back will allow for air to enter and exit the unit only from the front. This makes the placement requirements of the unit a lot more practical and simpler in the real world – it also means that the unit can be built into a confined space if needed – read the small print, as some manufacturers will require you to leave a 30cm gap around the cooler for ventilation.
Longevity, Durability and Reliability
A commercial beverage cooler would normally be expected to have a lifespan of 7+ years for a sufficient return on investment to be realised. Designing a unit to withstand the treatment and use that it will be subjected to during that period should be a priority. Using durable and robust materials in its construction, as well as designing key features such as door mechanisms, cosmetic features, etc to offer practicality and reliability in not only use, but also ease and availability of parts should repair/replacement be required.
Energy Efficiency and Cost of Ownership
A beverage cooler will require electricity in some way, shape or form in order to work. How it does this, and the overall design of the unit will influence the amount it requires drastically. This is an article in itself and is well worth a read if Total Cost of Ownership is something you are interested in.