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Freezers More Savings than a Cooler. Nothing shows more that the Freeaire is now a refrigeration system in any climate than the fact that Cooler Controllertm can control walk-in freezers. There are few places on earth that are frigid enough, for enough of the year, that outside air can be economically used in a freezer. However, the model 2001 Cooler Controller can still improve refrigeration and save even more energy and money in a typical walk-in freezer than it can in a walk-in cooler. The reason for this is that, due to its more difficult job of maintaining a larger temperature difference between inside and outside of the box, a freezer's condensing unit (compressor) is inherently less efficient than a cooler's. A typical 40°F(4°C) cooler's condensing unit might have a COP (Coefficient of Performance) of 2.5, meaning that it can remove 2.5 Btu's (British thermal units) of heat with the input of the energy equivalent of 1 Btu. (3.41 Btu/hour = 1 watt.) A 0°F (-14°C) freezer's COP is more likely to be about 1.67. Therefore, to remove a Btu of heat from a freezer requires about 50% more energy than to remove it from a cooler. All the electrical energy used to operate the evaporator fans inside a cooled space turns into heat needing removal by the condensing unit. For example, eight 130 watt evaporator fans operating continuously in a walk-in cooler or freezer use 25 kwh (kilowatt-hours) a day. It takes another10 kwh to remove their heat from a cooler, but 15 kwh, half again as much, to remove their heat from a freezer. Therefore, any energy saved in a freezer will result in even larger energy savings by the condensing unit than if that energy was saved in a cooler. And saving energy is what a Freeaire system does best. In a freezer it can do this in four main ways:
Eliminating Unnecessary Evaporator Fan Operation: Just as in a walk-in cooler, the model 2001 Cooler Controller will turn off the evaporator fans when they are not needed. In a freezer they are needed only about half the time, to deliver the cooling provided by the condensing unit. Once the freezer has reached its low limit (setpoint) there will be a short (1 or 2 minute) delay, after which the evaporator fans stop. This prevents them from adding more heat to the freezer, which in turn, prolongs the time until the condensing unit turns on again. Proper air circulation is maintained by having a high volume (500 cfm), but energy-saving (36 watts) Freeaire Circtm fan on whenever the evaporator fans are not operating. In the example sited above, a freezer with eight 130 watt evaporator fans that operated only half the time would save 19.6 kwh per day. . The refrigeration system always operates at peak efficiency because the evaporator coils are regularly kept clear of ice. Less evaporator fan and compressor operation makes them last longer and saves money on replacement as well as operating costs. Reducing Reach-in Door Heater Operation: Reach-in doors in walk-in freezers are even more prone to fogging than doors in walk-in coolers, because their lower temperature invites more condensation. Anti-fog heaters tend to be even hotter and use even more energy. However, just as in walk-in coolers, they need to be on more during humid weather than during the winter or times of dry weather. The Freeaire's Door Heater Humidistat can be set at that level of relative humidity (in the air inside the warm part of the building) at which condensation begins to become a problem. Whenever the air is drier than that setting the Cooler Controller will switch off the heaters. Anytime the door heaters can be off will result in energy saved by the heaters, as well as by the condensing unit which won't have to run as much to remove that part of the door heat which enters the freezer. Reducing Evaporator Fan Wattage: Evaptm fan motors are permanent split capacitor (PSC) evaporator fan replacement motors and are available for many common evaporator units. Their efficient design allows them to deliver as much airflow through the evaporator coils as standard 1/15th horsepower shaded-pole motors and use only about 2/3 as much energy (88 watts vs. 130 watts). These replacement motors can be used with or without the Cooler Controller. In fact, their payback period will be even faster when they are the only energy-saving measure taken. This is because when the evaporator fan operate 24 hours a day there is more runtime in which to accumulate savings. On-demand Defrost: Freezers cannot use "air defrost" during periodic evaporator coil defrosting cycles because the air in a freezer is too cold to melt the frost. Most walk-in freezers use electric heaters, controlled by an electric time clock, for defrosting the evaporators. The evaporator fans do not run during a freezer defrost cycle. There may be six 20-minute defrost periods of electric heater operation a day. Most of the time, that much defrost time isn't necessary, but a simple timer can't know that, so it has the same defrost cycles every day of the year. If the defrost cycle is longer than necessary and no ice is being melted at the end of the cycle, a lot of excess heat can be added to a freezer which only causes the condensing unit to run more just to remove it. A model 2001 Cooler Controller solves this problem in walk-in freezers by supplying defrost on demand. Open-ended defrost cycles occur after about 4 hours of accumulated compressor runtime and last as long, but only as long, as needed. A temperature sensor mounted in the evaporator coils keeps track of ice and knows when to end a defrost cycle. Once the sensor senses that all the ice is melted, the compressor will switch on, but not the evaporator fans, in order to remove any excess heat from the freezer. Once that is done, the evaporator fans begin operating and the defrost cycle is over. This defrost strategy reduces energy use by the defrost heaters as well as the condensing unit and, by reducing their runtimes, prolongs the life of both.
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