Do it Yourself or Rely on the Experts. Most Freeaire owners purchase their systems with the idea of saving money on their monthly electrical bills. How much they save depends on many variables, and there is no quick and easy formula. Someone has to "crunch the numbers."

The number most often used to determine if a Freeaire installation is a wise investment is the "payback period." The payback period is equal to the installed cost divided by the annual savings.

The installed cost can be an easy thing to find: Just ask your Freeaire dealer for a free estimate. You can put together a pretty good estimate yourself on our Worksheet, if you have a good familiarity with the installation site.

Accurately estimating the expected annual energy savings also requires some fairly detailed knowledge about the entire refrigeration and electrical systems. It will take some investigation effort on your end, since we aren't there to see it in person. If you use an energy services company (ESCO) or a utility energy conservation department to evaluate these things for you, go ahead and let them. They love investigating this cool stuff (pun intended)! They will understand even the more technical pages on this web site and give you a good understanding of what you can expect to save in terms of energy and money from the Freeaire. They especially love crawling around all that dirty, noisy, hot and cold equipment of yours located in all sorts of out-of-the-way places collecting information. (Don't you, fellas and gals?)

Known Facts and Educated Guesses. Further on in this web site, in Savings III: Worksheet , you can contact us to e-mail you our Worksheet, a custom-made Excel (98) document to determine just how much energy and money you can expect to save and what your payback period will be with a Freeaire System. You will need to supply a number of pieces of information, including perhaps some "educated guesses". In this page and the next two, we want to educate you and help you understand the various factors involved in the calculations on the Worksheet.

The Worksheet looks at each of the four main energy-saving measures that a Freeaire System might include: the Basic Freeaire System, door heater control, installing Cool Breeze Outside Air Package(s), and installing PSC evaporator fan motors. For each of the measures, all the affected refrigeration system components are analyzed to determine their energy use and costs, before and after, the work is done. As each area is discussed, we will tell you on which line of the Worksheet it is found.

For each component, the annual cost to operate = cost of energy ($ per kwh) x power (in kilowatts) x phase factor x duty cycle (percentage runtime) x 8766 hours in a year. The difference between this calculation for the before (or without) the energy saving measure and the calculation after the measure is done is the expected annual savings.

Cost of Energy. The cost of electricity is stated for each rate class on a utility rate sheet and/or electrical bills. It is entered into the Worksheet on lines 10-13. This can get complicated, with such things as on- and off-peak hours, seasonal rates and demand charges. (Basing cost estimates on today¹s rates is shortsighted, but fair, considering future electric rates have not been published yet. Who knows what the cost of electricity will be a year from now, let alone 10 years? The prospect of deregulation holds out the possibility of lower energy costs for some large energy users, but the average commercial ratepayer often feels that electric rates will do what they always have done: rise every year.)

Power. Power (in watts) = amps x volts x power factor. The power of refrigeration equipment is not usually stamped onto the nameplates of compressors, condensing fan motors, evaporator fan units, and reach-in door heaters. Instead, information is given from which the power can be calculated. Look on the nameplates for amps, usually FLA (Full Load Amps), but sometimes RLA (Running Load Amps, which is not to be confused with LRA: Locked Rotor Amps) and voltage. These things can also be measured with clamp-on ammeters and voltmeters. There are several lines on the Worksheet on which to enter voltages and amperages. The power in watts is not found simply by multiplying volts x amps, but also multiplying by the power factor of the specific equipment. Unfortunately the power factor of most equipment is not listed on the nameplate and estimates must be used. Electrical resistance loads like the door heaters are simple. Their power factor is 100% so the door heater wattage is simply volts x amps, and a separate line on the Worksheet is not needed. It is usually more or less accurate to assume that the power factor of the condensing unit (compressor and condensing fan) is about 85% (lines 58 and 63). Shaded-pole evaporator fan motors usually have a power factor of about 60% (line 24) and PSC motors about 95%. (There is no line on the Worksheet for the power factor of our PSC evaporator motor as this is already included in its wattage, on line 81.) An accurate way to arrive at the true wattage of particular equipment is to measure the power drawn with a wattmeter, or a true-rms ampmeter, which in effect, calculates the power factor for you.

Phase Factor: The phase factor for single phase loads is 1, while for 3-phase loads it is 1.73. evaporator fans motors are almost always single phase (line27), but compressors are often 3-phase (line 59).

Duty Cycle . Finding the percentage runtime, also called "duty cycle", of the various equipment is also needed to determine the annual energy cost. Once you own a Freeaire system, this is an easy job, as the Cooler Controller tells you exactly how long these things have run for any period up to the last year. This might not help you right now, of course, but one can still make informed estimates on how much of the time your equipment is now operating.

Evaporator fans almost always have a 100% duty cycle (line 29) since they run constantly, all 8766 hours per year, before a Basic Freeaire System is put in. After it is installed, we expect the typical installation to have its noisy, power-hungry evaporator fans silenced at least half the time, even if no outside air is used. That is, with a Basic Freeaire System the expected evaporator fan duty cycle will usually be reduced by 50-70% (line 30). For an undersized compressor that rarely seems to switch off, the evaporator fans may only switch off 30% of the time (a 70% duty cycle). But an oversized compressor that easily refrigerates a space may find its evaporator fans off 80% of the time (a 20% duty cycle) once a Freeaire is installed. It depends on how hard the compressor system was working before. When outside air is used, the evaporator fans' duty cycle will be 0% for the number of days the outside air system completely takes over the job of refrigeration. This depends on the climate and the size of the refrigeration load in relation to the size of the outside air fans. (See the next page, Savings II: Outside Air.)

Door heaters may have a duty cycle of 100% too, if they never get switched off in the electrical panel box or at the switches on the door frames. If they do sometimes get switched off, just try to find out who, how, and when, or make your best estimate. On the Worksheet, the duty-cycle reduction is calculated when you enter a number for " # of added days heaters can be off without fogging" (line 47). We suggest that you can usually assume that for buildings with air conditioning the door heaters can be switched off for 300 days and 200 days if there is no air conditioning. See the" Tale of the Totally Useless Door Heaters" below.

Condensing units: The duty cycle for condensing units changes daily and seasonally as product loads and indoor and outdoor temperatures fluctuate. In addition, a condensing unit can be over- or undersized for the walk-in it is serving and its efficiency can vary with maintenance (like cleaning the heat-exchange coils) and evaporator frosting conditions. It is difficult to determine the duty cycle exactly without attaching a runtime meter or clock to the unit for a complete year and there is no guaranty that each year is the same. The results of a short test can be extrapolated to a full year, if proper consideration is given to the time of year in which the test was done and other variables. A compressor located outside a building usually performs more efficiently all year-round than one located inside, but cold winter weather does not benefit it as much as one might think. An average outdoor unit might vary from 65% runtime in the summer to 35% (line 66) in the winter. It is hard to say without hard data. After a Basic Freeaire System or PSC evaporator fans are installed the condensing unit's % runtime will decrease due to the "Compressor Bonus" (see below). After an Outside Air Package is installed, the condensing unit's duty cycle is 0% for the number of days per year outside air takes over the refrigeration (line 67).

Compressor Bonus. There is a compounding of the savings from reduced evaporator fan use or wattage and it shows up as reduced compressor operation. When you cut the runtime for the evaporator fans, you cut the heat load of the condensing unit, so you also cut its runtime. This is figured for you on the Worksheet once you enter a figure for the Coefficient of Performance (C.O.P.) (line 36) for your compressor. A typical condensing unit for a walk-in cooler will have a C.O.P. of 2.5. This means that for every 2.5 units of energy in the form of heat removed from the space, 1 unit of energy will have to be expended by the condensing unit in the form of electricity consumed. This translates to a compressor bonus of 40% for every unit of energy removed from the walk-in cooler through reduced evaporator fan runtime. Because a condensing unit for a freezer has a harder job to do, its C.O.P. is usually about 1.67 and the compressor bonus is about 60%.

Demand Savings. Your electric utility may charge you for your highest demand for electricity during any short period time, usually 15 minutes, during a month. This is called a demand charge and is measured in $/kilowatt/month. It can make your calculations more complex, but if you can keep a large load, say the door heaters or the compressor, from operating at all during a month you can often save a lot of money. To be absolutely sure you won't be charged a demand charge for a particular load, you'll need to switch the the load off on the front of the Cooler Controller. There are places on the Worksheet where you need to fill in information about demand charges. Insert the figures from your utility's rate sheet on lines 11 and 13. If you aren't charged for demand If you are controlling door heaters, you need to estimate the additional number of months the door heaters can stay off for the entire month (line 50). If you are using outside air, there may be entire months when you will be able to switch the compressor system off (line 76). However, if the outside temperature gets too warm for just a few hours, you run the risk of the walk-in's getting unacceptably warm during that time. This could even be dangerous in the case of perishable food or dairy products, so we advise that the compressor system never be turned off if these thing are involved

The Tale of the Totally Useless Door Heaters. Once the humidistat is adjusted to the relative humidity at which door fogging becomes a problem, door heater operation can usually be drastically reduced. We have one store owner who has found that he never uses his door heaters anymore! No operation, no energy used, no demand charges incurred whatsoever. How is that for energy saving? It seems that, although he may have originally needed his door heaters on once in a while in the summer, he has since air conditioned his store and now the indoor air never gets humid enough to cause the sweating or fogging that is the problem. He had put in the Freeaire humidistat and wired the door heaters only to find out find out he could have just disconnected the heaters completely instead! A 100% savings is the exception rather than the rule. We are just suggesting that you might want to get your hopes up