Ever wonder how those Polarized Refrigerant Oil Additive (PROA) (Frigaid, Proactq, etc

salesmen “prove” that using their product produces a 20%, 30% or even 40% energy savings? --Let’s look at their math and see how it’s done:
The typical PROA sales approach is to get the potential customer to allow them to test their product on some well-used air conditioning or refrigeration unit. If the customer agrees, the first thing the salesman will do is perform a “pre-test” to establish “baseline” conditions. He will then inject some of the product and give it some time to circulate throughout the system. Then, usually a week or so later, he will return and run a “post-test”.
Now, here’s where they work their magic. Following the post-test, the salesman uses the pre-test and post-test DT’s to calculate a “correction factor”. The “average pre-test kWh” is then compared with the “average CORRECTED post-test kWh” to determine the percent efficiency improvement.
For the tests, the salesman usually takes (1) an indoor (dry bulb) temperature reading or thermostat setting, (2) an outdoor (dry bulb) temperature reading, and (3) compressor volts & amp readings. Then, to provide a “correction factor” for differences between pre-test and post-test conditions, he uses the formula “Q=h·A·DT, where ‘Q’ is total heat, ‘h’ is the heat transfer coefficient, ‘A’ is the surface area of the transfer medium, and ‘DT’ is the temperature difference across the transfer medium.”
As their literature* explains, “In the case of refrigeration, the Q, h, and A are basically constant regardless of the ambient temperatures outside the cooled areas. Therefore, in comparing the relative effect of a change in ambient temperatures, consideration of the temperature differences is essential.”
“As an example, assume the thermostat is set at 72 degrees F in an air-conditioned space and the ambient temperature is 90 degrees F, then the Delta T (DT) is 18 degrees F. Since the heat load (Q), the heat transfer coefficient (h), and the surface area of the walls and roof are basically constant, if the ambient temperature rises to 95 degrees F, the Delta T (DT) goes to 23 degrees F. Therefore, the heat load applied to the system is 28% higher than if the ambient temperature is 90 degrees F.”
“For this example, assume a thermostat setting of 72 degrees F, a pre-test temperature of 90 degrees F, and a post-test temperature of 95 degrees F. The correction factor would be calculated as follows:
| 1 |
|_______________________|
CF = | | (90 – 72) – (95 – 72) | |
| |__________________ |+1|
| | (90 – 72) | |
Correction Factor = 0.78 (or 0.7826)
This calculates the correction factor needed to bring the post-test to the same reference as the pre-test.” (Incidentally, you can get the same result by simply dividing 23 into 18.)
So, what’s really going on here? -- Why would this not provide an accurate method of adjusting for differences in compressor operating conditions?
First and foremost, remember that these are AIR CONDITIONING and REFRIGERATION SYSTEMS. The total heat formula, “QT = 4.5·cfm·Dh” provides a far more accurate statement of the heat transfer that takes place across an air conditioning or refrigeration system evaporator. Using this formula takes into account ALL the factors that make up the total heat load, because net refrigeration effect calculations must take into account both SENSIBLE and LATENT heat loads. Although the PROA salesman’s formula is useful in sizing heating systems, it simply does not apply here.
Also, note that because temperature differences between indoor and outdoor temperatures are being used in the above calculations, the “transfer medium” in the example is not a condenser or evaporator coil, but rather, the walls, floor, and ceiling of the space that is being cooled.
Now, for arguments sake, let’s say that the formula IS accurate and applicable. But, instead of adding any product or doing anything whatsoever to improve or change the unit, we run a pre-test and come back a week later and run a post-test. Let’s say the compressor pulled what amounts to 10.0 kWh during the pre-test with 72 degrees indoors and 90 degrees outdoors. Then, during the post-test, it was 72 degrees indoors and 95 degrees outdoors. Using their math, if the compressor pulls anything below 12.778 kWh, (12.778 kWh x 0.7826 correction factor = 10.0 kWh) we will have an energy savings… without doing anything to our system!
Thus, using only their math:
12.0 kWh = 6% energy savings
11.0 kWh = 14% energy savings
10.0 kWh = 22% energy savings
9.0 kWh = 30% energy savings
8.0 kWh = 37% energy savings
... and so forth.
To see just what kind of efficiency and improvements were possible using their math, I applied it to some actual test data derived from a walk-in cooler condensing unit test from several years ago. Using the test data, I paired readings from different days that had identical or close to the same run times. The walk-in cooler thermostat was set on 40 degrees F for the entire test, so the only significant variables were the kWh readings that were taken and the local daily mean temperature, which I obtained from the National Weather Service.
Using the difference between the daily mean temperature and the cooler thermostat setting to get the “Mean Temperature Difference”, I calculated a corresponding “Correction Factor” just as they do. A comparison of 14 sets of actual test readings yielded “efficiency improvements” as low as 3.0 % and as high as 129.8 %, with an average “efficiency improvement” of 42.1%. Eight out of the fourteen comparisons produced results in the 20% to 60% range.
Conclusion: whether you’ve modified a system or not, when you apply their math, claims of extraordinary efficiency improvements become possible. Without that advantage, you may see little or no improvement, or even a loss of efficiency. That’s because their calculations are erroneously based on the assumption that compressor energy consumption is linear and based entirely upon the dry-bulb temperature difference between indoor and outdoor temperature conditions… and that, as they say, is nothing more than “smoke and mirrors”.
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Source: Letter from MOLeTEC Corporation, to Whom It May Concern, dated January, 1995. MOLeTEC produces the PROA “Frigaid”.
Note: A copy of a test conducted on an ice machine at the Von Braun Civic Center in Huntsville, Alabama by PROATEQ revealed the use of the same “correction factor” calculation as MOLeTEC.