GREEN SYSTEMS | SOLAR SOLUTIONS | CONTINUED FROM PAGE 90
250°F (121C) Tyfocor L and Tyfocor LS Pre-mixed Premature aging will occur above 338F (170C), slow
thermal decomposition above 392F (200C). Dynalene Solar Glycol-XT (Bio Glycol made from corn.) Recommended Temperature Range Closed System : -17
°F to 350 °F (- 27 °C to 176 °C) DowFrost In Depth There is a wealth of information available for PG heat
transfer fluids, and one of the most prolific sources is from Dow available on the following web site location:
www.dow.com/heattrans/tech/data.htm There are many useful publications in PDF format on
this site available for free. One of the most comprehensive is the DowFrost Engineer Operating Guide, which is a goldmine of technical information about the properties of PG with advice about how to use it properly. If you want to know freezing point, boiling point, conductivity, specific gravity, density, viscosity, temperature limits and lots of other details this is the reference to get.
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Testing methods As the PG ages and degrades over time, the freeze
protection concentration can change, the acidity can change and the additives can lose their effectiveness. You
can quickly determine the condition of your fluid by examining its appearance and odor. Any drastic variation from the initial fluid specifications, such as a black or dark- gray color, presence of an oily layer, burnt odor, or any heavy sludge in the fluid may indicate the need for fluid replacement. Test equipment is also available to measure the quality
of the fluid. This can be done with test strips, supplied as a kit by the manufacturer, that resemble litmus paper. Test strips will tell you the pH, the freeze protection level (indicated by the percent concentration) and the state of the inhibitors. We often use a refractometer gauge that resembles a small telescope to quickly check the freezepoint/concentration, or a digital gauge that reads out percent and freeze value directly on an LCD display. Digital pH meters are available as well. The following advice is taken from the DowFrost
Engineer Operating Guide: “Control of pH between 8 and 10 is important to
minimize corrosion and glycol degradation. Using narrow range pH paper such as pHydrion Control paper with a 7.2 to 8.8 pH range is an easy and reliable way to read your pH level.” A pH tester can also measure alkalinity or acidity of the
fluid. The desirable pH range should fall between 8.0 and 10.0. Adjustments can be made by using a 50% solution of sodium hydroxide or potassium hydroxide if the pH is between 7.0 and 8.0. Any fluid with a pH below 7.0 should be replaced. An inexpensive pH tester is available from Misco Products. The accuracy of this instrument is +/- 0.5 pH. Misco also makes a Freezepoint/ Concentration tester. These articles are targeted
toward residential and small commercial buildings smaller than 10,000 square feet. The focus is on pressurized glycol/hydronic systems since these systems can be applied in a wide variety of building geometries and orientations with few limitations. Brand names, organizations, suppliers and manufacturers are mentioned in these articles only to provide examples for illustration and discussion and do not constitute any recommendation or endorsement. ;
Bristol Stickney is the chief technical officer for SolarLogic LLC in Santa Fe, N.M., where he is involved in development of solar heating control systems and design tools for solar heating professionals.
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phc august 2011
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