Technical Specifications

Heat Rejection
120
There are two basic types of additives:
• Corrosion inhibitors and
• Environmental stabilizers
The corrosion inhibitors function by forming a surface barrier that protects the metals from attack.
Environmental stabilizers, while not corrosion inhibitors in the strictest sense of the word, decrease
corrosion by stabilizing or favorably altering the overall environment. An alkaline buffer, such as
borax, is a simple example of an environmental stabilizer, since its prime purpose is to maintain an
alkaline condition (pH above 7).
The percentage of glycol to water must be determined by using the lowest design outdoor temperature
in which the system is operating. Table 51 indicates the solution volume of inhibited glycol required
to provide freeze protection at various ambient temperatures.
NOTICE
Risk of corrosive dilution water. Can cause piping system damage, coolant fluid leaks and
substantial building damage.
The quality of water used for dilution must be considered because water may contain
corrosive elements that reduce the effectiveness of the inhibited formulation. Surface water
that is classified as soft (low in chloride and sulfate ion content—less than 100 ppm each)
should be used.
Table 51 Glycol concentrations for freeze protection by ambient temperatures
Coolant Type
Temperature, °F (°C
20 (-7) 10 (-12) 0 (-18) -10 (-23) -20 (-29) -30 (-34) -40 (-40) -50 (-46)
Propylene Glycol
% by Volume
18 * 29* 36 42 46 50 54 57
Ethylene Glycol
% by Volume
17 * 26* 35 41 46 50 55 59
Based on Dowfrost
™
(PG) and Dowtherm
™
SR-1 (EG) product literature.
* Inhibitor levels should be adjusted to properly protect the system if solution concentrations are less than 30%.