CSLB C-46 Solar ContractorSolar Thermal System InstallationMedium
A solar thermal system installer needs to ensure that the heat transfer fluid in a closed-loop system will not freeze in winter conditions. The system uses propylene glycol. What is the MOST reliable method to verify the freeze protection level of the glycol solution in the field?
- AUse a pH meter to check the acidity/alkalinity of the solution.
- BVisually inspect the color of the glycol solution after filling.
- CMeasure the specific gravity of the solution with a refractometer.
- DCompare the solution's temperature against a known freeze chart.
Show answer & explanationAnswer & explanation
Correct answer: C. Measure the specific gravity of the solution with a refractometer.
A refractometer directly measures the refractive index of the glycol solution, which correlates accurately to its concentration and thus its freeze protection temperature. This is the most reliable field method.
Why the other options are wrong
- A. pH indicates corrosion protection additives, not freeze protection.
- B. Color can indicate dye, but not concentration or freeze protection level.
- D. This is not a practical or direct method; a refractometer is used to determine the freeze point based on concentration.
Glycol Freeze Protection Verification
The process of accurately determining the freeze protection temperature of a glycol-water solution in a solar thermal system.
- Crucial for preventing system damage in cold climates.
- Refractometers are the most common and accurate field tool.
- Specific gravity correlates directly to glycol concentration and freeze point.
Memory trick: To know your glycol's freeze-safe zone, the refractometer's light must be shone.