CSLB C-46 Solar ContractorSolar Thermal System InstallationHard
A solar thermal installer is troubleshooting a system where the collector fluid is getting very hot, but the storage tank temperature is not increasing sufficiently. The pump is running, and there are no obvious leaks or air binding. What component should the installer suspect as the MOST likely cause of inefficient heat transfer?
- AThe storage tank's immersion sensor is miscalibrated.
- BThe expansion tank is improperly charged.
- CThe heat exchanger is fouled or scaled.
- DThe differential controller is faulty.
Show answer & explanationAnswer & explanation
Correct answer: C. The heat exchanger is fouled or scaled.
If the collector is hot but the storage tank isn't heating, and circulation is confirmed, the most likely culprit for poor heat transfer is a fouled or scaled heat exchanger. Deposits on the heat exchanger surfaces significantly reduce its efficiency.
Why the other options are wrong
- A. Miscalibrated sensor would lead to incorrect pump operation, but if the pump IS running and the collector is hot, it doesn't explain the lack of tank heating.
- B. Improper expansion tank charge would affect pressure stability, not directly block heat transfer when the pump is running.
- D. A faulty controller would likely prevent the pump from running or cause short cycling, not inefficient heat transfer when running.
Inefficient Heat Exchanger
A condition where a heat exchanger fails to transfer heat effectively between two fluids, often due to internal deposits or damage.
- Commonly caused by scaling from hard water or fouling from glycol degradation.
- Results in high collector temperatures but low storage tank gains.
- Requires cleaning or replacement for resolution.
Memory trick: Hot collector, cold tank's woe, heat exchanger's gunk, makes transfer slow!