SHI Case Analysis & Practical Application 2

Question 1

A homeowner reports that their drainback solar water heater loses heat overnight even when the pump is off. What is the most likely cause?

Accepted Answer

Check valve failure allowing thermosiphon reverse flow

Answer

A failed check valve can allow cooler water to thermosiphon backward through the collector loop at night, draining heat from the storage tank.

Question 2

A closed-loop glycol system serving a radiant floor application shows a differential temperature of only 3°F across the collectors on a clear day. What is the most probable diagnosis?

Accepted Answer

Flow rate is too high, reducing heat pickup per gallon

Answer

An excessively high flow rate reduces the temperature rise across the collectors, resulting in a small differential temperature despite normal solar irradiance.

Question 3

During commissioning of a thermosiphon system, the installer notices flow occurs only intermittently. Which condition would cause this behavior?

Accepted Answer

Air trapped in the collector loop disrupting thermosiphon circulation

Answer

Air pockets in the loop create hydraulic resistance that can interrupt the gravity-driven flow of a thermosiphon system.

Question 4

A two-story building has solar collectors on the roof and a storage tank in the basement. The system uses a drainback design. What critical requirement must be met?

Accepted Answer

The pump must have sufficient head to lift fluid from the lowest drain-back point to the collector inlet

Answer

In a drainback system, the pump must generate enough head pressure to lift the heat transfer fluid from the drainback reservoir up to the collector level on every startup.

Question 5

A solar domestic hot water system in Phoenix, AZ is producing less than expected output in July. The storage tank reaches 160°F by noon and the pump shuts off. What is the most likely issue?

Accepted Answer

High-limit control is shutting down the pump to prevent overheating

Answer

When the tank reaches the high-limit setpoint, the controller shuts off the pump to prevent scalding and equipment damage, which is normal stagnation behavior in a hot climate.

(SHI) Solar Heating Installer Certification Practice Test

(SHI) Solar Heating Installer Certification Practice Test

SHI Case Analysis & Practical Application 2