A solar thermal installer is integrating a new pumped closed-loop system with an existing domestic hot water (DHW) tank. The existing tank is a standard electric water heater. To maximize the efficiency of the solar thermal system and ensure proper heat transfer, what is the optimal plumbing configuration for connecting the solar heat exchanger to the existing tank?
- AConnect the solar heat exchanger output to the existing tank's cold water inlet.
- BConnect the solar heat exchanger output to a dedicated lower port on a new, solar-ready tank.
- CConnect the solar heat exchanger output to a T-fitting on the existing tank's temperature and pressure relief valve port.
- DConnect the solar heat exchanger output to the existing tank's hot water outlet.
Show answer & explanationAnswer & explanation
Correct answer: B. Connect the solar heat exchanger output to a dedicated lower port on a new, solar-ready tank.
For optimal solar thermal performance, the solar heat exchanger should transfer heat to the coldest water in the tank, which is typically at the bottom. A dedicated lower port on a solar-ready tank allows for this stratification and efficient heat transfer. Connecting to the cold water inlet (A) would try to heat the entire tank from the top, which is less efficient. The other options are incorrect for heat transfer or safety.
Why the other options are wrong
- A. Connecting to the cold water inlet would introduce heated water to the top of the tank, disrupting stratification and reducing efficiency as it would mix with already hot water first.
- C. Connecting to the T&P relief valve port is a major safety violation and is not designed for regular water flow or heat transfer.
- D. Connecting to the hot water outlet would bypass the tank's heating element and serve no purpose for preheating the tank's water.
Solar DHW Tank Connection
The optimal method of plumbing a solar thermal heat exchanger to a domestic hot water storage tank to maximize stratification and heat transfer efficiency.
- Heat coldest water first
- Dedicated lower port on solar-ready tanks
- Promotes thermal stratification
- Maximizes solar contribution
Memory trick: Solar heat's best friend, the tank's cold end.