Question 26 CEL01 - Chief Engineer - Limited

The Correct Answer is A **Explanation of Option A (Correct):** Option A accurately describes the fundamental operation of a one-pipe (series-loop) hydronic heating system. In this design, all heating coils (such as baseboard radiators or convectors) are connected in **series**. The circulating hot water flows sequentially through the coils. 1. **Progressive Temperature Drop:** When the hot water passes through the first heating coil, it transfers heat to the room, causing the water temperature to drop. 2. **Different Inlet Temperatures:** This slightly cooler water then becomes the *inlet* water for the second heating coil. The temperature drop repeats in the second coil, and the resulting even cooler water serves as the inlet for the third coil, and so on. 3. **Conclusion:** Therefore, the inlet temperature to each successive coil is lower than the previous one, meaning that **each heating coil inlet temperature is different** and **progressively drops** as the water moves through the system. **Explanation of Why Other Options Are Incorrect:** * **B) Each heating coil inlet temperature is identical, as the hot water inlet temperature to each heating coil progressively drops as the water passes through each successive series-connected coil.** * *Incorrect because:* The first part of the statement contradicts the second. If the water progressively drops in temperature (which it does in a series system), the inlet temperatures cannot be identical. * **C) Each heating coil inlet temperature is identical, as the hot water inlet temperature to each heating coil progressively rises as the water passes through each successive series-connected coil.** * *Incorrect because:* In a heating system, the water transfers heat to the surroundings; therefore, its temperature must drop, not rise. The inlet temperatures are also not identical. * **D) Each heating coil inlet temperature is different, as the hot water inlet temperature to each heating coil progressively rises as the water passes through each successive series-connected coil.** * *Incorrect because:* While the inlet temperatures are different, the temperature of the water must progressively drop (transferring heat), not rise, as it passes through the heating coils.