🔍 Key Concepts

• Potable water heater design on ships and why multiple heat sources are installed • How main engine jacket water availability differs between in-port and underway conditions • Difference between redundancy (backup) and load sharing/meeting peak demand in machinery systems

💭 Think About

• Think about when jacket water is actually hot and circulating, and when shore power or ship’s electrical power is more available. How does that affect which heat source you can rely on at different times? • Ask yourself: is the main goal of two heat sources to always have one available if the other fails, or to be able to match different operating conditions and demands for hot water? • Consider what happens during periods of very high hotel load (lots of crew using showers, galley use, etc.). How would a dual‑source heater help compared to a single‑source heater?

✅ Before You Answer

• Clarify for yourself whether jacket water is normally available and hot only when propulsion engines or certain generators are running. • Decide whether a primary vs. backup arrangement is specifically mentioned in the question, or whether the wording suggests flexibility to use one or both sources. • Check which option best matches the real-world goal of keeping adequate hot water available both in port and underway, under varying demand conditions.