Question 27 DDE01 - Designated Duty Engineer - Unlimited HP

The Correct Answer is B **Explanation for why Option B (80°C) is correct:** The original thermostat begins opening at $180^\circ \text{F}$. To find the closest Celsius equivalent, we must convert the Fahrenheit temperature to Celsius using the standard conversion formula: $$C = (F - 32) \times \frac{5}{9}$$ Substituting $180^\circ \text{F}$ into the formula: $$C = (180 - 32) \times \frac{5}{9}$$ $$C = (148) \times \frac{5}{9}$$ $$C = 740 / 9$$ $$C \approx 82.22^\circ \text{C}$$ Comparing this calculated value ($82.22^\circ \text{C}$) to the available options, $80^\circ \text{C}$ is the closest standard thermostat setting. **Explanation for why the other options are incorrect:** * **A) $70^\circ \text{C}$:** This temperature is $12.22^\circ \text{C}$ lower than the required $82.22^\circ \text{C}$ (approximately $158^\circ \text{F}$). This would cause the engine to run too cool, potentially increasing fuel consumption and engine wear. * **C) $90^\circ \text{C}$:** This temperature is $7.78^\circ \text{C}$ higher than the required $82.22^\circ \text{C}$ (approximately $194^\circ \text{F}$). While closer than $70^\circ \text{C}$, it would cause the engine to run hotter than specified, increasing the thermal load on the cooling system and potentially reducing efficiency. * **D) $100^\circ \text{C}$:** This temperature is significantly higher than the required $82.22^\circ \text{C}$ (approximately $212^\circ \text{F}$, which is the boiling point of water at atmospheric pressure). This could lead to overheating issues in a typical cooling system.