Red Seal Plumbing Practice Exam

By what percent must an appliance's input rating be de-rated when moved from sea level to high altitude?

1. 5

2. 10

3. 15

4. 20

The correct answer is: 10

When an appliance is moved from sea level to high altitude, the air becomes less dense, causing a decrease in oxygen levels. This change in atmospheric conditions affects the appliance's combustion process, which can result in decreased efficiency and potential damage. In order to compensate for this change, the appliance's input rating must be de-rated by 10%. This means that the appliance's input rating must be reduced by 10% in order to maintain its safe and efficient operation at high altitudes. Options A, C, and D are incorrect because they do not accurately reflect the recommended de-rating percentage for appliances at high altitudes. Option A is incorrect because 5% is too small of a de-rating, while options C and D are incorrect because 15% and 20% are too large of a de-rating. Therefore, the correct answer is B 10%.