Which of the following can decrease boiler performance?

Excess scale build-up can significantly decrease boiler performance. Scale is formed from impurities in the water, which can deposit on the heat exchange surfaces of the boiler. This build-up acts as an insulator, reducing heat transfer efficiency. As a result, the boiler has to work harder to achieve the desired temperature, leading to increased fuel consumption and the potential for overheating components. This not only impacts the energy efficiency of the boiler but can also lead to increased wear and tear, potential system failures, and higher operational costs.

In contrast, proper insulation, high fuel quality, and regular cleaning contribute to optimal boiler performance. Proper insulation helps maintain temperature and reduces heat loss, high fuel quality ensures better combustion and efficiency, and regular cleaning removes any deposits that may inhibit performance. Therefore, the presence of excess scale build-up is detrimental to boiler operation.