How many fans should be used per electrical circuit during the air tightness test?

In a whole-building airtightness test, the standard practice is to use one fan per electrical circuit. Using a single fan allows for consistent pressure measurement and reduces the potential for electrical overload that could occur if multiple fans are connected to one circuit. This ensures that the testing conditions are controlled and that the airflow measurements are accurate.

Using one fan ensures that the testing is straightforward, and any effects from the fan's performance can be more easily isolated and understood. Additionally, it simplifies the setup and minimizes the chance of complications arising from multiple fans drawing power from the same circuit, which can lead to inconsistencies in the data collected.

While it is important to ensure that the fan selected is capable of handling the requirements of the specific building being tested, the correct approach involves maintaining a single fan approach per circuit to ensure operational efficiency and data integrity during the test.