We have been using the unit in the server room for a month and have not yet received any information from the manufacturer on how the fan can be switched off, even with a load of 0% (all units switched off) and firmware upgrades. The fan runs continuously and is very loud. The unit is certainly unsuitable for office use. Moreover, it is to be feared that this continuous fan operation would eventually lead to the failure of this fan. After that, the continued use of this UPS is also questionable. Not recommended.