The use of non computer type loads with a UPS, specific to Back-UPS, Smart-UPS SC.
Back-UPS, Back-UPS Pro, Smart-UPS SC
APC's Back-UPS and Smart-UPS SC product lines are designed for use with computer type loads only. They are not designed to be used with motor loads such as fish filters, air conditioning units, space heaters, vacuum cleaners or any other machinery.
One potential issue is the inrush current draw for a motor. It can easily overload a Back-UPS UPS model. Secondly, these models of UPSs output a stepped approximated sine wave when on battery. This waveshape, while ideal for computer type equipment, is not particularly compatible with most motor loads. The result may be that motors run very slowly, erratically, or not at all when the UPS is on battery.
To protect this type of equipment, APC recommends first determining the appropriate size UPS for the motor load in question. Ensure that the Volt Amp rating of the UPS is sufficient to handle the start-up inrush current draw of the motor. Secondly, select a UPS which outputs a pure sine wave when on battery, such as a Smart-UPS (minimum of a 750VA model), Smart-UPS Online, or Symmetra LX/RM.