Answer: There are 2 situations that can arise:

ISSUE #1: The Back-UPS product stays on battery power while attached to a generator:

This is generally due to the generator being undersized. To prevent voltage distortion and complications with a UPS, the generator must be selected so that it will supply the peak current required by the computer load, not only the average current. It has been determined experimentally that this typically requires that the generator have a rating at least 3 to 5 times the rating of the entire load to be connected to the generator. However, due to wide differences in output impedance for generators, it is not possible to specify an oversizing factor that guarantees compatibility with all systems.

SOLUTION: The only solution would be to use a properly sized generator.

ISSUE #2: The Back-UPS product keep transferring on line to on battery power:

Using non-linear loads with a smaller generator will result in the output waveform of the generator to be very distorted. This distortion will most likely result in the Back-UPS product frequently transferring back and forth from On-Line to On-Battery.

SOLUTION: If a Back-UPS UPS product is to be used with a small gas-powered generator, then APC recommends using one of the following SKUS that are organized by input voltage:

USA and Canada - BP700UC, BP500UC, BP500CLR, BP650S, BP650SC, BP420S, BP420SC, BP280S, BE350U, BE500U, BE725BB, BE600, BR1000, BR1500, BR800, BX1500,BX1500BP, BX1000, BX800, BK300 (no software required), BK500MC (no software required), BK650MC(no software required)

Europe: BP650SI, BP420SI, BP280SI, BR500I

These models are recommended because they can be desensitized thru their respective software to allow the unit to be more tolerant of voltage distortion and, therefore, make less transfers to battery. Though the UPS will still supply power to the load while on battery, this will deplete the battery life. APC does NOT recommend using the any other Back-UPS product besides the ones listed above with small gas-powered generators due to the inability to adjust their sensitivity.

In most cases, to desensitize the UPS you will need to install the Powerchute software that is included with the UPS. Once the Powerchute software is installed, you can lower the sensitivity from the default setting of High, to either Medium or Low.
***With a BK300, BK500MC, or BK650MC, you can adjust only adjust the low transfer point of the UPS. In order to lower the low transfer point, go to the back of the UPS. You will see 3-4 dipswitches. Moving dipswitch #2 up lowers the transfer point by 5 volts. Moving dipswitch #3 up lowers the transfer point by 10 volts. Moving both dipswitches #2 and 3 will lower the transfer point by 15 volts.

If you already are using an unlisted Back-UPS product with a generator and the UPS is constantly transferring back and forth from On-Line to On-Battery: These models cannot have their sensitivity adjusted.

**To determine if your Back-UPS product is listed model look on the rear of the unit at the white bar code sticker. This sticker contains both the "model number" and "serial number". The model number EXACTLY matches one on the list above to be desensitized.

Note about Building-size generators - Generally, generators used to back up an entire building or facility, such as those used for hospitals, are sized large enough and are of good enough quality that any APC UPS will operate fine.

Answer: APC's Back-UPS line is 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 SUA700), Matrix-UPS, or Symmetra Power Array.