An on line UPS always powers connected equipment from the battery. Utility power is used only to keep the batteries charged. On-line models perform a "double conversion" by changing utility power to DC to charge the batteries while inverting the battery DC voltage back to AC to continuously power connected equipment.
The batteries completely isolate the line and neutral leads from incoming power. No element of utility power can reach connected equipment. Protection is complete against surges, spikes, AC line noise and voltage fluctuations.
Zero Transfer Time
"Stand-by" and "Line-Interactive" or "Smart" UPSs switch from wall power to battery power once a low voltage limit is reached. Transfer and connect time is needed for the circuitry to recognize a voltage drop and for mechanical relays to energize. That process is fast. But, so are voltage surge and failure events. Because an on-line UPS always uses batteries as the power source, there is no transfer and no transfer-connect time.
Control and Monitoring
Commercial grade on-line UPS models usually feature better control and monitoring capabilities. Those include a front panel display as well as RS232 and optional web cards to allow remote power cycling as well as status monitoring.
Extended Run Time
Some AV and communications installations require longer battery run times for mission critical and life safety systems. External battery modules are usually available for on-line UPS models, but not for less expensive standby or line interactive designs. Additional battery capacity can extend backup power run time from several minutes to many hours.
Contact Juice Goose for support selecting the best UPS design for a particular installation.