Emerson 350-500VA Fascicule

The information below indicates various symptoms a user may 
encounter in the event the PowerSure PST experiences a problem. 
Use this information to determine whether external factors caused 
the problem. See Troubleshooting Chart for suggested remedy.

1. The Fault indicator 

illuminates, indicating the 
UPS detected a problem.

2. An alarm sounds, alerting that the 

UPS requires attention. The alarm 
can be silenced except for low 
battery, overload and 
overtemperature warning 
conditions.

3. Utility and/or Battery indicators 

may be illuminated as a diagnostic 
aid to the operator, as shown 
below: 

—

—

 

ON

UPS is 

operating in 

Normal Mode; 

no beep.

—

—

 Flashing

Battery Test 

has been 

initiated; no 

beep.

—

  Flashing

 ON

Site Wiring 

Fault; no beep.

  Flashing

—

 ON

The unit is 

overloaded; 

beep every 

half-second

  ON

—

 ON

The UPS has 

failed; 

continuous 

beep

  Flashing

—

—

Unit has shut 

down due to 

overload; 

continuous 

beep

  ON

—

—

The UPS shut 

down due to 

failure; 

continuous 

beep

—

—

  Flashing

The UPS is 

operating in 

Battery mode; 

beep every 5 

seconds.

—

—

  Flashing

UPS battery is 

low; beep every 

half-second

  Flashing

—

  Flashing

The unit is 

overloaded; 

beep every 

half-second

  ON

—

  Flashing

The UPS has 

failed; 

continuous 

beep

+

-

If the UPS fails to operate properly, turn off the unit and repeat 
the steps in the Installation section of this manual. If the prob-
lem persists, refer to the chart below:

Overload/

Short circuit

Check the circuit 

protector on the side of 

the UPS. If it is tripped, 

reset it and restart the 

UPS. 

For further help, call 

your local dealer, 

Liebert representative 

or the Liebert 

Worldwide Support 

Group.

UPS not 

plugged in

Plug in power cord 

securely.

Circuit 

protector 

tripped

Reset the circuit 

protector and restart the 

UPS.

Power not 

available at 

utility 

receptacle

Have the utility 

receptacle checked by a 

qualified electrician.

Input voltage 

below 

threshold

Wait until the voltage 

rises to an appropriate 

level or have the utility 

receptacle checked by a 

qualified electrician.

AC 

overvoltage

Wait until voltage lowers 

to an appropriate level 

or have the utility 

receptacle checked by a 

qualified electrician.

Overload/

Short circuit

Check the circuit 

protector on the rear of 

the UPS. If it is tripped, 

reset it and restart the 

UPS. 

If the problem persists, 

disconnect some of the 

equipment from your 

UPS—the total wattage 

of your equipment must 

not exceed the capacity 

of the UPS. For further 

help, call your local 

dealer, Liebert 

representative or the 

Liebert Worldwide 

Support Group.

Internal UPS 

fault

Line-neutral 

reversal/Poor 

ground 

connection

Have the utility checked 

by a qualified 

electrician. 

Overload

Reduce load.

Battery not 

charged due 

to a recent 

outage

Recharge battery.

The PowerSure PST UPS requires very little maintenance. Follow these 

practices to prevent problems.
CLEANING THE UPS
The following will help ensure trouble-free operation for years:
• Vacuum dust from the ventilation intake occasionally.
• Wipe the cover periodically with a dry cloth.
MAINTAINING BATTERIES
The batteries are valve-regulated, nonspillable, lead acid and must be 

kept charged to retain their design life. The UPS continuously charges the 

batteries when connected to the utility supply, even while the UPS is 

switched off.
When storing the UPS, it is recommended to plug in the UPS for at least 

24 hours every four to six months to ensure full recharge of the batteries.

To register for warranty protection:
• Visit the Quick Links section of our Web site at:

 

• Click on Product Warranty

Registration and fill in the form.

US: 800-222-5877

Outside the US: 614-841-6755