A Stand Alone Preventative Maintenance (PM) visit, is a comprehensive UPS health diagnostic review, preformed by an experienced and well trained Weissco UPS Field Service Technician. During a PM inspection, you can expect the technician to perform a series of visual and mechanical checks to determine the health of the unit.

Along with the UPS service, a battery maintenance service will be performed for the internal and/or external batteries.

Upon completion of the PM, our technician will outline the UPS’s current status and provide suggestions and, if necessary, recommendations for repairs. If you have any questions regarding the PM they will be able to answer those for you as well. Lastly, you will receive a detailed Field Service Report (FSR), outlining the findings discussed for you to review and keep on file. Request a Quote.


A Stand Alone PM will consist of a Major PM’s tasks. Below you will find the actions performed for a Stand Alone PM.

With customer approval to place critical load in maintenance bypass, perform the following items as they apply, if accessible

  • Prior to shutdown – infra-scan inverter and rectifier section of UPS
  • Inspect rectifier section for DC float voltage, DC recharge/Equalize Volt and filtered for DC ripple
  • Verify DC bus reading, calibrate if necessary
  • Inspect inverter section and circuits for frequency regulation, voltage regulation, commutation control, drive circuits and automatic operation
  • Inspect static switch for gate drive circuits, voltage redundancy transfer level set properly, retransfer time set
  • Calibration of equipment per operational specifications
  • Verify proper load sharing among modules
  • Check and torque mechanical connections
  • Test UPS switchgear transfer logic
  • Operational integrity verification, transfer and battery discharge, short duration battery run
  • Return unit to normal operational mode; verify output and float voltages
  • Submit a written report of the system load demands for the past year and make recommendations for future power demands
  • Check air filters; replace or vacuum it out if necessary
  • Inspect the environment, general room conditions, cleanliness, security, access to equipment,etc
  • Clean unit of dirt, and debris
  • Check all fans for proper operation
  • Check for proper air movement, in and out and around the equipment
  • Record the equipment display readings
  • Inspect the instrumentation
  • Check indication lamps
  • Inspect magnetics for signs of deterioration
  • Check all electrical connections for signs of excessive heat
  • Check the equipment for excessive vibration
  • Inspect the power and control wiring for damage, worn insulation and signs of burning or arcing
  • Check power and controls and control lugs and connections
  • Check all AC and DC filter cap connections Check all electrical nuts and bolts for tightness
  • Check the capacitors, swelling and leakage
  • Verify alarm levels and status indications/operation
  • Check output waveform parameters
  • Verify alarm and status indications
  • Check the free running oscillator
  • Inspect the switch-gear components for sign of heat
  • Check the switch-gear power and control wiring for damage
  • Exercise the operation of the UPS circuit breakers, if applicable
  • Inspect remote monitor
  • Check room temperature


  • Verify that there is adequate cooling for the UPS. Record the room temperature, ensure temp
  • Verify that the general area around the UPS is clean
  • Verify adequate service space around UPS and exit ways


  • Verify the kVA rating in the personalization file matches the kVA rating on the label plate
  • Document all optional communications options
  • Perform a thorough visual inspection of all the de-energized sections of any and all auxiliary cabinets, maintenance bypass cabinets, battery cabinets and distributions cabinets


  • Remove the sheet metal, dead front panels
  • Perform a thorough visual inspection of all de-energized power cables:
    Tug on as many available de-energized power cables to verify a solid mechanical connection
  • Verify proper system grounding
  • If there is an output transformer in the UPS, verify a single point ground to neutral bond
  • Perform a thorough visual inspection of all control wiring and ribbon cables, verify proper mechanical connection
  • Verify that the UPS interior is clean and that there is no loose hardware present.


  • Verify that the UPS input is with tolerance and is wired properly
  • Record the input and bypass, output and battery voltages; record the phase to phase values as well the phase to neutral / ground voltages, as well as DC voltage
  • Record input/ output and bypass frequency
  • If possible, measure all three phases of input / output / batterycurrent and record.


  • With the UPS on line (normal) record the measurements from front screen and compare for accuracy.
  • Determine if calibration is necessary

The following battery maintenance will be performed during a Stand Alone PM. If accessible:

  • Visual inspection of batteries, cabinets and environment
  • Measure and record all individual batteries float voltage and current (100%) using a calibrated, accurate (.0.25%) digital voltmeter with a minimum two (2) decimal place referenced right-handed digits capability
  • Measure and record 100% of all battery impedance
  • Measure and record full string charging voltage and current
  • Measure and record the AC ripple voltage and current
  • Measure and record the voltage to ground for each string/cabinet
  • Measure and record conductance of each jar
  • Review battery status and integrity and supply written report of status of batteries
  • Clean oxidation on any posts
  • Check and retorque loose connections
  • Inspect connection terminal, connections, cables and associated hardware
  • Record ambient room temperature
  • Check all batteries for leakage
  • Clean all normal dust and accumulation




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