Maintenance for UPS systems - Cabinets and APC racks
Maintenance for UPS systems - Cabinets and APC racks

Corrective and Preventive Maintenance

Maintenance of the UPS consists of preventive and corrective maintenance. Preventive maintenance consists of a scheduled list of activities. Performing these activities keeps the UPS in good working order and helps to prevent failures.

Corrective maintenance is performed as a result of a failure. Corrective maintenance fixes the problem and gets the unit working again.

A general guide for the maintenance requirements of the UPS systems modules, static switches, and controls is provided. Although electronic components are not subject to wear in the same degree as electromagnetic (EM) components, they do require systematic maintenance.

A standard maintenance procedure cannot be developed for all types and sizes of UPS units. The manufacturer’s user’s manual should always be consulted as to specific maintenance requirements and troubleshooting diagnostics guidelines.


Do not rely on memory. Follow the user’s manual guidelines. Such guidelines should provide safety precautions. If your user’s manual limits the maintenance that can be provided by the user, follow the manual’s instructions unless general instructions are supplemented with additional guidance. Physical maintenance or troubleshooting should only be performed by personnel trained on the system. Operating personnel not instructed in UPS maintenance must limit their efforts to identifying the symptoms of a fault. Always be aware of the DANGER, as voltages within the UPS modules and associated switchgear are lethal.

Lethal voltages are present even when the output circuit breaker in the UPS is open. It is necessary to open the circuit breaker in the distribution panel feeding the UPS and the UPS bypass circuit breaker, plus opening the direct current (dc) link connection to the battery, before all dangerous voltages within the UPS are eliminated. Capacitors may need to be discharged of their stored energy. Use CAUTION when operating UPS equipment to prevent serious injury or death.

Preventive maintenance

Periodic maintenance is required to maintain the integrity and lifetime of the battery. Power electronic equipment also requires scheduled maintenance even though solid-state devices are used. Preventive maintenance may require that the UPS system be shut down.

A transfer of the critical load which may not provide the power enhancement capabilities of an UPS system is something that the user must tolerate in order to obtain maximum reliability and minimize downtime and repair costs.

1. Records

Preventive maintenance is systematic maintenance. The objective is to minimize equipment operating problems and prevent failures by making minor or necessary repairs before major operating difficulties occur. The general condition of the equipment needs to be evaluated periodically, and records need to be maintained for comparison at subsequent inspections. Recorded information is more reliable than a maintenance technician’s memory.

Records should be concise but completely describe equipment conditions. Inspection records should provide complete information on the following topics, preferably on separate record sheets.

(a) Equipment record

This record should list the basic information on the equipment itself, e.g., manufacturer’s identification, style, serial, size, location, etc., and incorporate inventory-control data for spare parts. Warranty requirements covering uninterruptible operating conditions should be abstracted from the user’s manual.

(b) Repair cost record

This record should provide a history of repair and associated costs of maintenance for the UPS system. It is an essential diagnostic record for avoiding future difficulties, especially for systems determined to be of poor quality, misapplied, or marginal for the application.

(c) Inspection check list

This list should provide necessary and pertinent information on points to be checked and establish the recommended recurring dates when these checks should be made. Since shutdown may require a sliding window period, the amount of time for which this request must precede the shutdown window should also be stated.

(d) Periodic maintenance schedule

This schedule provides a complete listing of the day-to-day, weekly, monthly, and annual duties which should be reviewed on the same periodic time basis so that potential trouble situations can be investigated and corrected as soon as possible.

(e) Maintenance inspection and repair records

These necessary and vital documents should be completed in detail by the inspector or an assigned individual in the maintenance department. Maintenance personnel usually report their findings and corrective action on assignment sheets or job cards. Permanent records are a useful guide to each UPS system’s general condition and reliability. It is important to know the frequency and type of repair and how often there is a need for a complete overhaul.

2. Use of records

These records provide for a workable preventive maintenance program. The information obtained from the necessary periodic inspections can be quickly lost.

This is particularly true when test results are required. Unless records and data on the test and performance of equipment are retained, the maintenance program will be defeated. Unless records are updated at each succeeding test period, valuable information is lost. Comparative test data materially assists an UPS specialist in defining problems, especially when test results differ from manufacturers’ recommended settings or actual factory test data. Significant changes in comparative test data can, in general, be related to the equipment’s condition.

3. Scheduling

Scheduling of UPS and battery maintenance is normally based on the manufacturers’ recommendations. Since an UPS system is vital to the operation of critical loads, it may be considered advisable to provide more inspections than those the manufacturer recommends. Certain items on the UPS should be inspected daily or weekly.

This inspection can be done by operating personnel, but data should be recorded and sent to the appropriate maintenance point not more than 5 days after being recorded. Battery maintenance should be done by maintenance personnel. Visual monitoring data should be recorded daily for the UPS, and if recorded for the battery, the recorded data should be handled and sent on to the maintenance department on a weekly basis.

4. Periodic system status checks

The continued monitoring of the operating status of any electronic equipment greatly enhances the probability that failure of that equipment will be prevented. Daily observation is advised but do not provide less than weekly checks. Personnel involved in status monitoring should be those most concerned with the equipment’s proper functioning.

(a) UPS systems in computer rooms

Computer room operating personnel should become familiar with the equipment and its various operating indications. They should maintain records on all findings or occurrences during preventive maintenance. The operating personnel shall check all lamps on mimic bus and alarm status indicators.

They shall have maintenance personnel replace inoperative bulbs. Also, they shall check input, output, and bypass voltages and currents and all other system status readings and compare them to the required specifications.

A copy of the requirements which must be met, exceeded, or not exceeded should be included as a part of the inspection checklist. Maintenance personnel shall be called to apply troubleshooting procedures if abnormal values are indicated. Operating personnel may also ensure adequate ventilation and cooling by checking that all fans are operational; ensure all doors, drawers, and covers are secured; and check for unusual noises and odors.

(b) UPS system in dedicated UPS rooms

These systems will normally have remote displays and alarms. Display panels usually indicate problems only to the extent that they affect computer operations. Summary alarms keep the information simple and easy to understand.

A usual system would include “on battery,” “battery near discharge,” “overload,” and “UPS operating abnormality.” In a location where the UPS is in a dedicated room, the periodic monitoring records of the UPS system would be provided by maintenance personnel. Computer room operating personnel would only record battery cycling, time, discharge, overload, and abnormality and advise maintenance personnel at the time of an alarm indication of the problem displayed.

5. Major system inspections

These should be performed at least annually on small to medium systems and semiannually on large to very large systems. By performing this type of maintenance on a scheduled basis, it is possible to find and remedy potential problems before the system’s operation is affected. Table 5-1 provides general guidance for the major system inspection, however, the manufacturer’s recommendations should be strictly followed.

6. Minor system inspections

Minor system inspections should be provided either after 5 months from an annual major inspection or after 3 months from a semiannual major inspection unless a more frequent requirement is recommended by the manufacturer. Minor system inspections should include at least the first four items listed under major inspections. Off-line load testing is required if major component replacements are required.

 No.Table 5-1. Major system inspection general
1Perform visual checks and operational tests of all UPS equipment and associated switchgear.
2Review maintenance logs and log all alarm operations and output
3Complete a functional checkout and test of the UPS diagnostic systems.
4Check environment, temperature, dust, moisture, room vents, etc.
5Clean and tighten all power connections at the input and output terminals, at all circuit breakers, and at the terminal posts and fuses on the rectifier and inverter legs. During the inspection, check all power cabling for abrasions and burn spots. Visually check components for signs of overheating, swelling, leaking, etc.. Visually check printed circuit board alignments.
6Replace air filters at regular intervals. Site conditions will determine how often the filters should be replaced, but generally, they will need to be replaced at least every 6 months in clean environments. If more frequent replacement is required, the cleanliness of the environment should be upgraded.
7Check and calibrate each system, to include switchgear and circuit breakers, meters, and alarm levels for frequency, voltage, current, transfer, trip, alarm, etc.
8Perform system and component functional tests on all UPS equipment to insure proper functioning within specified parameters.
9Run all UPS system diagnostics, and correct all diagnosed problems.
10Resolve any previous outstanding problems, review operation with user personnel, and report any power enhancement or equipment operation recommended changes.
11Replace control batteries at least every 2 years. If the control batteries have been used without inverter or bypass AC power, they may need replacement sooner.
12Open all doors, drawers, and covers. Perform a thorough inspection of all cabinets for foreign objects. Perform a thorough dusting and vacuuming of all cabinet interiors. Use only rubber or plastic vacuum attachments to clean drawers and cabinets. Except for vacuuming, never attempt to clean the UPS subassemblies. Accumulated dust or grime should only be cleaned by the manufacturer’s service representative. The exterior panels can be cleaned with a mild cleaning solution. Transparent panels should be cleaned with a mild soap and water solution only. Restore all doors and covers to their secured condition.
13Off-line load test the UPS system to ensure that the system is completely functional.
14Return the UPS to service following the manufacturer’s recommended start-up procedures. Make sure that no damage to the UPS equipment or shutdown will occur because of inrush currents.

About Author //


Edvard Csanyi

Edvard - Electrical engineer, programmer and founder of EEP. Highly specialized for design of LV high power busbar trunking (<6300A) in power substations, buildings and industry fascilities. Designing of LV/MV switchgears.Professional in AutoCAD programming and web-design.Present on


  1. Jim
    Sep 30, 2016

    Nice article. A good UPS service provider will offer a reliable maintenance cover package to its customers. It should include a fast response guarantee to minimise any downtime. This is a good example.

  2. Trevor
    May 20, 2015

    I would like to know how to do maitenance on ups

  3. latha
    Dec 07, 2013

    hi,once you have posted regarding magnetic ballast for lighting cause for poor power factor,in article power quality….so i think its been replaced by electronic ballast…so no question of magnetic ballast so i like to say you to take off that point.

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  6. mannybarcelona69
    Oct 19, 2012

    I dont have so much exposure in UPS system but at least this site was a great helped to expand my understanding…. usually i ved always seen only the switching side because i’m involved in a company that manufactures the switchgear for UPS…..e.g BYPASS SWITCHES that operates from Off to Normal to Test and Bypass fitted with safety interlocks (mechanical and electrical).

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  8. SKuchle
    Jan 30, 2012

    Great write up, very valuable information. Might I also recommend for Safety the use of Personal Protective Equipment (PPE) when working with any live electrical equipment.
    Also if you need a UPS Maintenance Provider Jantech Services works all on all major manufactures.

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