Ups Warranties & Maintenance Plans

The primary function of uninterruptible power supplies (UPS) is to ensure continuous uptime of critical loads during power disturbances or interruptions. In order to do this, they themselves need to have some form of protection and preventative management. This comes in the form of warranties and maintenance contracts.

Standard UPS Warranties

Most uninterruptible power supplies and associated power protection equipment come with a warranty and the period of warranty will vary with UPS size. Typically, UPS up to 10kVA have a two-year warranty and larger systems a one-year. Many manufacturers offer warranty extension periods of up to five years (for a fee), which will often be achieved using ten-year design life battery sets in place of the standard five-year ones. Generators usually have a standard one-year warranty.

There are different types of warranty cover, which can affect the resilience of an uninterruptible power supply system. Below 3kVA, most UPS are covered by what is termed a Return to Base (RTB) warranty whereby the unit is returned to a service centre or service agent, repaired or swapped out. This usually applies to uninterruptible power supplies that are not hardwired. For those that are, an onsite warranty provides a higher level of service. Generators are usually supplied with this type of cover too. A standard onsite warranty provides a next working day response time.

Ensuring Speed of Response

Critical to any warranty is the speed of response. If an uninterruptible power supply unit is taken out of service and returned to a manufacturer or service centre, it could be several days before it is returned and resuming operation. During this absence, the UPS load may be unprotected. Additionally, if there is no maintenance bypass in place, loads will be disrupted when the UPS is disconnected and reconnected once repaired.

Organisations running critical loads more often than not opt for higher levels of warranty cover and maintenance contracts. A four-clock-hour response is the most common for this category of UPS customer.

Beware Hidden Costs

Often true uninterruptible power supply maintenance costs can be hidden under the guise of being a necessary expense, which they are but like everything they should add value to the system and can be greatly influenced by UPS topology and design of the power protection system itself. A single maintenance contract for a 200kVA UPS, found in a centralised approach, will cost far less than a site-wide contract for 100 x 2kVA UPS. 

In the case of uninterruptible power supplies, most warranties cover repair and labour, carriage and parts but not consumables such as batteries. That said, it is common for UPS batteries to be supplied by the manufacturer with a pro-rata warranty, which relates to the way battery performance can be influenced and affected by onsite conditions such as ambient temperature, mains power supply stability and number and duration of charge/discharge cycles.

Maintenance Plans Ensure Peace of Mind

Uninterruptible power supplies are robust and rarely break down, when they do they can usually be repaired in situ but if this is not possible, swap-outs are implemented whereby a new unit will replace the broken down one. In this instance, it is common for the warranty period to remain as it was and not be extended just because the existing unit has been replaced with a new one.

UPS maintenance plans are designed to provide more comprehensive cover than a warranty and a guaranteed emergency response time; defined in either working or clock hours. Where system resilience has to be ensured, uninterruptible power supplies are commonly designed in parallel-redundant systems, whereby two or more UPS units share the load and resume the total load should one be taken out of service through fault or for maintenance purposes. To further enhance systems resilience, maintenance plans are critical. Even in a parallel UPS system, failure of any single module can degrade the resilience of the entire system (unless it has N+2 or greater redundancy). The quicker a failed UPS module can be brought back into service, the better.

Maintenance plans, offered by suppliers of uninterruptible power supplies and generators are usually ranked in order of response times: twelve working hours, eight working hours or four working hours. Whatever approach is taken by customers and UPS suppliers (back-to-back arrangement with the manufacturer or via approved access to manufacturer certified engineers), a maintenance plan should give access to the necessary parts, software, firmware, service documentation and technical support.

This article was compiled using information available in The Power Protection Guide - the design, installation and operation of uninterruptible power supplies (ISBN: 9 780955 442803). By Robin Koffler and Jason Yates of Riello UPS.