Back it Up

CSE: To begin, let's examine the most significant technological advances backup power systems have accrued. COURTEMANCHE: In my opinion, perhaps the most significant advances have not so much been in the equipment itself, but in the monitoring and reporting systems associated with the equipment. For example, with today's systems, the owner/operator can continuously monitor the health of their b...

By Barbara Horwitz-Bennett, Contributing Editor May 1, 2003

CSE: To begin, let’s examine the most significant technological advances backup power systems have accrued.

COURTEMANCHE: In my opinion, perhaps the most significant advances have not so much been in the equipment itself, but in the monitoring and reporting systems associated with the equipment. For example, with today’s systems, the owner/operator can continuously monitor the health of their backup systems, be warned of impending failures and use history reporting to quickly restore the system in the event of a failure.

As for the equipment itself, the development of distributed, rack-mounted and battery-less UPS systems offers owners additional choices for addressing backup power needs. In the future, I also see the development of fuel cell technology emerging as the chief source of backup power or even as the prime power source for critical systems.

OLSON: Without question, there has been a steady evolution toward more power system integration as it relates to control and monitoring systems, and that trend will continue. These more sophisticated systems are making multi-generator, utility-parallel and soft-transfer applications easier to accomplish and more reliable. They also make remote monitoring more practical, which has the long-term effect of lowering facility operating costs.

Further, more sophisticated control systems allow for more precise control over engine emissions making exhaust after-treatment more practical. This should open the door for distributed generation in more areas of the country.

REPP: On the subject of integration, we also expect greater integration with generation, UPS and line-conditioning functionality, which should result in even higher efficiency. For example, UPS systems currently exist with higher operating efficiencies than traditional on-line UPS or rotary systems, in the 92% to 95% range. Naturally, the higher efficiency results in lower operating costs and lower heat load.

STEINER: I’ve seen proposals combining back-up generators with UPS in unique ways, but I have not seen sufficient advantages to specify them. Equipment-wise, however, the size of gas-driven reciprocating engines has increased, and this offers more opportunities in cases where natural gas is available and acceptable and where life safety is not an issue.

CSE: Cost is always an issue and is perhaps the biggest roadblock to getting owners to try new or redundant technology. How can engineers assist building owners and managers in determining the most ideal balance between level of electrical redundancy and cost?

OLSON: The effect of outages on each business enterprise may be different, so one key step is to assign a value to reliability so that standby power system performance can be evaluated economically. By determining the cost of an outage—loss of business revenue, product/data losses, downtime, compromises to life-safety systems—a balance can be struck that results in the proper level of power system redundancy.

COURTEMANCHE: The key to providing the right system for an owner is understanding the owner’s business. This allows the questions concerning the implications of losing power to be answered. The engineer can then perform a risk analysis to determine the level of reliability and redundancy required to meet the business needs and design a system based on that criteria.

CSE: In what ways might a specifier err when designing backup power systems?

COURTEMANCHE: Backup power systems can indeed be complex beasts. From configuration to design to coordination to permitting to construction to testing and commissioning, any number of pitfalls can arise. As an owner, I would expect that my consultant has the experience to minimize such occurrences.

That being said, consultants err by adopting “one-size-fits-all” and “bigger-is-better” mentalities in the conceptualization and design of these systems. Although these methods may produce a system that works at least in some fashion, the owner will probably not get the system he or she truly needs. Avoiding this kind of mistake goes back to the answer to the previous question: understanding the owner’s business and producing a system that has the right balance of reliability and cost to serve his or her business needs.

OLSON: Operational sequences are frequently too complex. This actually reduces reliability and unduly complicates initial startup and operation throughout the life of the system. More attention needs to be paid to making the system easy to understand, operate and troubleshoot. Training should be required for system supervisors so that they can effectively monitor and directly control the system when necessary.

Consequently, reliable basic control systems, distributed logic control designs and manual backup systems are preferred to complex, highly automated systems.

REPP: It’s easy to overlook the effect of SCR (silicon-controlled rectifier) or non-linear loads on generator sizing. Considerable non-linear loading can lead to excessive generator heating, or, in severe cases, significant voltage instability of the emergency power system. Many devices today—UPS, solid-state motor starting devices, medical equipment or most manufacturing equipment used in modern factories—incorporate SCRs in their design and can affect emergency generator sizing. To avoid the pitfalls of improperly sized emergency systems, an up-to-date generator sizing and specifying program can be a great tool and is offered by some power system manufacturers (see sidebar, “Sizing and Spec Tools”).

CSE: Please describe any significant discussion of recent changes/additions to codes or standards that may affect the specification of backup power systems.

OLSON: The emergence of the Institute of Electrical and Electronics Engineers (IEEE) 1547 standard on interconnection requirements will help standardize interconnections with utilities and improve safety, reliability and overall system performance. IEEE 1547 will also make it easier for designers to incorporate soft- transfer and cogeneration capabilities into systems.

COURTEMANCHE: Let’s not forget the development and implementation of Underwriters Laboratories (UL) 2200 Standard for Safety for Stationary Engine Generators, which I think is the most significant addition affecting the specification of this equipment. Essentially, UL 2200 is a comprehensive set of product requirements and safety tests which covers packaged engine generator sets from control panel to radiator. Successful manufacture and testing to UL 2200 allows the genset to be UL listed as an assembly. Prior to this standard, only some individual pieces of the set were covered by UL standards.

Manufacturers have begun offering UL 2200 generator sets and continue to offer non-UL 2200 sets. It’s important to be aware that UL 2200 has required manufacturers to build the units with different equipment, materials and requirements than the standard offering. This generally translates to higher costs to the owner, but with an improved product. Additionally, it is anticipated that the day will come when AHJs (authorities having jurisdiction) will require UL 2200 units.

CSE: Now that electric deregulation has already moved past its initial stages in some states, has all the hype about the projected growth of backup power installations actually materialized? What’s in the future?

OLSON: Deregulation, itself, has not been an influence for standby power system installations. However, in the larger sense, utilities are operating with less spinning reserves than in the past, and this increases the probability of outages and brownouts—and the need for standby power systems.

In the future, reciprocating diesel engine generators will continue to be the best choice for backup power systems from a performance, availability and economic perspective. Their fast-starting, short-circuit current tolerance and motor-starting ability will keep them at the forefront. The addition of paralleling and soft-transfer capabilities is also a wise move given the anticipated growth of distributed generation (DG).

STEINER: I also have not seen deregulation affect the need for standby power. This is because electric consumers are not availing themselves of real-time pricing that would enable them to buy electricity at non-peak times and generate their own power when electricity is expensive.

COURTEMANCHE: My read is that deregulation fears, which generally translate to the fear of increased business risk to an owner, have not resulted in an explosion of backup power installations. Rather, it has become a factor in deciding the level of reliability required by the owner when a system is needed. Deregulation effects, particularly the woes in California, have prompted owners to increase the size of their systems to cover larger portions of their operations.

In my crystal ball, I see deregulation plans continuing, but with modifications to rectify mistakes so that utility power reliability and availability are less impacted.

This is key because backup power systems carry a significant cost to the owner. If utility power quality is significantly reduced due to deregulation—thus costing owners more and more in backup power systems—businesses will move to areas where a utility power/ backup power mix meets their cost-benefit needs.

REPP: This is difficult to address given the current state of the economy. Natural gas prices are at record levels. And the spark spread—the gap between electricity and gas prices—has narrowed further, dampening distributed generation opportunities. The war has also slowed capital spending.

At the same time, distributed generation is alive and well. Investments are being made in on-site power generation to offset utility costs with significant returns boosted by the current cost of capital. The economy may have slowed the projected take off of DG, but the long-term view is still optimistic. Demand for electricity is not cyclical and continues to grow. Technology is developing and installation costs for DG equipment will continue to improve with technological gains.


David Courtemanche, P.E. , Chief Electrical Engineer, R.G. Vanderweil Engineers Boston

Sheldon Steiner , P.E., Flack + Kurtz, New York

Gary Olson , Technical Counsel, Cummins Power Generation, Fridley, Minn.

Mark Repp , Marketing Director, Kohler Power Systems Kohler, Wis.

Sizing and Spec Tools

A number of sizing and specification software programs can be useful tools for engineers when designing standby power systems.

One such mechanism is Kohler’s QuickSize and QuickSpec programs. These specification tools include all possible emergency loads, from PCs and solid-state motor starters to UPS systems and medical equipment.

To access this tool, visit

Similarly, Caterpillar offers a free downloadable Electric Power QuickSize program for small kW generator sets, accessible at