Vendor Response on Power Systems (Part 1) - How does Uninterruptible Power Supply figure into today's

September 1, 2009

, Healthcare Design

We asked representatives of several vendors to comment on Spring 2009's Build It Right column by answering a series of four questions. The following is the first of two parts of their responses.

The Spring 2009 issue of Healthcare Building Ideas featured a new regular department titled Build It Right wherein a selection of experts (an architect, engineer, maintenance expert, and owner) are asked questions about current considerations for installing, using, and maintaining systems such as roofing, flooring, IT infrastructure, etc. The latest column was focused on Power Systems. We asked representatives of several vendors to comment on the article by answering a series of four questions. The following is the first part of their responses, responding to the question: How does Uninterruptible Power Supply figure into today's scheme of things?

Wissam Balshe, Cummins Power Generation Inc.
With the increased need for reliable, high-quality backup power to feed critical loads in healthcare facilities, the use of Uninterruptible Power Supply (UPS) systems is essential. After determining what loads will be put on the standby generator set (whether legally required by code or optional), the electrical engineer has to identify the loads that cannot tolerate any interruption of power for more than one quarter cycles (such as computer servers and medical imaging devices). In general, loads that cannot tolerate a voltage dip of more than 10% or frequency dip more than 5% would be put on the UPS.

A dangerous and common error in the preliminary electrical design stage of a project is improper sizing of the electrical backup power equipment such as UPSs and generator sets. Due to cost and space considerations, many designers size the power system based on the actual facility load only. This would mean running the power supply systems near full capacity and does not allow for future growth. However, if the facility expands or if more equipment is later added to the site, the customer will require additional on-site power supply equipment, which is more expensive, increases the system’s complexity, and could require an expensive retrofit to the power distribution system.

On the other hand, designers that take into consideration future growth tend to oversize the UPS and generator set too conservatively, and end up running the UPS and generator set very lightly. This not only wastes energy, where UPSs have lower efficiency when load is less than 50%, but also causes other technical issues such as carboning and wet stacking on the engines in the generator set, and generator set-UPS misoperation and failure of the emergency power system at the facility. For example, running the UPS lightly loaded with large capacitors on it to filter harmonics may cause UPS generator set control issues. The large capacitor on the UPS is designed based on the full name plate rating of the UPS, and if the load is very light (less than 30 to 40% of rated capacity), the capacitor will export a lot of Var on the circuit, which would cause the voltage to rise. When connected to the generator set, the Automatic Voltage Regulator (AVR) on the generator set will lower excitation to lower the voltage output to an acceptable level, but if the capacitor continues to export Var, the AVR on the generator set will limit or “kill” excitation to drop the voltage, and at that point the generator set loses control of its voltage output, and the UPS disconnects due to the high-voltage levels. If the outage lasts a long time, the UPS batteries may completely discharge and the load will be dumped even if generator set power is available.

To conclude, the key is properly sizing the power supply equipment based on the equipment’s full name plate rating and battery charging requirements, keeping an average load of 50 to 70% of rated capacity. This will allow for future growth, and the slightly oversized generator will help minimize the effect of harmonic distortion when the generator is running. However, if the UPS load is run very light, then I would suggest switching off the capacitors when the generator is running, putting inductive loads on the circuit with lagging power factors on the generator set prior to the UPS load to absorb the exported Var, or investing in active dynamic filtering devices.

Dan Draper, Liebert products healthcare marketing, Emerson Network Power
An uninterruptible power supply (UPS) is essential if you want to avoid the risk of doctors standing around with a catheter in a patient's leg waiting for machines, servers, and images to reboot after a utility outage. It's important for everyone involved in patient care to realize that IT isn't isolated to the data centers and also to understand what will happen in the event of an outage or brown-out in a healthcare facility. In today's modern operating rooms, surgeons have workstations that bring patient records and digital images right into the surgical suite. The old days of waiting for generators to start is no longer practical because that 10-second outage, in reality, turns into 5 to 15 minutes as servers reboot and attempt to reacquire data after power has been restored. Healthcare IT systems are finding their way into just about every aspect of practicing medicine and the most cost-effective way to protect this growing number of critical loads is through a centralized or facility-wide UPS installation.

Chuck Gougler, Marketing Manager, Staco Energy Products Company
UPS is certainly used in hospitals and medical facilities for IT and office applications, ride-through for emergency back-up power (generators), and emergency (central inverter) lighting systems. Both single-phase and (primarily) three-phase UPS are critical components of the overall electrical power distribution system. Besides power interruptions, UPS equipment will also help to maintain the level of power quality, where surges, spikes, transients, etc. occur.

Martin Olsen, Vice-President, Active Power
The uninterruptible power supply (UPS) system is becoming an integral part of many facilities due to the strain on power generation capacity from power plants and on the grid itself. Demand is outstripping capacity combined with the fact that bringing a power plant online, and especially a nuclear plant, can take as long as five to six years to go through the approval processes at a cost of $2 to 3 billion. As a result of this, consumers will find that outages will start to occur at a higher frequency during certain periods of the day. Short, second-long outages may appear insignificant, but cause most systems like imaging equipment, IT, and machinery to come to a stop. Starting them again may not be as simple as turning on the switch, but may have caused data and raw material losses that amount to thousands or millions of dollars. So where certain consumers may think of their infrastructure as noncritical in respect to adding a UPS to protect it, it quickly becomes critical when longer outages occur more frequently causing their businesses to come to a halt.

Additionally, we will see more centralized deployment of UPS to protect a broader part of the infrastructure or building rather than the traditional compartmentalized focused on certain concentrated areas or applications. This, in turn, will make system maintenance, efficiency improvements, and predictability more manageable.

Tom Stryker, VP Sales & Marketing, CPN Power, Inc.
CPN Power has operated as a national power consultant specific to the medical equipment industry for 27 years. For the past seven years, our focus has shifted to applying and providing power conditioners and UPS systems for Diagnostic Imaging and Radiation Treatment applications. At this time, the market has gravitated toward UPS systems as the preferred solution over power conditioners alone. It is important to remember that the appropriate UPS for medical imaging applications should, first and foremost, be a great power conditioner. Our experience shows that utility-generated power outages don’t occur very often in most areas of the country. In fact, most outages are created by the monthly generator testing. There are exceptions to that rule. But, power anomalies take place almost every day. Those power anomalies are best eliminated via the power conditioning attributes of the UPS system. Good power conditioning dramatically reduces accumulative component damage assuring better system reliability and lower cost for replacement parts. In the end, that translates to increased revenue.

Though we provide individual UPS systems per given modality, our preference is to provide Central UPS to support Multi-Modality and Multi-Vendor applications. This central approach may only support 2 suites, such as (2) Cath Labs, or (1) MRI and (1) CT, or it may support 30 suites. Some projects also require support for network closets, patient monitoring, HVAC controls, or the hospital laboratory. We can provide protection for those areas as well.

For a long time, Cardiology equipment has been supported by the emergency generator in the vast majority of cases. Today, it has become much more common to support Cardiology equipment (Cath Labs, EP Labs, Angio Rooms, Special Procedure Rooms, Vascular Labs, and Interventional Labs) on UPS systems due to the invasive nature of these procedures. We used to hear the comment that UPS is not required because power is back within 10 seconds. This is a true statement, but the Cath Lab is not operational in 10 seconds. In fact, most new Labs require seven to eight minutes to reboot and older labs can take much longer. A harsh power outage is likely to be the time when component failures occur, possibly resulting in the Cath Lab not being operational at all after a power outage. Most cardiologists do not want to be in that position.

We find that radiology equipment is supported in some cases by the emergency generator and in some cases by UPS systems. If the radiology equipment is on the emergency generator, then that equipment is likely on UPS. Most hospitals today require a CT and/or MRI to be protected by emergency power in order to support the ER under any condition. It can also make sense to support the radiology equipment not protected by the emergency generator with a UPS system to assure better system reliability and uptime.

Oncology equipment today is most often protected by power conditioners and not UPS systems. We are beginning to see that trend change and the use of Central UPS to support Multi-Modalities is increasing. The central UPS approach can offer power protection for all modalities within Radiation Oncology for less money than many individual power conditioners and provide better protection at the same time. Some areas of the country require UPS due to severe voltage sags and/or outages impacting LinAc operation/reliability or patient scheduling.

The UPS system is also moving into the OR suite much more often. Some hospitals include (2) isolation panels in the OR. One isolation panel is protected by UPS power and the generator, where the second panel is only supported by the generator. The impact of electronics being applied to OR equipment can sometimes mean that a 10-second outage will result in a several minute outage, once power is restored. This may not be acceptable for some operating procedures. The increased placement of Cath Labs into hybrid OR suites and the MRI into intraoperative OR suites is also driving the use of UPS systems in OR applications.

In reference to the column contributors Brian McFarlane (HKS) and John Zabilowicz (Z&F Consulting), we agree with many of the comments under the UPS sections of their discussion. The use of central UPS systems for imaging applications is on the rise. The central approach is much more cost effective compared to individual UPS systems and better protection is offered to the whole device, not some limited portion of the device. We believe that it is important to support the entire device, including the X-ray generator or gradient amplifier. This comprehensive approach reduces long-term accumulative component damage of the most expensive component within the system.

For new construction, the cost for electrical distribution is not impacted whatsoever if the UPS is planned into the project early on. Adding the UPS after the design is complete can impact the cost for electrical distribution. In too many cases, the central UPS is designed into the project to provide cost savings and is then value engineered out of the project to meet construction cost overruns. The hospital then purchases individual UPS systems under a different budget and ultimately spends more money for less protection of the individual suites and protection is offered to fewer modalities.

Hospital management needs to understand the implications of these decisions and develop budgeting alternatives that best meet the overall goals of the new facility. It is also important for hospital engineering (facilities, biomedical, clinical), in conjunction with the radiology and cardiology departments, to understand the cost implications and review the requirements in detail. The medical equipment manufacturers do a good job of pushing off the UPS decision until the medical equipment is ordered. When the medical equipment is ordered, the electrical distribution is already in place and individual UPS seems to be the only logical approach. With good planning, the hospital can avoid this trap and end up with better protection—for more suites—at a lower cost. That is a win-win!

Existing facilities can also benefit from one UPS supporting Multi-Modalities, but often in a smaller format. The existing electrical distribution in existing facilities dictates the level to which Central UPS can be cost effective. These situations are more often best served by using mid size UPS to protect:

(2) Suites (350 amp distribution supported by a 225 kVA UPS)
(4-6) Suites (600 amp distribution supported by a 375 kVA UPS)

A 375 kVA UPS might offer protection for (2) Cath Labs, (1) EP Lab, and (2) Interventional Labs in the cardiology department. A second 375 kVA UPS might be used in radiology to support (2) CT Scanners, (1) MRI, (1) R&F Room, and (2) Digital Rad Rooms. The radiology department might also decide to protect strictly the MRI and (1) CT with a 225 kVA UPS. The remaining equipment may not need to operate during power outages.

These mid-size UPS systems offer dramatic cost and footprint savings over multiple individual UPS systems, as well as many additional benefits. This mid-size approach may also work best for new hospital projects. I should note that he UPS sizing noted above is based on UPS systems provided by CPN Power. Other UPS manufacturers or suppliers often require larger UPS sizing in order to properly support the harsh peak momentary current inrush associated with medical equipment loads.

CPN Power recently developed a new brochure that reviews the Central UPS approach in greater detail and provides the many benefits of this approach that are often forgotten when the ax needs to cut the construction budget.

Read Part two of this article here.