Modular Central Utility Plants: A Different Approach
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It may not be sexy to anyone but engineers, but the central utility plant (CUP) is a vital component of any hospital facility. A significant first cost and a driver of long-term operational costs for most hospitals, the CUP is typically housed in a separate building when designed as part of a new health-care project.
As a lead design engineer, I have utilized modular central utility plants (MCUPs) in two recent health-care projects for Banner Ironwood Medical Center and Highland Community Replacement Hospital. In both projects, the utilization of the MCUPs led to innovations in project delivery and dramatic reductions in first costs for new health-care construction. Furthermore, in both cases, the MCUP was designed to contain chillers, cooling towers, boilers, water treatment systems, pumps, heat exchangers, pressure reducing stations, VFDs, offices, and toilets.
The new MCUPs have many advantages when compared to traditional CUPs: they can be built off-site, thereby reducing construction time and disruption; they are customizable and are easily scalable to meet changing demands, ensuring you don’t under- or over-build capacity; and they can reduce operating and maintenance costs by improving efficiency and reliability. Of course, it is not quite a simple matter of buy and plug-in. The design process is different from the traditional design approach and requires the ability to understand the installation of a system of this type. There are also several challenges in ensuring that the installed system meets the design intent. This article will discuss the advantages of using a MCUP for hospital design and also examines the challenges that need to be overcome to ensure that the maximum benefits are truly achieved.
Lower installation cost. The cost of construction has been found to be 10% to 15% less than conventional CUPs.
Reduced space requirement. Since the MCUP is not a part of the building, it will not contribute to the net gross area of the hospital. Therefore, the client is permitted to fulfill department space requirements without compromise.
Scalability. CUPs for hospital projects are typically constructed to anticipate future demands. As such, they generally occupy more space than what is actually required. Conversely, the MCUP is built in modules and the hospital can easily add modules as the hospital grows or the demands for existing space increases. For example, Highland Community Replacement Hospital was designed to be a 60-bed, day-one facility [with plans to expand to 120 beds in the future. While the MCUP is designed to meet the requirements of a 120-bed hospital, only modules with a capacity to serve day-one loads will be installed initially. The complete MCUP will include three chillers, three boilers, and three cooling towers, whereas the day-one installation comprises two chillers, two cooling towers, and two boilers, along with the supporting accessories. Thus, the upfront capital costs are only spent on the equipment and associated enclosures that are needed to support day-one loads.
Simplified field installation. The system has a single-point hydronic, electrical, and control connection which requires less site coordination during the construction process.
Faster project completion (reduced lead time). Since the plant is assembled and tested in the factory, it can be transported to the site and reassembled at a faster rate than building a traditional CUP.
Single source responsibility. The entire plant is provided by one manufacturer, thus lowering the risk to contractors, designers, and the owner.
Cost of operation. The MCUP can be provided on a design-build or design-build-operate-maintain basis, which may or may not include third-party ownership. This unique arrangement allows the owner to shift performance risk to the manufacturer and can be used to ensure the long-term integrity of high-performance technologies. Using the lease arrangement frees up the hospital to focus on its core business and can decrease operating costs.
Inexperienced designers. MCUP is relatively new to the health-care construction market. Accordingly, the task of designing and delivering such a system depends on the designer and the manufacturer that is chosen to fabricate the plant. An inexperienced designer is faced with the daunting task of ensuring that there is no cost overrun and that the system specification is very stringent to ensure that the fabricator of the plant does not compromise the quality of the final product. Clients must ensure that any engineering company they choose has prior experience in designing a MCUP.
Insufficient specification. The construction documents should contain a complete specification section for a MCUP. This specification should detail all equipment that will be included in the MCUP. At a minimum, it should contain the following (as applicable to the specified design):
• Structural steel base
• Pumps and motors
• Piping, valves, and fittings
• Control valves
• Air separator
• Expansion tank
• Domestic and makeup water
• Tower sump sweeper system
• Cooling towers
• Steam or hot water boilers
• Water softeners
• Heat exchangers
Steam pressure reducing stations
• Equipment enclosure
• Combination starters
• Sequencing controls
Pressure, flow, and/or temperature transmitters
• BAS interface
Inexperienced manufacturers. After designing my first MCUP, I realized that there were many manufacturers claiming to have vast experience in the production of such systems. Unfortunately, I realized the hard way that this was simply not the case. It is very important that manufacturers that are listed in the specification have a minimum of least 10 years of experience in the manufacturing of modular plants. The packaged plant manufacturer should be listed by ETL as an approved manufacturer of factory-assembled chiller/boiler plants. The equipment should bear the ETL listing and label before shipment from the factory. This listing must cover the entire packaged plant as fabricated and assembled at the manufacturer’s factory. A separate listing for just the components is unacceptable. My two top MCUP manufacturers are Systecon and Johnson Controls. Both companies meet the criteria listed above.
Complete factory testing. Chillers, boilers, and sometimes pumps, are tested at the factory level for capacity and efficiency; the tests are mostly done at full load with other operating load points tested to a much lesser extent. Although chillers and boilers are the heart of the cooling and heating system (and are the two most expensive components and biggest energy consumers within the system), they do not drive total plant efficiency by themselves. The performance of the whole system also depends on other factors such as plant configuration, pump selection, piping design, and component control. The optimum plant performance has a lot to do with the energy efficiency of the system over the entire load spectrum. Factory testing of the entire system validates performance and identifies intrinsic deficiencies that can be corrected before the plant is shipped.
For the MCUP designed and installed for Highland Community Replacement Hospital in Mississippi, the testing was used as a pre-commissioning service. This was very beneficial to the owner because the manufacturer was able to rigorously test the plant before it was delivered to site. Factory efficiency testing of the chilled and/or hot water systems was done at 25%, 50%, 75%, and 100% of the design flow of the system. For all of these percentages, the following values were recorded: flow, system total dynamic head, and kW. It was also specified that the manufacturer demonstrate the transition points at which standby pump(s) are added and subtracted to achieve optimum system efficiency. These rigorous test regimes ensured that the MCUP for the hospital performed at a very high level of efficiency.
1. The designer should ensure that all system components are selected by the designer and that any selected items are approved products.
2. The submittal review process for the MCUP is very tedious and lengthy — time should be put aside for comprehensive submittal review. Designers should ensure that the submittal process is not dictated by the manufacturer and enough time is spent combing through the hundreds of pages of submittal information.
3. Equipment that does meet the specification standards should be rejected because such equipment will compromise the performance of the central plant.
4. Only manufacturers that have the experience in fabricating this type of plant should be included in the specification. The specification should clearly state that such manufacturers should have at least 10 years of experience manufacturing modular systems.
5. The rigorous factory test, although very expensive, should be included in the MCUP specification.
6. The plant should be modeled using 3-D software in order to ensure full equipment coordination and that the maintenance clearances are achieved.
7. Sprinkler systems should be installed as a part of the factory fabrication process.
8. Fire alarm and conduits should be installed as part of the factory fabrication process.
9. Designers should ensure that all sanitary and storm drains in the MCUP yard are fully coordinated with the civil engineering team.
10. Vent pipes from the heating system should be vented away from the cooling tower locations. ES