4 FM quick reads on HVAC
1. Benefits of an HVAC Upgrade
Facility managers know that major HVAC upgrades can be some of the most difficult projects of their professional careers. There exists tremendous potential for workplace disruption, unanticipated equipment challenges and the wide-ranging opinions from building occupants over the definition of comfort — a factor that should never be underestimated. But a healthy implementation plan, open communication between tenants and service providers, and realistic expectations can prevent HVAC equipment installation from being a bane.
The starting point is proper planning. Every savvy facility manager instinctively knows this. But the mantra can never be repeated often enough, according to Jim Cooke, national facilities operations manager for Toyota Motor Sales U.S. operations. "Plan, plan and plan prior to starting any physical work," he says.
He also recommends developing back-up scenarios for any disruptions to the schedule. Cooke's list of "what-ifs" include unfavorable weather, equipment delivery delays, structural considerations demanded by new HVAC units on existing roofs, crane availability and access, and more.
Rick Martorano, director of space and facility operations for Arizona State University, echoes the sentiment. In his case, he had to plan far in advance to accommodate the needs and requirements of lab users on ASU's campus.
"Make sure you have their buy-in, and leave room in the schedule for unforeseen issues since they're unavoidable on projects of this magnitude."
2. Pay Attention To Part Load Efficiency Of Heating And Cooling Distribution System
Today's tip from Building Operating Management comes from Daniel H. Nall of Flack + Kurtz. The creation of energy-efficient HVAC systems can be difficult. Many different and often conflicting factors must be optimized to achieve the best system. The prevailing climate and the function of the conditioned space are the main determinants of the most effective system. The challenge is to recognize the opportunities inherent in the climate and application so as to select the best heating and cooling sources and distribution system. One key step in the process of creating an energy-efficient HVAC system is to improve the efficiency of the heating and cooling distribution system for the building. This improvement should be thought of not only as improvement of peak-load efficiency but also of part-load efficiency, because most HVAC systems spend the preponderance of their operating life at part load.
Good part load efficiency for distribution system components often involves the use of variable speed drives along with components that allow those drives to operate at lower frequencies as often as possible. For fans and pumps, facilitating variable flow operation is a must.
For variable flow systems to be effective, capacity reduction should be accompanied by flow reduction. Two-way control valves should almost always be specified for hydronic distribution systems. Some systems require a minimum flow rate, so the use of a controlled minimum flow bypass may be required.
The bypass is preferred to the option of utilizing a limited number of three-way valves, because the three-way valves will increase flow through the system when the actual required flow is above the minimum, resulting in increased pumping energy.
Appropriate selection of the prime movers is also important for energy efficient distribution systems. Pump and fan curves can be compared to find the best selection for each application. In general, larger diameter, slow rotation speed selections are more efficient, up to a point, although the designer should avoid selections for which a slight miscalculation of the system pressure drop might result in an undesirable operating point.
3. Optimize Heating And Cooling Source Equipment To Increase HVAC Energy Efficiency
Today's tip from Building Operating Management comes from Daniel H. Nall of Flack + Kurtz. With the HVAC system's air and water distribution systems optimized, the heating and cooling source equipment can be optimized. There is a basic conflict between optimizing the efficiency of the distribution systems and optimizing the efficiency of the heating and cooling source equipment. For the distribution system, hotter hot water and colder chilled water can result in a greater temperature differential across the system, resulting in lower required flow and lower transport energy consumption. For the sources of heating and cooling, however, cooler hot water and warmer chilled water result in more energy-efficient production of these resources. Optimization of these conflicts will result in the most energy-efficient systems.
For both boilers and heat-pump-cycle heat sources, lower hot water temperature results in greater efficiency. Lower hot water temperature allows the utilization of condensing boilers and even lower hot water temperature increases the efficiency of the condensing boiler. Maximizing the efficiency of the entire system relies upon maximizing the thermal coupling between the distribution medium, air or water and the end use, the conditioned space. The key to optimal efficiency heating is thus close approach heating coils, or extended surface area convectors or radiant panels. By reducing the temperature differential between space and distribution medium (air or water), temperature differential across the transport system can be maximized while maintaining a lower-temperature heating source.
4. Data Issues Are Critical With Fault Detection And Diagnostics (FDD)
Today's tip from Building Operating Management comes from Jim Sinopoli of Smart Buildings LLC. Facility managers who are considering fault detection and diagnostics tools should be aware of the importance of data and network issues. Here are some points to keep in mind.
Lack of Data. Fault detection and diagnostics tools rely on data from building automation systems. If there are not enough sensors, if the sensors are inaccurate, or if the building has a legacy control system and for some reason accessing the BMS database or controllers is difficult, there can be issues with obtaining the accurate data required.
Using the Diagnostic Data. Many of the fault detection and diagnostics software tools can provide information to the technician or engineer regarding potential corrective actions. This information needs to be integrated into the work order system, which may be one application in a whole suite of facility management applications, in order to use the information effectively.
Applications in the Cloud. Many companies offering fault detection and diagnostics software will provide the application on the client site, but have an option to provide the application as "software as a service" (SaaS) or in "the cloud." Essentially the vendor hosts the application, and the facility manager accesses the application through a normal web browser. This can be an issue with many corporate IT departments because of the need to pierce the corporate IT firewalls and security to get to the BAS data the application needs.
Prognostics Data. While fault detection and diagnostics tools seem inherently capable of providing prognostic data — that is, it can analyze fault conditions or degradation faults and predict when a component will fail or not be able to perform correctly — very little has been developed in this area. In addition, prognostic data would allow for more proactive, condition-based maintenance, which would be a different approach for facility management organizations that are reactive and corrective.