4 FM quick reads on HVAC
1. Use Economizers To Reduce HVAC Energy Use
Today's tip from Building Operating Management comes from Daniel H. Nall of Flack + Kurtz. Facility managers looking for opportunities to reduce HVAC energy use should focus on airside and water side economizer strategies.
The first step to reducing HVAC energy consumption should be to make use of available environmental resources to help meet heating and cooling loads. These resources might include the outside air during portions of the year in many climates.
In the northeast, north central and in much of the west coast of the United States, the ambient outside air often has a lower enthalpy than does the interior room air. In such conditions, air returned from the occupied space can be dumped in preference for the lower enthalpy outside air, reducing the energy required to cool the supply air to the conditions necessary to maintain room temperature and humidity setpoints. This strategy is called airside economizer.
In buildings without sufficient architectural access to outside air, cooling towers can be used to make cold water when exterior conditions permit, providing chilled water without the energy penalty of refrigeration compressors. This process is called waterside economizer. Other resources that can be used to offset heating and cooling in the building can come from the building itself. Heat and moisture recovery from exhaust air can be used to temper incoming outside air, reducing the amount of energy required for heating when that outside air is very cold or cooling when that outside air is very hot or humid. Heat recovery can be a very effective strategy when high ventilation or exhaust rates are required, either because of occupancy or contaminant control.
Understanding How Fault Detection And Diagnostics (FDD) Tool Works
Today's tip from Building Operating Management comes from Jim Sinopoli of Smart Buildings LLC. With interest growing, facility managers should understand how fault detection and diagnostics (FDD) tools work.
FDD is an analytic tool that identifies faults in HVAC systems and provides advice about how to address those problems.
More technically, fault detection and diagnostics is based on research into faults in HVAC systems and the development of hierarchical relationships and rules between the different equipment and processes that make up the HVAC system.
A key relationship is between “source" and "load." A chilled water plant supplying air handling units is one relationship: The chilled water plant is the single "source" and the air handling units are multiple "loads." Another relationship is an air handling unit delivering supply air to terminal units: The air handling unit is the single "source" and the terminal units are the multiple "loads." It is these relationships and the rules within the relationships that are at the core of fault detection and diagnostics.
Fault detection and diagnostics tools basically monitor the data points in the HVAC control system in real-time (temperatures, flows, pressures, actuator control signals, etc.) and then apply a set of rules. For example, there is a set of rules for systems consisting of a chiller, a boiler, air handling units receiving hot and chilled water, and terminal units receiving supply air from the air handling units. A different set of rules would be applied if there was staged heating and cooling directly at the air handling unit or for single-zone air handling units. There are also different rules for the same equipment based on the state of the equipment. For example a chiller will have a certain set of rules when it is off, another set of rules at start-up and still another during its steady state. The analytics tool will identify a fault if the real time data doesn't conform to the rules or the optimal relationship.
Usually the tool would see faults in both the "source" and the "load," but the assumption is that the real problem is a fault in the "source," so the faults in the "load" should be suppressed. A simple example is a chiller supplying water that is too warm to an air handler. The air handler's cooling coil valve then becomes 100 percent open and supply air temperature is above set point, resulting in the VAV not being able to maintain air temperature in its zone. The software would get faults for all three pieces of equipment (chiller, air handling unit and VAV), but suppress the faults for the "loads" — the air handler and the VAVs.
The real beauty of the rule-based approach is the simplicity and transparency of the rules and the identification of the causality. Because most of the data points in a building are related to HVAC systems, there's just more data to analyze resulting in more reliable results.
Data Loggers, Temperature Guns Make HVAC Troubleshooting Easier
Temperature and humidity data loggers are relatively small battery-powered devices that can be tucked into the most obscure areas and can log thousands of data points. Depending on the task's requirements, technicians can set them to take a data point every second, every five minutes, or even every hour. These simple, easy-to-use devices provide flexibility and versatility, and they are relatively inexpensive. The least expensive devices have USB connections for downloading data. Newer wireless and web-accessible models offer automatic access and the ability to connect devices accessible through one access point.
Once, we had a dispute over whether or not a thermostat actually worked. A glove-wearing, perpetually cold person was convinced the system was set to freeze people out of the building, while the always-hot person insisted there was no way anyone could possibly stand the space being any warmer. A data logger settled it all by showing the thermostat, in fact, did work correctly and controlled the space as programmed. The issue was deemed personal. Gloves continued to be worn.
In another case, a building space experienced unusual, daily temperature fluctuations. Many theories arose, but no resolutions. While the building controls system could provide a great deal of temperature data, it was not the right information. Enter the data loggers. Technicians place data loggers throughout the system and in the space. After several days of monitoring, technicians downloaded the data and trended it. It became clear that the system had several issues, some of which related to the system and some to the controls. With the issues identified, the manager was able to implement the most effective solutions.
Factors to Consider When Choosing a Boiler and Water Heating Training Program
Just as there is a range of training formats available for boilers and water heaters, managers have options when it comes to program providers. Determining the most suitable provider for the facility depends on the manager's goals. For example, a number of different providers, such as those who conduct seminars or have online programs, can handle refresher training on the basics of boiler and water heater operations.
More specific training, such as would be required to learn the details of operating and maintaining an advanced boiler-control system, is often best handled by training representatives from the manufacturer.
Managers can start the selection process by getting a list of references from the prospective vendor or provider and talking with people who actually went through the training to better understand their experiences.
For each program being evaluated, managers must consider a number of factors. If the program is held at a remote location, what are the travel costs? Can people attend different sessions, or will all operators and maintenance personnel have to attend the same sessions? How often does the provider offer the program?
If the program is to be held in the facility, what does it cost to bring in the trainers? Does the facility have the necessary space and equipment? Can managers honestly expect operators and maintenance personnel to attend the sessions without interruption or being called away for an emergency?