4 FM quick reads on HVAC
1. Getting the Benefits of Free Cooling
Many building control systems offer facility executives the opportunity for free cooling – using the economizer cycle to bring in additional outside air rather than running the chillers. For that strategy to work, of course, the outside air has to be cool enough – typically in the mid 60s or below. When the outside air temperature falls below the low 50s, a facility may not need chillers at all.
The specific temperatures to be used for free cooling vary from building to building. One reason is that the needs of buildings are different, and so are their HVAC system designs. Another important reason has to do with outside humidity levels. Dryer air can be used at higher temperatures than air with more moisture in it.
But not all buildings that could run economizer cycles are getting the benefits of free cooling. It is possible that the controls aren’t correctly programmed. Or that dampers aren’t operating properly. It’s also possible that the temperature or humidity sensors are out of calibration. Those factors are all worth checking if the chiller is operating when the outside temperature is low enough for free cooling.
2. Make Sure New HVAC Systems Are Designed for Maintainability
I’m Ed Sullivan, editor of Building Operating Management magazine. Today’s topic is the importance of keeping maintenance in mind when designing new HVAC systems.
Facility executives have a lot to keep in mind when new HVAC systems are being designed. But there’s an important point that’s often overlooked: the maintainability of the system being designed.
Good maintenance is crucial to the operation of HVAC units. Without good maintenance, energy costs will rise, and equipment will need more frequent repairs and ultimately will fail sooner. The result will be significantly higher life cycle costs.
Designing for maintainability isn’t conceptually difficult. The biggest thing is to give HVAC mechanics the space to do their jobs. Mechanics need to be able to reach valves, access hatches, filters in air handling units, and so on. Moreover, they need room around the equipment. Taken together, those two points mean that HVAC units can’t be crammed into the least amount of space possible.
The good news is that many new HVAC systems are designed for ease of maintenance. That will make it far easier for facility executives who want to ensure that the new HVAC system will operate at the lowest possible life cycle cost.
3. Avoiding Ceiling Panel Bowing
Ceiling tiles need to stand up to some forms of use and abuse. If a facility executive cuts corners on ceiling durability for cost reasons, the ceiling panels may need to be replaced much sooner than anticipated, costing more money in the long run.
Schools and other seasonal-use facilities are spaces where special durability considerations are important, for example. When school isn’t in session, HVAC systems are usually turned off to save money. This is often the most humid part of the year, however. When HVAC systems are turned back on in the fall, the ceiling panels can bow. For spaces like these, ceiling panels designed to tolerate a high level of humidity and temperature fluctuation are important.
4. Why Some Geothermal Systems Will Save More Than Others
Geothermal heat pump systems promise to provide lower cost heating and cooling than conventional systems, with far less reliance on fossil fuels. But the amount of savings varies from system to system. To understand why, there are a couple of points facility executives should keep in mind.
One important point to remember is that geothermal systems offer more savings in cooling-dominated climates. But if the load between heating and cooling is balanced, geothermal systems can also operate cost effectively.
Another important point: The greater the temperature difference between the air and the ground, the more efficient the system.
A final efficiency consideration: With large systems, very warm ground temperatures — for example, on a hot day in late summer — may make it necessary to dissipate some heat in a fountain or other open water source or to use it for domestic purposes.