4 FM quick reads on HVAC
1. Demand Control Ventilation Can Reduce Energy Costs
Today's tip from Building Operating Management comes from Angela Cremeans and R. Stephen Spinazzola of RTKL: In spaces that have widely varying levels of occupancy, demand control ventilation can reduce energy use and costs.
Many spaces are unoccupied for significant stretches of time, including churches, auditoriums, offices and retail spaces. Despite that fact, most HVAC systems are designed to bring in the same level of outside air continuously. But if a space is unoccupied, heating, cooling and moving outside air to that space can waste a significant amount of energy and money.
Demand control ventilation is a sophisticated strategy that supplies outside air to a space only when it is needed. Demand control ventilation relies on the fact that people in a space produce carbon dioxide. Sensors measure carbon dioxide levels. As those levels rise, more outside air is brought into that space. If levels fall, the amount of outside air is reduced, cutting the cost of conditioning and moving outside air. The amount of air is tailored to the specific needs of a given zone.
In a demand control ventilation strategy, the level of carbon dioxide is taken as a general indicator of the level of other contaminants. By increasing the amount of outdoor air brought into a space when carbon dioxide levels rise, the concentration of those other contaminants is reduced, improving indoor air quality.
Demand control ventilation can save energy costs in three ways:
1. Less outdoor air has to be conditioned by the HVAC system, so heating or cooling system energy is saved.
2. Less air has to be moved, so fan energy is saved.
3. If a building has a heat recovery system using building exhaust, that can further reduce the amount of energy consumed.
2. How To Prepare and Inspect a Roof in High-Wind Situations
Today's tip is about how to prepare a roof for a hurricane or other high-wind storm, and how to inspect it afterward for damage. As we now know, after August's devastating Hurricane Irene, even northern cities like Philadelphia and New York City should be prepared for high-wind events.
The most important task when a high-wind event is impending is to secure any loose rooftop equipment. Walk the roof before the storm and take down any unsecured equipment. Pick up any loose items, like screws or loose pieces of metal flashing. Make sure that HVAC equipment is secured as tightly as possible. HVAC equipment that comes loose and cartwheels across a roof during a storm is a major source of damage, both to the roof, and to the facility interior when the roof leaks. Additionally, any other loose rooftop equipment can become a missile that attacks either your building or adjacent buildings.
Secondly, make sure to secure the services of a contractor you know will be available after the storm if worse comes to worse. This may mean finding a contractor outside the area as a backup in case contractors in the storm-affected area are too busy to provide immediate repairs.
It's also a good idea to educate building occupants about preparing the facility in case a leak occurs. This may mean covering furniture with plastic, moving items off the floor and removing expensive electronic equipment altogether. Remember, the value of a roof isn't the value of the roof itself. The value of a roof is that it protects the value of everything inside the building.
After a storm, get back up on the roof as soon as it's safe. Do a thorough walk-through to see where there may be obvious damage that may lead to further problems. Especially check around all penetrations and around the roof's edges - where peel-back may result in leaks. If repairs are required, get in touch with the contractor as soon as possible. And always keep upper management informed about progress.
3. Boiler Control Upgrades Plus Regular Maintenance Can Improve Energy Efficiency
Today's tip comes from James Piper, contributing editor for Building Operating Management and Maintenance Solutions magazines: Focus on boiler controls to reduce energy use.
New boiler controls can provide major gains in energy efficiency, performance, and safety at a much lower cost than replacing boilers. Older-generation boiler controls used mechanical linkages. With age and use, linkages wear and go out of adjustment, reducing the unit's efficiency. Older-generation controls also suffer from offset, which occurs when the system operates close to, but not exactly at, the desired setting.
Today's boiler controls incorporate microprocessors, solid-state sensors, and independent servo motors, which give managers accurate and reliable operation, eliminating problems such as offset.
When evaluating control options, it is important to remember boiler controls perform three basic functions: combustion control; water-level control; and flame safeguarding. If a facility uses multiple boilers, the control system must perform a fourth function: sequencing. Facility managers must factor all of these issues into their control decisions. Three types of boiler controls to consider upgrading are flue gas trim, sequencing and automatic blowdown.
Getting the proper controls installed is only the first step in achieving efficient and reliable boiler operation. To keep things operating that way over the life of the system, technicians must properly maintain controls. But the importance of proper maintenance goes far beyond efficiency and reliability issues. It also incorporates safe boiler operation.
Technicians must keep logs for boiler operations, recording operating parameters frequently enough to identify trends. Equally important, they must review those logs regularly to actually detect the trends.
At least once each month, technicians must test a boiler's safety equipment, such as the safety-relief valve, water-level control, and low-water fuel cutoff, according to the boiler manufacturer's recommendations. Larger boilers require more frequent testing.
They also should test all controls for proper operation and calibration at least once annually, and they should inspect, clean, and lubricate mechanical linkages according to manufacturer directions.
4. Replacing Rooftop Units Before They Fail Can Bring Significant Benefits
Today's tip comes from Building Operating Management: Look at the big picture to persuade top management it's worthwhile to replace rooftop HVAC units before they fail.
If your organization has made a practice of replacing rooftop HVAC units only when they fail, there are several arguments that you can use to try to persuade top management to replace them proactively instead.
The biggest consideration is the impact on business. Rooftop units often fail on the most extreme temperature days. Suppose one fails in the midst of a heat wave. Depending on the building, the indoor environment will be anywhere from unpleasant to unbearable.
How important is that? The extent of the impact will depend on the type of organization. An office building may be able to stay open and put up with grumbling from employees. But in a retail facility, customers can't be told to stay. And even with office space, if it's a leased building, the tenants aren't likely to forget the inconvenience.
Getting a replacement in as quickly as possible will be a top priority, of course. But that may mean having to accept a less than optimal replacement unit because it is the first one available.
When making the case to top management, remember to focus on business issues. Talk to department heads or other business leaders whose functions will be affected by failure of a rooftop unit. Find out if they can provide any estimates of cost to the organization. Talk to contractors about how long it would take them to install a new unit and what impacts a rush order might have on choices, then translate all of that into business terms such as higher first costs, overtime costs, or higher long term energy costs.