Following are some the most commonly asked questions of HVAC and building automation systems.
The Building Automation Department
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How are our buildings heated and cooled ?
The majority of the buildings on campus are heated with hot water or steam and cooled with chilled water or cooler outside air. This differs from the normal heating/cooling arrangement in the typical home. Home units may use electric strip (resistance) heating, electric baseboard heating, hot water baseboard or a heat pump. Most home cooling is done with a typical direct exchange unit with the condenser outside and the evaporator inside. We use water because it is much more efficient for large applications.
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Why is my building hot in the winter when it is comfortable outside?
Some buildings on our campus were not designed to operate in both the heating and cooling modes simultaneously, this is often referred to as a dual temperature system or two pipe system. Generally this does not cause a problem except during the Spring and Autumn when day anad night time temperatures or daytime temperatures during the same week can vary by as much as 50 to 60 degrees F. These outdoor air temperature fluctuations can test even the best HVAC systems and can cause internal temperatures to vary by as much as 15 degrees F on a temporary basis inside some campus facilites. Some of the buildings are capable of heating and cooling simultaneously while others, as mentioned earlier, do not have cooling systems so heat is turned off during the summer months. Some buildings have heating and cooling systems but they are not designed to run simultaneously so there can be a 5-6 hour delay in the switchover while the HVAC system temperatures stabilize. Some buildings have automatic switchover (from heating to cooling or vise versa) wihle others still require a manual swithover.
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What should I do if I am uncomfortable in my work area ?
One of the main reasons Radford University uses a building automation system is to save energy. It is never our intention to do so at the expense of occupant comfort. The system we use is very complex and uses many hundreds of pieces of electrical, electronic, mechanical and computer equipment and it does fail from time to time. Sometimes the failure is limited to just a small area. Other times it may impact an entire building.
Please, never hesitate to call work control at 831-7800 if you are uncomfortable. Sometimes a simple adjustment of the desired temperature is all that is necessary. Although we continually monitor the many systems involved, there are times that something might slip by.
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Why don't more of us have adjustable thermostats ?
The primary purpose of using a building automation system is to reduce energy costs. One of the biggest costs is usually the result of waste. The most common waste involves temperature settings that are either too high or too low. Sometimes thermostats may be turned down for a brief increase in cooling and then forgotten. The result is a space that becomes too cool and is maintained at that temperature even when there is no occupants present. For that reason, most of our zones utilize temperature sensors only.
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What are some of the methods you use to conserve energy?
There are many methods available and Radford uses a great majority of them. Depending upon the system in use by a particular building, it may use a few or all of these techniques.
In order to understand how these methods work, it is necessary to establish some baselines from which we can operate the system. Let's assume we have a building that is a 4-pipe system with heating from hot water and cooling from chilled water available at all times. One of the easiest and least expensive methods is temperature reset. The temperature lines below may help us to understand.
60 55 50 45 CHILL WATER TEMP
180 170 160 150 140 130 120 110 100 90 80 HOT WATER TEMP
0 10 20 30 40 50 60 70 80 90 100 OUTSIDE AIR
Using the above temperatures as an example of the reset system used, as the Outside Air temperature drops to 0 degrees F, the Hot Water temperature rises to 180 degrees F. Inversely, as the Outside Air temperature rises the Hot Water temperature drops until the Chill Water temperature becomes active and is reset from 65 degrees F to 45 degrees F. You can see that as the outside air temperature gets cooler, the water used to heat the building is heated to a higher temperature and as the outside air gets warmer, the heating is reduced and the cooling is made proportionally cooler. On some of our systems we use what is called "Free Cooling". What this means is if the outside air temperature is less than 55 degrees F, we open Outside Air dampers more than the minimum required and bring in more cool outside air to "free" cool the space if needed. This not only saves energy, but it has the added advantage of minimizing the effects of defective control systems. For example, if a control process were to fail on a 65 degree F day, it would be more uncomfortable for the occupants if the heater were delivering 180 degree F air instead of the 80 degree F called for.
Another metod of energy savings is load rolling. Each hour throughout the day, certain motors and fans are turned off for a few minutes. Here at Radford, we turn off some units for 10 minutes of each hour. That reduces the electrical consumption by 10/60 or 1/6 (16.6%).
We also use demand limiting which turns off certain pieces of equipment if the electrical consumption exceeds a pre-set level. This not only reduces the consumption, but also reduces the electrical billing rage which may be tied into the peak demand of the campus.
Radford University also has several buildings that use ice production to lower cooling costs. Though the systems which control this are complex, the concept is quite simple. Basically, we produce a vast quantity of ice that is stored in underground tanks and used at a later time for cooling. The advantage of this is that we can produce the ice during the night while you are sleeping and electrical rates are lower and use it during the day when electrical rates are higher.
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This all sounds quite fascinating, but how can I help?
Perhaps you may have forgotten, but you are the key ingredient to energy savings. Since you are not likely to have control over the temperature of your area, there are many other things you can do:
Turn off lights when not needed including flourescent lights. The old saying "It takes more electricity to run them on and off than to leave them on" is simply no longer true.
Turn off computers when not being used. Resist the urge to perform computer courtesies like turning on every machine in the office if you are the first to arrive. Make sure they are off at night. Activate the power management mode of monitors, PC's, printers and copiers. Screen savers are great entertainment, but the Energy Star features of your equipment will save lots of energy, reduce greenhouse emissions, and make your room temperature more comfortable.
Turn off copiers and laser printers when not needed. Both use heaters which not only consume electricity but add heat to your workspace.
Be aware of when buildings are being heated and cooled mechanically and close windows when appropriate.