Energy savings through improvements in operations can be achieved with minimal expense. Establishing and implementing SOP (Standard Operating Procedures) programs can reduce energy costs with little or no layout of capital funds. Numerous studies have been conducted that prove that significant energy savings can be obtained through minor operational changes, such as improved maintenance or repair of malfunctioning equipment.
The following guidelines will help you to design an SOP program regarding heating and cooling systems. While these generic guidelines are mostly applicable to facilities anywhere, be sure to consult your local building standards and codes for additional details and requirements.
Ultimately, your building design will dictate operating conditions such as temperatures and times of operation. Air and hydronic balancing must be considered when making any system adjustments. Keep in mind that manufacturers’ recommendations should always be followed for proper equipment operation.
- Reduce the use of heating and cooling systems in spaces that are used infrequently or only for short periods of time.
- Heat office buildings to 68°F when occupied, 50 to 60°F when unoccupied. This does not mean that air should be cooled if the temperature exceeds 68°F. Interior office spaces tend to experience significant heat gains due to lighting, equipment, and people. Systems servicing most areas use a combination of recirculated inside air and some outside air. As a result, the temperature may tend to stay at or above 68° F.
- Preheat a building so that it achieves 65°F by the time occupants arrive. Complete warm- up should occur during the first hour of occupancy. Lighting, people, and office equipment use will aid in warm- up.
- Cool the office building to 76°F when occupied. Do not utilize mechanical cooling when unoccupied. Special consideration, however, must be given to computer rooms. Generally, the primary criterion is a constant temperature/ humidity relationship. Manufacturers should be contacted to determine permissible ranges.
- Begin precooling operations so the building is at operating temperature by the time occupants arrive. Complete cooldown should occur during the first hour of occupancy.
- Minimize outdoor air except in the winter when outdoor temperatures are such that the air can be used as “free cooling.” Always ensure that you are complying with local outdoor air codes.
- Allow variations from 30 to 60 percent relative humidity in occupied spaces.
- When appropriate, consider closing supply registers and radiators, reducing thermostat settings, or turning off the electric heaters in lobbies, corridors, and vestibules.
- Where sill-height electric heaters are used, adjust thermostats so that heat provided is just sufficient to prevent cold downdrafts from reaching the floor.
- Turn heat off during the last hour of occupancy.
- During cooling season evening and night hours, flush the building with cooler outdoor air.
- Turn off humidifiers whenever the building is closed for extended periods of time, except when process or equipment requirements take precedence.
- In mild weather, lower the cooling effect by running room cooling fans at lower speeds.
- Ensure that all exhaust fans move no more than the amount of air that they were designed to expel from a building.
- Turn off reheat in all areas during summer, except where equipment requirements necessitate humidity control.
- Reduce internal heat generation as much as possible during the cooling season. Typical sources of heat generation include lighting, people, machines, and cooking equipment.
- Adjust and balance system to minimize overcooling and overheating, which result from poor zoning, poor distribution, improper location of controls, or improper control.
- Ramp up the compressors and chillers to meet demand. Keep in mind that with some of the more efficient chillers, running two chillers at partial load is more efficient than running one at full load.
- Ensure that the condenser water system is operating at design temperature.
- Ensure that the chilled water pumps and cooling tower fans are operating as designed.
- Operate boilers at design pressures and temperatures.
- Consider using cold, idle boilers as an alternative to using hot standby boilers if facility size and steam demand will allow.
- When making these types of changes, the system may need to be rebalanced. Operate only the heating water pumps necessary.
- Examine operating procedures when more than one boiler is involved. With newer boilers, it may be more efficient to operate two boilers at 45 percent capacity each than one at 90 percent capacity. Check the manufacturer’s guidelines to determine the best operating procedure for your system.
- Check flue gas analysis on a periodic basis: the efficient combustion of fuel in a boiler requires burner adjustment to achieve proper stack temperature, CO2 level, and excess air settings. Check settings to provide stack temperatures of no more than 150°F above steam or water temperature. There should be no carbon monoxide. For a gas-fired unit, CO2 should be present at 9 to 10 percent; for #2 oil, 11.5 to 12.8 percent; for #6 oil, 13 to 13.8 percent. In some regions, this may not be applicable—check your local codes.
- Adjust the air-to-fuel ratio of firing equipment and maintain it properly. If there is insufficient air, the fire will smoke, causing tubes to become covered with soot and carbon, and thus lowering heat transfer efficiency. If too much air is used, unused air will be heated by combustion and exhausted up the stack, wasting energy.
- Use an oil additive to provide better combustion.
- Use automatic viscosity controllers to achieve better oil combustion atomization. Automatic viscosity controllers also permit mixing or using different grades of oil.
You will need to individualize your own standard operating procedures. Are there items you would include that are not on this list? Share your thoughts on BOMI’s LinkedIn community.
This article is adapted from BOMI International’s course Energy Management and Controls. More information regarding this course is available by calling 1-800-235-2664. Visit BOMI International’s website, www.bomi.org.