By Grainger Editorial Staff 1/1/17
A significant amount of energy loss is actually temperature related. Hot or cold air leaks from a building are obvious examples. It took energy to condition that air, and when it dissipates due to a leak, you’ve wasted that energy.
Many other systems and pieces of equipment also manifest their wasted effort/energy in terms of heat. Motors, pumps and electrical boxes will generate heat and lose energy efficiency as they begin to fail. Unlike regular digital cameras that capture images of the visible light reflected by objects, thermal imagers create pictures by measuring infrared energy or heat. The thermal imager then assigns colors based on the temperature differences it measures.
With a small amount of training, most people can readily spot abnormal temperatures and follow the heat trail to energy waste. The technique works best when used by people who already possess a good working knowledge of the structures and systems being scanned and can better interpret the temperature variances they see on camera.
A typical scan can show energy saving opportunities of up to 15 percent, with varying degrees of repair investments. Thermal imaging experts suggest that building owners, building managers and/or facilities engineers inspect the following systems to identify energy losses:
“Building envelope” refers to the building structure as well as the climate controls within it. The envelope is what separates the outside environment from the inside, and it’s frequently imperfect. The key to building envelope inspection is that since the degree of temperature variance may be very small—one or two degrees, the best time to scan is during a heating or cooling season, when the outside temperature is at least 10°C higher or lower than the inside temperature.* Similarly, beware of thermal loading, or other environmental factors, which could mask or distort potential problems. For instance, don’t scan an exterior wall when the sun is shining on it. When performing roof scans, make sure that the roof has been dry and free of water or ice. The best inspections should be performed on clear, windless evenings after dusk, or before dawn, when thermal differentials in the roofing materials are in a transient state. (Be aware that not all roofs can be effectively inspected using infrared thermography.)
The Department of Energy estimates that following up on the findings of an energy audit of a building’s envelope saves most facilities at least 15 percent on energy bills.
The heating, ventilation and air conditioning (HVAC) system is usually one of the biggest areas of energy consumption within a facility.
Studies indicate that commercial buildings with constant-air volume systems often experience energy losses from air leakage of as much as 33 %. Also, studies indicate that air-supply temperature differentials due to conduction losses can be as great as 6 °C (10.8 °F) or more.1 Considerable savings can be achieved in with duct-sealing and insulation remedies.
Electrical motors also use a significant amount of energy in a facility. Overheating and malfunctioning motors and generators tend to indicate mechanical or electrical inefficiencies that can lead to more energy use and ultimate failure. Since generators are, in a sense, “reverse motors,” diagnostics are similar for both kinds of units.
With motors and generators, specific energy losses are usually of less consequence than failure of the unit. The impact of a motor or generator failure will be contingent upon the nature of the enterprise and the system(s) affected. That said, the two best ways to reduce motor energy expenditures are to:
Today, steam systems are more common in industrial settings than commercial settings, but some commercial buildings still use them for central heating.
In a 100-psig-steam system, if a medium-sized trap fails, opening it can waste about $3,000 per year.
Boilers, of course, are the heart of steam and hot water heating systems.
In boilers, major energy losses— those associated with stack losses as well as radiation and convention losses—typically represent 10 to 20% of fuel input, depending upon fuel type. Insulation and boiler economizers can reduce these losses. 2
Many people don’t realize that electrical systems can actually waste money. As components degrade and resistance increases, incremental waste can occur.
According to some estimates, lighting accounts for about 20% of all electricity use in the U.S. and more than 40% of electricity use in offices, stores, and other commercial buildings. While complete retrofits of lighting systems are producing significant returns on investment, keeping lighting controls (time clocks, photo sensors, occupancy detectors, etc.) operating properly will help save energy.
Thermal imagers have come down so far in price that most facilities can recoup the cost of purchase in terms of energy savings within a relatively short period of time. Incorporating this practice into regular maintenance adds a host of efficiencies to a maintenance team as well as helping them identify and prevent expensive electro-mechanical failures.
* ASTM Building Standard C 1060-90 Appendix X2.2 (Standard Practice for Thermographic Inspection of Insulation Installations in Envelope Cavities of Frame Buildings) states that a minimum temperature differential of 10 °C (for a period of at least four hours prior to inspection) is preferred for infrared inspections of frame construction. ISO 6781 5.1a (Thermal insulation—Qualitative detection of thermal irregularities in building envelopes—Infrared method) states that: For at least 24 hours before the start of the examination, and during the examination, the air temperature drop across the building envelope shall be at least 10 °C.
This information is from the Canadian Office of Energy Efficiency.
Source: Fluke Corporation
The information contained in this article is intended for general information purposes only and is based on information available as of the initial date of publication. No representation is made that the information or references are complete or remain current. This article is not a substitute for review of current applicable government regulations, industry standards, or other standards specific to your business and/or activities and should not be construed as legal advice or opinion. Readers with specific questions should refer to the applicable standards or consult with an attorney.