November 4, 2016 - Energy Efficiency
By John Anderson, FLIR Systems Inc.
Performing facility maintenance and engineering tasks is like sailing among icebergs. What technicians can’t see will sink them — or their facilities. Thermal imaging technology gives technicians the ability to see the unseen, making it easier to spot failing motors and electrical components, HVAC condensate leaks, bad ductwork, and leaky roofs. Technicians then can fix problems before they become large headaches, as well as reduce heating and cooling costs as part of sustainability initiatives.
By understanding the way thermal imaging works and implementing a step-by-step plan for successful thermal inspections of key building components — HVAC, electrical, and plumbing systems and building envelopes — managers can deliver bottom-line benefits to their departments and organizations.
Insights on infrared
Human eyes can detect electromagnetic radiation in the visible light spectrum but cannot see any other forms of electromagnetic radiation, including infrared. A thermal imaging camera records the intensity of radiation from the infrared band of the electromagnetic spectrum and converts it into the visible image.
Infrared thermography is the art of turning an infrared image into a radiometric one, which allows technicians to read temperature values from the image. The camera converts every pixel in the radiometric image into a temperature measurement by using complex algorithms in the camera’s software. A properly calibrated infrared radiation camera can provide accurate, noncontact temperature measurements of the objects it records.
Thermal imaging cameras offer a variety of advantages over other noncontact temperature measurement technologies.
Infrared (IR) thermometers are useful for single-spot temperature readings, but given all the systems and equipment that must be surveyed as part of facilities maintenance, it is too easy to miss critical faults when surveying with a spot IR thermometer. In contrast, thermal imaging cameras offer thousands of temperature measurements for every image recorded.
For example, consider a thermal imaging camera with 80 by 60 resolution for a total of 4,800 pixels per image. Each pixel provides a temperature measurement, so one image is equivalent to using 4,800 IR thermometers simultaneously.
Planning an inspection
Managers seeking to ensure that technicians conduct an effective, productive thermal inspection can follow these steps:
Define the task. Consider the conditions of the facility. Has there been a recent increase in energy usage? Is it cold inside? Is there a noticeable draft? Then determine both the inside and outside temperatures to ensure there is a sufficient temperature difference — at least 10 degrees Celsius — for an inspection.
Start from the outside. Missing insulation or cold bridges can be located quickly from the outside. Be sure to include images from areas where nothing appears to be wrong. Comparing areas with faults to the “good” areas offers a better way to evaluate the extent of the problem.
Continue inside. Before an interior thermal scan, take steps to ensure an accurate result, such as moving furniture away from exterior walls and removing hanging pictures at least six hours before the inspection. While scanning each room, note where each thermal image was taken by marking the location with arrows on a floor plan.
Scan the systems. Check the HVAC system for loose electrical connections, misaligned ducts, air leaks, clogged air filters and leaking condensation. Scan the thermostat to ensure its readings are not affected by a light switch or other warm connection nearby. Next, inspect the electrical systems, starting with the breaker box. Look for overheating, overloaded circuits, and loose connections. Check smoke and carbon monoxide alarms to make sure they are active. Finally, scan near plumbing lines, bathrooms, and along walls for evidence of water leaks.
Set up an air tightness test. If the building continues to lose energy after resolving any HVAC issues, conduct a blower door test to make the smallest cracks visible.
Analyze and report. When all rooms have been inspected, analyze the images and summarize the findings in a report. Some camera makers pair their products with reporting software that simplifies drawing up comprehensive building inspection reports.
HVAC applications
Technicians performing HVAC inspections with a thermal imaging camera can locate misrouted and leaking ducts, identify electrical or mechanical HVAC system faults, confirm the source of energy losses, spot missing insulation, and discover air conditioning condensate leaks. Surveying an HVAC system with an IR thermometer or other contact-measurement tool is extremely time-consuming and would run the risk of missing small faults that affect the entire system.
The process of evaporation has a cooling effect on wet ceilings, walls, and floors, so an condensate leak will appear cold in relation to the rest of the room when scanned with a thermal imaging camera. Once technicians identify the leak source and begin remediation, they can use the camera to monitor the area as it dries.
Temperature differences can also highlight problems with insulation, weatherization and ductwork. Air leaks are often the result of poorly installed insulation or building cracks around windows, doors and vents. The resulting drafts can cause noticeable temperature differences, especially when cold air seeps into a warm room through leaky window seals.
To prevent breakdowns, technicians must regularly inspect the many electrical and mechanical elements of an HVAC system, including thermostats, gas heaters and boilers, air-handling systems and AC condensers. Given that components tend to heat up as they begin to fail, a thermal imaging camera can be invaluable for spotting worn belts and motors, checking electric circuits, and seeing if the system is overheating. Hot circuits and fuses can indicate a potential electrical short. A scan of the air handling system that shows that it is running hot might indicate a clogged air filter.
Eye on electrical and plumbing
Left unchecked, plumbing problems can lead to leaks and mold growth. Electrical faults can cause outages, melt connections, and start fires. Thermal imaging cameras can identify both of these types of problems, and they can help technicians locate hot or loose connections, find overloaded circuits, motors, and wiring, trace water leaks to their source, determine the level of moisture buildup; and monitor drying.
Electrical current inevitably creates heat as it flows through a circuit, causing circuits or fuse connections to appear brighter than their surroundings when scanned with a thermal imaging camera. Excessive resistance in a circuit or a high current flow often indicates an impending failure.
Loose connections, load imbalances, and corrosion also can increase resistance and temperature. Technicians can detect this temperature rise long before the circuit fails. Thermal imaging cameras also can visualize failures, such as internal fuse damage, circuit breaker faults, and potential short circuits.
Plumbing leaks and water intrusion also can affect the building envelope. To visualize these leaks, technicians can take advantage of solar loading. During the day, the sun warms the exterior walls and the moisture trapped inside them. When the walls cool down after sunset, the moisture remains warm longer. Technicians using a thermal imaging camera can detect the temperature difference between the dry walls and the wet areas, pinpointing the leak’s location.
Sealing the envelope
Thermal imaging cameras offer a non-invasive way for technicians to monitor and diagnose a building’s condition, including visualizing cracks that cause energy loss, detecting missing or defective insulation, finding moisture trapped in insulation, walls, and roofs; locating thermal bridges; finding disruptions in district heating supply lines; locating water infiltration in flat roofs; and detecting construction failures.
For the most accurate results, technicians should make thermal scans when temperature differences are most noticeable. For example, many thermal imaging cameras need a 10 degrees Celsius temperature difference between a building’s interior and its exterior to detect missing insulation or energy losses. Cameras with high image resolution and high thermal sensitivity can detect even smaller temperature differences, but they can be expensive.
Moisture damage is the most common form of building deterioration. Wet insulation takes a long time to dry and becomes a prime location for mold and fungi. A thermal survey can identify the moist areas where mold can grow, and it can detect water infiltration in flat roofs.
Air leakage can account for up to one-half of the energy consumed for heating. A thermal imaging camera allows technicians to spot the characteristic patterns that occur when cold air seeps in through a leak in the construction, goes along a surface, and cools the surface down. But both a temperature difference and pressure difference are needed to detect these leaks.
Air-leak inspections should always take place on the side of the construction with negative pressure. This negative pressure can be exaggerated with the help of the pressurization method known as the blower door test. A blower door system has three components: a calibrated fan; a door panel system; and a device to measure fan flow and building pressure.
Technicians temporarily seal the blower door fan into an exterior doorway using the door panel system. The fan blows air into or out of the building, which creates a pressure difference of about 50 Pascal between the inside of the building and the outside air pressure.
In a cold climate, the door would be set up to blow air out of the building. This creates a pressure difference that forces outside air to rush into the room through existing cracks. The colder outside air will cool down the crack, making a temperature difference that shows up clearly in a thermal image. The operator can use the cold areas of the image to locate and map the air infiltration pathway accurately.
Thermal imaging technology is also useful for monitoring the quality of new electrical wiring, looking for plumbing leaks, and ensuring that insulation is installed correctly during renovations. During construction-drying, thermal imaging allows technicians to determine the progress of the drying procedures.
The ‘right’ tool
An effective thermal imaging camera should offer:
• ruggedness to withstand a drop from a height of 1-2 meters. It also should be easy to carry in one hand and feature user-friendly buttons and menus.
• enough resolution to create clear, crisp images that users can enlarge if necessary. For example, the newest cameras offer image enhancements, such as FLIR’s Multi Spectral Dynamic Imaging (MSX®), which embosses visual details onto the full-resolution thermal image, adds perspective to the scene, and allows reading text and labels.
• reporting functions that simplify generating a report so technicians can make repair plans.
To learn more about thermal imaging technology can simplify facilities maintenance, request a free copy of the Thermal Imaging Guidebook for Facilities Maintenance from FLIR Systems Inc.
