Thermal Imaging with Digital Photography

Pre-Inspection

Before any service is performed on air conditioning, it often becomes necessary to perform a pre-inspection to make sure that no unexpected hot spots are found before the unit is placed out of service for adjustments or repairs. Since these areas are usually not ordinarily accessible without removing equipment panels, we train service technicians in thermal imaging to scan for problems before doing any work.

In some cases, this may also save them from adding unnecessary parts or labor costs if a problem has already been detected without having to dismantle any heat pumps, plumbing, air duct vents, or other HVAC system components.

Heat Pumps

Heat pumps are an excellent example of when thermal imaging makes equipment troubleshooting fast and easy. Even if the compressor is not running, the cooling fins on its exterior condenser typically radiate heat due to forced air convection or their proximity to other hot objects. Cooling fins that are warm to the touch indicate that some degree of heat rejection is occurring and that the cooler side of the heat pump's heating cycle is still working.

Thermal imaging can also show hot spots in your air conditioning which indicate blocked access ports or areas where insulation may be inadequate. These problems are usually more prevalent on older units than newer ones, but they do occur on equipment of all ages.

Airflow Measurements

Thermal Digital Photography can generate air conditioning airflow and fluid (steam, gas, chemical) leak detection reports. Digital images of airflow patterns within ventilation hoods or other anemometers allow for calculating volumetric airflow rates and directionality. This data can then be used to compare against the known design criteria for a system to detect insufficient or improperly-aligned hoods.

Refrigerant Leak Detection

Leaks within the cooling system of a heat pump typically occur at either the expansion valve or capillary tube. Since these components are usually located inside a coil housing or cabinet, their hot spots cannot be seen with the naked eye. However, if they are visible to thermal imaging, their location can be determined by matching them up with the rest of your air conditioning system's temperatures.

HVAC Engineers often use thermal imaging to find leaks in refrigerant lines by holding the camera up to a section of tubing and moving it around until they detect a hot spot. If the equipment list indicates that the unit is either overcharged or has an undersized recovery cylinder, this can be confirmed by measuring the operating pressure to see if it matches the known design criteria.

Equipment Adjustment

Improperly adjusted or undersized air conditioning controls can also be detected by observing if excessive hot or cool areas are seen in particular zones since this would indicate that airflow rates were either too high or too low for an acceptable HVAC load calculation.

Thermography is also frequently used during the installation and commissioning of HVAC equipment to ensure that it is properly balanced and that airflow rates and temperatures meet design criteria before the unit is placed into service.

Heat exchangers

Leaks in a heat exchanger can lead to serious problems with your HVAC systems if they go undetected for too long. Since the hottest parts of the equipment are typically at its welded joints, focus points for thermal imaging are often located near these areas. When a leak is suspected, the system designer's calculations can be used to calculate the change in temperature across a defective section to determine if it has reached an unacceptable threshold. If not, the area just downstream will give a good idea as to where the leak is located.

Component Inspection

Thermography is also used to inspect the interior surfaces of heat exchangers for other defects such as pitting, corrosion, or erosion. Since these conditions can have a negative impact on HVAC system efficiency, they are typically identified during routine plant tours so that they can be repaired before any significant damage occurs.

Steam Traps

Even though they are usually not found on most HVAC equipment, steam traps can also be inspected with thermal imaging to make sure they are operating properly. Since their heat source is typically a coil of vaporizing liquid, hot spots will only be found when the valve begins to open and allow condensate to flow back into the system. This is normally detected during a walk-thru before the unit begins to produce steam.

Heat Recovery Units

On larger HVAC systems with multiple sources of heat, it may occasionally become necessary to recover waste heat from one source and use it elsewhere to meet plant requirements. Since this is also an energy-efficient approach that can reduce operating costs over time, it has grown in popularity over the years.

These units typically include valves, filters, condensate tanks, and pumps not found on conventional HVAC systems; their paint or insulation can sometimes be damaged by leaks or other damage. This will usually show up as a hot spot that should be investigated to prevent further corrosion or other problems from developing.

Moisture Detection

In addition to finding hot spots, thermal imaging can also detect cold areas if excessive moisture is present. Although this may be difficult in some cases when steam or other fluids are present, it is usually more apparent on the service floor where water-based solutions are used during cleaning operations. Since these areas will show up as cool spots on the image, it is essential to recheck them during each cleaning period.

Environmental Monitoring

When HVAC equipment is located in an unoccupied space, thermal imaging can be used as a continuous monitoring tool since hot or cold spots may indicate that there are problems with natural ventilation or temperature settings. While this requires someone to monitor the equipment around the clock, the benefits of shutting down equipment before it fails are usually well worth the additional costs. Alternatively, thermal cameras can be integrated with your data logging solution to remove the need for physical monitoring.