When inspecting building envelopes for heat loss, thermographers tend to focus their imaging efforts on the sidewalls and roof.  For some buildings, it is important to also thermographically inspect the underside of the building.

In many parts of the United States a common building practice for commercial structures is to elevate the building on support columns and place an unheated parking garage directly below the first story.  This practice exposes the underside of the first occupied level and its associated plumbing to the outside environment.

In colder regions a common approach is to construct a suspended ceiling for the garage and to create a heated space between the underside of the first occupied floor and the garage ceiling so that water, waste, and sprinkler pipes do not freeze. To minimize heat loss, batts of glass fiber insulation are often laid directly on top of the ceiling tiles.

Photo shows typical suspended ceiling in open parking garage.
  Image provided by Wayne Swirnow

When performed under proper conditions, an infrared inspection of the garage ceiling can quickly reveal thermal patterns caused by missing, misapplied, or damaged insulation.  Areas exhibiting excess energy loss may then be visually inspected to ascertain cause.

	Thermal images indicate areas of missing batt insulation as warm areas.
	Images provided by Wayne Swirnow.

Infrared inspection of building envelopes is of the many topics covered in the Infraspection Institute Level I Certified Infrared Thermographer® training course.  For course information or to obtain a copy of the Standard for Infrared Inspection of Building Envelopes, visit Infraspection Institute online or call us at 609-239-4788.

Statistically, overloaded circuits are the second most common cause of exceptions found during infrared inspections of electrical systems. Although overloads are quite common, they can be tricky to accurately diagnose.

As electrical current flows through a conductor, heat is generated. As circuit load increases, so does the amount of heat. Electrical circuits are designed so that loads will not exceed the circuit’s ability to safely carry a sustained load and the amount of heat associated with such load.

Typically, overcurrent protection devices such as fuses or circuit breakers are designed to protect circuits from overload conditions. These devices will interrupt the circuit when the current reaches a predetermined level for a specified period of time.

Serious problems such as fires can be caused by sustained overloads. Such overloads may be caused by: improperly sized wiring, and improperly sized or defective overcurrent protection. Fortunately, a thermal imager can be used to detect the thermal patterns associated with sustained overloads.

When using a thermal imager to detect potential overloads, one should keep the following in mind:

• Overloaded conductor(s) will be uniformly warm throughout entire length
• For polyphase circuits, all conductors may be uniformly warm
• Depending upon ambient conditions and imager settings, overloaded circuits may not appear remarkably warmer than adjacent circuits

Because an infrared imager cannot measure electrical current, suspected overloads must be confirmed with an ammeter while observing all requisite safety precautions. For greatest accuracy, a true RMS sensing ammeter is recommended. Circuits found to be overloaded should be immediately investigated for cause and corrected.

When performing infrared temperature measurements, reflected infrared energy can be a significant error source. This potential error source can be overcome by using the proper radiometer and test procedure.

All thermographers have experienced reflected energy when inspecting low emittance targets. For qualitative imaging, single-point reflections may be avoided by changing viewing angle.

With quantitative imaging, failing to compensate for reflected energy can account for significant measurement errors. The infrared energy received by a radiometer is the sum of emitted, reflected and transmitted energy (E+R+T=1.0). For targets with a transmittance of zero, the error sources are emittance and reflectance. Using a quality radiometer, reflected energy can be measured and compensated for by using the Reflector Method described below.

1. Set radiometer Emittance control to 1.00

2. Locate radiometer at desired distance from target to be measured

3. Aim and focus imager

4. Position diffuse reflector in front of, and parallel to, face of target

5. Measure apparent temperature of reflector surface and remove reflector

6. Enter value obtained in Step 5 into radiometer’s computer under reflectance input – commonly labelled Background, TAmbient, or Reflected Temperature.

Lastly, be sure to maintain a safe working distance from any energized or potentially dangerous targets.

The topic of reflected temperature is covered in depth in the Infraspection Institue Level II Certified Infrared Thermographer training course. Copies of Infraspection Institute’s Standard for Measuring and Compensating for Reflected Temperature Using Infrared Imaging Radiometers are available in PDF format from the Infraspection Online Store.

For years, thermographers have traditionally reported apparent Delta T measurements when documenting their findings. Using a default emittance value between .8 and 1.0, apparent temperature measurements are recorded regardless of actual target emittance. While this methodology is fast and easy, it can lead to significantly understated Delta T repair priorities.

The temperature displayed by a radiometer is largely dependent upon the emittance and reflected temperature values entered into the radiometers computer. Typically, errors in either of these settings will cause temperature measurement errors that are exponential in nature and can cause large errors in reporting Delta T’s.

Example: Using an emittance value of 1.0 a thermographer measures the apparent Delta T between two, uninsulated electrical bus bars to be 44ºC. How much can observed temperature vary due to emittance values?

From the above, the following observations can be made:

• Emittance can have a significant impact on Delta T measurements
• The greater the variation between an object’s true emittance and radiometer settings, the more understated the Delta T
• Repair priorities may be significantly understated if accurate emittance values are not utilized

As there is no way to correct for errors introduced by apparent Delta T measurements, thermographers should utilize correct emittance values whenever possible. As always, all thermal anomalies detected during an infrared inspection should be investigated and proper corrective measures undertaken as soon as possible.

Resolution is one of the most important objective specifications for a thermal imaging system. Due to a lack of standardization, this term is used in a variety of ways, many of which can be confusing or misleading.

Simply stated, resolution describes the capability of a thermal imager to clearly depict a target. Imager resolution is determined by an interdependent set of circumstances, the most important of which are described below.

• Detector: Some manufacturers offer total pixel count of the detector as a measure of resolution. Resolution generally increases with the number of pixels; however, pixel viewing angle (IFOV) also affects detector resolution. Meaningful IFOV data are frequently unavailable.
• Optics: Changing lenses affects an imager's ability to clearly resolve a target at a given distance. Generally, telescopic lenses increase optical resolution; wide angle lenses decrease resolution.
• Signal-to-noise ratio: Generally, higher ratios equate to increased image resolution. Imagers with poor ratios will provide imagery that is grainy, thereby compromising image quality.
• Display Monitor: To maximize performance, the pixel count of an imager display monitor should equal, or exceed the number of detector pixels. Compact or monocular displays can severely limit resolution. Use of a high resolution monitor cannot compensate for low detector resolution.

When considering an imager for purchase, be certain to try the imager under the same circumstances that you will encounter in the future. Because there is no objective method to determine imager resolution, one should physically compare subject imagers to each other.

Infrared imager operation and maintenance are two of the many topics covered in the Infraspection Institute Level I Certified Infrared Thermographer® training course. For more information or to register for a course visit us online at www.infraspection.com or call us at 609-239-4788.

A perpetual quest among professional thermographers involves seeking a standard contract for their inspection services.  In this Tip, we offer a time-tested solution that can help to increase sales and improve customer satisfaction.

A contract is a binding legal agreement that is enforceable in a court of law. Simply put, a contract is an exchange of promises, which if broken, have remedy in the law.  Among other things, an infrared inspection contract should address the responsibilities of the thermographer and the client, work to be performed, applicable standards and procedures, pricing, delivery, and payment terms.

Due to the diverse nature of infrared inspection services, preparing a one-size-fits-all contract can be very difficult.  This challenge becomes even greater when ancillary services such as providing electricians or moisture verification are required as part of a project.  In many areas, preparing a contract requires the assistance of a legal professional in order to ensure that the final contract meets all regulatory and legal requirements.

For professional thermographers, the first step in approaching any new project should be to generate a formal proposal.  This proposal should contain all information pertinent to the project and be sufficiently detailed to reflect the responsibilities of all parties including the client and the thermographer.  Once a proposal has been deemed satisfactory by a client, a Purchase Order or contract may then be prepared and forwarded to the thermographer for review and acceptance. 

Infraspection Institute offers standard proposal templates for several different types of residential and commercial infrared inspections. Each template provides suggested wording and format for preparing a comprehensive and professional proposal.

Eight proposal templates are currently available covering the following applications: electrical systems, mechanical systems, electro/mechanical systems, building envelopes, insulated roofs, process equipment, steam traps, and underground piping.  Each template outlines scope of work, pricing options, client and thermographer responsibilities, applicable standards, additional services, and terms.

All templates are provided in a Microsoft Word file and can be modified to suit the user's particular needs. Templates may be used as core language for contract documents.  Purchase price includes license for unlimited use of template by the original purchaser. Templates are available individually or as a complete set of eight through the Infraspection Online Store.

What is the financial liability of a hotspot within an electrical system? Probably less than you think since electrical hotspots waste surprisingly little energy even when operating at high temperatures.

Over time, many have stated that the cost of infrared inspections can be justified through the detection and subsequent repair of hotspots associated with loose/deteriorated electrical connections. Although these types of defects can produce temperature rises of hundreds of degrees, the amount of energy wasted in the form of excess heat is often surprisingly small.

When detected in their formative stages, loose/deteriorated connections may contribute to only a few watts of energy loss. Even large temperature rises associated with significantly degraded connections will usually produce energy losses of less than 100 watts. We can calculate the financial impact of such an exception as follows:

0.1 kw x 24 hours = 2.4 kwh per day

2.4 kwh x 365 days per year = 876 kwh per year

876 kwh per year x $0.14 per kwh = $122.64 per year

It is important to note the above illustration is for an extreme hotspot operating undetected 24 hours per day for an entire year. While the above potential savings may seem significant, it would be hard to justify the expense of an infrared inspection program based upon energy savings alone. Justification would be even harder if the dissipated energy were only a few watts.

The real value of information obtained from infrared inspections comes from reducing unscheduled downtime, increasing reliability, improving safety, and avoiding losses associated with catastrophic failure.

Infrared inspection of power distribution systems is one of the many topics covered in the Level I Infraspection Institute Certified Infrared Thermographer® training course. For information on thermographer training or to obtain a copy of the Standard for Infrared Inspection of Electrical Systems & Rotating Equipment, visit us online at www.infraspection.com or call us at 609-239-4788.

Data obtained during infrared inspections can often be improved by incorporating other tools. When it comes to building inspections, a blower door can be useful in detecting air leakage sites and helping to gauge the airtightness of a building.

Air leakage is often a major source of energy loss in buildings. Although an infrared imager can help detect evidence of air leakage sites, it cannot pinpoint all air leakage sites nor can it quantify the amount of air leakage occurring. Many thermographers overcome these limitations by utilizing a blower door in conjunction with their infrared inspection.

A blower door consists of an instrumented, high volume fan that is temporarily placed in a doorway to create a positive or negative pressure within a building. In depressurized mode, the blower door simulates a wind blowing equally on all sides of the building. Conducting an infrared inspection with the building depressurized enables a thermographer to detect air leakage sites that would not be visible under natural conditions. With special software, it is possible to estimate the relative leakage of a structure as well as the total area of all leak sites.

Natural condition	Depressurized condition

A blower door can provide a thermographer with some advantages; however, there are challenges associated with their use. Using a blower door during an infrared inspection represents a “worst case” scenario and may not be indicative of natural conditions. This may invalidate thermal imagery that is destined for use in a legal case. Since blower doors can cause backdrafts from fireplaces, stoves, and heating equipment, they should be operated only by persons who are properly trained in their application and use.

Infrared inspection of building envelopes is one of the many topics covered in the Infraspection Institute Level I Certified Infrared Thermographer® training course. For more information or to register for a course, visit Infraspection Institute or call us at 609-239-4788.

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Numerous injuries result from slips and falls on icy sidewalks, parking lots, roads and other outdoor locations every year. Snow removal, sanding and salting of these type areas can help but, many times, total elimination of snow/ice hazards are impossible and other measures must be used to cope with these problems.
 
Focus on your walking path and pick steps that minimize or eliminate your exposure to icy slips.  This is a time during which keeping your "eyes and mind on path" is more critical than ever.  
 
Accept and anticipate the fact that you are at risk of falling at any given moment when walking on ice. Adjust your stride so your center of gravity is maintained as directly above your feet as possible by taking shorter steps than usual.

Don't ignore the hazard presented by a slippery surface in your immediate path or work area.  Take the time to spread sand, salt, or calcium chloride on icy areas and notify your Supervisor if further action is necessary. Keep in mind that salt (chloride) containing material is incompatible with stainless steel and is not to be used where contact can be made.
 
Footwear should have slip resistant soles. Avoid leather soled shoes. Equate this to driving a car with bald tires in the winter. You need something suitable to grip the surface you intend to walk on.
 
Wipe your feet off at the entrance of buildings so others won’t slip and fall on melted snow that has been tracked into the building.
 
Like the ice under your feet, beware of icicles over your head; they can be dangerous. Although you cannot stop them from forming, you can minimize their effects by controllably knocking them down.
 
Whether you’re dealing with an overhead or underfoot ice hazard, if you can’t control it, barricade or rope the area off.

When walking down stairs with or without an item in one hand, Safety In Motion has a technique that can reduce your chance of falling down the stairs. Grasp the handrail in the palm up position trailing behind you instead of your direction of travel. Your feet should be positioned at a slight angle toward that railing. Should you loose your balance, your grip on the handrail in this position will cause you to come to a stop against the handrail instead of falling down the stairs. Try the technique and become comfortable with it before you need it. Make protecting yourself a top priority!

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Parallel conductors are a common feature on many electrical circuits.  When properly used, an infrared imager can detect evidence of serious problems that might otherwise go undetected.

Insulated conductors play a vital role in electrical systems by carrying current to connected devices.  Single phase circuits in receptacle and lighting panels use individual conductors to perform this function. Feeder type conductors however, are typically much larger in size and load carrying ability and quickly reach a point where it becomes impractical to install them using only one conductor per phase.  In these cases, parallel conductors are used.

In theory, each parallel conductor should be the same diameter and length for a specified feeder circuit in order that the carried load is shared evenly among the conductors.  Properly functioning parallel conductors on the same phase should exhibit equal temperatures with no discrete hotspots.

During a recent inspection at an industrial site, a 25 F degree temperature rise was observed on one of two, 400 amp rated parallel feed conductors that linked an 800 amp 3-phase breaker to the main lugs of a motor control center.  An ampere reading showed that the warm conductor was carrying 450 amps while the paired conductor had less than 1 amp.

Parallel feed cables on an 800amp 3-phase breaker
showing one cable 25 F degrees warmer than its pair.

An infrared inspection at the main lug compartment of the motor control center showed the same thermal relationship as observed at the main breaker and led to the discovery of a deteriorated connection that no longer was capable of carrying load.  Under normal inspection protocol at this facility, this motor control center was not scheduled for infrared inspection for another year.  If not for our investigation as to the cause of the thermal anomaly at the main breaker, this overload condition would have persisted and potentially caused a catastrophic failure.

Thermal and visual images of conductor connection at the main lug of the motor control center.

When performing infrared inspections of parallel feed conductors it is important to understand that paired conductors are sharing load and therefore should have identical thermal patterns.  Differing thermal patterns between paired conductors should always be investigated as overload conditions may develop on one or more conductors.  Conductors operating at cooler temperatures are usually the result of broken conductors, conductors of drastically different resistance, or connections that have failed completely.

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