Commercial and industrial applications have long made use of infrared (IR) heating systems in order to keep occupants warm in wide-open spaces, such as warehouses, garages, and airplane hangars. The technology is effective and energy efficient because it works the same way the sun does, by heating people and objects directly.
“Like standing in the sun on a cold day, people working under infrared heaters absorb radiant energy and stay warm in a building with a lower ambient air temperature,” said Randy Niederer, director of marketing, Cambridge Engineering, St. Louis. “This saves energy by allowing building owners to turn down the thermostat and still keep occupants comfortable.”
Even though IR heating technology has been around a long time, the demand is increasing in certain markets, which is creating opportunities for contractors who install and service IR systems.
More Comfort, Less Energy
IR is ideal for commercial spot heating needs within large open facilities where small groups of people gather for assembly or factory work, machining, or in areas where some type of administrative or production work happens in relatively small areas, said Jesse Robbennolt, EIT product manager, Modine Mfg. Co., Racine, Wisconsin. “There’s real value in not having to heat an entire warehouse, for instance. After all, operating expense becomes a more important consideration each year as energy prices increase.”
Generally speaking, IR is not best-suited for the heating of entire facilities, Robbennolt said, because its thermal efficiencies are about 70 percent, while forced-air units and condensing boilers boast thermal efficiencies of 90 percent-plus or higher. “But beyond spot heating, IR can be applied with great results to provide partial building heat — say for areas such as an assembly line or office section located in an open area of a warehouse.”
Robbennolt is also noticing a healthy increase in the use of IR systems for outdoor patio spaces, bars, and restaurants as bans on indoor smoking become the norm, and more and more patrons enjoy al fresco dining. “We see this trend in larger cities like Denver and Phoenix, where they enjoy dry climates with cool evenings. By using an IR system, owners can extend the season by increasing the comfort of outdoor spaces and patios.”
Tim Seel, North American sales and marketing manager, Superior Radiant Products, Kennesaw, Georgia, acknowledged IR use is growing in mild climate applications. “While IR sales have been steady or growing slightly over the last 10 years, use is often limited by the available expertise of contractors who may not be knowledgeable about IR, so they default to forced-air heating, which they know better.”
This is unfortunate, added Seel, as one of the main benefits of using IR heat is providing occupant comfort at much lower air temperatures, which can provide savings when compared to conventional air heating equipment in the same setting. “As a result, 30-50 percent savings are not uncommon in our installations. Together with high-radiant-factor infrared or high-thermal-efficiency infrared, the savings can be substantial. Installed cost is competitive with air heating in certain applications, but because infrared is a distributed heat, installation costs can be slightly higher in some applications.”
Even though IR may be more expensive initially, the comfort achieved with these systems cannot be compared to other equipment, said Robert Rush, vice president of sales, Solaronics, Rochester, Michigan. “IR warms all objects in its path or coverage area and creates a heat sink in the floor. When the heat rises, it will also warm by convection,” he said. “With a forced-air system, warm air will blow around in the space, and that warm air will rise to the ceiling leaving your feet and body cold. With IR, occupants will feel warm while the IR unit is running and continue to stay warm via convective heat after the unit has shut off. Because of the way an IR unit heats, the thermostat can typically be set for 5° to 10°F lower than that of a warm air unit, which saves on energy costs.”
Just the Two of Us
There are two types of IR technology available: high-intensity (ceramic) heaters and low-intensity (radiant tube) heaters. According to Robbennolt, high-intensity systems usually come equipped with a ceramic tile burner for maximum heat transfer, often housed in a metal frame. The flame burns on the outer surface of the tile(s) with the infrared energy efficiently directed by a reflector mounted on the metal frame, and source temperatures can range from 1,800° to 2,200°.
“These units are certified for indoor use only and operate unvented,” said Robbennolt. “A minimum positive air displacement of 4 cfm per 1,000 Btuh input for natural gas or 5 cfm per 1,000 Btuh input for propane gas is required for proper ventilation. High-intensity IR systems are ideal for spot heating of single work stations like a loading dock, or a work station in a cold storage facility.”
Low-intensity IR units are made up of a burner box, a metal heat exchanger tube, and a polished reflector that focuses infrared energy, explained Robbennolt. The burner is mounted at one end of the tube, and exhaust gases are vented out the other end. Tube systems are available in either straight or U-tube configurations, and source temperatures near the burner end of tube systems can reach 1,200°.
“Vented units are typically available as pressurized-type systems, which provide a power exhauster mounted at the same end as the burner to force the products of combustion through the tube. Units can be used for indoor or outdoor applications,” said Robbennolt. “Low-intensity units are best suited for larger areas in unconditioned space like an assembly line or where people move in a relatively fixed or predictable path or in chilly, open spaces.”
Two-stage units — both radiant-tube and high-intensity ceramic heaters — can provide additional energy savings and added comfort compared to a single-stage model, said Rush. “They are ideal for areas with frequent temperature changes, such as auto service garages and dealerships, loading docks, hangars, carwashes, etc. The high-heat mode is reserved for those times when additional heat is needed, such as when an overhead door is opened, and provides quicker recovery times after that door has been closed.”
Rush added it is very important to choose the correct type of IR system for each application. If a system is specified or chosen incorrectly, the equipment’s life can be shortened and it may result in uncomfortable conditions. “For example, if a standard economy-model radiant-tube heater is used in a carwash application, it may not perform as well or have the same lifespan as a fully stainless steel unit. It is also very important to size the unit correctly because if the Btuh input is too low or too high, the space will either be under- or over-heated, making it uncomfortable.”
High-temperature surfaces, such as those that occur in high- and low-intensity IR equipment, should also not be used in areas requiring explosion-proof apparatus or Class 1 electric equipment, said Seel. “Contractors should establish relationships with local distributors who can assist them with layouts and specifications because, like most types of heating equipment, all IR heaters are not alike.”
Local distributors can also help contractors stay up to date on the latest changes as IR systems continue to evolve. “Controls are continually improving, and their use with infrared systems will undoubtedly improve energy use going forward,” said Seel. “In addition, there are now constant-rate and modulating-continuous systems, which have equal firing rates at each burner location. And there have been additional improvements made in reflector design, insulating technology, and burner performance, which improve energy efficiency.”
Perhaps the most significant issue going forward, noted Seel, is the need for those in the HVAC industry to become better educated in the proper use, application, and availability of IR equipment. With training readily available through most manufacturers and distributors, there is really no reason why contractors interested in IR technology cannot learn how to properly specify and install this energy-saving equipment.
Publication date: 10/13/2014