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I n 1921, Homer A. Thrush commit- ted himself to developing superior hot water heating systems. He also developed and patented the first non-gravity heating system in the United States. Many of the heating, circulation and air removal products associated with the heat generation industry today were a result of that original system design. H.A. Thrush & Company pro- duced the first heating circulator pump to the growing hydronics industry in 1928. This innovation brought the ad- vantages of hot water to virtually every home and business. Thrush was also known for the first heating system fill valve and the first vertical pump developed to meet the needs of the U.S. Navy for a space-sav- ing footprint on submarines. H.A. Thrush & Company merged with another company in 1980 and operated "business as usual" until the Thrush Company was sold in 1997 to an investment group who has contin- ued operating as Thrush Co. Inc. Since then, the company has continued pro- ducing heating system enhancement products. One such example is the Aar- O-Vent. First introduced in 2004, the Aar-O-Vent was patented in 2012. EVOLUTION OF AAR-O-VENT All hydronic systems must have a device that will eliminate air from the system. An air-free, properly designed system should be able to run for several years without a problem. Hydronic systems that do not have a means to eliminate air will experience loud system noises, corrosion of piping due to dissolved oxygen, pump seal failures and other component problems. There are three forms of air that can be found in a closed-loop system: free air, entrained air and dissolved air. Air elimination devices (e.g., automatic air vents or air purgers) can remove either free or entrained air but, to be able to remove all three forms of air, a highly efficient air and dirt separator with coalescing media is required. The pat- ented Thrush Aar-O-Vent is designed as such. The Aar-O-Vent can remove and eliminate air down to a level that can actually absorb and remove air trapped in pockets and high points in the system. This device eliminates corro- sion in piping systems and eliminates heat transfer problems, as well as numerous pumping problems associ- ated with trapped or entrained air in piping systems. Third-party testing by an independent laboratory concluded that the Aar-O-Vent can consistently remove greater than 99.7 percent of the dissolved oxygen content in a closed piping system. Removal percent- ages approaching 100 percent will be achieved after sufficient time is allowed. HOW IT WORKS As the Aar-O-Vent removes air from the system, large air bubbles quickly rise to the top of the vessel and into the vent. Entrained air is pulled out of a solution and forms micro bubbles. Mi- cro bubbles coalesce and form larger bubbles, which then rise up and out the air vent. Air is not the only contaminant that affects system performance and com- ponent life. Dirt particles can erode pump impellers, seals, valve seats and mechanisms and other system compo- nents, as well as the piping itself. By us- ing an Aar-O-Vent combination air and dirt separator, dirt such as sand, metal shavings, iron oxide and other harmful materials can be separated out of the circulating fluid. The Aar-O-Vent dirt separator is unlike a filter or a strainer. As the Aar-O-Vent removes dirt from the sys- tem, the particles drop to the bottom sediment collection area of the vessel and out of the flow path. This results in zero change in pressure drop as the particles are collected, which requires less pumping energy than filter- or strainer-equipped systems. Particles are easily removed by opening the blow down valve at the bottom of the vessel. ADVANTAGES Stainless steel coalescing medium provides superior corrosion resistance. Its non-soldered construction provides more durability and is not affected or damaged when installed in sweat-fit systems. Air elimination models utilize Thrush's unique and popular model 720 Air Eliminator, which will not allow air back into the system even if a vacuum occurs. This design provides the highest air elimination performance as compared to the competition, and low negligible pressure drop through the unit. On dirt separation models, pressure drop does not increase as the dirt collection area fills. WHERE WE ARE GOING… The company continues to grow and expand, and has taken the Aar- O-Vent to the next level. Thrush Co. Inc. recently introduced the Aar-O- Vent 4X, a solution for hydraulic separation. The Thrush Aar-O-Vent 4X performs three important tasks in a hydronic heating system: It removes entrained, free and dissolved air; it removes suspended dirt particles and will balance the pressures between the primary and secondary circuits. Superior product quality has earned Thrush its leadership position along with personal responsive service, prompt delivery, expert technical support and a high standard of business ethics. A professional network of representatives and distributors, as well as an in-house service department, are available to meet needs and ensure satisfaction. When in need of heating and cooling products, think Thrush. CHECK OR CIRCLE #164 Evolution of Thrush + the makings of Aar-O-Vent A History of Firsts Thrush Co. Inc. recently introduced the Aar-O-Vent 4X, a solution for hydraulic separation. > Right: The patented Thrush Aar-O-Vent, an air elimination device designed for hydronic systems, was fi rst introduced in 2004. profi le /thrush H.A. Thrush & Company produced the first heating circulator pump to the growing hydronics industry in 1928. This innovation brought the advantages of hot water to virtually every home and business. HVACPproducts.com HVAC & Plumbing Product News \ Summer 2017 28