Heating and cooling become simpler and more complicated as time goes on

A return to simple refrigerants is under way, with carbon dioxide being marketed as R744. Of course, in commercial buildings the HVAC systems are anything but simple, using smart technologies to anticipate energy needs and thereby running more efficiently than in the days of simple thermostats. Getty Images

Mankind has been using energy to create heat for 1 million to 2 million years. According to the U.S. Patent office, we have been using energy to go the other direction, removing heat, for less than 200 years. That’s a big difference, but of course it’s easy to explain. The first was a matter of figuring out how to start and control fire, a natural phenomenon; the second required machinery and wasn’t destined to take place until sometime after the start of the Industrial Revolution.

The first patent for a chilling machine was issued in 1851. Although it wasn’t a commercial success, it demonstrated that mechanical principles could be used for cooling a fluid successfully. Devised by a medical doctor, John Gorrie, to cool patient rooms, the system compressed ambient air (which heated it), drew some of the heat off of it, then released the pressure (which cooled it). In Gorrie’s setup, the cooling process pulled heat from a brine solution, bringing its temperature down to about 26 degrees F. From that point, it was a simple matter to put water-filled trays into the brine to make ice. Willis Carrier used a similar concept of compressing a gas to devise the first modern air-conditioning system in 1902.

Other developers used other gases, such as ether and ammonia. Ammonia is still used in some systems to this day, but many of the other early gases were phased out and replaced by synthetic refrigerants. An alphabet soup of compounds has been used over the years, but environmental legislation has put an end to many of them.

Simplify, simplify, simplify

Folks who tuned in for a recent online seminar, “Trends in HVAC Manufacturing,” learned that the latest trend is to simplify the matter by using carbon dioxide for the refrigerant. Hosted by T-Drill with a contribution by the Copper Development Association, the session discussed use of CO₂ (marketed as R744), new system designs with sturdier pipe, and the alloys and tools needed to build them.

The two advantages of CO₂ are its contributions to ozone depletion (which is null) and its contribution to global warming (nearly null). The reference gas for global warming potential (GWP) is CO₂, which has a rating of 1. Freon-based R22 is rated at 2,400, meaning that 2,400 lbs. of CO₂ has the same GWP as 1 lb. of R22.

Using CO₂ has a couple of downsides. First, although it’s a natural compound, it’s heavier than air, so if a system leaks and it displaces ambient air, it poses an asphyxiation hazard. Second is that a system that uses R744 requires higher system pressures and generates higher temperatures than synthetics (1,300 to 1,900 PSI and 320 degrees F). Needless to say, this has led to a rethinking of system design and the use of a copper alloy with additional iron for strength: C19400. It’s 97% copper with some iron content, from 2.1% to 2.6%, to make it stronger than a standard copper used for HVAC systems, C12200.

Although the material is stronger—the ultimate tensile strength is 68,000 PSI versus 50,000 PSI for C12200—it’s not too hard. The CDA rates C19400 as “excellent” for cold working, and T-Drill reports that it’s well within the working range for its tools.

Complicate, complicate, complicate

Of course modern heating, ventilation, and air conditioning (HVAC) systems for commercial buildings do much more than their predecessors. This is where things start to get complicated.

We all want to cut down on bills and energy consumption, don’t we? Of course we do. As part of this effort, the latest HVAC control systems have far more sensors than ever before and have self-monitoring, analysis, and reporting (SMART) capability.

Folks who tuned in for a recent online seminar, “Trends in HVAC Manufacturing,” learned that the latest trend is to simplify the matter by using carbon dioxide for the refrigerant. Hosted by T-Drill with a contribution by the Copper Development Association, the session discussed use of CO2 (marketed as R744), new system designs with sturdier pipe, and the alloys and tools needed to build them.

Many factors affect the heating or cooling needed in a commercial or industrial building, such as the time of the year, outdoor temperature, and the number of people in the building (or in one portion of the building). The SMART system’s sensors measure temperature, humidity, CO₂, and occupancy to maintain the building’s comfort. The control system builds a profile so it can anticipate energy needs rather than merely react. Instead of the boiler or AC portion activating and simply running full blast, the system can get ahead of the game, ramp up somewhat gradually, and consume energy more efficiently. In a large building with several compressors, the system uses only as many compressors as it needs at a given time, and it can vary the speeds of the blowers to modify the output and distribution of conditioned air.

Wait, wait! It gets better. A study on the impact of a building’s environment on cognitive ability, the COGfx Study, showed that better air quality improved cognitive responses in nine areas. And on some evaluations, people demonstrated a doubling in cognitive ability when they were tested in a better environment. The measures of air quality included the concentration of volatile organic compounds (VOCs). In the most advanced buildings with SMART HVAC, the VOC load was less than 50 micrograms per cubic meter; in conventional buildings, it was at least 10 times that amount, between 500 and 700.

Granted, the study’s primary backer was Carrier, but nevertheless the report is the result of a three-year-long academic study conducted by people at a variety of universities, so it has the hallmarks of legitimacy. Carrier also contributed to a study on the health effects of using a modern HVAC system, the HEALTHfx Study.

Anyway, the next time you see one of the people from your building’s maintenance department looking through a user manual in two or three volumes, don’t bother to ask what he’s doing. He’s troubleshooting the HVAC system. It certainly looks like a big hassle, and the maintenance team probably relies on specialists from the contractor that installed the system to optimize its operation—yes, it’s that complicated—but a SMART HVAC system can pay for itself in energy efficiency and worker productivity.