MILWAUKEE — Establishing demand-control ventilation for smaller rooftop markets has been a pie-in-the-sky ambition up until now.

An offshoot of the last energy crisis, economizers are all too often installed as an afterthought, according to Johnson Controls’ Don Albinger, director of hvac control products.

They are specified and installed as an accessory, rather than as a subsystem, and then languish with little maintenance or adjustment — “economizing” only in name.

Today, Johnson Controls is introducing a line of economizer controls with integrated electronic actuators via the oem market. They incorporate a compact, “more robust microprocessor” previously found only in larger systems such as high-rise office building applications.

This newer product line will find its way into controlled ventilation of one- to three-story retail shopping centers, smaller malls up to around 100,000 sq ft, and other applications where you would typically find 3- to 20-ton rooftop a/c equipment.

This is where the growth currently is in the U.S. construction market, but unfortunately, was also where you would find a wide array of out-of-control hvac equipment that relied on relatively limited controls, such as electronic programmable or even simpler, mechanical-type thermostats.

CO₂ option

An option with this new system even allows ventilation based on carbon dioxide levels, something that is still relatively new even to the high-rise market.

Upon setup, the economizer can be programmed to operate according to various parameters, from the number of building or space occupants (CO₂-based), temperature, humidity, ventilation rate, etc.

With the CO₂ option, the economizer can reduce the amount of ventilation according to occupancy, providing enough outside air when it is needed but not over-ventilating or wasting energy when there is low or no occupancy. The CO₂ level can be preselected from 800 to 1,400 ppm.

In some areas, you might want to program the economizer to operate with minimal outside air where temperatures are extremely high or very humid. In other cases, you can program it to operate as a true economizer should, bringing in moderate outside air so you aren’t constantly cycling the air conditioner on and off — which not only wastes energy, but shortens compressor and other a/c components life.

The economizer is direct gear-driven with no linkages subject to potential failure, with its own prewired, preattached, factory-tested components for field installation.

This is more than just a new product for Johnson Controls, the company says, because it has required fuller engineering cooperation in working with the oem’s. This, in turn, frees up some of the oem engineering staff to concentrate on other areas of product improvement or feature enhancement.