Residential HVAC products aren't the only ones experiencing an emergence of new features based on sophisticated controls. Light commercial systems also are seeing the benefits of increased availability of refined technology, placing these systems at the high end of their markets.

In a way, high-tech components and designs are finding their way to traditionally low-tech applications. The technology is helping to create mechanical systems that are technologically advanced, yet easy to use.

The VentPak was installed at Franklin South Elementary School.

Ventilation Control

Kevin Estepp of Mesa, Ariz., created and patented a ventilation system for a school district in the state that was facing a possible lawsuit due to indoor air quality (IAQ) issues. The VentPakâ„¢ system is designed to control room ventilation by measuring CO2 and using it as a gauge of occupancy. A proportional control adjusts outside air dampers based on those readings.

The system goes beyond traditional CO2 monitors, he said, because it can be digitally linked to the rest of the mechanical systems via DDC technology. This allows it to perform sophisticated functions and, as a result, reduce ventilation costs and extend HVAC equipment life.

Mesa Schools was awarded both the Environmental Protection Agency (EPA) Indoor Air Quality Tools for Schools Excellence Award, as well as the Governor's Award For Energy Efficiency. The two awards, Estepp said, are a testament to the product's versatility.

VentPak "started as a solution for the portable classroom dilemma," said Estepp, president of Dilution Solutions Inc., "but it is mainly applied in brick-and-mortar structures."

The VentPak is compact enough to be installed on smaller systems, like this Bard unit.


The VentPak system is "a universal retrofit vent module," he said. It controls HVAC and DDC functions (dial-out alarms, economizer control, and demand-controlled ventilation). Because of its CO2 occupancy sensors, it meets ASHRAE 62 requirements for ventilation air, according to Estepp.

The system is a ventilation module that adapts to almost any 2- to 10-ton packaged rooftop HVAC unit, converting it into "a state-of-the art temperature and ventilation control system," the manufacturer said.

The system uses a proprietary communications protocol, Lon-

Talkâ„¢. "We wrote the code," Estepp said. Circon Controls, Richmond, British Columbia, developed the ventilation strategy. After a review process, 17 code changes were made to meet the needs pointed out by Circon, Estepp indicated.

The unit itself is by 15- by 16-inches tall and can be mounted onto any duct configuration, he continued. "The damper retracts into the housing," he explained, to prevent clearance problems. The system fits "Bard units and larger," he said. "There is no rooftop or wall-mount unit that we can't be applied to."

The system offers three primary functions:

1. Demand-controlled ventilation.

2. Economizer.

3. HVAC unit control.

Every morning, the system's purge cycle opens the fresh air damper long enough to flush the building of accumulated indoor air pollutants, the company said. The start time and duration of the purge are adjustable. The purge continues until outdoor and indoor CO2 levels are equal; the controller marks the CO2 level as the outdoor ambient reading. All other setpoints reference this baseline and control indoor levels in terms of the difference between indoor and outdoor levels.

"Technology has come down to the consumer level," Estepp stated.

His product gives a degree of flexibility, if you will, to buildings with fluctuating occupancy. For instance, when schools are used as after-hours community centers, the CO2 sensors continue to monitor occupancy. If levels rise, the system enters a two-hour override mode for the temperature setback; after two hours, the system automatically returns to the unoccupied mode, Estepp explained.

In addition, an "extreme ambient reset" mode is activated during any of the following conditions:

  • The ambient temperature is extremely hot or cold, causing outside air infiltration to exceed the HVAC unit's Btu capacity.

  • The HVAC unit is not performing to capacity (due to refrigerant leak, dirty condenser coil, failed compressor or outdoor fan motor, etc.).

    The system will enter extreme ambient reset and generate a "load shedding" alarm if all of the following conditions exist:

  • Mechanical heating or cooling mode has been activated.

  • The damper is open more than its minimum position (ventilating for occupancy, not economizer).

  • The room temperature has drifted more than 2 degrees F away from setpoint.

    The extreme ambient reset mode causes the damper to close just enough to allow the room temperature to return to within 2 degrees of setpoint. The damper will not close further than its minimum occupied position, the company said.

    "This sequence is designed to allow only a temporary compromise in ventilation cfm in order to avoid compromising occupant comfort or equipment longevity," said the company. "It is also valuable in notifying building managers of underperforming HVAC equipment in early stages of failure."

    Training And Installation

    The manufacturer provides HVAC personnel training that lasts about two hours, Estepp said. "Some DDC background is preferred, but it doesn't need to be extensive. Most techs are used to working with circuit boards and thermistors. Everything's got electronics these days." Techs need to understand the basic sequence of operation, he said.

    The system's DDC system can control all HVAC unit functions, Estepp said. Benefits include:

  • Remote control via modem, Ethernet, or Internet.

  • Occupied/unoccupied time scheduling.

  • Holiday scheduling.

  • Setpoint limiting.

  • Trend logging.

  • Alarming.

  • Optimum start.

    System modules also can be electronically networked together, allowing the building operator to monitor and control multiple HVAC units on multiple buildings at multiple sites.

    The system uses the LonTalk communications protocol, utilizing Echelon's latest platform. "It can be added to any existing LonWorksâ„¢-based building automation system," the company said, "with seamless connectivity."

    VentPak mounts to the existing return-air duct or HVAC unit and uses the existing 24-V power supply. The entire ventilator uses 4 watts of power. There are no roof penetrations or line voltage circuits, the company said.

    For more information, contact Estepp at 602-233-0404;

    Publication date: 06/28/2004