FRESH AIR ECONOMIZER (Power Saver)

The Ontario Building Code calls for a minimum of 10% fresh air in a work environment to overcome the effects of normal human respiration that consumes oxygen and produces carbon dioxide. Inadequate ventilation can make you feel drowsy if carbon dioxide levels are elevated. These levels will increase as the day progresses in occupied spaces. An exhaust fan for a small washroom can put a building into a negative pressure that results in infiltration of outside air or factory air through every crack in the structure. This entering air is unfiltered and in the case of factory air can be contaminated with fumes from production equipment. The purpose of an economizer is to take outside air, filter it and pump it into the office to maintain a neutral or slight positive pressure in the space preventing infiltration from unwanted areas and also replenish the oxygen levels. It is conceivable that the fresh air economizer (econo) could over pressurize the space so there is a barometric relief damper that vents any excess pressure automatically.

An econo is two sets of motorized dampers that mount in a weather hood on the side of a roof top HVAC unit. The dampers are controlled by the room thermostat and a thermostat and humidity sensor in the outdoor air hood. The dampers are also positioned for minimum fresh air by a motor control that can set the minimum from 10% to 25% fresh air. The word economizer or power saver is derived from the fact that under certain temperature and humidity conditions, the outside air can provide all your cooling requirements without starting the compressor in the unit. During these times the econo dampers open fully, introducing 100% outside air into the building to cool the space and “lockout” the compressor operation. When the space temperature set point is reached the dampers close back to the minimum position setting to provide ventilation air. This option can provide considerable saving on hydro, plus provide fresh air and positive pressure in the space to prevent odor and dirt migration. Should the outside air conditions (temperature and/or humidity) be outside of the set parameters for the econo controls, the dampers will go to the minimum position and allow the compressor to cycle on to maintain temperature in the space. This all takes place automatically to control the temperature, humidity and filtration of the outside air that is introduced. It is important to know that any economizer only functions when the fan in the roof unit is running. Most of the better quality, programmable thermostats are designed to provide constant fan operation during occupied times and close the econo dampers completely during unoccupied times, switching the fan back to auto cycle for operation with demand for heat or cooling.

This option can be added to most existing systems made within the last ten years and is common on all new buildings. Save money on energy and provide a cleaner work environment with an economizer.