Fresh Air Economizer Systems

Fresh Air Mode The need for Fresh Air has been increasing over the past 10 years. Homebuilders are building tighter homes with no provisions for fresh air. Older homes have been found to have damp stale air, and some office buildings are deemed to have “sick building syndrome”.

EWC Controls is introducing the cure. During Fresh Air operation the HK2000 has the flexibility to bring in as much, or as little Fresh Air as needed. The cycle timer is adjustable from 0 (off) to 12 cycles (continuous) per hour. When the cycle timer is set to 4 cycles per hour, representing 20 minutes of Fresh Air, the HK2000 will activate the Fresh Air mode for 5 minutes in the 1st quarter hour, 5 minutes in the 2nd quarter hour, 5 minutes in the 3rd quarter hour and 5 minutes in the 4th quarter hour. The cycles per hour feature on the HK2000 is designed to help maintain the Indoor Comfort level and satisfy Fresh Air requirements of the home owners and occupants during extreme weather conditions as well as minimizing the load on the HVAC system.

The HK2000 also offers the added flexibility of controlling the exhaust air, the return air as well as the fresh air intake. This built in feature prevents over pressurization in homes and buildings maintaining a safe number of air changes per hour helping to prevent, and cure, a “sick building or home”.

Economizer Mode The economizer feature of the HK2000 allows for the use of outside air to satisfy the need of indoor cooling. This form of “Free Cooling” is monitored and controlled using several methods. Dry Bulb Method, also known as outdoor temperature method, will sense the outside air temperature and determine if that air is acceptable to use to satisfy a cooling call. The determining temperature range for this method is adjustable by the installer between 42° F and 78° F. The outside air temperature is monitored using the supplied OAS sensor. If the outside temperature is above the adjusted set point on the HK2000 the system will start the air conditioning unit. If the system goes into the dry bulb method, using the outside air for cooling, the HK2000 will also monitor its success. If it does not satisfy the cooling call within 15 minutes using the outside air, the HK2000 will shut down the economy mode and start the air conditioning system.

During Enthalpy Method an optional enthalpy control can be used to sense the outside air for appropriate conditions. Enthalpy controls allow for a more accurate method of measuring temperature and humidity when using the economizer function. The enthalpy mode will not use the 15-minute timer described above. The enthalpy control will either satisfy the cooling call using outside air or energize the air conditioning using its own settings.

The most economical advantage of the HK2000 is the Mechanical Cooling Assistance mode. In this mode the HK2000 will monitor the return air temperature through the use of an optional return air sensor and compare it to the outside air temperature. If the outside air is 7° F cooler than the return air, the HK2000 will bring in the outside air and mix it with the return air. The mixing of these two sources will reduce the load on the air conditioning and satisfy the cooling demand sooner. This correlates to real savings. The HK2000 can control up to three (3) 24 VAC dampers: Outside Air, Return Air, and Exhaust Air. The HK2000 is suitable for all new construction and most retro-fit applications.

Click here for submittal sheet.

The system consists of an EC (Enthalpy Control), a fresh air control panel and outside air dampers. The EC is a control that will sense the temperature and humidity in the air around it. This is adjustable for the desired set point. With the EC in operation this will allow for a very economical way to cool your home or building with fresh air. The EC is wired to an HK2000 which will open the outside air damper and turn on the fan to circulate the air to where it is needed. This will only happen when there is a thermostat calling for cooling and the EC senses that the outside air can do the job before using the air conditioning. Once the outside air is not acceptable, the fresh air system will shut down and turn on the air conditioning.