Bard Economizers With Exhaust EIFM-3B - Manual (Page 10)

Manual 2100-390
Page 8
ECONOMIZER – WA, WL & WH SERIES
FEATURES
• One piece construction – easy to install with no
mechanical linkage adjustment required.
• Exhaust air damper – built in with positive closed
position. Provides exhaust air capability to prevent
pressurization of tight buildings.
• Actuator motor – 24 volt, power open, spring return
with built in torque limiting switch.
• Proportioning type control – for maximum “Free
Cooling” economy and comfort with up to 100%
outside air.
• Enthalpy control to monitor outdoor temperature and
humidity – adjustable.
• Minimum position potentiometer – adjustable to
control minimum damper blade position.
• Mixed air sensor to monitor outdoor and return air to
automatically modulate damper position.
ECONOMIZER SEQUENCE OF OPERATION
CONDITION A – COOL OUTDOORS
First stage cooling closes and powers the economizer
dampers to economizer mode and the indoor blower
starts. Mixed Air Sensor senses a mixture of return air
and outdoor air and modulates the dampers accordingly.
Compressor operation is inhibited. (See Figure 6.)
If second stage closes on the thermostat, the dampers
return to the closed or minimum position setting and the
compressor starts for mechanical cooling.
MIS-347
FIGURE 6
ECONOMIZER OPERATION