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Marvair ComPac Installation & Operation Manual
12/2017 Rev.16
2.8 Vertical Economizer and Gravity Dampers (HVESA 36 & 60 Models Only)
Gravity Dampers:
There is a gravity-operated economizer exhaust
outlet damper located on each side of the HVESA unit. The dampers
are covered by a hood to exhaust the air in upward direction, away from
the economizer inlet. The hood also prevents rain, debris and pests from
entering the unit.
The gravity damper is limited to 85 degrees of travel and doesn’t pass
the 90 degree position so the weight of the damper always makes it
rotate at the hinge point and close the room exhaust air outlet.
Note:
The gravity dampers ship uninstalled with all units and are field
installed.
Economizer Open:
During economizer operation, the sectors at 12
O’ clock and 6 O’ clock position are closed by the bow tie damper
This allows fresh air to be bought into the unit through the condenser
section of the unit and enter the 3 O’ clock and 9 O’ clock sectors on
the bottom plate and the top plate into the blowers and pushed inside
the room through supply grille. Once the shelter is pressurized, the
gravity dampers on the sides of the unit open to allow the warm room
exhaust to exit the shelter. No re- ingestion of the air is allowed because
the cold air is drawn in through the bottom of the unit and warm air
exhausted above it in the middle part of the unit.
Economizer Closed:
The sectors at 3 O’ clock and 9 O’ clock position
are closed during mechanical cooling (non- economizer operations)
as shown. No fresh air is being drawn into the unit and room air is
recirculated by passing thorough 12 O’ clock and 6 O’ clock sectors
and into the evaporator, cooled and is then returned to the room. The
gravity damper is closed during this operation since the room is not
pressurized.
Economizer Modulating:
During operation when the outside air is
cold enough to satisfy the heat load in the room and there is a need to
modulate to maintain a set mixed air temperature, the bow tie damper
rotates and partially closes the sectors as shown to provide a proper
mix of outside air and room air to maintain the mixed air temperature
without dropping below a set point. The gravity damper partially opens
and closes as needed to maintain the airflow balance.
Cool Outside Air
Warm Return Air from Shelter Interior
