Installation, Operation and Maintenance Manual
Marvel Mini
22
Subject to change without notice.
120.9-IM (1218)
Supply Air Blower
Once the Outdoor Air Damper is open either by time delay
timeout or by proof of the damper end switch contact closure,
the controllers blower output for the Supply Air Blower
energize the blower contactor for the Supply Air Blower
Motor During the Occupied Mode, the blower will operate
continuously unless the system is set to operate based on
system demands (Cooling, Heating, Dehumidification, or
Humidification). The unit controller has a selection to set
the blower(s) to operate solely based on System Demands
(Cooling, Heating, Dehumidification, or Humidification) only
on units with Constant Air Volume and non-Outdoor Air
systems
Supply Air Blower – Variable Air Volume
(option)
Once the Outdoor Air Damper is open either by time delay
timeout or by proof of the damper end switch contact
closure, the output for the Supply Air Blower is energized
to the Variable Frequency Drive (VFD) The supply air
blower will provide a percentage of air volume based on
change in duct pressure As the duct static pressure falls
due to VAV boxes connected to tenant occupied spaces
opening for their requirement to provide conditioned air,
the controller will increase the output demand to the VFD
causing the Supply Air Blower(s) to speed up thus providing
an increase in airflow. As tenant occupied VAV boxes close
requiring less conditioned air, the duct static pressure starts
to increase causing the controller to decrease the output
demand to the VFD which slows down the speed supply air
blower(s)
Upon startup of the Supply Air Blower the blower(s)
will ramp to the Minimum Speed (field adjustable set to
18 Hertz default) set into the Marvel Multi-Application
controller provided for the VFD After a Sixty (60) second
field adjustable time delay the VFD starts to follow the
static pressure demand to increase (increase on startup)
or decrease based on the Static Pressure Set Point 100
inches of water column (iwc) (default but field adjustable).
As the Duct Static Pressure increases or decreases above
or below the Duct Pressure Set Point ± the Duct Pressure
Proportional Band Set Point 0.2 iwc (default but field
adjustable) the controller starts to increase or decrease
the output demand to the VFD causing the blower to speed
up or slow down If the Duct Pressure is within the Duct
Pressure Dead Band Set Point range Duct Pressure Set
Point and Duct Pressure Dead Band Set Point ±015 iwc
there is no output adjustment the VFD so the blower speed
will remain constant
On units with Electronically Commutated Blower Motors,
the output adjustment is the same only without the VFD
interface since Electronically Commutated Motors have
motor speed control built directly into the housing of the
motor Duct pressure is maintained by regulating the speed
of a supply air blower by increasing or decreasing the
demand to the Electronically Commutated “EC” Motor to
increase or decrease the blower speed
Room Pressure Control (option)
Typical applications for this type of control are Clean
Rooms and Isolation Rooms Room Pressure Control is
an option designed to maintain the air pressure within a
room at a Room Pressure Set Point This option requires
a factory provided wall mountable, field installed, pressure
transducer to monitor air pressure within the room being
controlled against any adjoining room(s) The room
pressure is then maintained as close to the pressure set
point as possible using factory or field provided damper and
damper actuators
When the Room Pressure rises above the Room Pressure Set
Point plus Room Pressure Band Set Point, the controller will
modulate field provided-field installed damper(s) actuator(s)
closed until the Room Pressure Set Point is achieved If the
Room Pressure falls below the Room Pressure Set Point,
the controller will modulate the damper(s) actuator(s) open
to increase the room pressure until the room pressure set
point is achieved
Airside Economizer Mode (option)
Airside Economizer is an optional feature for free cooling
that requires a factory-provided duct mount type, field-
installed, Outdoor Air Temperature and Humidity sensor,
a factory provided wall or duct mountable Return Air
Temperature and Humidity sensor, and a factory supplied
duct mount Supply Air or Mixed Air Temperature sensor
With the Airside Economizer Option, there is a minimum
damper position set point to maintain a minimum amount of
fresh outdoor air based on regional code requirements Also
with the Airside Economizer Option, there is a maximum
damper position set point to maintain a maximum amount of
outdoor air based on maximum outdoor air and airflow limits
required The minimum and maximum outdoor air damper
set points are field adjustable under the Technician Menu -
Economizer Setup
