Installation, Operation and Maintenance Manual
Marvel Mini
27
Subject to change without notice.
120.9-IM (1218)
password protected Technicians Menu to prevent easy
access
Once the outdoor air, dry bulb and wet bulb temperatures
are set, dehumidification will operate based on the supply
air dew point set point as selected by the customer When
the controller is set up for a Dedicated Outdoor Air System,
the default Supply Air Dew Point Set Point is 55 degrees
If the outdoor air dew point as calculated by the outdoor
temperature and humidity sensor is greater than the supply
air dew point set point, the Dedicated Outdoor Air System
controller setup shall enable dehumidification mode.
Compressors 1 and 2 are sequenced ON/OFF based on
the settings previously described Compressor 1 is always
cycled ON if the Outdoor Air Dew Point is greater than the
Supply Air Dew point Set point Compressor 2 is cycled
on based on a pre-calculated set point called an enthalpy
set point This set point is calculated by the outdoor air dry
bulb and outdoor air wet bulb, temperature set points for
the geographic location of installation If the outdoor air
enthalpy is lower than the enthalpy set point, the controller
shall operate Compressor 1 only If the outdoor air enthalpy
is above the enthalpy set point, Compressor 2 is sequenced
ON with a delay between the stages
Modulating Hot Gas Reheat (Dedicated
Outdoor Air System - option)
While the system is dehumidifying, since the leaving air
temperature will be much colder leaving a Dedicated
Outdoor Air System’s Evaporator Coil, Compressor 1 shall
always have Hot Gas Reheat as a Standard Compressor
1 and Modulating Hot Gas Reheat shall be used to temper
the leaving air temperature back to either the Supply Air
Temperature Set point or the Space Temperature Set point
Cooling Assist (Dedicated Outdoor Air
System - option)
The controller has the ability to provide primary cooling
assistance utilizing Compressor 2 There are two key
components required to provide primary cooling assistance
with this dedicated outdoor air system
(a) a) System has to be sized appropriately
(b) b) Cooling Assist must be enabled
When the system is set up for Cooing Assist, Compressor 1
will operate to provide cooling If Compressor 1 cannot meet
the demand for cooling and the Cooling Demand remains
equal to 100% for greater than 10 minutes, Compressor
2 shall be cycled on to provide Cooling Assistance The
Cooling Demand is calculated by the Space or Supply
Temperature (based on system setup for control method by
supply or return temperature); Space or Supply Temperature
Set Point and Space or Supply Temperature Band Set Point
The Cooling Demand is equal to 100% when the Space or
Supply Temperature is greater than or equal to the Space
or Supply Temperature Set point plus ½ of the Space or
Supply Temperature Band Set Point
Unoccupied Mode
During Unoccupied Mode, all outputs are de-energized The
Supply Air Blower has an option to operate continuously
during the unoccupied period The system also has the
capability for both a Night Set Up and a Night Set Back
function to maintain minimum temperature and humidity
settings during the unoccupied mode These Temperature
and Humidity Set Points are located under the Unoccupied
Control menu Temperature and/or Humidity Control are
based on the options ordered with the equipment For
instance in order to maintain a Return Air Temperature Set
Point of greater than 60 degrees Return Air Temperature,
when the temperature falls below 60 degrees, the system
will require some form of heating option
Unoccupied Override
There are three methods of Unoccupied Override that may
be utilized to override the Unoccupied Mode, temporarily
starting the unit to continue the conditioning process The
methods for Unoccupied Override are initiated 1) by User
Interface, 2) by Digital Input, or 3) by BMS point interlock
The system will accept all three methods for Unoccupied
Override mode so if connected to either a digital input or
a BMS system, Unoccupied Override can be initiated from
any of the three methods
Unoccupied Override by User Interface
The User Interface has an Unoccupied Override trigger
built in on the last page of the main System Status screens
Simply press the Up Arrow button one time to get to this
page quickly then enable the Override to the ON position
Set the Unoccupied Override timeout time for the system to
go back into Unoccupied Mode Press the Enter button to
drop the cursor under the Override Time and change it to the
desired Override Time by pressing the UP/DOWN buttons
Press the Enter button to initiate the time into memory The
