Greenheck MPX (472695) - Manual (Page 4)

Product Overview
This model is a horizontally configured make-up
air unit designed for outdoor installations. It has
an integral DX package for cooling and optionally
contains either an electric heater or one or two highly
efficient indirect gas-fired furnace(s) to provide a
primary heat source for the building or to simply
temper the air that is supplied to the building. The unit
is designed to provide sufficient air to replace air that
is exhausted from the building and also heat and cool
as needed. The make-up air volume produced by the
unit is constant, but can be optionally modulated to
provide a variable volume (VAV).
The DX system comes fully charged with R-410A
refrigerant from the factory and is ready for operation
upon arrival.
All units are equipped with two compressors as
standard. The smallest units may have only one
compressor. If the digital scroll compressor option
was selected, the lead circuit will have a digital
scroll compressor and if a second compressor is
present, that one will be a standard fixed scroll type.
All units with multiple compressors allow for staging
of compressors to meet a wider range of outdoor
air loads while reducing the number of cycles per
compressor.
Compressed Refrigerant
All of these make-up air models are charged with
environmentally-friendly R-410A compressed
refrigerant. Do not use tools or parts designed for
other refrigerants on this unit.
Airflow Arrangement
This model is designed for 100% outdoor air and
can be combined with a Variable Air Volume (VAV)
capability for greater flexibility in response to building
air handling needs. The optional VAV function involves
a Variable Frequency Drive (VFD) controller for the
blower motor.
Safety Listing
The models are listed per ANSI/UL 1995, Heating and
Cooling Equipment and are ETL Certified.
Supplemental Installation, Operation and
Maintenance Manuals
Refer to the following Installation, Operation and
Maintenance manuals for additional information:
• Plenum and Plug
• Indirect Gas-Fired Furnace, Model PVF
• PCO3 Controller
MPX Subassemblies
Blower
Each unit has just one backward curved blower
(centrifugal fan). For further information refer to the
Plenum and Plug IOM.
Coils
Every unit is supplied with a single DX evaporator coil.
If there is only one cooling circuit, then the DX coil
is not divided. If two cooling circuits are specified,
then the DX coil will be an interlaced design. A reheat
coil may be optionally installed in the unit and is
connected to the lead compressor. Multiple condenser
coils are attached to the exterior of the model.
Dampers
There is only one damper that may be found in the
unit. It is an optional low-leakage motorized damper
located inside the cabinet in the intake airstream, near
the air intake weatherhood.
DX System
The DX system in the model is a complete, sealed
unit with compressed R-410A refrigerant. It consists
of one or two compressors (digital scroll optional),
evaporator and condenser coils and the following
integral components:
• expansion valves
• liquid line filter driers
• service / charging valves
• moisture indicating sight glass
• hot gas bypass (not present on optional digital
scroll compressors)
• crankcase heater on each compressor
Each DX system incorporates the following:
• high pressure manual reset cutout
• low pressure auto-reset cutout
• time delays for compressor protection
Electric Heater
An electric heater is optionally available for the model
and is used for tempering of the make-up air.
Filters
Each unit is optionally equipped with washable metal
filters in the outdoor air intake and with pleated
papers filters in the air intake stream. Paper filters may
be MERV 8 only, or the MERV 8 filters may be installed
as pre-filters for the optional MERV 13 paper filters or
optional MERV 15 filters.
Indirect Gas-Fired Furnace
The model may optionally include as many as two
indirect gas-fired furnaces. See also Indirect Gas-
Fired Furnace, Model PVF Installation, Operation and
Maintenance Manual.
4 Model MPX Make-Up Air Unit
®