The Greenheck model VSU provides a 100% efficient
direct gas-fired heating and ventilating unit in a
vertical configuration. This configuration removes
the equipment weight load from the roof and offers
an easier means of installation. Ground level filters,
dampers, and controls also simplify servicing.
The VSU is specifically designed for providing heating
and make-up air for manufacturing facilities and
warehouses. Airflow volumes up to 60,000 cfm and
heating capacities up to 7,000,000 Btu/hr. are offered.
Durable Construction
Designed for maximum weather resistance, VSU
Housings are constructed of heavy gauge G90
galvanized steel. Lifting lugs are standard.
Direct Gas-Fired System
• Cast aluminum burners with
stainless steel mixing plates
• Maxitrol burner modulation
control
• Flame safeguard with digital
fault indicator capability
• 25:1 turn down ratio
Control Center
The control center includes the
following standard components:
• Magnetic motor starter
with solid state overload
protection
• Control transformer with
fusing
• Integral door interlocking
disconnect switch
• Separately fused motor
• Distribution terminal strip
Premium grade control components are selected
for reliable operation. All electrical components are
UL Listed, recognized or classified and factory prewired
for single point power connection.
Vibration Isolators
The entire fan and motor
assembly is mounted on
vibration isolators to minimize
noise transmission into the
building.
2
Access Doors and Panels
Large access doors and panels are provided for
easy inspection and maintenance of motors, drives,
fan wheels, filters, and heater controls.
Centrifugal Blowers
Double width, double inlet forward curved wheels
for high efficiency and low sound levels are
constructed of heavy gauge steel. Wheels are
balanced to ensure vibration free operation.
Factory Wired and Tested
All units are
tested prior to
shipment. Units
are checked
for vibration
and proper
operation.
Application
100% Make-Up Air
The 100% Make-Up Air system is recommended when outdoor air is required to replenish a constant volume
of exhaust air. This system provides efficient heating of the make-up air and minimizes unwanted infiltration.
Some of the most popular applications include paint booths, warehouses, kitchens and factories. Benefits of
this system include low operating cost, low initial cost, simplicity and reliability. See page 5 for a wide range of
factory supplied accessories.
Variable Volume System
The variable volume option is recommended when a
building’s exhaust volumes are variable. This option
enables the make-up air volume to track with the
exhaust volume, providing only the amount of
make-up air that is required.
The variable volume VSU saves energy in two ways.
First, the fan power is reduced whenever make-up
air requirements are less than the maximum. Second,
whenever lower air volumes are sufficient, the VSU
requires less gas to heat the outdoor air.
Airflow Control Strategies
Greenheck offers four methods of controlling the
make-up air volume. All four vary the fan speed for
maximum energy savings.
• Variable Frequency Drive controlled by building pressure.
• Variable Frequency Drive controlled manually with
a remote potentiometer.
• Variable Frequency Drive controlled by a 2-10 VDC
or 4-20 mA signal.
• 2 speed motor controlled manually with a remote
switch.
Burner By-Pass
Damper
The variable volume
option includes a
patented burner
by-pass damper,
which maintains
the pressure drop
across the burner as
air volumes change.
This assures that
complete and proper
combustion occurs.
The by-pass damper
is self-adjusting,
designed for minimal
maintenance, and
requires no controls.
Discharge
Arrangements
For installation flexibility, fan
discharges are available in either
Horizontal or Upblast Discharge.
Horizontal Discharge
Upblast Discharge
3
Application
Recirculation System
The recirculation option is recommended when
the ventilation equipment provides the primary
source of heating for the space.
This option recirculates up to 80% of the supply
air and efficiently heats it to maintain the desired
space temperature. A minimum of 20% outdoor
air is mixed with the recirculated air to provide a
continuous source of fresh air.
Only outdoor air is used for combustion. This
eliminates the possibility of contaminants in the
recirculated air from crossing the burner.
Airflow Control Strategies
Greenheck offers four methods of controlling the
recirculated air to outdoor air ratio. The ratio is
determined by the outdoor air and recirculated
air damper positions. The methods for adjusting
damper positions are outlined below:
• Modulating actuator controlled by building pressure.
• Modulating actuator controlled manually with
a remote potentiometer.
• Two position actuator controlled manually
with a remote switch.
• Modulating actuator controlled by a 2-10 VDC
or 4-20 mA signal.
In all cases, the fan provides a constant volume
of supply air.
Burner By-Pass
Damper
The recirculation
option includes a
patented burner
by-pass damper, which
maintains the pressure
drop across the burner
as air volumes change.
This assures that
complete and proper
combustion occurs.
The by-pass damper
is self-adjusting,
designed for minimal
maintenance, and
requires no controls.
Benefits vs Air Turnover
The recirculation system provides the
space heating function with several
advantages over indirect gas-fired air
turnover units.
More Efficient - The recirculation
direct fired burners are 100% efficient,
compared to 80% efficient (maximum) for
air turnover units.
Fresh Air - The recirculation system
provides a continuous source of fresh
outdoor air and positively pressurizes the
building.
Outdoor Installation - Since the
recirculation system is installed outdoors,
valuable floor space is not lost.
4
Accessories
Remote Control Panels
A wide variety of remote control
panels are available. Specify the
desired combination of switches,
thermostats, temperature selectors
and indicator lights (see examples
at right). A terminal strip at the unit
control center and remote panel
simplify control wiring.
Temperature Control
There are three temperature control
options for heat: 1) Discharge Control, 2)
Space Control, and 3) DDC Interface
Control. Cooling controls are by others.
Discharge Control
A factory installed modulating system
controls the gas valve to provide the
desired temperature based on a sensor
at the fan discharge. A room override
option is available to boost the discharge
temperature when the space is too cool.
Basic remote
control
panel with
thermostat
for room
temperature
control
option.
Lockable remote
panel with room
thermostat
located inside
the box. Keyed
switch also for
setting operation
mode.
Room Control
Specify this option when the VSU has the primary
responsibility for controlling the room temperature.
A manually adjusted room thermostat provides
feedback to the unit controls, which vary the discharge
temperature in order to maintain desired room set point.
DDC Interface Control
Allows for an external signal (0-10 VDC or 4-20 mA)
from the building management system to modulate
the burner output to satisfy monitored conditions.
Additional Accessories
V-Bank Filters
Washable 2-inch aluminum mesh filters or 2-inch 30%
efficient disposable filters are available.
Motorized Dampers
Intake or discharge dampers are available to prevent
backdrafts when the fan is not in operation. Intake
dampers are factory mounted and wired.
Fiberglass Insulation
Fiberglass insulation is used to line the housing to
prevent the formation of condensation and to form an
acoustical barrier.
Double Wall Construction
An interior metal liner is available to isolate the 1-inch
fiberglass insulation from the airstream.
Freezestat
An on/off type discharge duct stat (with a timer)
prevents the discharge of cold air into the building
when the burner is not providing adequate tempering.
115 Volt GFCI Service Receptacle
A 115 volt GFCI outlet is mounted externally in a NEMA
3R box for the convenience of field service personnel.
A separate 115 volt power source is required.
Equipment Stand
The equipment stand raises the VSU intake above the
ground to prevent debris, rain and snow from being
drawn into the unit. The standard stand height is
24 inch, with other heights available.
Air Filter Gauge
The air filter gauge indicates when filters become
dirty. An indicator light may be wall/beam mounted or
provided with a remote control panel.
Inlet Air Sensor
An on/off type duct stat automatically de-energizes the
gas system and interrupts the flow of gas to the burner
when the inlet air temperature is above the desired
setting.
Gas Pressure Regulator
Required if building gas line pressure exceeds VSU
maximum inlet gas pressure.
Special Coatings
Greenheck’s Permatector coating is available for
a durable, long lasting finish. Decorative paints
are also available in a variety of colors to match
existing building fixtures. Consult your Greenheck
representative for paint selections.
Service Platform
A stable platform that provides easy access for
servicing the unit.
Note: The air performance data shown does not include internal static pressure losses due to items such as filters, dampers,
and coils. For exact air performance data based on specific unit configuration, use the Greenheck CAPS selection program.
38,000
45,000
44,000
52,000
60,000
RPM446482515548
BHP12.113.815.416.9
RPM491523553582610638
BHP18.019.821.923.925.727.5
RPM547575603629655679
BHP27.429.531.633.936.338.7
RPM401429456483509535
BHP16.818.921.223.726.329.0
RPM446470494516539562
BHP24.927.329.832.235.038.0
RPM494514535556576596
BHP36.238.340.943.946.749.5
0.751.001.251.501.752.00
TOTAL STATIC PRESSURE in inches of WG
Maximum
BHP
3,830
4,550
5,390
5,270
6,050
6,050
AAB
C
D
24 in. Min.
AAB
C
D
24 in. Min.
24 in. Min.
Dimensional Data
Housing Sizes
20 & 30
Housing Sizes
40 & 50
Housing Sizes
20 thru 50
PRESSURE DROP DATADIMENSIONS
Housing
Size
20404078128
30525392146
401115495144
5015663107184
All dimensions are shown in inches.
ABCD
Housing
Size
20
30
40
50
CFM
2,5000.110.02
6,5000.170.09
6,0000.120.03
12,0000.200.10
14,0000.140.05
28,0000.280.16
30,0000.140.04
60,0000.280.15
30% Efficient Filter
Equipment Stand Height
The minimum distance from the ground to the filter
intake is 24 inches. For housing size 50, the minimum
distance is 48 inches. This minimizes debris and
moisture from being entrained in the make-up air.
In locations where heavy snow fall is common, this
dimension may need to be greater. Specify the
minimum clearance dimension when ordering.
2-inch
SIDE VIEWFRONT VIEW FRONT VIEW
Inlet
Damper
Gas
Burner
0.625
0.625
0.625
0.625
7
Typical Specifications
General: Make-up air unit shall be as manufactured by
Greenheck or approved equal provided all specifications are
met. Greenheck Model VSU equipment is used as the basis of
design. Performance to be as scheduled on plans. Make-up
air unit shall be ETL listed to ANSI Z83.4 -1999, CSA 3.7 - M99
(for 100% outdoor air) or ANSI Z83.18-2000 (for recirculation).
Gas Train and Controls: Direct gas-fired system shall have
a draw through design and field adjustable burner baffles.
Gas trains up to 400,000 Btu/hr shall include a direct spark
ignition system. Gas trains greater than 400,000 Btu/hr shall
include a pilot ignition system and shall have digital coded
fault indicator capability. Fault indicator shall provide service
history by storing codes for the last five faults. Dual safety
shutoff valves shall be industrial duty and use 120 VAC control
signals. Temperature control shall incorporate a Maxitrol
electronic modulation control system.
Unit Casing and Frames: Unit shall be of internal frame type
construction of galvanized steel. All frames and panels shall
be G90 galvanized steel. Where top panels are joined there
shall be a standing seam to insure positive weather protection.
All metal-to-metal surfaces exposed to the weather shall be
sealed, requiring no caulking at job site. All components shall
be easily accessible through removable doors.
Insulation: Unit casing to be lined with 1-inch fiberglass
insulation where specified. Insulation shall be in accordance
with NFPA 90A and tested to meet UL 181 erosion requirements.
Double wall shall be provided where specified.
Fan Section: Centrifugal fans shall be double width, double
inlet. Fan and motor shall be mounted on a common base and
shall be internally isolated. All blower wheels shall be balanced.
Ground and polished steel fan shafts shall be mounted in
permanently lubricated ball bearings or ball bearing pillow
blocks. Bearings shall be selected for a minimum (L10) life in
excess of 100,000 hours at maximum cataloged speeds.
Motors and Drives:Motors shall be energy efficient,
complying with EPACT standards, for single speed ODP
and TE enclosures. Motors shall be permanently lubricated,
heavy duty type, matched to the fan load and furnished at the
specified voltage, phase and enclosure. Drives shall be sized
for a minimum of 150% of driven horsepower. Pulleys shall
be cast and have machined surfaces, 15 horse power and less
shall be supplied with an adjustable drive pulley.
Electrical: All internal electrical
components shall be prewired for single
point power connection with exception
of the larger evaporative cooling
sections. All electrical components
shall be UL Listed, recognized or
classified where applicable and wired in
compliance with the National Electrical
Code. Control center shall include
motor starter, control circuit fusing,
control transformer for 24 VAC circuit,
integral disconnect switch and terminal
strip. Contactors, Class 20 adjustable
overload protection and single phase
protection shall be standard.
Filter Section: Filter section shall be
designed such that velocities across
the filters do not exceed 550 feet per
minute. Filters shall be 2-inch washable
aluminum mesh or 2-inch disposable.
Weatherhood: Weatherhood shall be constructed of G90
galvanized steel with birdscreen mounted at the intake.
Recirculation (optional): Recirculation airflow shall be
controlled by adjustment of return damper position. Input
signal for return damper shall be from building pressure
sensors, potentiometer, external signal, or manual switch.
Recirculated air shall not be permitted to pass across the
burner. Return air shall be filtered.
Variable Volume (optional): Volume shall be varied by either
a 2-speed motor or variable frequency drive. Input signal for fan
speed shall be from building pressure sensors, potentiometer,
external signal, or manual switch. A self-adjusting burner
bypass damper shall maintain a constant air volume across
the burner to ensure proper gas combustion. Bypass damper
shall operate automatically without an electronic signal.
Our Warranty
Greenheck warrants this equipment to be free from defects in material and workmanship for a period of
one year from the purchase date. Any units or parts which prove defective during the warranty period will
be replaced at our option when returned to our factory, transportation prepaid. Motors are warranted by
the motor manufacturer for a period of one year. Should motors furnished by Greenheck prove defective
during this period, they should be returned to the nearest authorized motor service station. Greenheck will
not be responsible for any removal or installation costs.
As a result of our commitment to continuous improvement, Greenheck reserves the right to change
specifications without notice.