Greenheck Fan 470654 User Manual

Part #470654

®

®

VSU Make-Up Air Unit

with Direct-Fired Gas Heater

Installation, Operation and Maintenance Manual

Installation, Operation and Maintenance Manual

Please read and save these instructions. Read carefully before attempting to assemble, install, operate or maintain the

Please read and save these instructions. Read carefully before attempting to assemble, install, operate or maintain the
product described. Protect yourself and others by observing all safety information. Failure to comply with instructions could

product described. Protect yourself and others by observing all safety information. Failure to comply with instructions could
result in personal injury and/or property damage! Retain instructions for future reference.

result in personal injury and/or property damage! Retain instructions for future reference.

Model VSU

3. Motor must be securely and adequately grounded.

4. Do not spin fan wheel faster than the maximum
cataloged fan rpm. Adjustments to fan speed
significantly affects motor load. If the fan RPM is
changed, the motor current should be checked to
make sure it is not exceeding the motor nameplate
amps.

5. Do not allow the power cable to kink or come in
contact with oil, grease, hot surfaces, or chemicals.
Replace cord immediately if damaged.

6. Verify that the power source is compatible with the
equipment.

7. Never open blower access doors while the fan is
running.

General Safety Information

Only qualified personnel should install this unit.
Personnel should have a clear understanding of these
instructions and should be aware of general safety
precautions. Improper installation can result in electric
shock, possible injury due to coming in contact with
moving parts, as well as other potential hazards. Other
considerations may be required if high winds or seismic
activity are present. If more information is needed,
contact a licensed professional engineer before moving
forward.

1. Follow all local electrical and safety codes, as well
as the National Electrical Code (NEC), the National
Fire Protection Agency (NFPA), where applicable.
Follow the Canadian Electric Code (CEC) in
Canada.

2. The rotation of the wheel is critical. It must be free
to rotate without striking or rubbing any stationary
objects.

DANGER

Always disconnect power before working on or near a
unit. Lock and tag the disconnect switch or breaker to
prevent accidental power up.

CAUTION

When servicing the unit, motor may be hot enough
to cause pain or injury. Allow motor to cool before
servicing.

FOR YOUR SAFETY

If you smell gas:

1. Open windows.

2. Do not touch electrical switches.

3. Extinguish any open flame.

4. Immediately call your gas supplier.

FOR YOUR SAFETY

The use and storage of gasoline or other flammable
vapors and liquids in open containers in the vicinity
of this appliance is hazardous.

WARNING

Improper installation, adjustment, alteration, service
or maintenance can cause property damage,
injury or death. Read the installation, operating
and maintenance instructions thoroughly before
installing or servicing this equipment.

Model VSU Make-Up Air Unit

1

Receiving

Upon receiving the product check to make sure all items
are accounted for by referencing the bill of lading to
ensure all items were received. Inspect each crate for
shipping damage before accepting delivery. Notify the
carrier if any damage is noticed. The carrier will make
notification on the delivery receipt acknowledging any
damage to the product. All damage should be noted on
all the copies of the bill of lading which is countersigned
by the delivering carrier. A Carrier Inspection Report
should be filled out by the carrier upon arrival and
reported to the Traffic Department. If damaged upon
arrival, file claim with carrier. Any physical damage to
the unit after acceptance is not the responsibility of
Greenheck Fan Corporation.

Unpacking

Verify that all required parts and the correct quantity
of each item have been received. If any items are
missing, report shortages to your local representative to
arrange for obtaining missing parts. Sometimes it is not
possible that all items for the unit be shipped together
due to availability of transportation and truck space.
Confirmation of shipment(s) must be limited to only
items on the bill of lading.

Handling

Units are to be rigged and moved by the lifting brackets
provided or by the skid when a forklift is used. Location
of brackets varies by model and size. Handle in such
a manner as to keep from scratching or chipping the
coating. Damaged finish may reduce ability of unit to
resist corrosion.

Storage

Units are protected against damage during shipment. If
the unit cannot be installed and operated immediately,
precautions need to be taken to prevent deterioration of
the unit during storage. The user assumes responsibility
of the unit and accessories while in storage. The
manufacturer will not be responsible for damage during
storage. These suggestions are provided solely as a
convenience to the user.

Inspection and Maintenance during Storage

While in storage, inspect fans once per month. Keep a
record of inspection and maintenance performed.

If moisture or dirt accumulations are found on parts,
the source should be located and eliminated. At each
inspection, rotate the fan wheel by hand ten to fifteen
revolutions to distribute lubricant on motor. Every three
months, the fan motor should be energized. If paint
deterioration begins, consideration should be given to
touch-up or repainting. Fans with special coatings may
require special techniques for touch-up or repair.

Machined parts coated with rust preventive should be
restored to good condition promptly if signs of rust
occur. Immediately remove the original rust preventive
coating with petroleum solvent and clean with lint-free
cloths. Polish any remaining rust from surface with
crocus cloth or fine emery paper and oil. Do not destroy
the continuity of the surfaces. Wipe thoroughly clean
with Tectyl® 506 (Ashland Inc.) or the equivalent. For
hard to reach internal surfaces or for occasional use,
consider using Tectyl® 511M Rust Preventive or WD-40®
or the equivalent.

REMOVING FROM STORAGE — As units are removed

from storage to be installed in their final location, they
should be protected and maintained in a similar fashion,
until the equipment goes into operation.

Prior to installing the unit and system components,
inspect the unit assembly to make sure it is in working
order.

1. Check all fasteners, set screws on the fan, wheel,
bearings, drive, motor base, and accessories for
tightness.

2. Rotate the fan wheel(s) by hand and assure no parts
are rubbing.

OUTDOOR — Units designed for outdoor applications

may be stored outdoors, if absolutely necessary. Roads
or aisles for portable cranes and hauling equipment are
needed.

The fan should be placed on a level surface to prevent
water from leaking into the unit. The unit should be
elevated on an adequate number of wooden blocks so
that it is above water and snow levels and has enough
blocking to prevent it from settling into soft ground.
Locate parts far enough apart to permit air circulation,
sunlight, and space for periodic inspection. To minimize
water accumulation, place all unit parts on blocking
supports so that rain water will run off.

Do not cover parts with plastic film or tarps as these
cause condensation of moisture from the air passing
through heating and cooling cycles.

Model VSU Make-Up Air

2

®

Table of Contents

General Safety Information ....................1

Receiving, Handling and Storage ...............2

Product Overview ............................4

Subassembly Overview:

Filter Section / Vertical Mounting Stand ..........4

Optional Service Platform .....................4

Burner, Blower and Control Center Overview ......5

Burner Subassembly .......................6

Control Center ............................6

Dampers ...................................6

Installation

Concrete Slab ..............................7

Service and Access Clearance .................7

Clearance to Combustibles ....................7

Burner/Blower Section ........................7

Install Ductwork .............................7

Complete Installation .........................8

Optional Service Platform ..................8-9

Electrical Wiring ............................10

Direct Gas Piping ...........................11

Building Pressure Control, optional .............12

Start-Up

Checklist .................................13

Blower ................................14-15

Direct Gas .............................15-18

Operation

Optional VAV Units ..........................19

Optional Recirculating Units ..................20

Electrical ...............................20-21

Troubleshooting

Blower Does Not Operate ....................22

Motor Overamps ...........................23

Insufficient Airflow ..........................24

Too Much Airflow ...........................24

Excessive Noise or Vibration ..................25

Heater Does Not Operate (Pilot Ignition) ......26-28

Heater Does Not Operate (Direct Spark) ......29-30

Maintenance

Routine ...................................31

V-Belt Drives .............................31

Motors ..................................31

Wheels .................................31

Filters ..................................31

Bearings ................................32

Fall ......................................32

Start-Up ................................32

High Limit ...............................32

Gas Train ................................32

Reference

Typical Gas Train Layout ..................33-34

Control Center Layout .......................35

Maintenance Log .....................Backcover

Warranty ............................Backcover

®

Model VSU Make-Up Air

3

DESCRIPTION

REV.

DRAWING NO.

CAD DRAWING NO.

TOLERANCE UNLESS NOTED

HOLE or EDGE to

FORM:

+/- .008

HOLE or EDGE to

HOLE or EDGE:

A

DATE

SUPERSEDES

TITLE

DRAWN BY

1

ENG. REF.

of

1

SCALE

SHEET

+/- .015

P.O. BOX 410 SCHOFIELD, WI 54476-0410

ECO #

DESCRIPTION

GAUGE

MAT'L

PART NO.

GREENHECK

PART NO

.

Product Overview

Subassemblies

The model is a vertically-configured make-up air unit
designed for outdoor installations. It contains a highly
efficient direct-fired gas burner to provide a heat source
for the building or to simply temper the air. The unit is
designed to provide sufficient air to replace air that is
exhausted from the building and will also produce heat
as needed. The make-up air volume produced by the
unit can be regulated in a number of different ways,
depending on the characteristics of the building.

The unit draws in fresh, outdoor air through a filter bank
in the bottom of the unit and it then moves upward
through a combustion chamber or through an optional
burner bypass damper. A blower mounted in the top of
the unit then forces the air into the building ductwork.

Airflow Arrangement

The unit can be ordered in a number of different
configurations to provide 100% outdoor air or 80%
recirculated air and 20% outdoor air. These units
can also be ordered with a variable air volume (VAV)
capability for flexibility in response to building air
handling needs.

100% Outdoor Air

If the unit is configured only for 100% outdoor air, it
draws outdoor air as needed through the filter bank
at the bottom. The air moves upward through the
combustion chamber and then it is blown into the
building through user-supplied ductwork. The supply air
volume is typically constant and can only be altered by
changing the blower or motor pulleys.

80/20 Recirculated Air

When the unit is used as a primary heat source for
the building, the unit will draw 80% of the needed air
from the building and mix it with a minimum of 20%
fresh outdoor air. Outdoor air is drawn through the
combustion chamber and then mixed with the indoor
air after the direct-fired gas heater has heated the air.
The supply air volume is typically constant but the
percentage of recirculated air can be modulated.

Variable Air Volume (VAV)

The VAV function can be selected when the outdoor air
volume required by the building varies. This requires
the installation of one bypass damper and selection of
an appropriate motor/blower control system. This may
involve installation of a Variable Frequency Drive (VFD)
controller. Both bypass damper and VFD are factory
installed.

Filter Section / Vertical Mounting Stand

The filter section of the unit is factory installed in the
mounting stand and shipped ready for installation on
the concrete mounting pad. Each filter unit has a large
access panel on the control end of the unit except for
the housing size 50, which has an access door on both
ends. Filters are either 2 in. thick pleated paper or 2in.
thick permanent metal type. Filters are changed by
removing the access door(s) and sliding the filters in or
out on their tracks.

The unit’s vertical mounting stand is fabricated of
heavy-gauge, painted angle iron and flat stock steel.
The nominal 24 in. high stand will support the entire unit
so that the bottom of the filter unit is held 24 in. above
ground level. For housing size 50, a nominal 48 in. high
stand is minimum. In locations where heavy snowfall
is common, greater minimum clearance should be
specified in order to minimize the possibility of clogging
filters with snow or debris. The stand with filter bank is
shipped to the jobsite as a separate assembly. The unit
filter bank is permanently installed in the mounting stand
prior to shipment.

Optional Service Platform

A service platform
is available
for permanent
attachment to the
mounting stand.
The platform
is shipped
unassembled
and requires
field assembly.
It is attached to the
vertical mounting stand
by installing bolts with spacers
between the two assemblies.
The service platform should be
attached to the unit only after the
burner and blower assemblies are
permanently set in place.

Model VSU Make-Up Air

4

®

Burner, Blower and Control Center Section

The burner section, blower section and control center
of the unit are all combined into one assembly which
is installed in the field on top of the filter and stand
section. The burner section is the lowest part of the
burner / blower unit and it sits directly on the filter
assembly. The burner section contains the gas train
with its own access door and directly above that is
the control center door. A number of different options
are available for the gas train, whick include type, size
and location of burners and many different ignition and
safety controls.

The blower section of the unit consists of one motor and
either one or two forward curved blowers. It is the top­most assembly in the unit. If two blowers are used, their
drive shafts are connected and driven by a single motor.
Supply air discharge openings may be located either on
the side wall of the unit for horizontal discharge, or may
be configured for upblast discharge through the roof of
the unit. One large access door is located directly above
the control center, for inspection and maintenance of
the motor and blower(s).

Blowers

Control Center/

Gas Train

Filters

Burner

Open View

®

Model VSU Make-Up Air

5

Gas Train

(Burner Subassembly)

Burner Subassembly

The burner subassembly consists of the gas train with
its controls, valves, pressure regulator, burner(s), and
combustion chamber. The primary gas connection to
the gas train is made through the side wall grommet
into the factory-supplied female pipe fitting.

Dampers

There are four locations where optional dampers may
be found. An optional motorized intake damper may be
located horizontally on the bottom of the burner section.
A patented passive control damper may be found
adjacent to the burner opening plates if a VAV is ordered
and a motorized damper may be installed vertically on
the side of the burner section if recirculating air mode is
chosen. In addition, an outlet damper may be shipped
with the unit for field installation.

Optional Field-Installed

Outlet Damper

Optional Motorized

Recirculating Damper

Control Center

The control center is located on the end of the unit,
directly above the gas train access door. The control
center contains electronic components and some
elctromechanical devices that monitor and control
the operation of the entire unit. A unit-specific wiring
diagram is affixed to the inside of the access door.

High voltage supply wiring
terminates at a manual on/off
switch located on the face or
the side of the unit, adjacent to
the control center.

Low voltage control wiring from
the building terminates on the
terminal strips.

Passive Control Damper

Optional Motorized

Intake Damper

Manual High Voltage

On/Off Switch

with Lockout

Model VSU Make-Up Air

6

®

Installation

Concrete Slab

The first step in unit installation is to pour a concrete
slab capable of holding the unit weight as a base. The
slab should have a proper gravel drainage bed.

Concrete Slab Dimensions

Housing Size A B C D E

20 64 64 42 40 40
30 77 76 42 52 53
40 78 135 42 54 111
50 87 180 42 63 153

All dimensions are shown in inches.

NOTE

If optional service platform is included, a minimum of
42 inches must be added to Dimension B.

Building Wall

Approx. Stand Feet Locations

Concrete Slab

Burner/Blower Section

Use a crane and a spreader bar hooked to the factory
lifting lugs (shown below) to lift and center the unit onto
the filter stand section. The sections should be caulked
together.

Spreader Bar

A

12

D

E

12

B

Concrete Slab and Unit Footprint

Unit Control Side

Required with service

C

platform only

Service and Access Clearance

The slab should be positioned to allow 3 feet of
clearance on the control end of the unit and 2 feet of
clearance on the other three sides. Housing size 50
requires 3 feet of clearance on both ends because of
filters access. Note that the concrete forms a 1 foot
wide apron on all four sides of the unit unless a 42 in.
extension is added to the control end of the unit.

Clearance to Combustibles

Floor Top Sides Ends

Insulated/

Units

Non Insulated

Units

Clearance to combustibles is defined as the minimum distance required
between the heater and adjacent combustible surfaces to ensure the
adjacent surface’s temperature does not exceed 90 degrees above the
ambient temperature.

0 in.

(0 mm)

0 in.

(0 mm)

0 in.

(0 mm)

6 in.

(152.4 mm)

0 in.

(0 mm)

6 in.

(152.4 mm)

0 in.

(0 mm)

6 in.

(152.4 mm)

Install Ductwork

This table shows the duct sizes and straight lengths
recommended for optimal performance (AMCA
Publication 201-90). Using duct sizes less than
recommended will affect fan performance. Good
duct installation practices should be followed for the
remaining ductwork.

Recommended Supply Ductwork Sizes

VSU

Blower Size

108 10x13 32

109 14x13 38

110 16x14 42

112 18x16 48

115 19x16 49

118 24x22 64

120 28x28 79

218 68x24 114

220 68x26 118

225 104x37 175

230 104x37 203

Duct Size

(in.)

Straight Duct Length

(in.)

®

Model VSU Make-Up Air

7

Complete Installation

A typical horizontal discharge installation is shown. Gas
and/or electrical lines can be connected at this time.

For upblast units, a duct elbow may be needed to turn
the ductwork into the building. Follow proper ductwork
methods recommended by AMCA to make this elbow to
minimize duct losses.

Installation of Optional Service Platform

TOOLS REQUIRED

• (2) 9/16 in. sockets or wrenches

• Drill with 7/16 in. drill bit and 5/16 in. drill bit

• A crane or forklift is recommended for assembly and

attachment.

Service Platform Material List

(1) Left Hand Rail with

Safety Chains

(1) Platform Base Unit with

predrilled holes for hand
rails, legs and attachments.

Fasteners

(3)

(2)

(18)

(1) Right Hand Rail

Hex Head Bolts

3/8 in. x 1-1/2 in.

Thread Cutting

Screws

3/8 in. x 1 in.

Hex Head Bolts

3/8 in. x 3/4 in.

(2) Legs

(1) Leg Cross Member

Model VSU Make-Up Air

8

(27)

Hex Head Nuts

3/8 in.

®

Assembly

1. Position platform base as shown below in FigureA
with the grate side up.

2. Attach the left and right handrails to the platform
base with (3/8 in. x 3/4 in.) hex head bolts and (3/8
in.) hex nuts as shown in Figure A. Use six bolts and
nuts on each rail.

3. Raise the platform base, grate side up, with a crane
or forklift.

4. Attach legs to the slots on sides of platform base
with two (3/8 in. x 3/4 in.) hex head bolts and
(3/8in.) hex nuts.

6. Facing the control panel side of the unit, find the
center of the housing and drill a (7/16 in.) hole
through the housing and support stand (3/8 in.)
above the form line as shown in FigureC.

3/8 inch

Form Line

12

inches

12 inches

Figure C

Next, drill two more (7/16 in.) holes through the

housing and support stand (12 in.) on either side of
the center hole, (3/8 in.) above the form line. These
holes are used to attach the platform base to the
unit.

7. Attach the service platform to the control panel
side of the housing by inserting the three (3/8 in. x
1-1/2in.) bolts of platform base into the three holes
of the housing. Securely fasten with three (3/8 in.)
hex nuts.

8. Level service platform if necessary by adjusting
legs and then attach leg cross member with two
(3/8 in. x 3/4 in.) hex head bolts and 3/8 in. hex head
nuts.

9. Securely fasten all nuts and bolts. Make sure all
nuts and bolts are tight.

10. Attach arm rails of service platform to the housing
by first drilling a 5/16 in. hole through the housing at
the attachment point as shown in Figure D. Secure
arm rails to the housing with (3/8 in. x 1 in.) thread
cutting screws. Be sure not to over-tighten screws.

11. Attach safety chains to the right hand rail, across
the entryway. Assembly is complete.

Figure A

5. Fasten three (3/8 in. x 1-1/2 in.) hex head bolts into
the side of the platform
base. Secure each bolt
with two (3/8 in.) hex
head nuts placed back
to back on each bolt as
shown in Figure B. These
bolts will be used to
attach the platform base

Figure B

to the unit.

®

Attachment Points

for Step 11

Figure D

Model VSU Make-Up Air

9

Installation of Electrical Wiring

IMPORTANT

Before connecting power to the unit, read and
understand the following instructions and wiring
diagrams. Complete wiring diagrams are attached on
the inside of the control center door(s).

IMPORTANT

All wiring should be done in accordance with the
latest edition of the National Electric Code ANSI/
NFPA70 and any local codes that may apply. In
Canada, wiring should be done in accordance with
the Canadian Electrical Code.

IMPORTANT

The equipment must be properly grounded. Any
wiring running through the unit in the airstream must
be protected by metal conduit, metal clad cable or
raceways.

CAUTION

If replacement wire is required, it must have a
temperature rating of at least 105ºC, except for an
energy cut-off or sensor lead wire which must be
rated to 150ºC.

DANGER

High voltage electrical input is needed for this
equipment. This work should be performed by a
qualified electrician.

CAUTION

Any wiring deviations may result in personal injury or
property damage. Manufacturer is not responsible
for any damage to, or failure of the unit caused by
incorrect final wiring.

IMPORTANT

Manufacturer’s standard control voltage is 24VAC.
Control wire resistance should not exceed 0.75ohms
(approximately 285 feet total length for 14gauge
wire; 455 feet total length for 12gauge wire). If the
resistance exceeds 0.75 ohms, an industrial-style
plug-in relay should be wired in place of the remote
switch. The relay must be rated for at least 5 amps
and have a 24 VAC coil. Failure to comply with these
guidelines may cause motor starters to chatter or not
pull in, resulting in contactor failures and/or motor
failures.

Determine the Size of the Main Power Lines

The unit’s nameplate states the voltage and the unit’s
MCA. The main power lines to the unit should be sized
accordingly. The nameplate is located on the outside of
the unit on the control panel side.

Determine the Size of Electric Heater Wiring

An optional electric heater may require a separate
power supply. The power connection should be made
to the factory provided electric heater disconnect and

must be compatible with the ratings on the nameplate,
supply power voltage, phase and amperage. Consult
ANSI/NFPA 70 and CSA C22.1 for proper conductor
sizing.

Connect the Main Power

Connect the main power lines to the disconnect switch
and main grounding lug(s). Torque field connections to
manufacturer’s recommendations.

Wire the Optional Convenience Outlet

The convenience outlet requires a separate 115V power
supply circuit. The circuit must include short circuit
protection which may need to be supplied by others.

Wire the Optional Accessories

Reference the ladder diagram on the inside of the
control center door for correct wiring of the following
accessories:

• Selectra Stat • Indicating Lights

• Room Override • Dirty Filter Indicator

• Blower Switch • TSCP

• Heat Switch • KSCP

NOTE

Wiring to the Selectra Stat should be in separate
conduit or run with shielded cable.

NOTE

TSCP has number-to-number wiring.

NOTE

Large evaporative coolers may require a separate
power supply.

Connect Field-Wired Low Voltage Components

Most factory-supplied electrical components are
prewired. To determine what electrical accessories
require additional field-wiring, refer to the unit-specific
wiring diagram located on the inside of the control
center access door.

The low voltage control circuit is 24 VAC and control
wiring should not exceed 0.75 ohms.

Control wires should not be run inside the same conduit
as that carrying the supply power. Make sure that
field-supplied conduit does not interfere with access
panel operation. All low voltage wiring should be run in
conduit wherever it may be exposed to the weather.

If wire resistance exceeds 0.75 ohms, an industrial­style, plug-in relay should be added to the unit control
center and wired in place of the remote switch (typically
between terminal blocks R and G on the terminal strip).
The relay must be rated for at least 5 amps and have a
24 VAC coil. Failure to comply with these guidelines may
cause motor starters to “chatter” or not pull in which
can cause contactor failures and/or motor failures.

Model VSU Make-Up Air

10

®

Installation of Direct Gas Piping

IMPORTANT

All gas piping must be installed in accordance
with the latest edition of the National Fuel Gas
Code ANSI/Z223.1 and any local codes that may
apply. In Canada, the equipment shall be installed
in accordance with the Installation Code for Gas
Burning Appliances and Equipment (CGA B149) and
Provincial Regulations for the class. Authorities having
jurisdiction should be consulted before installations
are made.

WARNING

All components of this or any other gas-fired heating
unit must be leak tested prior to placing the unit into
operation. A soap and water solution should be used
to perform this test. NEVER test for gas leaks with an
open flame.

WARNING

If pressure testing in excess of 1/2 psig (3.5kPa), the
heater and manual shutoff valve must be disconnected
from the supply gas line.

WARNING

If pressure testing at or below 1/2 psig (3.5kPa), the
heater must be isolated from the supply gas line by
closing its manual shutoff valve.

IMPORTANT

All piping should be clean and free of any foreign
matter. Foreign material entering the gas train can
damage the valves, regulators and burner.

IMPORTANT

Do NOT connect the unit to gas types other than
what is specified and do NOT connect the unit to
gas pressures that are outside of the pressure range
shown on the label.

NOTE

When connecting the gas supply, the length of the
run must be considered in determining the pipe size
to avoid excessive pressure drop. Refer to a Gas
Engineer’s Handbook for gas pipe capacities.

Determine the Supply Gas Requirements

The unit’s direct gas nameplate states the requirements
for the gas being supplied to the unit. The direct gas
nameplate is located on the outside of the unit on the
control center side.

Minimum gas pressure for

maximum output

MAX BTU/HR
BTU/H MAX

NORMAL MANIFOLD
PRESSURE
PRESSION DÕADMISSION
NORMALE

MIN GAS
PRESSURE
PRESSION DE GAZ

MIN BURNER
PRESSURE DROP
PERTE MIN DE PRESSION
DANS LE BRULEUR

TYPE OF GAS
NATURE DU GAZ

EQUIPPED FOR

CONCU POUR

Type of gas

AGAINST

SCFM

CONTE

Direct Gas Nameplate

MIN BTU/HR
BTU/H MIN

MIN GAS PRESSURE
FOR MAX OUTPUT

“ WC

PRESSION DE GAZ MIN
POUR PUISSANCE MAX

MAX GAS
PRESSURE

“ WC

PRESSION DE GAZ
MAX

MAX BURNER
PRESSURE DROP

“ WC

PERTE MAX DE PRESSION
DANS LE BRULEUR

DESIGN ∆T
∆T NORMALE

“ WC

Maximum gas pressure

“ WC

“ WC

PSI

F

EXTERNAL STATIC PRESSURE

PRESSION STATIQUE EXTERIEURE

Install Additional Regulator if Required

When the supply gas pressure exceeds the maximum
gas pressure shown on the direct gas nameplate, an
additional regulator (by others) is required to reduce the
pressure. The regulator must have a listed leak limiting
device or it must be vented to the outdoors.

NOTE

The regulator located inside the unit is used to adjust
the unit’s maximum output temperature.

®

Model VSU Make-Up Air

11

Connect the Supply Gas Line

A manual shut off valve (gas cock), 1/8 in. plugged test
port and 6 in. drip leg must be installed prior to the gas
train. The valve and the test port must be accessible for
the connection of a test gauge. Supply gas connections
must be made by a qualified installer and are not
furnished by manufacturer.

To

Controls

Gas Cock

Ground Joint Union

From

Gas

Supply

1/8 in. Plugged Tap

6 in. Trap

Supply Gas Line

WARNING

Reference the National Fuel Gas Code for additional
vent line requirements.

Pipe the Optional Vent Line

If an optional vent line is located between the safety
shutoff valves it must be piped to the outdoors.

Vent Line Solenoid

To Outdoors

Installation of Building Pressure
Control (optional)

Mount Pressure Tap

Using the factory provided bracket, mount the pressure
tap to the outside of the
unit. Choose a location
out of the prevailing
winds and away from
supply or exhaust fans
to assure accurate
readings.

Run Pressure Tap Lines

Run a pressure tap line from the pressure tap on the
outside of the unit to the low pressure tap on the back
of the photohelic gauge. Run a second pressure tap line
from the high pressure tap on the back of the photohelic
gauge to the space. Fifty feet of tubing is supplied with
the unit.

Set the Building Pressure

The pressure gauge is used to set the desired building
pressure. The pressure is set by adjusting the knobs for
the upper and lower pressure limits. Typical settings are

0.0 in. wg for the lower and 0.10 in. wg for the upper
pressure setting.

High Pressure Tap

Factory Wiring

to space

Vent Line

To Burner

Safety

Shut-off Valves

From Supply

Optional Vent Line

Test the System for Leaks

Check both the supply lines and the factory piping for
leaks. Apply a soap and water solution to all piping and
watch for bubbling which indicates a leak.

WARNING

NEVER test for a gas leak with an open flame.

NOTE

The factory piping has been checked for leaks, but
should be rechecked due to shipping and installation.

Low Pressure Tap

to outside

Connections for Photohelic Gauge

Typical Photohelic Gauge Settings

Pressure Indicating

Needle

Pressure Setting Knobs

Pressure Setting

Needles

Model VSU Make-Up Air

12

®

Start-Up - Checklist

Unit Model Number _______________________________

Unit Serial Number _______________________________

Start-Up Date _______________________________

Start-Up Personnel Name __________________________

Start-Up Company _______________________________

Phone Number _______________________________

(e.g. VSU-H20)

(e.g. 10111000)

Pre Start-Up Checklist – check boxes as items

are completed.
oCheck tightness of all factory wiring connections
oVerify control wiring wire gauge
oHand-rotate blower to verify free rotation
oVerify supply voltage to the main disconnect
oVerify the supply gas pressure
oVerify remote controls wiring
oCheck V-belt drive for proper alignment and

tension

Start-Up Blower Checklist – refer to Start-Up -

Blower section for further detail.

oCheck line voltage L1-L2 __________

L2-L3 __________
L1-L3 __________
oCheck blower rotation

oCheck for vibration
oSupply fan RPM _________ RPM
oMotor nameplate amps _________ Amps
oActual motor amps _________ Amps
oActual CFM delivered _________ CFM

Optional Accessories – refer to Start-Up - Blower,

Set-Up Optional Components, pg. 15 for further detail.

oHeating Inlet Air Sensor

________ Actual Setting

Typical setting 60º-70ºF

oCooling Inlet Air Sensor

________ Actual Setting

Typical setting 75ºF

oBuilding Freeze Protection

________ Actual Setting

Typical setting 5 minutes; 45ºF

oDirty Filter Gauge

________ Actual Setting

Typical setting varies

Start-Up Direct Gas (Pilot Ignition) – refer to

Start-Up - Direct Gas section for further detail.

oCheck supply gas pressure

________ Maximum

________ Minimum

________ Actual

oCheck Pilot Gas Pressure

________ Actual Setting
Typical 3.0 in. wg

oSet optional High Gas Pressure Switch

________ Actual Setting
Typical 8.0 in. wg

oSet optional Low Gas Pressure Switch

________ Actual Setting
Typical 3.0 in. wg

oSet Burner Pressure Differential

________ Actual Setting
Typical 0.65 in. wg

oSet the maximum firing rate

________ temp rise

oSet the minimum firing rate

________ check

oSet the unit’s operating temperature

________ ºF

Start-Up Direct Gas (Direct Spark) – refer to

Start-Up - Direct Gas section for further detail.

oCheck supply gas pressure

________ Maximum

________ Minimum

________ Actual

oSet optional High Gas Pressure Switch

________ Actual Setting
Typical 8.0 in. wg.

oSet optional Low Gas Pressure Switch

________ Actual Setting
Typical 3.0 in. wg.

oSet Burner Pressure Differential

________ Actual Setting
Typical 0.65 in. wg

oSet the maximum firing rate

________ temp rise

oSet the minimum firing rate

________ check

oSet the unit’s operating temperature

________ ºF

®

Model VSU Make-Up Air

13

SUP HP

MCA

EXH HP

MOP

VOLTS HZ PH

Unit’s Total MCA

Voltage, Hertz, Phase

Start-Up - Blower

WARNING

Check the housing, blower, and ductwork for any
foreign objects before running the blower.

WARNING

Disconnect and lock-out all power and gas before
performing any maintenance or service to the unit.
Failure to do so could result in serious injury or death
and damage to equipment.

SPECIAL TOOLS REQUIRED

• VoltageMeter(withwireprobes)

• AmperageMeter

• PressureGauges–(refrigerant)

• Tachometer

• Thermometer

• Inclinemanometerorequivalent

Check the Voltage

Before starting the unit, compare the supplied voltage,
hertz, and phase with the unit and motor’s nameplate
information.

VOLTS HZ PH

SUP HP

MCA

Voltage, Hertz, Phase

EXH HP

MOP

Electrical Nameplate

Check the Blower Rotation

n

Open the blower access door
and run the blower momentarily
to determine the rotation. Arrows
are placed on the blower scroll to
indicate the proper direction or
reference the example shown to
the right.

To reverse the rotation on three phase units,
disconnect and lock-out the power, then interchange
any two power leads.

To reverse the rotation on single phase units,
disconnect and lock-out the power, then rewire the
motor per the manufacturer’s instructions.

If the blower is rotating in the wrong direction, the unit
will move some air, but will not perform as designed.
Be sure to perform a visual inspection to guarantee
the correct blower rotation.

NOTE

NOTE

IMPORTANT

o

i

t

a

t

o

R

Blower Rotation

Blower

Housing

Check for Vibration

Check for unusual noise, vibration or overheating of the
bearings. Reference the Troubleshooting section for
corrective actions.

IMPORTANT

Excessive vibration may be experienced during
the initial start-up. Left unchecked, it can cause a
multitude of problems including structural and/or
component failure.

IMPORTANT

Generally, fan vibration and noise is transmitted
to other parts of the building by the ductwork. To
minimize this undesirable effect, the use of heavy
canvas duct connectors is recommended.

Motor Check

Measure the motor’s voltage, amps and RPM. Compare
to the specifications. Motor amps can be reduced by
lowering the motor RPM or increasing system static
pressure.

IMPORTANT

Additional starters and overloads may be provided in
the make-up air control center for optional exhaust
blowers. Any additional overloads must be checked
for proper voltage, amps and RPMs.

Air Volume Measurement and Check

Measure the unit’s air volume (cfm) and compare it with
the rated air volume. If the measured air volume is off,
adjust the fan’s RPM by changing/adjusting the drive.

NOTE

The most accurate way to measure the air volume is
by using a pitot traverse method downstream of the
blower. Other methods can be used, but should be
proven and accurate.

IMPORTANT

Changing the air volume can significantly increase
the motor’s amps. If the air volume is changed,
the motor’s amps must be checked to prevent
overloading the motor.

NOTE

To ensure accuracy, the dampers are to be open
when measuring the air volume.

Model VSU Make-Up Air

14

®

Start-Up - Direct Gas

Set-Up Optional Components

Adjust the settings on the optional components. See
the unit’s specific wiring diagram located on the access
door or the unit.

• Heating Inlet Air Sensor
Typical setting: 60-70ºF

• Building Freeze Protection
Typical setting: 5 minutes; 45ºF

• Dirty Filter Gauge
Typical setting: Settings vary greatly for each unit.
(see Reference section for adjusting information)

IMPORTANT

For proper unit function and safety, follow the start-up
procedure in the exact order that it is presented.

IMPORTANT

This start-up should begin after all of the installation
procedures and the blower start-up have been
completed.

Check the Supply Gas Pressure

Check the supply gas pressure and compare it with
the unit’s nameplate pressure requirements. Adjust
the supply regulator as needed until the supply gas
pressure is within the specified range. The direct gas
nameplate is located on the outside of the unit on the
control center side.

MAX BTU/HR
BTU/H MAX

NORMAL MANIFOLD
PRESSURE
PRESSION DÕADMISSION
NORMALE

MIN GAS
PRESSURE
PRESSION DE GAZ

MIN BURNER
PRESSURE DROP
PERTE MIN DE PRESSION
DANS LE BRULEUR

TYPE OF GAS
NATURE DU GAZ

EQUIPPED FOR

CONCU POUR

Minimum and maximum gas

pressures for maximum output

MIN BTU/HR
BTU/H MIN

MIN GAS PRESSURE
FOR MAX OUTPUT

“ WC

PRESSION DE GAZ MIN
POUR PUISSANCE MAX

MAX GAS
PRESSURE

“ WC

PRESSION DE GAZ
MAX

MAX BURNER
PRESSURE DROP

“ WC

PERTE MAX DE PRESSION
DANS LE BRULEUR

DESIGN ∆T
∆T NORMALE

SCFM

AGAINST

CONTE

EXTERNAL STATIC PRESSURE

“ WC

PRESSION STATIQUE EXTERIEURE

“ WC

“ WC

PSI

F

Type of gas

Direct Gas Nameplate

Check the Pilot Gas Pressure

Check the pilot gas pressure. The recommended
gas pressure is 3 in. wg. Adjust the pilot regulator as
needed. See the Gas Train Layout in the Reference
section for the location of the pilot pressure test port
and pilot regulator.

Check the Optional High and Low Gas Pressure
Switches

Check the settings on the high and low gas pressure
switches. The high gas setting is typically 8in. wg
(2kPa) and the low gas setting is typically 3 in. wg
(0.7kPa). The switches are set at the factory and should
not need adjustment. Adjust the settings if needed. See
the Gas Train Layout in the Reference section for the
high and low pressure switch location.

IMPORTANT

The purpose of the high and low gas pressure
switches is to automatically shut down the burner
if the inlet gas pressure is too low for the burner to
safely light, or if the manifold pressure is too high for
the burner to operate properly.

®

Model VSU Make-Up Air

15

Set the Burner Air Pressure Differential

9

8

With the fan running and discharging 70ºF (21ºC) air,
connect a U-Tube manometer to the outer sensing
probes (see below) and measure the static pressure
across the burner.

Outer Sensing Probes

7

0.625 - 0.675 in. wc

6

U-Tube

Manometer

Measuring the Pressure Drop

IMPORTANT

Proper air velocity over the burner is critical on direct­fired gas units. If the air velocity is not within the unit
specifications, the unit will not operate efficiently,
may have sporadic shutdowns, and may produce
excessive carbon monoxide (CO) or other gases.

The proper static pressure should be between 0.625
and 0.675 in. wg (155.68 and 168.64 Pa). If needed,
evenly adjust the baffles on both sides of the burner,
keeping the burner centered in the opening until the
required pressure is obtained.

NOTE

The pressure drop was set at the factory and may not
need adjustment.

NOTE

When required pressure is obtained, be sure to
reconnect the outer sensing probes.

IMPORTANT

This process may need to be repeated until the proper
pressure is achieved. This adjustment will change the
air quantity delivered by the unit and therefore the air
quantity delivered should be rechecked. Refer to the
Blower Start-Up section.

NOTE

To increase the static pressure decrease the opening.
To decrease the static pressure increase the opening.

Set the Maximum Firing Rate

Monitor the unit’s actual temperature rise by placing
a thermocouple in the unit’s inlet and a second in the
discharge, three duct diameters downstream of the burner.

Send the unit to maximum fire by disconnecting and
isolating the wire connected to Terminal 3 on the Maxitrol
14 or the Maxitrol 44. See images on page 18.

While monitoring the units temperature rise, set the
maximum firing rate by adjusting the regulator until the
designed temperature rise is achieved. After setting the
maximum firing rate, reconnect the wire to the amplifier.

NOTE

Do not set the burner maximum firing rate based on gas
pressure. It should be set based on the unit’s designed
temperature rise shown on the direct gas label.

Adjustable

Baffle

Burner

Airflow

Burner and Baffles

Airflow

Adjustable

Baffle

MIN GAS
PRESSURE
PRESSION DE GAZ

MIN BURNER
PRESSURE DROP
PERTE MIN DE PRESSION
DANS LE BRULEUR

TYPE OF GAS
NATURE DU GAZ

EQUIPPED FOR

CONCU POUR

MAX GAS
PRESSURE

“ WC

PRESSION DE GAZ
MAX

MAX BURNER
PRESSURE DROP

“ WC

PERTE MAX DE PRESSION
DANS LE BRULEUR

DESIGN ∆T
∆T NORMALE

SCFM

AGAINST

CONTE

EXTERNAL STATIC PRESSURE

“ WC

PRESSION STATIQUE EXTERIEURE

Direct Gas Nameplate

Maximum firing
rate adjustment

Combined Regulator Valve

“ WC

PSI

F

Model VSU Make-Up Air

16

®

IMPORTANT

Setting the maximum firing rate during mild weather
conditions may cause the high limit to trip out during
extreme conditions requiring manual resetting.

NOTE

Gas trains are equipped with either separate
regulators and modulating valves or with a combined
modulating valve.

NOTE

Clockwise rotation increases the temperature rise,
counterclockwise rotation decreases the temperature
rise.

NOTE

The minimum setting for the maximum firing rate
may be higher than required. This is acceptable. The
burner will modulate as needed.

Regulators and Modulating Valves

Remove cap to access

maximum firing rate

adjustment

Minimum
firing rate
adjustment

Separate Regulator and Modulating Valves

Minimum firing

rate adjustment

Remove one wire to

send the unit to the
minimum firing rate

Maximum firing
rate adjustment

Set the Minimum Firing Rate

Disconnect and isolate one of the wires running to the
modulating valve to send the unit to its minimum firing
rate. Set the minimum firing rate by adjusting the needle
valve indicated.

After setting the minimum firing rate, shut off the pilot
to ensure that the flame safeguard can still read the
main flame signal. Reconnect the wire to the modulation
valve and open the pilot shut-off valve.

IMPORTANT

The proper minimum firing rate setting results in a
small ribbon of continuous flame which covers the
flame rod and runs across the entire burner.

IMPORTANT

Do not allow the disconnected wire to come in
contact with a potential ground. Damage to the
amplifier or transformer could result.

IMPORTANT

On units with a 42 inch or greater burner, the flame
safeguard will automatically shut off the pilot after the
burner has been ignited.

NOTE

Gas trains are equipped with either separate
regulators and modulating valves or with a combined
modulating regulator.

NOTE

Adjusting the maximum and minimum firing rate
requires the inlet air sensor to be set higher than the
outdoor air temperature in order to start the burner(s).
Once high and low fire have been set, the inlet air
sensor should be set to the desired temperature.

NOTE

Counterclockwise rotation increases the minimum fire
rate setting, clockwise rotation decreases the setting.

Remove one wire to send the unit

to the minimum firing rate

Combined Modulating Regulator

®

Model VSU Make-Up Air

17

Set the Unit’s Operating Temperature

Set the operating temperature. The operating
temperature setting depends on which Maxitrol
controller is used.

Maxitrol Series 14 – 8 Terminals: The Maxitrol

Series 14 should be set to the desired discharge
temperature mode. Place dipswitch in the “UP” position
for local control and in the “DOWN” position for remote
control. Keep LFST dipswitch in the “UP” position at all
times for 10 second delay.

Fig. A is required for remote control.

Terminal 3 - Remove wire to

send unit into maximum fire.

Maxitrol SC25S: The SC25S is an analog signal
converter that will change a 0-10 VDC or a 4-20 mA
control signal provided by an owner supplied Building
Management System into an output level capable of
driving one or more modulating gas valves. The SC25S
also limits the minimum and maximum discharge
air temperatures. Reference the unit-specific wiring
diagram and Maxitrol data sheets included in the IOM
packet.

Discharge

temp

dipswitch

Set the discharge temp
Typical: 65°F
Minimum: Typical: 55°F
Maximum: Typical: 90°F

Maxitrol Series 14 — 8 terminals

Low fire

setting
(LFST)

dipswitch

Fig. A
Remote
controller

Maxitrol Series 44 – 9 Terminals: The Maxitrol
Series 44 should
be set to the
desired discharge
temperature.

Set the space
temperature
Typical: 70

º

F

The temperature
selector is a stand­alone dial. The
stand-alone dial
may be mounted
remotely.

Series 44 Temperature Setting

(shown as space temperature control)

Maxitrol SC25S

Flame Signal Check - Pilot Ignition

To measure the flame signal connect a standard DC
voltmeter to the flame amplifier test jacks + and - (com)
as shown to the
right. The flame
signal should be
above 1.25 VDC
and steady.

Check the flame
signal with the
burner at pilot only,
minimum fire, mid
fire and high fire.

IMPORTANT

If the flame signal is not above 1.25 VDC and steady,
consult the troubleshooting section.

DC Voltmeter and

Flame Amplifier

Minimum discharge
temperature setting

(Typical: 50ºF)

Low fire time delay setting

(75% of maximum)

Maxitrol Series 44 — 9 terminals

Model VSU Make-Up Air

18

Terminal 3 - Remove wire to

send unit into maximum fire.

Maximum discharge

temperature setting

(Typical: 100ºF)

®

Operation - VAV Units (optional)

NOTE

Blower Start-Up, as shown on page 14, should be
performed before the blower is run.

NOTE

For maintenance issues associated with variable
frequency drives, consult the drive’s manual supplied
with the unit. The drives are programmed at the
factory and should not need any adjustment during
installation and start-up. For kitchen applications, the
drive may be located in the kitchen or in the unit.

Variable Volume Operation

The variable volume option is recommended when
a building’s exhaust volume may vary. This option
enables the make-up air volume to track with the
exhaust volume, providing only the amount of make­up air required. Control strategies include 2-speed and
modulating blowers. Before the unit is left in service, the
variable volume control system should be tested.

2-Speed

A variable frequency drive (VFD) is used to control
air volumes. The VFD can be switched to low or high
speed from a remote control panel. Turn the fan speed
switch on the remote control panel to each position and
confirm that the fan speed adjusts accordingly.

Modulating

Potentiometer Control — a variable frequency drive
is controlled by input from a remote
speed selector (potentiometer). This
unit allows easy manual adjustment
of make-up air volumes. To test
potentiometer operation, turn the
potentiometer to the two extremes.
With variable volume, make sure the
fan goes to maximum and minimum
speed.

When the potentiometer is at 0, the
fan speed will be at its minimum.
When the potentiometer is at 100,
the fan will be at its maximum speed.

Potentiometer

EXHAUST

(OPTIONAL)

SUPPLY

HEAT

70

75

65

80

60

85

55

90

Control

BLOWER

MAIN VALVES

DIRTY FILTERS

(OPTIONAL)

GREENHECK

®

Building Pressure Control —

a variable frequency drive is
controlled according to input from

EXHAUST

SUPPLY

HEAT

(OPTIONAL)

BLOWER

MAIN VALVES

a pressure sensing device.

Turn both knobs to the upper
most pressure setting. You may

DIRTY FILTERS

70

75

65

80

(OPTIONAL)

60

85

55

90

have to remove the outdoor
pressure tap tubing. VAV systems

PHOTOHELIC

should go to maximum speed. Set
both knobs at the lowest setting
and the VAV systems should go to
minimum speed.

Pressure Control

®

Building

GREENHECK

Reset the correct pressure limits
before starting the unit.

This picture depicts a typical

Pressure Indicating

Needle

Pressure Setting

Needles

photohelic setting. Typical
settings are 0.0 in. wg for
the lower pressure setting
and 0.10 in. wg for the upper
pressure setting. The needle
indicates a negative building
pressure. During correct
operation, the indicating
needle will remain between or
near the setting needles.

Pressure Setting Knobs

Photohelic Gauge

External Signal — a variable frequency drive is

controlled according to input from an external 2-10 VDC
or 4-20 mA signal (by others).

A 2 VDC or 4 mA signal will send the blower to low
speed. The blower will go to maximum speed with a 10
VDC or 20 mA signal.

Variable Kitchen Control — A variable frequency
drive is controlled by input from a remote speed control.
This unit allows automatic adjustment of make-up air
volumes based on varying cooking loads.

Burner Bypass Damper (optional)

The self-adjusting burner bypass damper is a device
used in variable
volume units. Its
function is to maintain
proper combustion by
providing a constant
airflow over the burner
when outside air
volumes are changed.
It is located underneath
the burner as shown in
the picture.

Burner

Bypass Damper

Burner Bypass Damper

WARNING

The burner bypass damper is set-up at the factory.
The weights should not be adjusted in the field. The
damper may not fully close during minimum outside
air mode.

®

Model VSU Make-Up Air

19

Operation - Recirculating Units
(optional)

NOTE

Blower Start-Up, as shown on page 14, should be
performed before the blower is run.

Recirculation Operation

The recirculation operation option is recommended
when the ventilation equipment provides the primary
source of heating for the space. A minimum of 20%
outdoor air is mixed with up to 80% filtered recirculated
air. Control strategies include 2-position and modulating
dampers.

Before the unit is left in service, the recirculation control
system should be tested.

2-Position Damper

A 2-position spring return actuator is used to control
the return air amounts. The
damper moves from open to
closed. If power is cut to the unit,
the outdoor air damper will fail to
close.

Turn the recirculating switch on
the remote control panel to each
position and confirm that the return
air damper adjusts accordingly.
The damper actuator may take a
few minutes to open or close.

Modulating

Potentiometer Control — a modulating spring return
actuator is used to control the return air amounts.
The return air damper modulates
from fully open to fully closed
based on a signal from a remote
potentiometer.

To test potentiometer operation,
turn the potentiometer to the two
extremes. With 80/20 recirculation,
confirm that the return air damper
fully opens and fully closes. When
the potentiometer is at 0, the return
air damper will open. When the
potentiometer is at 100, the return
air damper will close. The damper
actuator may take a few minutes to open or close.

EXHAUST

SUPPL Y

HEA T

RECIRCULA TION

75

80

85

90

70

(OPTIONAL)

65

60

55

BLOWER

MAIN V AL VES

DIRTY FIL TERS

(OPTIONAL)

GREENHECK

®

2-Position

Damper Control

BLOWER

EXHAUST

(OPTIONAL)

SUPPLY

MAIN VALVES

HEAT

DIRTY FILTERS

70

75

65

80

(OPTIONAL)

60

85

55

90

GREENHECK

®

Potentiometer

Control

Building Pressure Control — a

modulating spring return actuator
is used to control the return air

EXHAUST

SUPPLY

BLOWER

(OPTIONAL)

MAIN VALVES

HEAT

amounts. The return air damper
modulates from fully open to fully
closed based on a signal from a

DIRTY FILTERS

70

75

65

80

(OPTIONAL)

60

85

55

90

remote pressure sensing device.

Turn both knobs to the upper most

PHOTOHELIC

pressure setting. You may have
to remove the outdoor pressure
tap tubing. The return air damper
should close.

Pressure Control

GREENHECK

®

Building

Set both knobs at the lowest setting and the damper
should open. It may take one to two minutes for the
damper to reach the desired position.

Reset the correct pressure limits before starting the unit.

This picture shows a typical

Pressure Indicating

Needle

Pressure Setting

Needles

photohelic setting. Typical
settings are 0.0 in. wg for the
lower and 0.10 in. wg for the
upper pressure setting. The
needle in this photo indicates
a negative building pressure.
During correct operation, the
indicating needle will remain
between or near the setting
needles.

Pressure Setting Knobs

Photohelic Gauge

External Signal — a modulating spring return actuator

is used to control the return air amounts. Return air
damper modulates from fully open to fully closed based
on an external 2-10 VDC or 4-20 mA signal (by others).

The return air damper will close with a 10 VDC or 20mA
signal. The return air damper should open with a 2VDC
or 4mA signal. The damper actuator may take a few
minutes to open or close.

Operation - Electrical

Electrical Sequence

1. Exhaust Fan Contact (S1) Closed
(optional)

• Power passes to N.C. exhaust overload contact

(ST2 OL) (optional)

• Power passes to exhaust starter(s) ST2

• N.O. exhaust starter switches are energized and

closed

• Power passes to exhaust fans

• Exhaust fan(s) (M2) start

2. Supply Fan Contact (S2) Closed

• Power passes through N.C. eld supplied re

contact (FSC)

• Power passes through N.O. exhaust fan contact

(ST2), which is closed when the exhaust relay
(ST2) is activated (optional)

Model VSU Make-Up Air

20

®

• Power passes to N.C. supply overload contact

(ST1 OL)

• Power passes through N.C. contact on optional

freeze protection timer (RT4) which remains
closed if the temperature has remained above the
set point

• Power passes to optional inlet damper which

opens

• When damper is fully opened, damper relay

(D1) is energized and optional N.O. damper limit
switch (DL1) closes

• Power passes to and energizes supply starter

relay (RF)

• Power passes to N.O. fan contact (RF), which is

energized and closed

• Supply starter (ST1) is energized

• Supply starter contact (ST1) closes and power

reaches and energizes supply fan

• Supply fan (M1) starts

3a. Heat Contact (S4) Closed - Pilot Ignition

• Power passes to N.O. fan relay (RF) which is

energized and closed

• Power passes to optional inlet air sensor contact

(TS4) which is energized and closed if the inlet air
temperature is below the set point

• Power passes to and energizes the heat relay

(RH)

• N.O. heat relay contact (RH) closes

• Power passes to and energizes terminal 5 of the

Flame Safeguard (FSG). Power light on FSG is on.

• Power passes to N.C. high limit control contact

(HLC1) which is closed if temperature has
remained below set point

• Power passes to optional N.O. and N.C. high and

low gas pressure contacts (PS4 and PS3), which
are both closed if gas pressure is within the set
range

• Power passes to terminal 6 of the Flame

Safeguard (FSG)

• Power begins direct gas burner sequence
(see Direct Gas Burner Sequence)

3b. Heat Contact (S4) Closed - Direct Spark

• Power passes to N.O. fan relay (RF) which is

energized and closed

• Power passes to optional inlet air sensor contact

(TS4) which is energized and closed if the inlet air
temperature is below the set point

• Power passes to and energizes the heat relay

(RH)

• N.O. heat relay contact (RH) closes

• Power passes to N.C. high limit control contact

(HLC1) which is closed if temperature has
remained below set point

• Power passes to optional N.O. and N.C. high and

low gas pressure contacts (PS4 and PS3), which
are both closed if gas pressure is within the set
range

• Power passes to N.O. and N.C. airow switches

(PS2) which are closed if there is proper airflow
across the burner

• Power passes to terminal TH on the Flame

Safeguard (FSG) which begins it’s sequence
(see Direct Gas Burner Sequence)

Direct Gas Burner Sequence - Pilot Ignition

1. Supply Fan Contact Closed

• Power passes to the supply fan and heat switch

2. Heat Contact Closed

• Power passes to the heat relay then to the Flame

Safeguard

3. Flame Safeguard (FSG) Sequence

• Checks for proper airow

• Veries no ame present at burner

• Initiates 10 second prepurge

• Sends power to open pilot gas valve (V1) and

energizes the spark generator (SG) (clicking of the
spark generator may be heard)

• Tries for up to 10 seconds to light pilot and

confirm flame

• Powers the main gas valves open

• Shuts down spark generator

• Continuously monitors the ame and airow

• Performs self-diagnostic check every ve

seconds.

Direct Gas Burner Sequence - Direct Spark

1. Supply Fan Contact Closed

• Power passes to the supply fan and heat switch

2. Heat Contact Closed

• Power passes to the heat relay then to the Flame

Safeguard

3. Flame Safeguard (FSG) Sequence

• Checks for proper airow

• Veries no ame present at burner

• Initiates 15 second prepurge

• Sends power to open gas valve (V2) and

energizes the spark generator (clicking of the
spark generator may be heard)

• Tries for up to 10 seconds to light and conrm

flame

• Shuts down spark generator

• Continuously monitors the ame and airow

®

Model VSU Make-Up Air

21

Troubleshooting

Blower Does Not Operate

Proper supply power at

main disconnect

Yes

24 VAC between

terminals R and X?

Yes

24 VAC between

terminals G and X?

Yes

24 VAC across

terminals 3 and X?

Yes

24 VAC across

terminals 4 and X?

No

No

No

No

No

Check main voltage.

Reference: Start-Up - Blower, Check the Voltage, pg. 14

Main disconnect (DS1) off.

Turn main disconnect (DS1) on.

Primary fuses blown.

Replace fuses.

Main transformer (TR1) defective.

Replace transformer.

Supply switch (S2) off.

Turn supply switch (S2) on.

Fire system contact (FSC) tripped/not installed.

Correct, replace.

Supply fan overload (ST1 OL) tripped.

Reset and check motor amps.

Reference: Start-Up - Blower, Motor Check, pg. 14

Optional exhaust fan interlocks (ST2-ST5) open.

Correct, replace.

Yes

24 VAC across A2 and A1 on

supply contactor (ST1)

Yes

(Optional) freeze protection (RT4) tripped.

Reset.

No

(Optional) damper limit switch (DL1) holding.

Wait for actuator to open fully or adjust limit switch.

(Optional) damper limit switch jumper missing.

Install jumper, reference the units ladder diagram for terminals.

Fan relay (RF) is not energized.

Check for loose connection. Repair or replace relay.

Broken fan belt.

Replace.

Reference: Maintenance - Routine, V-Belt Drives, pg. 31

Defective motor or capacitor.

Repair, replace.

Blown motor fuse.

Replace.

One or more legs of three-phase is out.

Restore missing legs.

At this time the supply contactor (ST1) should

pull in, passing power to the supply motor

and the blower should start.

Model VSU Make-Up Air

22

®

Troubleshooting

Motor Overamps

Air volume too high?

No

Actual static pressure

lower than design?

No

Blower rotation correct?

Yes

Motor voltage correct?

Yes

Motor horsepower too low?

No

Yes

Adjust drives or increase external

static pressure as needed.

Reference: Start-Up - Blower, Air Volume Measurement and Check, pg. 14

Yes

Adjust drives to reduce blower RPM.

Reference: Start-Up - Blower, Air Volume Measurement and Check, pg. 14

No

Reverse blower rotation.

Reference: Start-Up - Blower, Check the Blower Rotation

No

Provide proper power supply.

Reference: Start-Up - Blower, Check the Voltage, pg. 14

Yes

Resize motor.

Shorted windings in motor?

Yes

Everything is working

properly, consult factory.

Yes

Replace motor.

®

Model VSU Make-Up Air

23

Troubleshooting

Insufficient Airflow

Damper(s) not fully opened?

No

System static losses too high?

No

Blower speed too low?

No

Filters dirty or clogged

No

Leaks in ductwork

No

Yes

Adjust damper linkage(s), or replace faulty actuator(s).

Damper actuators may take a few minutes to open.

Yes

Reduce losses by improving ductwork.

Yes

Adjust drives as needed.

Reference: Start-Up - Blower, Air Volume Measurement and Check, pg. 14

Yes

Clean or replace filters.

Reference: Maintenance - Routine, Filters, pg. 31

Yes

Repair leaks.

Belt slipping

Yes

Everything is working properly,

consult factory.

Too Much Airflow

Blower speed too high?

No

Filters not in place?

No

Insufficient external

static pressure?

No

Yes

Replace or tighten belt.

Reference: Maintenance - Routine, V-Belt Drives, pg. 31

Yes

Adjust drives as needed.

Reference: Start-Up - Blower, Air Volume Measurement and Check, pg. 14

Yes

Install filters.

Yes

Everything is working properly,

consult factory.

Model VSU Make-Up Air

24

Increase external static pressure.

®

Troubleshooting

Excessive Noise or Vibration

Belts worn or loose?

No

Sheaves aligned?

Yes

Wheel unbalanced?

No

Bearings worn or

need lubrication?

No

Wheel rubbing on inlet?

Yes

Replace worn belts or tighten loose belts.

Reference: Maintenance - Routine, V-Belt Drives, pg. 31

No

Align sheaves.

Reference: Maintenance - Routine, V-Belt Drives, pg. 31

Yes

Clean and/or balance wheel(s).

Yes

Replace worn bearings or lubricate bearings as needed.

Reference: Maintenance - Routine, Bearings, pg. 32

Yes

No

Adjust wheel(s) or inlet.

At this time noise and vibration

should be at acceptable levels.

®

Model VSU Make-Up Air

25

Troubleshooting

Heater Does Not Operate (Pilot Ignition)

Does not attempt to light (No visible spark)

24 VAC between

terminals W1 and X?

Yes

115 VAC between

terminals 102 and 101?

Yes

115 VAC between

terminals 103 and 101?

Yes

115 VAC between

terminals 104 and 101?

Yes

115 VAC between

terminals 106 and 101?

Yes

Continuity between

terminals 107 and 108?

Yes

No

No

No

No

No

No

Heat switch (S4) off.

Turn heat switch (S4) on.

Heat switch not wired.

Wire heat switch (S4).

Primary fuses blown.

Replace fuses.

Main transformer (TR4) defective.

Replace transformer.

(Optional) inlet air sensor (TS4) holding.

Adjust TS4 setting.

Reference: Start-Up - Blower, Set-Up Optional Components, pg. 15

Heat relay (RH) defective.

Replace heat relay (RH).

The power light on the flame safeguard should

blink approximately every 5 seconds as it

performs a self-diagnostics check.

High limit (HLC1) tripped.

Reset or replace high limit (HLC1).

Check on cause of control loss.

(Optional) high/low gas pressure switch(es)

(PS3 and PS4) tripped.

Correct gas pressure and reset.

Reference: Start-Up - Direct Gas, Check the Pilot Gas Pressure, pg. 15

Airflow switch (PS2) holding for proper airflow.

Correct airflow across burner.

Reference: Start-Up - Direct Gas,

Check the Optional High and Low Gas Pressure Switches, pg. 15

Model VSU Make-Up Air

26

At this time the heater should attempt to light.

The pilot light on the flame safeguard should illuminate.

®

Troubleshooting

Heater Does Not Operate (Pilot Ignition)

Attempts to light, but no pilot (visible spark)

Check inlet gas pressure.

Reference: Start-Up - Direct Gas,

Check the Supply Gas Pressure, pg. 27

Yes

Reference: Start-Up - Direct Gas, Check the Supply Gas Pressure, pg. 27

Note: The minimum and maximum gas pressures

for your unit are shown on the direct gas label.

Gas pressure between the

minimum and maximum shown

on the direct gas label?

Air in the gas line?

No

Check for proper airflow.

Reference: Start-Up - Direct Gas,

Set the Burner Air Pressure Differential, pg. 16

Yes

Pressure drop across the burner

between 0.625 and 0.675 in. WC?

Yes

Proper spark?

Yes

No

Yes

No

No

Correct gas pressure.

Reference: Start-Up - Direct Gas, Check the Supply Gas Pressure, pg. 27

Purge gas line.

Verify gas at the pilot.

Note: The airflow may satisfy the airflow switch, but may
make lighting the pilot difficult. Adjust the pressure drop

across the burner between 0.625 and 0.675 in. WC

Reference: Start-Up - Direct Gas,

Set the Burner Air Pressure Differential, pg. 16

Adjust burner baffles.

Reference: Start-Up - Direct Gas,

Set the Burner Air Pressure Differential, pg. 16

Crossed flame and spark wires.

Uncross wires and reconnect.

Incorrect spark plug gap.

Set spark plug gap to 0.062 inches.

Defective spark plug.

Replace spark plug.

Check for proper pilot pressure.

Reference: Start-Up - Direct Gas,

Check the Pilot Gas Pressure, pg. 15

No

Pilot pressure correct?

Yes

®

No

Note: A high pilot pressure will make lighting more difficult.

Lower the pilot pressure in increments until the unit lights.

Then set the pilot per the instruction.

Reference: Start-Up - Direct Gas, Check the Pilot Gas Pressure, pg. 15

Adjust the pilot pressure.

Reference: Start-Up - Direct Gas, Check the Pilot Gas Pressure, pg. 15

With proper airflow, gas pressure and spark,

the unit should light.

If problems remain, consult the factory.

Model VSU Make-Up Air

27

Troubleshooting

Heater Does Not Operate (Pilot Ignition)

Visible pilot

Measure the flame signal

when there is a visible pilot

Flame signal greater

than 1.25 VDC

Yes

Check for proper airflow

Reference: Start-Up - Direct Gas,

Set the Burner Air Pressure Differential, pg. 16

Pressure drop across the burner

between 0.625 and 0.675 in. WC?

Yes

Note: The flame signal should be steady and

above 1.25 VDC with a visible pilot.

Reference: Start-Up - Direct Gas,

Flame Signal Check - Pilot Ignition, pg. 18

No

Unit is not grounded.

Properly ground unit.

Flame rod is grounding out.

Adjust the flame rod to avoid contact with the burner or the unit.

Cracked porcelain on flame rod.

Replace flame rod.

Note: When the pressure is low or marginal and the unit

begins heating, the air density will change. This can cause the

pressure to drop below the minimum setting. Also, low airflow

can cause the flame to walk out of the burner and away from

the flame sensor, causing the unit to recycle.

No

Adjust burner baffles

Reference: Start-Up - Direct Gas,

Set the Burner Air Pressure Differential, pg. 16

Check the minimum firing rate

Reference: Start-Up - Direct Gas,

Set the Unit’s Operating Temperature, pg. 18

Is the minimum firing rate

set correctly?

Yes

Does the flame signal

remain constant?

Yes

Note: Burners greater than 36 inches in length use an

interrupted pilot. The pilot is turned off 10 seconds after

lighting the main burner and the flame safeguard monitors the

main flame instead of the pilot flame. If the minimum fire is set

too low, the flame safeguard may not be able to sense it.

No

Adjust the minimum firing rate.

Reference: Start-Up - Direct Gas,

Set the Unit’s Operating Temperature, pg. 18

No

If the signal slowly drops off, typically the airflow is too low.

Reference: Start-Up - Blowers, Set the Maximum Firing Rate

If it suddenly drops to zero, the flame rod is grounding out.

Adjust the flame rod to avoid contact with the burner or the unit.

If the flame signal is above 1.25 VDC and constant,

the main gas valves will remain open until the call

for heat is interrupted or the unit is shut down.

Model VSU Make-Up Air

28

®

Troubleshooting

Heater Does Not Operate (Direct Spark)

Does not attempt to light (No visible spark)

24 VAC between

terminals W1 and X?

Yes

24 VAC between

terminals 22 and 21?

Yes

24 VAC between

terminals 23 and 21?

Yes

24 VAC between

terminals 24 and 21?

Yes

24 VAC between

terminals 26 and 21?

Yes

Continuity between

terminals 26 and 27?

Yes

No

No

No

No

No

No

Heat switch (S4) off.

Turn heat switch (S4) on.

Heat switch not wired.

Wire heat switch (S4).

Main transformer (TR2) defective.

Replace transformer.

(Optional) inlet air sensor (TS4) holding.

Adjust TS4 setting.

Reference: Start-Up - Blower, Set-Up Optional Components, pg. 15

Heat relay (RH) defective.

Replace heat relay (RH).

High limit (HLC1) tripped.

Reset, replace high limit (HLC1).

Check on cause of control loss.

(Optional) high/low gas pressure switch(es)

(PS3 and PS4) tripped.

Correct gas pressure and reset.

Reference: Start-Up - Direct Gas, Check the Pilot Gas Pressure, pg. 15

Airflow switch (PS2) holding for proper airflow.

Correct airflow across burner.

Reference: Start-Up - Direct Gas,

Check the Optional High and Low Gas Pressure Switches, pg. 15

At this time the heater should attempt to light.

®

Model VSU Make-Up Air

29

Troubleshooting

Heater Does Not Operate (Direct Spark)

Attempts to light, but no flame (Visible spark)

Is the low fire set properly?

Reference: Start-Up - Direct Gas,

Set the Minimum Firing Rate, pg. 17

Yes

Check inlet gas pressure.

Reference: Start-Up - Direct Gas,

Check the Supply Gas Pressure, pg. 15

Gas pressure between the

minimum and maximum shown

on the direct gas label?

Yes

Air in the gas line?

No

Check burner pressure drop

Reference: Start-Up - Direct Gas, Check the

Optional High and Low Pressure Switches, pg. 15

No

Adjust the low fire setting.

Reference: Start-Up - Direct Gas,

Set the Minimum Firing Rate, pg. 17

No

Correct gas pressure.

Reference: Start-Up - Direct Gas,

Check the Supply Gas Pressure, pg. 15

Yes

Purge gas line.

Pressure drop across the burner

between 0.625 and 0.675 in. WC?

Yes

Proper spark?

Yes

No

No

Adjust burner baffles.

Reference: Start-Up - Direct Gas,

Check the Optional High and Low Gas Pressure Switches, pg. 15

Crossed flame and spark wires.

Uncross wires and reconnect.

Incorrect spark plug gap.

Set spark plug gap to 0.062 in.

Defective spark plug.

Replace spark plug.

With proper airflow, gas pressure and spark,

the unit should light.

If problems remain, consult the factory.

Model VSU Make-Up Air

30

®

Maintenance - Routine

MOTOR

FAN

MOTOR

CAUTION

Lock-out the gas and the electrical power to the
unit before performing any maintenance or service
operations to this unit.

V-Belt Drives

V-belt drives must be checked on a regular basis for
wear, tension, alignment, and dirt accumulation.

Check the tension by measuring the deflection in the
belt as shown below.

Check the alignment by using a straight edge across
both sheaves as shown below.

IMPORTANT

Premature or frequent belt failures can be caused by
improper belt tension or misaligned sheaves.

• Abnormally high belt tension or drive misalignment

will cause excessive bearing loads and may result in
failure of the fan and/or motor bearings.

• Abnormally low belt tension will cause squealing on
start-up, excessive belt flutter, slippage, and
overheated sheaves.

IMPORTANT

Do not pry belts on or off the sheave. Loosen belt
tension until belts can be removed by simply lifting the
belts off the sheaves.

IMPORTANT

When replacing V-belts on multiple groove drives,
all belts should be changed to provide uniform drive
loading.

IMPORTANT

Do not install new belts on worn sheaves. If the
sheaves have grooves worn in them, they must be
replaced before new belts are installed.

Deflection =

Belt Span

64

Motors

Motor maintenance is generally limited to cleaning and
lubrication (where applicable).

Cleaning should be limited to exterior surfaces only.
Removing dust and grease build-up on the motor
assures proper motor cooling.

Motors supplied with grease fittings should be
greased in accordance with the manufacturer’s
recommendations.

IMPORTANT

Do not allow water or solvents to enter the motor
or bearings. Motors and bearings should never be
sprayed with steam, water or solvents.

IMPORTANT

Greasing motors is only intended when fittings are
provided. Many motors are permanently lubricated,
requiring no additional lubrication.

Wheels

Wheels require little attention when moving clean air.
Occasionally oil and dust may accumulate on the wheel
causing imbalance. When this occurs the wheel and
housing should be cleaned to assure proper operation.

Filters

Filter maintenance is generally limited to cleaning and
replacement.

Aluminum mesh filters can be washed in warm soapy
water.

An adhesive spray can be added to aluminum mesh
filters to increase their efficiency.

IMPORTANT

When reinstalling filters, be sure to install them with
the airflow in the correct direction. An airflow direction
arrow is located on the side of the filters.

IMPORTANT

Replacement filters should be from the same
manufacturer and the same size as the original filters
provided with the unit.

Belt Span

Belt Tension

®

Drive Alignment

Model VSU Make-Up Air

31

Bearings

The bearings for the fans are carefully selected to
match the maximum load and operating conditions
of the specific class, arrangement and fan size. The
instructions provided in this manual and those provided
by the bearing manufacturer will minimize any bearing
problems.

IMPORTANT

Lubricate bearings prior to periods of extended
shutdowns or storage and rotate shaft monthly to aid
in corrosion prevention. If the fan is stored more than
three months, purge the bearings with new grease
prior to start-up.

Recommended Bearing Lubrication Schedule (in Months*)

Fan

1

RPM

⁄2 - 1 11⁄8 - 11⁄2 15⁄8 - 17⁄8 115⁄16 - 23⁄16 27⁄16 - 3

750 6 5 4 3 3

*Suggested initial greasing interval is based on 12 hour per

day operation and 150°F maximum housing temperature.
For continuous (24 hour) operation, decrease greasing
interval by 50%

• If extended grease lines are present, relubricate while in

operation, only without endangering personnel.

• For ball bearings (operating) relubricate until clean grease is

seen purging at the seals. Be sure not to unseat the seal by
over lubricating.

• For ball bearings (idle) add 1-2 shots of grease up to 2in.

bore size, and 4-5 shots above 2 in. bore sizes with a hand
grease gun.

• For roller bearings add 4 shots of grease up to 2 in. bore

size, and 8 shots for 2-5 in. bore size with a hand grease
gun.

• Adjust re lubrication frequency based on condition of

purged grease.

• A high quality lithium based grease conforming to NLGI

Grade 2 consistency, such as those listed here:

Mobil 532
Mobilux #2

Bearing Bore Size (inches)

Texaco Multifak #2
Texaco Premium #2

B Shell Alavania #2
Exxon Unirex #2

Maintenance - Fall

Start-Up

Repeat the information as outlined in:

• Start-Up - Blower (page 14)

- Air Volume Measurement and Check

• Start-Up - Direct Gas (pages 15 and 16)

- Check the Supply Gas Pressure

- Check the Pilot Gas Pressure

- Check the Optional High and Low Gas Pressure
Switches

- Set the Burner Air Pressure Differential

This will ensure that the gas and air are set properly
before the heating season begins and should lead to
trouble free operation all winter.

High Limit

The high limit switch may have tripped over the
summer; it should be checked and reset if necessary.

Burner

Inspect the burner for accumulation of scales on both
the upstream and downstream sides of the mixing
plates. Any scaling or foreign material should be
removed with a wire brush.

Visually check that all holes in the mixing plates are
clear. If any burner ports are plugged (even partially),
clear them with a piece of wire or another appropriate
tool.

Replace or tighten any loose or missing fasteners on the
mixing plates. Always use zinc-plated or stainless steel
fasteners.

Inspect and clean the flame and spark rod. Occasional
replacement of the flame rod and spark rod may be
necessary to ensure optimum unit performance.

WARNING

Do not enlarge burner ports when clearing a blockage,
performance could be affected.

NOTE

Flame rods can last many years, but because of
thermal expansion of the porcelain, flame rods can fail
over time.

Model VSU Make-Up Air

32

Gas Train

The gas connections, joints and valves should be
checked annually for tightness. Apply a soap and water
solution to all piping; watch for bubbling which indicates
a leak. Other leak testing methods can be used.

®

Reference

Typical Gas Train Layout with Modulating Valve (Pilot Ignition)

Burner Differential

Pressure Sensor

High Gas

Pressure Switch

(optional)

Burner Gas

Pressure
Test Port

Modulating

Burner Manual

Shut-Off Valve

Pilot Gas Pressure

Test Port

Valve

Safety Shut-Off

Valves

Pilot

Solenoid

Low Gas

Pressure Switch

(optional)

Regulator

Typical Gas Train Layout with Modulating Regulator (Pilot Ignition)

Pilot

Regulator

Manual Pilot

Shut-Off Valve

Pilot

Solenoid

Burner Differential

Pressure Sensor

Modulating/Regulator

High Gas

Pressure Switch

(optional)

Burner Gas

Pressure
Test Port

®

Burner Manual

Shut-Off Valve

Pilot Gas Pressure

Valve

Test Port

Low Gas

Pressure Switch

(optional)

Safety Shut-Off

Valves

Pilot

Regulator

Manual Pilot

Shut-Off Valve

Model VSU Make-Up Air

33

Reference

Typical Gas Train Layout with Direct Spark Ignition

This is a typical gas train. The gas train in your unit may be different.

Burner Differential

Pressure Sensor

(Airflow Switch)

To Burner

High Gas

Pressure

Switch

(Optional)

Burner Manual
Shut-Off Valve

High Gas

Pressure
Test Port

Modulating

Valve

Combination

Shut-Off Valve/

Regulator

Low Gas

Pressure Switch

(Optional)

Low Gas

Pressure

Test Port

Gas

Connection

Model VSU Make-Up Air

34

®

Reference

Control Center Layout

13 22

1914

18

17

20

21

1. Supply Motor Starter — 24 volt magnetic
contacts for starting supply motor.

2. Supply Overload — provides electronic overload
protection to supply motor.

3. Low Voltage Transformer — provides low
voltage to fan/heat/cooling enable controls.

4. Control Terminal Block — provides wiring
access to controls.

5. Fan Relay — allows power to pass to energize
motor starter.

6. High Voltage Enclosure — provides protection
from high voltage circuits.

7. Auxiliary Contact (optional) — provides one
normally closed and one normally open contact for
other equipment.

8. Exhaust Motor Starter (optional) — 24 volt
magnetic contacts for starting exhaust motor.

9. Exhaust Overload (optional) — provides
electronic overload protection to exhaust motor.

10. Transformer Fuse (optional) — provides proper
fusing for cooling transformer.

11. Terminal Block — provides wiring access to high
voltage circuits.

12. Exhaust Fuses (optional) — provides proper
fusing for exhaust fan motor(s).

13. Dirty Filter Switch (optional) — monitors filter
pressure drop, turns on indicating light when
pressure drop is above field adjustable set point.

14. Inlet Air Sensor (optional) — outdoor air stat
that automatically controls the heating and/or
cooling based on outdoor air temperature.

15. Remote Temperature Selector (optional) —
allows for remote temperature set point.

16. Heat Relay — allows power to pass to heating
controls.

17. Heating Terminal Block — provides wiring
access to heating controls.

24

26 28

15

25

27

10

11

3

4

23

16

5

6

12

1 78

29

18. Flame Safeguard/Spark Generator (Direct
Spark) — monitors flame, shuts down unit when

unsafe conditions are detected.

19. High Limit — prevents unit from discharging air
above a set point.

20. Low Voltage Transformer — reduces voltage to
Maxitrol system.

21. Amplifier — controls modulating valve, assures
the desired temperature is delivered.

22. Transformer (optional) — provides voltage to
optional evaporative cooling pump.

23. Cooling Relay (optional) — allows power to
pass to cooling controls.

24. Cooling Terminal Block (optional) — provides
wiring access to cooling controls.

25. Low Voltage Transformer (optional) — reduces
voltage to cooling controls.

26. Reset Timer (optional) — resets cooling system
to run a time interval.

27. Auto Drain Relay (optional) — assures supply
pump does not operate during drain interval.
Allows pump to operate in cooling mode.

28. Cooling Timer (optional) — allows for automatic
draining of the evaporative cooling system based
on time schedule.

Dirty Filter Switch

Common

Normally Open

Normally Closed

CCW to Decrease Trip Point
CW to Increase Trip Point

Negative Pressure

after the filters

Positive Pressure

before the filters

®

Model VSU Make-Up Air

35

Maintenance Log

Date ___________________Time _____________ AM/PM

Notes: ___________________________________________

_________________________________________________

_________________________________________________

_________________________________________________

_________________________________________________

Date ___________________Time _____________ AM/PM

Notes: ___________________________________________

_________________________________________________

_________________________________________________

_________________________________________________

_________________________________________________

Date ___________________Time _____________ AM/PM

Notes: ___________________________________________

_________________________________________________

_________________________________________________

_________________________________________________

_________________________________________________

Date ___________________Time _____________ AM/PM

Notes: ___________________________________________

_________________________________________________

_________________________________________________

_________________________________________________

_________________________________________________

Date ___________________Time _____________ AM/PM

Notes: ___________________________________________

_________________________________________________

_________________________________________________

_________________________________________________

_________________________________________________

Date ___________________Time _____________ AM/PM

Notes: ___________________________________________

_________________________________________________

_________________________________________________

_________________________________________________

_________________________________________________

Warranty

Greenheck warrants this equipment to be free from defects in material and workmanship for a period of one year from the
shipment 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.

Greenheck’s Model VSU catalog provides additional
information describing the equipment, fan performance,
available accessories, and specification data.

®

Phone: [phone] • Fax: [phone] • E-mail: [e-mail] • Web site: www.greenheck.com

470654 • Model VSU IOM, Rev. 1, March 2012 Copyright 2012 © Greenheck Fan Corporation

36

AMCA Publication 410-96, Safety Practices for Users and
Installers of Industrial and Commercial Fans, provides
additional safety information. This publication can be obtained
from AMCA International, Inc. at: www.amca.org.