Nortek VENMARCES VHC-36 Manual

VHC
Energy Recovery Ventilators with Enthalpy Wheels and
Integrated Heating and Cooling
Installation, Operation and Maintenance Instructions Manual
Capacity: 800 to 5,500 cfm
Model: VHC-36, VHC-42, VHC-50
IMPORTANT
The use of this appendix is specifically intended for a
qualified installation and service agency. A qualified in-
stallation and service agency must perform all installation
and service of these appliances.
FOR YOUR SAFETY
What to do if you smell gas:
1. Open windows if appliance is indoors.
2. Do not touch electrical switches or use any phone
in the building.
3. Extinguish any open flame.
4. Leave the building immediately.
5. Immediately call Gas Supplier.
WARNING
Improper installation, adjustment, alteration, service or
maintenance can cause injury or death. Read the instal-
lation, operation and maintenance instructions thor-
oughly before installing or servicing this equipment.

Table of Contents
Nomenclature.......................................................................................................................................................................3
Safety Considerations ..........................................................................................................................................................4
General Information..............................................................................................................................................................4
Recommended Spare Parts...........................................................................................................................................4
Inspection on Arrival.......................................................................................................................................................5
Unit Application Limitations ...........................................................................................................................................5
Installation ............................................................................................................................................................................5
Unit Location Requirements...........................................................................................................................................5
Roofcurbs Supplied by Venmar CES (External Applications Only) ................................................................................6
Roofcurbs Supplied by Others.......................................................................................................................................6
Rigging and Lifting the Unit............................................................................................................................................7
Exhaust Dampers ...........................................................................................................................................................7
Field Fabricated Ductwork .............................................................................................................................................8
Hood Installation ............................................................................................................................................................9
Access Panels ................................................................................................................................................................9
Internal Packaging..........................................................................................................................................................9
Electrical Connections..................................................................................................................................................10
Coil or Water Source Heat Pump (WSHP) Piping Connections ...................................................................................12
Condensate Drain Trap ................................................................................................................................................13
Refrigeration Systems ..................................................................................................................................................13
Start-up ..............................................................................................................................................................................14
Pre Start-up Procedure ................................................................................................................................................14
Start-up Procedure.......................................................................................................................................................15
Optional Controls and Accessory Sequence and Interlocks .......................................................................................16
Frost Control ................................................................................................................................................................17
Airflow Balancing..........................................................................................................................................................18
Maintenance.......................................................................................................................................................................19
Air Filters ......................................................................................................................................................................19
Interior of Unit...............................................................................................................................................................19
Fans..............................................................................................................................................................................20
Enthalpy Wheel.............................................................................................................................................................22
Testing and Replacement of the Damper Actuator......................................................................................................23
Coils .............................................................................................................................................................................24
Refrigerant Systems.....................................................................................................................................................24
System Operation Check .............................................................................................................................................25
Appendix A: Service Clearance Dimensions......................................................................................................................26
Appendix B: Hood Installation............................................................................................................................................34
Appendix C: Rigging Drawing ............................................................................................................................................35
Appendix D: Equipment Data.............................................................................................................................................36
Appendix E: Effect of Undersized Straight Duct and Elbows on Forward Curved Fans....................................................37
Appendix F: Electrical Data ................................................................................................................................................38
Appendix G: Standard Field Wiring Terminals ...................................................................................................................42
Appendix H: Terminal Control Diagrams............................................................................................................................44
Appendix I: Water Source Heat Pump Water Line Piping Requirements and Field Mounted Options and Accessories ..48
Appendix J: VHC-36, -42 and -50 Start-up Form and Checklist .......................................................................................57
Appendix K: Gas-fired Furnace Module Installation and Maintenance..............................................................................63
Appendix L: Electric Heating Coil and Controls Information..............................................................................................79
Appendix M: Enthalpy Wheel Pressure Drop vs. Flow Formulae and Curves ...................................................................81
Appendix N: Troubleshooting.............................................................................................................................................82
Appendix O: VHC-36, -42 and -50 Maintenance Summary Chart.....................................................................................84
Appendix P: Forward Curved Fan Bearing Relubrication Schedule ..................................................................................86
Appendix Q: How to Measure, Assemble and Install Link Belt..........................................................................................87
Appendix R: Adjusting Refrigerant Charge ........................................................................................................................89
Appendix S: Temperature Rise Over Gas-fired Furnace....................................................................................................91
VCES-VHC-IOM-1F – VHC-36, -42 & -50 2

Nomenclature
©Nortek Air Solutions Canada Inc. 2004. All rights reserved throughout the world.
Illustrations cover the general appearance of Venmar CES products at the time of publication and Venmar CES reserves the
right to make changes in design and construction at any time without notice.
™® The following are trademarks or registered trademarks of their respective companies: Venmar Select from Nortek Air
Solutions, Variable Refrigerant Control (VRC) from Nortek Air Solutions and Tefzel from DuPont.
Nortek Air Solutions, LLC d/b/a Venmar CES furnishes equipment pursuant to its then-current Terms and Conditions of Sale
and Limited Warranty, copies of which can be found under the Terms & Conditions of Sale and Warranty link at
www.nortekair.com. Extended warranties, if any, shall be as offered and acknowledged in writing by Venmar CES.
VHC-XX
V
entilator with
heating and
cooling
Nominal wheel
diameter
– 36
– 42
– 50
VCES-VHC-IOM-1F – VHC-36, -42 & -50 3

Safety Considerations
Warning, Caution and Important notes appear through-
out this manual in specific and appropriate locations to
alert Installing Contractors and maintenance or service
personnel of potential safety hazards, possible equipment
damage or to alert personnel of special procedures or in-
structions that must be followed as outlined below.
Hazards may exist within this equipment because it con-
tains electrical and numerous moving components. Only
qualified service personnel should install or service this
equipment. Untrained personnel may perform basic main-
tenance such as maintaining filters. Observe precautions
marked in literature and on labels attached to the unit. Fol-
low all safety codes.
General Information
This manual is designed to provide general information on
the common operation of all standard and optional com-
ponents that may have been installed in the unit. Note that
some sections of this manual may not apply to your unit.
This manual has been designed for general purpose and
describes all options offered by Venmar CES that could
be included in the unit. Consult the manual from the Com-
ponent Manufacturer if more detailed technical information
about a specific component is required.
All documentation that was specifically designed for your
unit has been included in the pocket of the control panel,
including (if applicable):
• Electrical schematics
• VHC-36, -42 and -50 DDC Controls Package Manual
Recommended Spare Parts
Spare parts should be ordered at the time the installation
is accepted by the Owner. Spare parts will reduce the
down time in the event of a failure.
The list of spare parts outlined below is considered mini-
mal. Installation in remote locations or when the operation
of heating equipment is essential may require more spare
parts than listed. Please contact the Service Department
at Venmar CES for recommendations.
Minimum spare parts include:
• Two sets of fuses
• One matching set of fan belts
• One set of filters
• One burner control relay module, flame signal ampli-
fier and purge card (optional)
• One flame sensor (optional)
• One spark igniter (optional)
CAUTION
Identifies an instruction which, if not followed, might se-
verely damage the unit, its components, the assembly or
final installation.
IMPORTANT
Indicates supplementary information needed to fully
complete an instruction or installation.
WARNING
Identifies an instruction which, if not followed, might cause
serious personal injuries including possibility of death.
WARNING
Disconnect the main power switch to the unit before
performing service or maintenance. Electric shock can
cause personal injury or death.
VCES-VHC-IOM-1F – VHC-36, -42 & -50 4

Inspection on Arrival
Inspect the equipment exterior and interior for any dam-
age on arrival that may have occurred during unit ship-
ment and for shipped loose parts. Ensure that there is
no damage to any protruding exterior components such
as door handles, disconnect switch handle, etc., or to
internal components such as fans, motors, dampers, en-
thalpy wheel and structures. File a claim with the shipping
company if the unit is damaged. Check the packing slip
against all items received. If any items are missing, sign
the carrier’s bill of lading with the notation “Shipment Re-
ceived Less Item #___”. Contact the factory immediately
if damage is found. No return shipment will be accepted
without authorization.
Installation
Unit Location Requirements
Consult local building codes and electrical codes for spe-
cial installation requirements and note additional require-
ments listed in this manual. In choosing the installation
location of the unit, consider the following factors:
• The unit should be installed to allow easy access for
maintenance and for systems operation. See the ser-
vice clearance dimensions in Appendix A.
• When possible, mount the unit over an unused area
such as a hallway. Although fans and motors are
mounted on vibration isolators or are dynamically
balanced, the unit will be even less perceptible if po-
sitioned away from busy offices.
• Locate the unit in an area requiring the least amount
of ductwork and direction changes to allow optimum
performance, to reduce pressure loss and to use
less electricity to achieve proper ventilation. Duct-
work must be in accordance with ducting mechani-
cal rules to prevent sound issues and system effects.
• The fresh air intake hood must be positioned away
from sources of contamination such as hot chimneys
or kitchen exhaust vents.
• Fresh air intake must also be positioned in a direction
opposite to that of prevailing winds to reduce entry
of snow or rain.
• The unit should be mounted on a level foundation to
allow condensation to flow into internal drains. The
foundation must provide adequate continuous sup-
port to minimize deflection of the unit base frame to
not more than 1/16” [1.6 mm] over entire length. In
addition to these recommendations, a Structural En-
gineer must be involved to properly size supporting
structural elements.
• When mounting the unit indoors, if drain connections
are required, mount the unit on a housekeeping pad
of sufficient height to allow for drain trap height and
condensate lines to slope toward the building drain.
• When mounting the unit on a roofcurb check the
height from the finished roof to the bottom of the
intake hood. Consult with Local Authorities or your
building code for minimal intake hood height for the
water-tight height from and above the finished roof
and, in snow prone areas the buildup of snow, to
determine the height of the roofcurb. Venmar CES
optional roofcurbs measure 18” [457 mm] in height.
If additional height is required from the finished roof
to the top of the roofcurb, to the bottom of the intake
hood or if other than level, custom height roofcurbs
must be ordered.
Unit Application Limitations
Using Venmar CES units for temporary ventilation dur-
ing construction is subject to the unit warranty terms and
should be reviewed carefully before proceeding, as this
may void the standard warranty conditions.
Fine dust, larger particulate matter, solvents, varnishes
and other chemicals may cause filter clogging and el-
evated cabinet pressures, higher power consumption and
possible irreparable damage to the desiccant material of
the enthalpy wheel, which could reduce energy recovery
performance of the wheel and also reduce the heat trans-
fer effectiveness of other components. Potential damages
include, but are not limited to, these examples.
IMPORTANT
The hoods for these units are not installed from the fac-
tory for shipping purposes and must be installed on site.
They should be installed after the unit is installed. Hoods
are shipped on top of the unit. See Rigging and Lifting
the Unit section.
WARNING
Venmar CES equipment is not designed to be used for
temporary heating, cooling and/or ventilation during
construction.
VCES-VHC-IOM-1F – VHC-36, -42 & -50 5

Roofcurbs Supplied by Venmar CES (External Applications Only)
Roofcurbs supplied by Venmar CES should be mounted
as follows:
• The roofcurb is shipped knocked-down with assem-
bly hardware and instructions provided. The roofcurb
must be field erected, assembled and set in place by
the Installing Contractor.
• Roofcurb dimensions are submitted with the unit
mechanical drawings which can also be found in the
unit control panel pocket or by calling Technical Sup-
port personnel from the Venmar CES factory.
• After the roofcurb has been assembled, ensure that
the roofcurb dimensions suit the unit for which it is
designated.
• The cross members must be positioned as per
the roofcurb drawing. Field supply and install addi-
tional cross members completing the perimeter and
matching the unit opening dimensions to properly
support the ductwork plenums for bottom vertical
return and supply connections and for stability.
• Ensure that the assembled roofcurb is square, plumb
and level to within 1/16” [1.6 mm] over the entire
length. The building structure must provide continu-
ous structural support to the full perimeter of the
roofcurb and all cross members requiring support.
The roofcurb may be shimmed as required to pro-
vide continuous support.
• The roofcurb must be fastened to the building structure.
• The Installing Contractor is responsible for making the
roofcurb water-tight by caulking all roofcurb joints.
Roofcurbs Supplied by Others
Roofcurbs supplied by others must be designed with the
same dimensions and cross member arrangement as per
Venmar CES roofcurb drawings and must be designed to
evenly withstand perimeter and cross section static loads.
IMPORTANT
Venmar CES is not liable for any damages, costs or other
issues arising from roofcurbs supplied by others.
IMPORTANT
The following items must be completed prior to setting
the unit on the roofcurb:
• The roofcurb roofing must be completed including
insulation, cant strip, flashing and counter-flashing.
• Vertical ductwork must be attached to the roofcurb
cross members and building structure, not to the
unit. See the mechanical drawings for information
on roofcurb installation, recommended ductwork
attachment and dimensions.
• If there is no building roof access underneath the
unit and drain or piping connections must be made
(in the roofing), it is recommended to do so before
unit installation using the appropriate materials pro-
vided by the Installing Contractor.
• Remove the length of 3/8” x 1½” [9.5 x 38 mm]
polyvinyl gasket strip with adhesive backing sup-
plied with the unit and apply a continuous strip to
the top perimeter of the roofcurb and duct opening
connections for an air- and water-tight seal.
IMPORTANT
The gasket between the unit and the roofcurb is critical
for an air- and water-tight seal. An improperly applied
gasket can result in air and water leakage and poor unit
performance. Position the unit with equal spacing all
around between the roofcurb and inside unit base rail
using ½” [13 mm] wood shims as it is being lowered.
VCES-VHC-IOM-1F – VHC-36, -42 & -50 6

Rigging and Lifting the Unit
Unit shall be lifted by cables attached to all the lifting
points provided on the unit base. When lifting the unit
use spreader bars and cables to prevent damage to the
unit casing. Provide additional blocking and coverings
(as required) to prevent damage to the unit finish and/or
components. The spreader bars will help to maintain a
certain distance between the cables and the unit. Venmar
CES will not be responsible for any damage caused to
the unit casing during the lifting process. The lifting point
must be at the center of gravity to ensure that the unit is
level during hoisting and prior to setting. When commenc-
ing to hoist, take up the slack in the hoisting cables slowly
and gradually increase the cable tension until the full unit
weight is suspended. Avoid sudden, jerking movements.
Do not permit the unit to be suspended by the lifting lugs
for an extended period of time. Lifting holes are provided
in the base rails as shown in Appendix C. Refer to submit-
tal documents for overall unit dimensions and Appendix D
for unit weights.
Exhaust Dampers
Exhaust dampers are optional, but must be included with
the recirculation defrost option when selected in Venmar
Select™ Web Edition. A gravity backdraft damper or mo-
torized damper is available as an option for the exhaust
discharge.
On indoor units, exhaust dampers are shipped loose
with the units for field installation. On outdoor units with
end exhaust air discharge (complete with hood) or side
exhaust air discharge (complete with hood), the exhaust
dampers are factory mounted inside the hoods and
shipped loose with the units for field installation. If outdoor
units have exhaust air discharge (ducted) and include
an exhaust damper, it will be included with the unit and
shipped loose for field installation. See Table 1 for exhaust
damper dimensions.
The gravity backdraft dampers are for horizontal airflow
installations only, are non-insulated, for installed in duct
installation and are ¼” [6 mm] smaller ‘outside of frame’
than the duct size listed.
The motorized dampers are for flanged to duct installation
and are the same size as the duct size listed ‘inside of the
damper frame’. The damper frame is 2” [51 mm] larger
outside than the dimensions listed, is non-insulated with
the damper actuator mounted outside of the frame on the
drive pin and with the linkage mounted outside the frame
on the opposite side. There is no specific air entering or
leaving side. Access to both sides of the damper frame
must be provided.
The damper should be mounted sufficiently far enough
downstream from the exhaust fan discharge to avoid
system effect added pressure losses. A straight length
of duct same size as the unit exhaust discharge and
length as indicated in Field Fabricated Ductwork fol-
lowed by a gradual transition to ‘duct size’ for damper is
recommended.
Motorized dampers are available with insulated or non-
insulated opposed blades; damper actuators are 24 VAC,
available in power open/spring return, power open/power
closed or modulating designs. See submittals for the type
of damper and actuator supplied.
A 24V wiring harness is factory provided on the actuator
and a matching wiring harness with spade connectors is
factory provided on the unit when ordered with the unit for
field connection. Length of wiring harness is approximately
48” [1,219 mm] total. Any additional length required must
be field provided.
IMPORTANT
The hoods for these units are not installed from the
factory and must be installed on site. They should be
installed after the unit is installed. Hoods are shipped
on top of the unit. When rigging the unit, make sure
the hoods are secured and are not damaged by the
spreader bars. See Appendix B for hood installation.
CAUTION
All panels must be in place when rigging.
Table 1: VHC-36, -42 and -50 Exhaust Dampers Duct
Dimensions
Model Duct Size (H x W) Damper Type
VHC-36 18” x 18”
[457.2 x 457.2 mm]
Backdraft (pressure open/
gravity closed)
Motorized
VHC-42 21” x 21”
[538.4 x 538.4 mm]
Backdraft (pressure open/
gravity closed)
Motorized
VHC-50 26” x 26”
[660.4 x 660.4 mm]
Backdraft (pressure open/
gravity closed)
Motorized
VCES-VHC-IOM-1F – VHC-36, -42 & -50 7

Field Fabricated Ductwork
On bottom vertical duct connections, secure all ducts to
the roofcurb and building structure prior to unit installation.
See Roofcurbs Supplied by Venmar CES (External Applica-
tions Only). Do not secure ductwork to the unit.
On other duct connections, make connections to the
casing by applying caulking around the connection and
screwing flanged ducts directly to the casing and/or flange
with self-drilling sheet metal screws. It is important to seal
all duct connections to prevent air leakage and system
performance problems. Ductwork must be supported by
the building structure.
For unit and duct opening sizes see submittal drawings.
Insulate and weatherproof all external ductwork, joints and
roof openings with counter-flashing and mastic in accor-
dance with applicable codes. Ductwork running through
roof decks must comply with local fire codes. Ducts pass-
ing through unconditioned spaces must be insulated and
covered with a vapor barrier. Flexible connectors should
be installed close to the unit in the duct leading to occu-
pied spaces to minimize noise transmission.
Duct Design Considerations
The discharge ductwork immediately downstream from
the double width double inlet fan (excluding units with gas
furnace or plenum fan options) is critical for successful
applications. Poorly designed ductwork can degrade fan
performance and contributes to excessive pressure drop
and noise.
When designing ductwork in the field, it is important to
use a straight discharge duct of the correct dimensions to
obtain maximum fan performance. The straight section of
ductwork helps the airflow to develop a uniform velocity
profile as it exits the fan and allows the velocity pressure
to recover into static pressure. See Figure 1.
For 100% recovery of velocity pressure into static pres-
sure, the straight portion of the discharge duct must be at
least 2.5 times the ‘equivalent duct diameter’ of the rect-
angular duct connection up to 2,500 fpm outlet velocity
or less. Add one duct diameter for each additional 1,000
fpm outlet velocity to the length of the straight portion of
discharge duct. The equivalent duct diameter is equal to
square root of (4ab/Pi) where ‘a’ and ‘b’ are the rectangu-
lar dimensions of the fan discharge opening.
Refer to Appendix E to determine the effect of undersized
straight sections of duct with or without duct elbows
within the 100% minimum effective duct length (reference
AMCA publication 201, Fans and Systems).
Example:
For a VHC-50 with a supply flow rate of 5,500 cfm with a
bottom supply fan discharge connection with rectangular
connection (from submittal documents) of ‘a’ = 17.4” and
‘b’ = 18.8” the length of straight duct is 24” before enter-
ing a 90 degree elbow is reached in position A as shown
in Appendix E, Figure E1:
• The equivalent duct diameter is equal to square root
of (4 x 17.4 x 18.8/Pi) = 20.41”
• The outlet velocity is equal to
5,500 cfm/(17.4 x 18.8/144) = 2,421 fpm
• Therefore, the minimum length of straight duct for
100% effective recovery needed would be equal to
20.41 x 2.5 = 52” rounded up to the next whole inch
• The effective straight duct was 24” long or
24/52 x 100 = 46% effective
• Using Table E1, with elbow position A and 46% ef-
fective duct length, would be using a curve value,
(50−46)/(50−25) = 0.16 of the way between the ‘U’
curve at 50% and ‘R–S’ curve at 25% for SWSI fans
• All VHC units with forward curved fans are DWDI,
therefore following note ‘C’ below Figure E2 would
use a 1.0 multiplier for the DWDI fans on the pres-
sure drop curves in Figure E2
• From Figure E2, at 2,421 fpm and
1.0 x (0.16 x ((P−Q)−S)+S) curve values added pres-
sure drop is 1.0 x (0.16 x (0.38−0.15)+0.15) = 0.19”
w.c. which must be added to the external pressure
drop for the unit
The minimum straight duct length on the discharge of the
fan for 100% recovery of velocity pressure into static pres-
sure at maximum cfm for the different models are in Table 2.
Table 2: Length of Straight Duct on Fan Discharge for
100% Recovery
Model Max CFM Minimum Straight Duct Length
Supply Exhaust
VHC-36 2,500 42” [1,066.8 mm] 42” [1,066.8 mm]
VHC-42 3,500 52” [1,320.8 mm] 52” [1,320.8 mm]
VHC-50 5,500 52” [1,320.8 mm] 62” [1,574.8 mm]
Centrifugal fan Cutoff Discharge duct
100% effective duct length
2½ diameters at 2,500 FPM
Figure 1: Duct design
VCES-VHC-IOM-1F – VHC-36, -42 & -50 8

Internal Packaging
Open access doors or panels and remove all packaging
from the unit. Note that there is packaging for wheel sup-
port during shipping. Removal of all packaging is critical.
Hood Installation
Intake and exhaust hoods for these models are shipped
separately from the unit. To install hoods see Appendix
B. A quick connect for the damper motors is provided to
connect to the main body of the unit. Make sure that all
screws are secured to maintain proper support and keep
seals water-tight.
Access Panels
Handles for lift off exterior access panels with screw door
fasteners are provided but must be installed on site. Han-
dles and fasteners are secured inside the unit.
IMPORTANT
Securing door fasteners too tightly has negative effects
on the door gasket and should be avoided.
VCES-VHC-IOM-1F – VHC-36, -42 & -50 9

Electrical Connections
Power Supply
The unit is factory wired (unless otherwise specified) ex-
cept for power connections, shipped loose sensors/items
or remote control options as indicated in the electrical
schematics. The unit may or may not have an optional
factory installed door interlocking disconnect in the unit
control panel. If the unit control panel disconnect is not
supplied, the Electrical Contractor must provide and install
a disconnect outside the unit as per local electrical codes
and run single-point power supply wiring to the control
panel.
Should the unit have optional electric pre-heating coil and/
or electric post-heating coil with kW rating in excess of
24 kW for 208/3/60V, 27 kW for 230/3/60V, 67 kW for
460/3/60V or 84 kW for 575/3/60V, the Electrical Con-
tractor must also provide and run a separate two-point
power supply wiring to the electric heater circuit breaker
located in the unit control panel.
• Units are available in all voltages and phases. Please
see Appendix F for electrical data.
• Check nameplate for correct power supply require-
ments.
• See electrical schematics located in the control panel
pocket for field wiring of power connections, shipped
loose sensors/items and remote control interlocks.
The Electrical Contractor must locate, install and wire
sensors/items as per electrical schematics.
• Numbered terminal strips are included in the control
panel for ease of connection and service.
• Install copper wiring of proper size to handle current
load.
All field wiring must comply with NEC and local require-
ments. In Canada, electrical connections must be in ac-
cordance with CSA C22.1 Canadian Electrical Code Part
One.
Field Connection
For single-point or two-point power connections, high
voltage connection holes are located on the outside of the
unit with knockout; see submittal drawings for location.
A field installed disconnect switch must use a liquid-tight
connector between the disconnect switch and the outside
panel of the unit eliminating any water penetration into the
control box.
A low voltage field wiring (FW) interface is provided near
the control panel (PNL) terminals for shipped loose or field
supplied controls, sensors or interlock connections. The
location of the field wiring and panel terminals may vary
depending upon options selected as illustrated in Figure 2.
The low voltage field wiring entry is made through the side
of the unit below the input power supply connection (see
Appendix G) which runs through the outside casing and
requires a liquid-tight connector or conduit to avoid water
penetration.
Should the Electrical Contractor decide to run the power
feed cable through the roofcurb, he/she must determine
location, routing, drill necessary holes (avoid drilling holes
through drain pan) and seal after completion. Remote
control wiring can be located next to the power feed cable
provided it is inserted in a shielded cable that will protect
it from electro-mechanical interference. Ensure the power
feed cable ground is securely connected to the terminals
located in the control panel.
Electrical Contractor must provide wiring for controls that
are supplied optionally and shipped loose or field sup-
plied. All field supplied low voltage wiring must be Class
2. Mark the field wiring terminals schematic (Appendix G)
with the connections completed and leave with the unit for
start-up and service.
Units will require a start contact interlock from a remote
time clock, light sensor, occupancy sensor, manual selec-
tor switch or remotely through BACnet from a building
management system (BMS) depending on ventilation con-
trol scheduling mode required. Select required interlock
and ventilation control scheduling mode from description
below.
See Appendix G and Appendix H for wiring terminal con-
trol diagram examples and standard field wiring terminal
and interlock connections available.
Units Supplied with DDC Control Package
The DDC control package enables stand alone opera-
tion of the VHC unit and includes a factory installed,
programmed and run tested stand alone microprocessor
based controller, all necessary sensors and interfaces to
provide control of optional post conditioning functions.
See the VHC-36, -42 and -50 DDC Control Package
Manual (VCES-DDC-IOM-1 (500020459)) for overview,
installation and start-up.
An intelligent programmable interface device (BacStat II)
with built-in room sensor is included for communication,
display, setpoint control and to allow for servicing, and is
shipped loose for field wiring and installation at the unit or
remotely. Determine required location for installation and
WARNING
When installed, the unit must be electrically grounded in
accordance with local codes or, in the absence of local
codes, with the National Electrical Code, ANSI/NFPA 70,
and/or the Canadian Electrical Code CSA C22.1. Unit
cabinet must have an uninterrupted, unbroken electrical
ground to minimize the possibility of personal injury if an
electrical fault should occur. Failure to follow this warning
could result in the Installer being liable for personal injury
of others.
VCES-VHC-IOM-1F – VHC-36, -42 & -50 10

connect using two twisted pair cables, the first for power
connection. The LinkNet cable needs to be balanced 100
to 120 ohm nominal impedance twisted shielded pair
cable, nominal capacitance of 16 PF/FT or lower.
Units Supplied with an Electro-mechanical
Controls (EMC) Package
The EMC controls package or dry contact control op-
tion includes: all relays, motor starters, motor overloads,
damper actuators, heating and cooling initiate contacts
and selected option pickup points. All necessary con-
nections are wired to a terminal strip in the control panel
for field wiring connections to a building management
system, for field supplied DDC or standard controls and
thermostats. See the Control Contractor’s flow and wiring
schematics for connection details.
Ventilation Control Scheduling Modes
Occupied Ventilation (Ov)
If the occupancy contact closes or a jumper is placed
across terminals FW 304–305 this will enable the unit to
run in 100% fresh air mode. Free cooling and defrost will
initiate based on the setpoint.
Unoccupied Recirculation (Ur)
If the unoccupied recirculation contact closes or a jumper
is placed across terminals FW 305–306 the unit will turn
off unless there is a call for heating/cooling or dehumidi-
fication across the heating/cooling or dehumidification
contacts. This must come from an optional thermostat or
humidistat. The unit will run in recirc mode upon a call.
Occupied Recirculation (Or) (DDC Control Package
Only)
If the occupied recirculation contact closes or a jumper
is placed across terminals, heat wheel starts (not in free
cooling), defrost recirculation damper closes (if equipped),
outside and exhaust air dampers (if equipped) begin to
open; after outside air damper opens fully the supply
blower starts; after exhaust air damper opens fully the
exhaust blower starts, the occupied recirculation damper
opens and outside and exhaust dampers modulate to the
minimum setpoints.
Unoccupied (Un)
If the contact opens or jumper removed on any of the ter-
minals 304, 305, 306, 307 or 308 the unit will turn off.
PNL
FW
PNL
FW
Figure 2: Possible terminal strip locations in electrical
panel
VCES-VHC-IOM-1F – VHC-36, -42 & -50 11

Coil or Water Source Heat Pump (WSHP) Piping Connections
Cooling and heating coil connections (water and steam)
are available in external or internal piping connections.
See submittals for type. External piping connections are
located on the supply side of the unit. Internal connections
are extended through the middle partition into the return
air compartment.
Split system cooling coil suction line connection is ex-
ternal, and liquid line is internal and located on the sup-
ply side of the unit. The liquid line does not include the
thermal expansion valve. With the coil access panel re-
moved, a field supplied and installed liquid line TXV can
be mounted inside the unit with an external equalizer line
connected to and a thermostatic sensing bulb strapped
to, the suction line. The TXV sensing bulb must be
strapped to the suction line at the 4 o’clock position. The
liquid line must be insulated and field extended outside of
the casing through the access panel and sealed.
WSHP water piping connections are external and factory
piped and extended to the end of the return air side of the
unit. See Appendix A for location.
Connections to the unit coil or WSHP system is by oth-
ers. External supply and return piping design and all other
safety, freeze protection or control piping requirements for
system operation are the sole responsibility of the Install-
ing Contractor and/or Design Engineer. Refer to ASHRAE
handbooks and local building codes for correct piping
procedures and proper installations. Refer to the submit-
tals for coil performance design information.
See Appendix I for WSHP water line piping requirements
and field mounted options and accessories.
A water flow switch is recommended to be installed in line
to prevent possible freeze-up due to loss of water flow.
An air vent must be installed on the high side of the water
line to discharge the non-condensable air in order to avoid
unexpected high head pressure and poor cooling/heating
performance. Manual shut-off valves are recommended to
be installed for the convenience of future service.
A circuit balancing valve with pressure and temperature
gauge connections is recommended to be installed in the
water line for balancing and service.
Before connecting piping to the unit, the water supply line
and return line must be flushed to eliminate the foreign
material.
CAUTION
On open loop systems, a field supplied and installed
water strainer (16–20 mesh minimum, 20–40 mesh best)
must be used in the water inlet or supply line to eliminate
contaminants for 14, 16 and 21 ton dual circuit WSHP
units which utilize a brazed plate heat exchanger con-
denser. Warranty will be voided without the presence of
the proper strainer.
CAUTION
For WSHP units, a water and glycol mixture is used for
factory installed water piping system tests and to prevent
any possibility of freezing during transit and/or storage.
Some glycol may remain in the system. Flush the system
in the field, prior to connection to the main supply and
return lines, if no glycol traces are desired.
In low temperature applications, the water supply line
and return line must be insulated to prevent condensate
and an antifreeze solution must be used to protect wa-
ter-to-refrigerant heat exchanger from freezing damage.
The concentration of water/glycol solution depends on
the field application.
CAUTION
Internal coil connections (water or steam) may only be
field extended through the cabinet within designated
areas. Refer to the interior coil connections label on the
floor of the coil access compartment. A pipe chase or
access openings to extend piping must be field cut by
the Installing Contractor then sealed air- and water-tight
as the access compartment is under a negative pres-
sure. If insulation was removed to create floor access
openings, insulation must be put back in place to avoid
condensation. Do not cut or drill holes through floor of
unit in non-designated areas without consulting the fac-
tory first. The structural integrity of the floor may be com-
promised and possible leaks may develop.
IMPORTANT
If the unit includes heating coil external connections and
split system direct expansion (DX) cooling coil connec-
tions on the supply side of the unit, the thermal expan-
sion valve (TXV) installation and refrigerant liquid line pipe
extensions must be completed with the coil access panel
removed before completing the heating coil and refriger-
ant piping connections.
VCES-VHC-IOM-1F – VHC-36, -42 & -50 12

Condensate Drain Trap
Cooling coil drain pan is provided with a 1¼” MPT drain
connection. A drain trap and condensate line of equal size
must be field provided on the drain connection to prevent
air or sewer gases from being pulled into the unit caused
by the negative (suction) pressure and forcing water out of
the pan into the unit.
A label with recommended trap height is provided on the
unit as per Figure 3.
The trap height allows for the maximum suction pressure
after the cooling coil with intake damper, dirty pre and final
high efficiency filters, high efficiency heat wheel plus 1”
w.c. per ASHRAE guidelines for outdoor units with intake
hood or indoor unit with up to 0.5” w.c. external static in-
take duct.
Slope the drain lines downward in direction of flow 1/8”
per foot referring to local codes for proper drainage re-
quirements. Installing a plug for cleaning of the trap is
recommended. Prime the trap by filling with water before
start-up. Winterize the drain line before freezing on out-
door units.
On integrated cooling units with rotating compressors
and fans on internal vibration isolation, there is potential
for vibrations. Condensate drain lines near the unit should
include isolation supports, turns or flexible tubing.
Check and clear drains annually at start of cooling sea-
son. Drainage problems can occur should drains be inac-
tive and dry out, or due to reduced water flow caused by
buildup of algae. Regular maintenance will prevent these
from occurring.
6.0” [152 mm] minimum
6,0 po [152 mm] minimum
3.0” [76 mm] min.
3,0 po [76 mm] min.
PN 500005436
Condensate drain must be trapped as shown.
Refer to IOM for further instructions and maintenance.
Le drain de condensation doit être fabriqué et intallé tel que
le croquis ci-bas. Voir le manuel d’installation,
opération et maintenance pour instructions.
Unit baserail
Traverses
de base
Curb
Bordure
Curb support
Support
Removable plug
Bouchon amovible
Cleanout
Orifice de nettoyage
Removable plug
Bouchon amovible
Cleanout
Orifice de
nettoyage
6.578” [167.08 mm]
6,578 po [167,08 mm]
3.375” [85.73 mm]
3,375 po [85,73 mm]
Figure 3: Condensate drain trap label
Refrigeration Systems
On units with integrated DX or WSHP cooling the re-
frigeration system is factory completed, leak tested and
charged with R410a refrigerant. The type of refrigerant
and charge is based on calculated volumetric capacity
and stamped on the nameplate. On units with split refrig-
erant systems where the condenser/compressor sections
are remotely installed, the Installing Contractor is respon-
sible for designing and completing the refrigerant system,
calculating the charge, leak testing, evacuation, charging
the refrigerant and adjusting the charge.
VCES-VHC-IOM-1F – VHC-36, -42 & -50 13

Start-up
Pre Start-up Procedure
Before requesting start-up, check that the installation is
complete and unit is ready. Complete the pre start-up
check list below and in the Appendix J for each unit as
items are checked. For torque values on set screws, belt
tension, etc., check under Maintenance.
1. Set the electrical disconnect to the ‘Off’ position.
2. Check the unit for obstructive packaging, objects
near or in blowers, dampers, enthalpy wheel, etc.
Remove all red tie down bolts on fan assemblies and
heat wheel if so equipped.
3. Check that the fans and heat wheel are rotating freely.
4. Check blower wheels and drive set screws. Tighten
if required.
5. Check belt alignment and tension.
6. Check that the air filters are installed and clean.
Replace if necessary. If filters are equipped with
optional differential pressure switch, check desired
setpoint does not exceed factory setting of 0.8” w.c.
[200 Pa].
7. Check coils (if equipped) if fins have been damaged
in transit or construction and are clean. Straighten
fins with fin comb and clean coil if required (not appli-
cable to brazed aluminum heat exchangers).
8. Check the refrigerant components and piping that
they are in good condition and have no damage or
leaks from shipping or installation.
9. Check that the clearance around the air cooled
condenser is within minimum clearance and the dis-
charge is not blocked.
10. Check that the water strainer has been installed
for a water source heat pump with a brazed heat
exchanger.
11. Check that ductwork is connected and complete.
12. Check that condensate drain connections have been
trapped, installed correctly and filled.
13. Check that all shipped loose or field supplied com-
ponents have been correctly installed and wired and
that start interlocks have been completed for the
ventilation control desired.
14. Check that the standard field wiring terminal diagram
has been marked up accordingly and left with the
unit.
15. Check that all power supplies and control wiring
have been inspected and approved by the Local Au-
thorities having jurisdiction.
16. Check all factory and field wiring connections for
tightness. Tighten if necessary.
17. Check that any pipe chase or access opening to ex-
tend piping or wiring through the casing or floor has
been sealed air- and water-tight.
18. Check that all fuses are properly installed in holders.
19. Check the voltage at the disconnect switch against
the nameplate and against phase-to-phase readings
on three-phase. If the voltage is not within 10% of
rated or 2% of phase-to-phase, have the condition
corrected before continuing start-up.
20. Check that all field piping and venting installation and
connections for the heating and cooling options have
been completed and tested.
21. Set the heating and cooling enable switches to the
‘Off’ position.
VCES-VHC-IOM-1F – VHC-36, -42 & -50 14

Start-up Procedure
To ensure proper operation of each unit, qualified per-
sonnel should perform the start-up and complete the
checklist below and the start-up form in Appendix J for
permanent record. A completed checklist will provide
valuable information for personnel performing future
maintenance.
All units are factory run tested. Blowers, heat wheel and
compressors (if equipped) are set up to run correct when
power is connected. If any one blower is running back-
wards or compressor is making loud noises disconnect
power and switch two leads (on three-phase power) to
ensure proper rotation and avoid damage.
If units are equipped with compressors power must be
turned on for 24 hours prior to a call for cooling, for the
compressor crank case heaters to be energizing to pre-
vent possible damage.
The BacStat II interface module (if equipped with DDC
control package and mounted remotely) may be tem-
porarily connected at the unit for checkout. Ensure it is
connected to the Net 2 contacts otherwise it will not give
readings.
1. Before proceeding complete the pre start-up
checklist.
2. Check that all access panels or doors are closed.
3. Turn the main disconnect to the ‘On’ position.
4. Set the timer, selector switch or BMS contact to the
ventilation control scheduling mode selected and
check operation according to sequence. Only one of
the following modes selected can have their contacts
closed or jumped.
a. Occupied ventilation (Ov): With the occupancy
contact closed or a jumper placed across ter-
minals, heat wheel starts (not in free cooling),
defrost recirculation damper closes (if equipped),
outside and exhaust air dampers open fully,
the supply blower starts and after exhaust air
damper opens fully, the exhaust blower starts.
b. Unoccupied recirculation (Ur): With the unoc-
cupied recirculation contact closed or a jumper
placed across terminals, heat wheel stops, de-
frost recirculation damper opens, outside and
exhaust air dampers (if equipped) begin to close
and supply blower starts.
c. Occupied recirculation (Or) (DDC control pack-
age only): With the occupied recirculation con-
tact closed or a jumper placed across terminals,
heat wheel starts (not in free cooling), defrost
recirculation damper closes (if equipped), outside
air damper (if equipped) opens. After outside air
damper opens supply blower starts, exhaust air
damper (if equipped) opens; after exhaust air
damper opens, exhaust blower starts, occupied
recirculation damper opens, outside and exhaust
air dampers modulate to the damper minimum
setpoints.
5. Check that dampers are operating properly.
6. Check that blowers and enthalpy wheel are rotating
in the correct direction.
7. For occupied recirculation scheduling mode the out-
side air and exhaust air dampers must be adjusted
during start-up to achieve the required outside and
exhaust air volumes. See Airflow Balancing for fur-
ther information.
8. Re-check the voltage at the disconnect switch
against the nameplate and against phase-to-phase
readings on three-phase with all blowers operating.
If the voltage is not within 10% of rated or 2% of
phase-to-phase have the condition corrected before
continuing start-up.
9. Check amperage draw to each motor on each phase
against motor nameplate FLA. If significantly different,
check ductwork static and/or take corrective action.
10. Before activating the compressor on WSHP units,
are water shut-off valves open and is water circulat-
ing through the water-to-refrigerant heat exchanger.
11. Enable cooling and check if the sound of the com-
pressor is normal or if there is excessive vibration.
12. Check all field and factory refrigerant and water pip-
ing connections for leaks and correct.
13. On units with gas-fired furnace module, check that
the manual reset high limit switch is closed (press
reset button) and check supply air proving interlock
switch setting to ensure minimum supply airflow prior
to burner operation. Set the switch to open below
the minimum supply airflow on the furnace rating
plate.
14. Enable heating options, see start-up and check out
instructions in Appendix K for gas furnace and Ap-
pendix L for electric coil and complete.
15. Check the operation of the control options provided
on the unit. A functional description is provided
below and in the VHC-36, -42 and -50 DDC Control
Package Manual.
16. Check the setpoints on the DDC Points Reference;
adjust and record changes as required.
17. When unit has achieved steady state take measure-
ments and complete the readings section of the
Start-up Form in Appendix J for each operating cycle
to verify all components are functioning properly and
send copy of the Start-up Form to Venmar CES to
validate warranty. Maintain a copy of the report at
the unit for future reference.
IMPORTANT
A completed copy must be sent back to the factory for
warranty validation and for factory assistance.
VCES-VHC-IOM-1F – VHC-36, -42 & -50 15

Optional Controls and Accessory Sequence and Interlocks
Free Cooling
Power connected, unit ventilating, free cooling call. Wheel
stops rotating.
Variable Speed Setpoint Free Cooling
Power connected, unit ventilating. Wheel modulates to
keep discharge temperature air at setpoint.
Coil Low Limit (Coil Units Only)
Low limit temperature protection is not provided. Coils
must be protected with glycol or field installed low limit
temperature protection if the coil entering air temperature
is expected to go below 35°F [1.7°C].
DDC units do not use low limit temperature protection. In-
stead, if discharge air temperature falls below the low limit
setpoint (adjustable), for five minutes (adjustable), the unit
will shut down and the HW valve will stroke to 100% heat.
Power to the DDC unit must be disconnected and recon-
nected to reset the ‘LS’ (low supply air) alarm.
Unit Fault
An external unit fault can be initiated by removing the dry
contact jumper to the field wire terminal in the control
panel. This contact is normally closed and requires an
open contact to initiate a fault and shut down the unit.
Dirty Filter Sensor
The VHCs can be equipped with dirty filter sensors which
monitor the pressure across the filters and close the con-
tacts when the filters become restricted with dirt. Dirty filter
sensor is factory set to close contacts at 0.8” w.c. [200
Pa]. Field wired connections can be made to the terminal
interface for both the supply and exhaust filter sensors
(electro-mechanical controls units only).
Remote Fan Control
Remote fan control can be achieved by connecting dry
contacts to the terminal interface (during occupied or un-
occupied recirculation). These controls could also be the
following: SPDT switch, dehumidistat, CO2sensor, light
sensor, heat sensor, timer, building management system,
etc.
CO2Ventilation Control
VHC units’ air volume with the VFD motor control option
can be directly controlled by a CO2ventilation control (ac-
cessory or field supplied) by connecting normally open
high speed contacts to the supply and exhaust fan high
speed input terminals for two-speed (High–Low) ventila-
tion control (see Appendix H, CO2 Ventilation Control).
Alternatively, connect the CO2ventilation control 0 to 10
VDC output signal to the supply and exhaust fan modulat-
ing (0 to 10 VDC) input terminals for proportional ventila-
tion control (see Appendix G). As the CO2levels exceed
acceptable limits, dry contacts close or VDC increase rais-
ing high speed fan ventilation. VFD motor control is factory
limited to a minimum motor speed of 40 Hz (double width
double inlet fans only) or 2/3 air volume.
Smoke Detector
VHCs can be equipped with a duct mount smoke detec-
tor which will monitor the air when passing through the
duct system into the unit. When sufficient smoke is de-
tected, an alarm condition is activated. By connecting the
occupied terminals to the NC (normally closed) alarm aux-
iliary contacts on the duct sensor, an alarm condition will
open the auxiliary contact and stop operation of the VHC.
Locate in a normally occupied area of premises. Recom-
mended for compliance to NFPA 90A and IMC code 606.
Cooling Override (DDC Controls Units Only)
These terminals are available for a room or return air sum-
mer thermostat. All thermostats are field installed and
wired.
Dehumidification (DDC Controls Units Only)
These terminals are available for a room or return air de-
humidistat. All dehumidistats are field installed and wired.
Heating Override (DDC Controls Units Only)
These terminals are available for a room or return air winter
thermostat. All thermostats are field installed and wired.
For standard field wiring terminals diagram, refer to Ap-
pendix G.
IMPORTANT
Removal of dry contacts that close on high speed termi-
nals is required for VFDs to modulate.
IMPORTANT
A separate low limit dry contact for DDC units is available
on the FW terminal strip 363–364. This contact signal is
provided by others. When the dry contact is made, it will
turn off the unit and stroke the HW valve to 100%.
VCES-VHC-IOM-1F – VHC-36, -42 & -50 16

Frost Control
During cold temperatures, defrost and frost prevention are
controlled by the unit’s integrated controls as follows.
Recirculation and exhaust only defrost remove the frost
from the enthalpy wheel to maintain proper operation but
do not provide continuous ventilation or make-up air. This
removal of frost occurs when a damper closes the outside
airstream or closes both outside and exhaust airstreams
and opens a recirculation damper to allow warm room air
to circulate through the enthalpy wheel.
Pre-heat and Variable Speed Drive (VSD) will prevent frost
formation on the enthalpy wheel to maintain proper opera-
tion and provide continuous ventilation and make-up air.
This prevention occurs when a pre-heater is energized to
maintain an outdoor air temperature higher or when the
wheel speed is reduced to maintain an exhaust air tem-
perature higher than minimum required for the enthalpy
wheel to operate frost free.
The requirement for frost control is based upon the out-
door air temperature and humidity content of the return
air. In areas where the winter outdoor air condition falls
below 5°F [−15°C] or the return air relative humidity is
above 30%, frost control is probably required.
Recirculation Defrost
The exhaust fan is de-energized. There is no outdoor
air ventilation for the duration of defrost. Enthalpy wheel
stops rotation. Return air is recirculated through the wheel
and back into the building space.
Exhaust Only Defrost
Supply fan is de-energized. There is no outdoor air ventila-
tion for the duration of defrost. Enthalpy wheel maintains
rotation. Return air is exhausted outdoors.
Pre-heat Frost Prevention
Pre-heat frost prevention is an outdoor air temperature
controlled function that allows for continuous ventilation by
ensuring a minimum enthalpy wheel entering air tempera-
ture of 5°F [−15°C]. The temperature sensor is located be-
tween the open wire electric heating coil and the enthalpy
wheel. The electric heating coil is selectable in 1 kW incre-
ments and available in two-stage, four-stage or SCR con-
trol. With staged control, one stage cycles to maintain 5°F
[−15°C] temperature to the enthalpy wheel as the other
stages are continuously on as the outdoor air temperature
drops. If the selected kW is insufficient, based upon the
entered design conditions, Venmar Select™ Web Edition
software automatically adjusts the minimum kW required
to maintain the minimum wheel entering air temperature.
Variable Speed Drive Frost Prevention
This variable speed frost control option is an exhaust air
temperature controlled function that allows for continu-
ous ventilation by reducing the enthalpy wheel rotational
speed. The rotational speed and therefore effectiveness of
the enthalpy wheel, is modulated to maintain an exhaust
air temperature of 33°F [1°C]. This modulation maintains
the wheel operating temperature at conditions that pre-
vent frost formation. Special consideration must be given
to applications where supply air is being heated, as the
heating capacity maximum condition will be during the
frost prevention cycle.
Non-defrost
No frost control is required in areas where the winter out-
door air condition stays above 5°F [−15°C] and the return
air humidity level is below 30%.
Frost Control Options with Recirculation
In certain design applications, it may be required for the
energy recovery unit to have a frost control option and the
option for recirculation ventilation. For units requiring both
these options, it is important to recognize that these op-
tions do not operate at the same time. Recirculation op-
eration allows the unit to recirculate return air to the supply
airstream. Frost control options operate as described in
the previous paragraphs.
IMPORTANT
VSD frost control may cause supply air temperatures to
be below freezing. Adequate freeze protection, such as
glycol or low limit temperature protection for downstream
coils or re-heat to protect building systems, must be field
provided.
VCES-VHC-IOM-1F – VHC-36, -42 & -50 17

Airflow Balancing
For proper performance the unit must operate at the
specified supply and exhaust flow rates. Unit fan speed(s)
and damper positions are theoretically set at the factory
based on the ductwork static pressures and flow rates
specified with the order and in the performance data.
If conditions change or verification is required, airflow
measurements should be taken using AMCA suggested
methods. This would normally be a velocity traverse mea-
surement or flow measuring station (FMS) installed in the
ducts. Where space is limited in the outdoor air and ex-
haust air, pressure drop readings can be taken across the
enthalpy wheel and read or calculated from the Enthalpy
Wheel Pressure Drop vs. Flow Formula and Curves lo-
cated in Appendix M for the wheel diameter and thickness
or efficiency rating. Heat recovery performance is tested in
accordance with AHRI Standard 1060 and is accurate to
within +/− 5% if there is no dirt buildup in the heat recov-
ery wheel.
It is important to locate the FMS in the ‘warm side’ duc-
twork to minimize the effect of differences in air density,
especially when balancing during extremely cold outside
conditions or to take temperature readings and make the
necessary corrections if installed in the ‘cold side’ duct-
work. Air density variations can affect the FMS by more
than 15%. The FMS should be located downstream from
straight sections of duct and not immediately after fans or
obstructions that will cause turbulent flow.
Refer to Appendix K for optional gas-fired furnace module
air balancing information. The installation is to be adjusted
to achieve the air throughput within the range specified on
the gas-fired furnace module rating plate.
Imbalanced airflow may cause supply air temperatures to
be below freezing. Adequate freeze protection such as
glycol or low limit temperature protection for downstream
coils or re-heat to protect building systems must be field
provided.
Setting Flow Rate
Units supplied with belt driven double width double inlet
fans have an adjustable motor sheave factory set at the
midpoint of travel at rpm for the flow rate and external
static specified. With optional VFD driven motors this fac-
tory setting is at 60 Hz. For 100% outdoor and exhaust,
flow rate should be balanced with motors operating at
high speed and at 60 Hz by adjusting the motor sheave
pitch diameter. The VFD can be used for fine tuning de-
pending on sequence.
With the optional direct driven plenum supply fan the VFD
is used for speed setting and balancing at the required
Hertz.
With the optional internal bypass the airflow rate may be
reduced. Consult the factory for setting the flow rate dur-
ing internal bypass.
IMPORTANT
On initial power up, the unit will perform a system check
and operate at high speed for five seconds.
VCES-VHC-IOM-1F – VHC-36, -42 & -50 18

Maintenance
Refer to Appendix K for more gas-fired furnace and Ap-
pendix L for electric heating coil for service and mainte-
nance information. See Appendix I for water source heat
pump water line piping requirements and field mounted
options and accessories. See Appendix N for trouble-
shooting information.
Please refer to Appendix O for a recommended list of rou-
tine maintenance items and time intervals. A more detailed
description of major maintenance items follows.
Air Filters
The standard medium efficiency filters and optional high
efficiency filters are disposable and should be replaced
every three months. More frequent replacement may be
required under extremely dirty operating conditions.
To replace the filters, open the filter access door, grasp
the filters and pull straight out. The filters will slide com-
pletely out of the unit. Slide the new filters into the frame
and close the filter access door.
WARNING
Disconnect the main power switch to the unit before per-
forming service and maintenance procedures.
Interior of Unit
Remove the filters from the unit. Wipe the interior galva-
nized liner, surfaces and enthalpy wheel cassette panels
with a soft cloth and mild cleaning solution.
VCES-VHC-IOM-1F – VHC-36, -42 & -50 19

Fans
Fan wheels and housings should be checked for dirt
buildup. If the forward curved supply or exhaust fan is
dirty, it will be necessary to remove the blower assembly
to clean the dust out through the fan discharge.
The forward curved supply or exhaust fan is fitted with
regreasable bearings. The grease type, quantity and
regreasing interval depends on bearing (fan size) and rev-
olutions per minute (rpm) and are indicated in the tables in
Appendix P. Clean the grease nipple first, then rotate the
fan shaft slowly by hand while regreasing. The regreasing
intervals are theoretical and will depend on site conditions,
hours of operation and temperature. It is recommended
to make periodic inspections of the bearings before these
theoretical intervals.
Forward Curved Supply or Exhaust Fan and
Motor
To remove the motor and blower on units with down, side
or end discharge, disconnect the four-wire service con-
nector from the motor (#1, Figure 4). Loosen the four bolts
(#2, Figure 4) and all screws that fasten the blower to the
flex collar. Slide the fan assembly out of the unit. The fan
assembly may have to be lifted over the fan assembly
plate bolts (#3, Figure 4).
To remove the motor and blower on units with a gas-fired
furnace option or with top supply or exhaust discharge,
disconnect the four-wire service connector from the motor
(#1, Figure 5). Loosen the two adjustment bolts (#2, Figure
5) on the base plate. Rotate the motor and base plate to
remove the belt. Remove the four bolts (#3, Figure 5) and
slide the motor assembly out. To remove the blower, re-
move the four bolts (#4, Figure 5) and all screws that fasten
the blower to the flex collar. Slide the blower out.
The belt tension is adjusted by the positioning of the rotat-
ing motor base plate. Loosen the two adjustment bolts
(#4, Figure 4 or #2, Figure 5) on the base plate. Rotate the
motor and base plate to achieve the maximum belt deflec-
tion as described under belt tension adjustment below.
Tighten the adjustment bolts (#4, Figure 4 or #2, Figure
5). Verify that the sheave and pulley faces are still parallel.
The fan rpm can be adjusted to achieve the design airflow
by setting the adjustable sheave on the motor shaft. The
pulley set screw torque setting is 110 in-lbs to 130 in-lbs.
Belt Tension Adjustment
1. Measure the belt span with a span scale (see Figure
6).
2. Divide the belt span by 64 to determine the belt de-
flection needed to check tension.
3. Set the O-ring on the span scale to the required de-
flection value.
4. Set the small O-ring at zero on the force scale.
WARNING
Disconnect the main power switch to the unit before per-
forming service and maintenance procedures.
Figure 4: Motor and blower orientation for down, side
and end supply/exhaust options
Figure 5: Motor and blower orientation for gas units
and top supply/exhaust options
VCES-VHC-IOM-1F – VHC-36, -42 & -50 20