Bosch FHP RT-20 User manual

1Model RT
Installation, Operation and Maintenance Manual
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 result in personal injury and/or property damage! Retain instructions for future reference.
Part #970-458
Energy Recovery Ventilators
Only qualified personnel should install this system.
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,
including environmental. 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. All moving parts must be free to rotate without
striking or rubbing any stationary objects.
3. Unit must be securely and adequately grounded.
4. Do not spin fan wheel faster than maximum
cataloged fan RPM. Adjustments to fan speed
significantly effects 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 access doors to the unit while it is
running.
General Safety Information
DANGER
• Always disconnect power before working on or
near this equipment. Lock and tag the disconnect
switch or breaker to prevent accidental power up.
• If this unit is equipped with optional gas
accessories, turn off gas supply whenever power
is disconnected.
CAUTION
This unit is equipped with a compressed refrigerant
system. If a leak in the system should occur,
immediately evacuate and ventilate the area. An
EPA Certified Technician must be engaged to make
repairs or corrections. Refrigerant leaks may also
cause bodily harm.
CAUTION
When servicing the unit, the internal components
may be hot enough to cause pain or injury. Allow
time for cooling before servicing.
Model RT

2Model RT Energy Recovery Unit
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
clean thoroughly 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.
Receiving/Inspection
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 the
Traffic Department. If damaged upon arrival, file
claim with carrier. Any physical damage to the unit
after acceptance is not the responsibility of FHP
Manufacturing.
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. See also Installation/
Lifting.
Handling
Units are to be rigged and moved by the lifting
brackets provided or by the skid when a forklift is
used. Number and location of lifting brackets varies
by model and size. Handle each piece in such a
manner as to keep from scratching or chipping the
coating. Damaged finish may reduce ability of the 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 units 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 all moving components by hand
ten to fifteen revolutions to distribute lubricant on
motor and bearings. If paint deterioration begins,
consideration should be given to touch-up or
repainting. Units with special coatings may require
special techniques for touch-up or repair.

3
Model RT Energy Recovery Unit
Table of Contents
General Description. . . . . . . . . . . . . . . . . 4
Models and Capacities . . . . . . . . . . . . . . . 4
Supplemental Installation, Operation and
Maintenance Manuals . . . . . . . . . . . . . . 4
Owners Information
Product Overview . . . . . . . . . . . . . . . . . . 5
Subassemblies Coils . . . . . . . . . . . . . . . . 5
Dampers . . . . . . . . . . . . . 5
Energy Wheel . . . . . . . . . . . 5
Filters . . . . . . . . . . . . . . . 6
Heat Pump Module . . . . . . . . 6
Optional Electric Heaters. . . . . 7
Optional Indirect Gas Furnace . . 7
Operating Concerns
Low Ambient Operation. . . . . . . . . . . . . . . 8
Reduced Airflow . . . . . . . . . . . . . . . . . . 8
Environmental Concerns . . . . . . . . . . . . . . 8
Installation
Installation Concerns . . . . . . . . . . . . . . . . 9
Unit Weights and Roof Opening . . . . . . . . . . 9
Dimensional Data . . . . . . . . . . . . . . . . . 10
Access Door Description and Location . . . . . 10
Service Clearances . . . . . . . . . . . . . . . . 11
Handling and Lifting . . . . . . . . . . . . . . . 12
Roof Curb Mounting / Dimensions / Weights . . 13
Rail Mounting / Layout . . . . . . . . . . . . . . 13
Vibration Isolators. . . . . . . . . . . . . . . . . 14
Lifting Lug Removal. . . . . . . . . . . . . . . . 14
Exhaust Weatherhood . . . . . . . . . . . . . . 14
Ductwork Connections . . . . . . . . . . . . . . 14
Drain Trap . . . . . . . . . . . . . . . . . . . . . 15
Plumbing
Coil Application Recommendations . . . . . . . 16
Water Coils / Water Connections. . . . . . . . . 16
Heat Pump Airside Coils . . . . . . . . . . . . . 16
Electrical Information
General Electrical Information . . . . . . . . . . 17
Field Power Connection . . . . . . . . . . . . . 17
Control Center Components . . . . . . . . . . . 18
Optional Preheater . . . . . . . . . . . . . . . . 19
Optional Post-Heater . . . . . . . . . . . . . . . 19
Post-Heater Control Panel . . . . . . . . . . . . 19
Electric Heater Application / Operation . . . . . 19
Optional Service Outlet . . . . . . . . . . . . . . 19
Optional Vapor Tight Lights . . . . . . . . . . . 19
Typical Wiring Diagram . . . . . . . . . . . . . . 20
Microprocessor Controller
Sequence of Operation . . . . . . . . . . . . .21-22
Energy Wheel
Sequence of Operation . . . . . . . . . . . . . . 23
Electrical Controls
Frost Control Application / Operation . . . . . . 24
Timed Exhaust Frost Control . . . . . . . . . . . 24
Modulating Wheel Frost Control . . . . . . . . . 24
Economizer Application / Operation . . . . . . . 25
Modulating the Wheel. . . . . . . . . . . . . . . 25
Variable Frequency Drive (VFD) . . . . . . . . . 26
Optional Remote Control Panel and Schematics 27
Rotation Sensor . . . . . . . . . . . . . . . . . . 28
Dirty Filter Sensor. . . . . . . . . . . . . . . . . 28
DDC Temperature Control Package . . . . . . . 28
Sensor Schematic . . . . . . . . . . . . . 29
Compressed Refrigeration System
Heat Pump Overview . . . . . . . . . . . . 31
Heat Pump Controls . . . . . . . . . . . . 32
Heat Pump Fault Indicators . . . . . . . . . 33
Energy Recovery Wheel . . . . . . . . . 34
Refrigeration Schematic . . . . . . . . 35
Typical Operating Conditions. . . . . . . 35
Initial Start-up Procedure
Start-Up Information/Checklist/Procedure . 36-39
Troubleshooting
Airflow. . . . . . . . . . . . . . . . . . 40
Unit . . . . . . . . . . . . . . . . . .41-42
Refrigeration Circuit . . . . . . . . . . 43-47
Maintenance
Overview. . . . . . . . . . . . . . . . . 48
Maintenance Frequency . . . . . . . . . . 48
Maintenance Procedures . . . . . . . . 48-50
Maintenance Log . . . . . . . . . . . 51
Warranty . . . . . . . . . . . . Backcover

4Model RT Energy Recovery Unit
Supplemental Installation,
Operation and Maintenance
Manuals
Refer to the following Installation, Operation and
Maintenance Manuals for additional details:
Part #462844 — Exhaust Weatherhood
Part #468280 — RT Curb Assembly Instruction
Part #461006 — Model PVF, Indirect Gas Fired
Furnaces for Energy Recovery Units
Additional manuals are available for each accessory
used in the RT. These additional manuals are provided
by the respective manufacturers and are included
with unit shipment.
Models and Capacities
The RT is manufactured in four different platform
sizes; 20, 45, 55 and 90. Each platform has multiple
options for heating and cooling capacities.
Every RT unit has an energy wheel which greatly
boosts heating and cooling capacity of the heat pump
and a number of additional factory-installed options
are available to produce further increases.
All 4, 5 and 6 ton capacity units have a single scroll
type compressor and
all other units have two
scroll type compressors
and use a split airside
heat pump coil.
Heat Pump Capacity
Unit Size Tons
RT-20 4, 5, 6
RT-45 8, 10, 12.5, 15
RT-55 15, 17.5, 20
RT-90 20, 25, 30
General Description
The RT brings in fresh, outdoor air and removes
stale exhaust air from the building. The intake and
exhaust airstreams move through the RT in opposite
directions in separate passages, and each airstream
passes through an energy wheel. In cooling mode, the
energy wheel removes both heat and moisture from
the incoming airstream and rejects it into the exhaust
airstream. In heating mode, the energy wheel removes
heat and humidity from the exhaust air and rejects
it into the intake air, thus reclaiming energy already
expended to heat the building air.
In addition to the energy wheel, the RT incorporates a
heat pump that is connected to an airside coil inside
the unit. This coil provides significant, highly efficient
heating and cooling by using an outside water source
as a heat sink.
For purposes of providing temporary emergency heat,
an optional secondary heating source such as indirect
gas furnace, hot water coil or electric heaters may
also be installed.
Simply put, this unit preconditions the outdoor air to
save money on heating and cooling costs and then
provides supplemental heating and cooling by means
of a highly efficient heat pump.
Coaxial
Refrigerant-to-Water
Heat Exchanger
Heat Pump Module
(component locations
will vary)
Heat Pump
Compressor(s)
Supply Air
Motor & Blower
Reheat
Coil
Heat Pump
Airside
Heating and
Cooling Coil
Energy
Wheel
Cassette
Filters
Outdoor
Air Intake

5
Model RT Energy Recovery Unit
Wheel Cassette
Coil Section
Exhaust
Hood
Ooutdoor Air
Hood
Exhaust Air
Intake
Electrical Box
Filters
Filters
Indirect Gas Heater
The following summary highlights some important
notes to help avoid premature failure and possible
voidance of warranty.
Product Overview
FHP Manufacturing RT Models integrated with a heat
pump system are designed with the purpose of being
a self-contained source for heating and cooling in
both commercial and institutional applications. This
is done in a highly efficient manner through the use
of a rotary air-to-air total enthalpy wheel called an
“energy wheel”. The wheel allows the compressors
and cooling equipment to be downsized in the unit,
therefore being more cost effective to operate. The
heat pump system comes from the factory fully
charged with refrigerant and is ready for connection
to a water source upon arrival. The smaller tonnage
units (4-6 tons) contain a single compressor, allowing
for one stage of cooling. Larger units (8-30 tons)
come standard with two compressors and a split
airside coil. This allows for staging of compressors
to meet a wider range of outdoor air loads while
reducing the amount of cycles per compressor.
Subassemblies
The following subassemblies are used or are
optionally available in all models of the RT.
RT Coils
In the RT, there is only one coil that will be present
in every unit and that is the airside coil. The airside
coil is connected to the heat pump compressor(s)
and is the primary vehicle for heating and cooling
of the building. A reheat coil is optionally available
and is installed in the supply air stream adjacent to
the airside coil. The reheat coil is also connected
to the heat pump but is used only when the unit
is in cooling mode and its function is to control
humidity in the conditioned air stream. It does this by
reheating the chilled air coming from the airside coil
and then delivering the dehumidified air at a neutral
temperature to the space.
A hot water coil is available as an option and is used
for supplementary heat for the building. If present,
this coil will be installed in the supply airstream,
mounted vertically on the interior wall that separates
the supply air blower and motor from the airside coil
compartment.
Owner’s Information
Motorized Recirculating
Air Damper
Motorized Outdoor
Air Intake Damper
Motorized Exhaust
Air Damper
Gravity Type
Exhaust Damper
Optional Heat Pump
Reheat Coil
Heat Pump
Airside Coil
Optional Hot Water
Coil Location
RT Dampers
There are four locations where dampers are optionally
installed. If an exhaust weatherhood is installed, a
gravity type damper is included with that fixture.
Optional dampers may be located in the air stream
and are always motorized. The exhaust damper and
outside damper are either “low leakage” or “insulated
low leakage”. There is one additional optional damper
that permits 100% recirculation of exhaust air when
the Outdoor Air damper is closed and the Exhaust
Air Blower is off and is intended for use during
unoccupied conditions. It is located in a vertical
position on the interior wall separating the intake
airstream from the exhaust airstream.
RT Energy Wheel
Every RT unit contains a rotary air-to-air total enthalpy
wheel known as an “energy wheel”. The energy wheel
rotates through both the incoming air and the exhaust
air streams, removing both sensible (heat) energy and
moisture from one airstream and transferring it to the
other air stream. The energy wheel is incorporated
into a subassembly known as an “energy wheel
cassette”. The energy wheel itself is comprised of
segments which can be removed for servicing or,
in many cases, the entire cassette can be removed.
The cassette consists of a rigid frame with bearings,
a motor and the energy wheel. It is constructed and
installed
to prevent
air leakage
around the
energy wheel,
forcing
the entire
airstream to
pass through
the wheel. Drive Belt
Adjustable
Air Seals
Label showing
cassette serial #
and date code
Bearing Support
Drive Pulley

6Model RT Energy Recovery Unit
RT Heat Pump Module
Every RT has an integral heat pump module that
contains hermetic scroll-type compressor(s), a coaxial
refrigerant-to-water heat exchanger(s), refrigerant flow
reversing valve(s), expansion valve(s), liquid line filter
drier, high pressure manual reset cutout, crankcase
heater(s) and various sensors, service ports and
safety devices which allows the unit to run at less
than full capacity and results in fewer compressor
cycles. The heat pump is intended to be connected
to an external water source such as a water cooling
tower or boiler, a geothermal source or even a
ground loop. The module is piped to the airside coil
located in the intake airstream and optionally to a
reheat coil that will control humidity. The location
of components in the module will vary. Control
circuitry and the Unit Protection Module (UPM) for the
heat pump module are
located in the heat pump
module. The UPM is a
printed circuit board and
has LED fault indicator
lights to indicate various
alarm conditions and
also power status. A
unit-specific schematic
for electrical circuits is
located in the Control
Center and another unit-specific schematic for heat
pump circuitry is located in the heat pump module.
See also the Typical Refrigerant Flow Schematic in
this IOM.
In normal use, the heat pump module requires only
periodic inspection and cleaning. Any servicing
or repairs must be performed by an EPA Certified
Technician.
Unit Protection Module
(UPM)
Refrigerant
Reversing
Valves
Water
Intake and
Discharge
Connections
Coaxial
Refrigerant-
to-Water
Heat
Exchangers
High
Efficiency
Scroll Type
Compressors
RT Heat Pump Module
Wheel Cassette
Coil Section
Exhaust
Hood
Ooutdoor Air
Hood
Exhaust Air
Intake
Electrical Box
Filters
Filters
Indirect Gas Heater
Two-inch thick MERV 8 or
MERV 13 pleated filters
Permanent Metal Filters
RT Filters
There are three locations in the RT where filters will be
found. In the Outdoor Air Intake, there are permanent
metal filters that are accessed by removing the filter
access panel on the side of the louver assembly. The
metal filters require regular cleaning, see Routine
Maintenance section of this manual.
In the outdoor air intake portion of the RT, a set of
2-inch thick MERV 8 or MERV 13 pleated filters are
used. These filters are located directly in front of the
energy wheel cassette and require frequent inspection
and periodic replacement. See Routine Maintenance
section of this manual.
In the exhaust air intake stream there is an additional
set of 2-inch thick MERV 8 or MERV 13 pleated filters.
These filters are located between the exhaust air
intake and the energy wheel cassette. See Routine
Maintenance section of this manual.

7
Model RT Energy Recovery Unit
RT Optional Electric Heaters
There are two optional electric heaters available for
the RT. One is a preheater and is used to prevent
frost buildup on the energy wheel. It is located
directly in front of the intake air filter assembly. The
second optional heater is used as a supplementary
emergency heat source for the building and is
integrated into the supply air stream by installing
the heater in a vertical position on the interior wall
separating the coil compartment from the supply air
motor and blower compartment.
Supply Air Motor and
Blower Assembly
Furnace Housing with
access to burners, vest
plate and circuitry
Optional Electric
Heater Location
Model PVF
Indirect Gas
Furnace
Optional Electric
Preheater Location
Supply Air Motor and
Blower Assembly
RT Optional Indirect Gas Furnace
An optional Indirect Gas furnace may be installed in
the RT and its function is to provide supplementary
emergency heat to the building. The Model PVF
Indirect Gas Furnace is installed into the supply air
stream by means of raising the supply air motor
and blower assembly and installing that assembly
directly on top of the furnace. An additional housing
is installed on the end of the RT module, providing
access to the burners, vest plate and furnace
circuitry. A complete IOM for the furnace as well as
a unit-specific wiring diagram are located inside the
furnace housing access door.

8Model RT Energy Recovery Unit
IMPORTANT
Do not release refrigerant to the atmosphere! If
required service procedures include the adding or
removing of refrigerant, the service technician must
comply with all federal, state and local laws. The
procedures discussed in this manual should only be
performed by a qualified EPA Certified Technician.
CAUTION
Unit is designed for outdoor or indoor installation.
Follow all guidelines in this manual for proper
installation.
Operating Concerns
Low Ambient Operation
Care has been taken to ensure low ambient operation
does not cause damage to the refrigerant system. A
factory-installed temperature sensor in the outdoor
air intake prevents refrigerant system operation at
ambient conditions below 55ºF. Crankcase heaters
will still be engaged provided the main power has not
been disconnected. If cooling is desired at ambient
temperatures below 55ºF, economizer operation
(wheel start/stop or wheel modulation) should be
employed.
Reduced Airflow – pumping oil and liquid
refrigerant
Lack of maintenance will lead to filters and airside
coils building-up with dirt and debris. As this occurs,
the airflow through the unit will decrease. Airside coils
are sized to handle a particular airflow volume and a
reduction in airflow can cause the airside coils to get
too cold. As this happens, ice buildup on the face
of the coil is possible, further reducing airflow. The
result of the airside coil operating at temperatures
below design limits, is that excessive liquid refrigerant
will be returned to the compressor(s). The liquid
refrigerant buildup in the compressor(s) will displace
the necessary oil needed for proper lubrication. The
combination of these two events will significantly
reduce the life of the compressor(s) and could result
in compressor failure.
To maintain the proper airflow and system efficiency,
follow all procedures in the Maintenance section.
Environmental Concerns
This equipment contains R-410A refrigerant. It
provides performance similar to that of R-22
refrigerant, but it offers a great advantage. It is an
HFC refrigerant and does not contain any ozone
depleting HCFC’s or CFC’s. When working with
FHP fully charged refrigerant systems, it is strongly
recommended that caution is undertaken during
installation, operation, and routine maintenance.
Systems using R-410A refrigerant operate at
significantly higher pressures and R-22 service
equipment or components should not be used on
R-410A refrigerant systems. To comply with the U.S.
Clean Air Act, anytime there is residual refrigerant, the
proper equipment shall be used and methods should
be followed to reclaim the refrigerant so that it can be
recycled, reprocessed, or destroyed.

9
Model RT Energy Recovery Unit
Installation Concerns
The RT will most often be installed on a rooftop but
in some cases it may be preferable to install the unit
at ground level beside the building, or even indoors.
This portion of the IOM applies directly to roof top
installations but most of the concerns remain the
same regardless of where the unit is installed.
Determine the best location, taking into consideration
proper air movement around the unit, proper
support of the unit and space around the unit for
periodic maintenance. Refer to architect / engineer’s
instructions in the plans and specifications. Verify the
load bearing capacity where the unit is to be installed
and make certain that supporting structural members
will not conflict with openings needed for ductwork.
The RT must be elevated to isolate it from certain
weather/temperature conditions and to permit proper
installation of a condensate P trap and drain. Some
installations will use FHP model GKD roof curb
and an installation manual is included with it. It is
preferable that the GKD roof curb be installed prior to
installation of roofing membrane so that the curb can
be properly flashed. If the owner chooses to fabricate
a base in the field from materials supplied by others,
observe all area building codes and use industry Best
Practices to accomplish proper unit support and
elevation. See also “Rail Installations” in this manual.
If more than one unit is to be installed, make certain
that the discharge air from one unit is not directed
toward the outdoor air intake of any other unit.
Clearance for exhaust air and return air ducts may
be accomplished either by cutting individual duct
openings or by opening the entire space within the
roof curb unit. If the entire space within the curb is
opened, higher radiated sound levels may result.
Whenever supply or warm air ducts pass through
a combustible roof, clearance of at least one inch
(25 mm) must be maintained between the outside
surfaces of the ductwork and any combustible
materials in accordance with NFPA Standard 90.
Installation
The system design and installation should follow
accepted industry Best Practices, such as described
in the ASHRAE Handbook. Adequate space should
be left around the unit for piping coils and drains,
filter replacement, and maintenance. Sufficient space
should be provided on the side of the unit for routine
service and component removal should that become
necessary.
See Service Clearances/Access Panel Locations
section for more details.
Unit Size U V Approximate
Weight (pounds)
RT-20 46 37 2150
RT-45 54 39 3500
RT-55 65 47 4450
RT-90 85 49 5300
All dimensions are in inches. Unit weights assume rooftop
configuration with weatherhoods, filters, outdoor air
damper, six row DX coil, integral condensing section and
an indirect gas-fired furnace.
Supply
Discharge
Exhaust
Intake
U
V
1/2 inch 1/2 inch
1/2 inch
Position the unit roof opening such that the supply
discharge and exhaust inlet of the unit will line up
with the corresponding ductwork. Be sure to allow
for the recommended service clearances when
positioning opening (see Service Clearances).
Do not face the outdoor air intake of the unit into
prevailing wind and keep the intake away from any
other exhaust fans. Likewise, position the exhaust
discharge opening away from outdoor air intakes of
any other equipment.
Unit Weights and Recommended Roof
Opening

10 Model RT Energy Recovery Unit
Dimensional Data
Access Door Description and Location
1. Heat Pump and Unit Protection module (2 doors)
Coaxial heat exchanger
2. Control Center with all electrical controls
3. Exhaust air filters
Exhaust air intake damper (optional)
Control panel and fuses for optional electric
post-heater
Energy wheel access
Bypass damper (optional)
4. Exhaust motor and blower
5. Permanent aluminum filters (access panel
located on intake hood)
6. Energy wheel and motor, belt and seals
Outdoor air filters
Outdoor air intake damper (optional)
Frost control sensors (optional)
Economizer sensors (optional)
Electric preheater (optional)
7. Airside coil access
Drain pan
8. Outdoor air blower / motor (if equipped with
optional (IG furnace)
9. Outdoor air blower / motor / electric post-heater
(if equipped with optional electric post-heater)
Model RT with Heat Pump
Model
Overall Exterior Dimensions
Width
(including Lifting Lugs)
Overall Width
(with Exhaust Hood)
Overall Length
(with Outdoor Air Hood)
RT-20 59.5 75 116
RT-45 69.5 86 122
RT-55 79.5 101 134
RT-90 99.5 123 147
All dimensions shown are in inches.
Following is a list of items accessible through the access doors shown on the diagrams. Some items are
optional and may not have been provided.
Exhaust
Weatherhood
4
3
Outdoor Air
Intake
9
1
2
5
6
7
8
1

11
Model RT Energy Recovery Unit
Service Clearances
RT-20, -45, -55, and -90 units require minimum clearances for access on all sides for routine maintenance. Filter
replacement, drain pan inspection and cleaning, energy wheel cassette inspection, fan bearing lubrication and
belt adjustment are examples of routine maintenance that must be performed. Blower and motor assemblies,
energy wheel cassette, coil and filter sections are always provided with a service door or panel for proper
component access. Clearances for component removal may be greater than the service clearances, refer to
drawings for these dimensions.
RT-20
RT-45
RT-55
RT-90
Clearances for service and component removal on RT-20 and RT-45
* Clearance for energy wheel removal on RT-20
** Clearance for energy wheel removal on RT-45
Clearances for service and component removal on RT-55 and RT-90
WHEEL CASSETTE
COIL SECTION
ACCESS PANEL
ACCESS PANEL
ACCESS PANEL
ACCESS PANEL
ACCESS PANEL
ACCESS PANEL
ACCESS PANEL
EXHAUST
HOOD
OUTDOOR AIR
HOOD
INTAKE
EXHAUST AIR
ELECTRICAL BOX
FILTERS
FILTERS
ACCESS PANEL
IG HEATER
CLEARANCE
WITH IG HEATER
MINIMUM
36 IN
36 IN
*48 IN **64 IN
52 IN
36 IN
WHEEL CASSETTE
COIL SECTION
ACCESS PANEL
ACCESS PANEL
ACCESS PANEL
ACCESS PANEL
ACCESS PANEL
ACCESS PANEL
ACCESS PANEL
EXHAUST
HOOD
OUTDOOR AIR
HOOD
INTAKE
EXHAUST AIR
ELECTRICAL BOX
FILTERS
FILTERS
ACCESS PANEL
IG HEATER
CLEARANCE
WITH IG HEATER
MINIMUM
42 IN
42 IN
36 IN
42 IN
52 IN

12 Model RT Energy Recovery Unit
Handling
While this unit was constructed with quality and
dependability in mind, damage still may occur during
handling of the unit for installation. Exercise extreme
caution to prevent any damage from occurring to
the refrigerant system. This unit contains a system
pressurized with refrigerant that if damaged, could
leak into the atmosphere or cause bodily harm due
to the extreme cold nature of expanding refrigerant.
Use protective equipment such as gloves and safety
glasses to minimize or prevent injury in case of a
system leak during installation.
The system design and installation should follow
accepted industry practice, such as described in
the ASHRAE Handbook. Adequate space should be
left around the unit for piping coils and drains, filter
replacement, and maintenance. Sufficient space
should be provided on the side of the unit for routine
service and component removal should that become
necessary.
See Service Clearances/Access Panel Locations
section for more details.
Lifting
1. Before lifting, be sure that all shipping material
has been removed from unit.
2. To assist in determining rigging requirements,
weights are shown below.
3. Unit must be lifted by all lifting lugs provided on
base structure.
4. Rigger to use suitable mating hardware to attach
to unit lifting lugs.
5. Spreader bar(s) must span the unit to prevent
damage to the cabinet by the lift cables.
6. Always test-lift the unit to check for proper
balance and rigging before hoisting to desired
location.
7. Never lift units by weatherhoods.
8. Never lift units in windy conditions.
9. Preparation of curb and roof openings should be
completed prior to lifting unit to the roof.
10. Check to be sure that gasketing has been
applied to the curb prior to lifting the unit and
setting on curb.
11. Do not use fork lifts for handling unit.
WARNING
All factory provided lifting lugs must be used when
lifting the units. Failure to comply with this safety
precaution could result in property damage, serious
injury, or death. Unit weights assume rooftop
configuration with weatherhoods, filters, outdoor air
damper, six row DX coil, integral condensing section
and an indirect gas fired furnace.

13
Model RT Energy Recovery Unit
Curb Outside Dimensions and WeightsRoof Curb Mounting
Rooftop units require curbs to be mounted first. The
duct connections must be located so they will be
clear of structural members of the building.
1. Factory Supplied Roof Curbs: Roof curbs are
Model GKD, which are shipped in a knockdown kit
(includes duct adapter) and require field assembly (by
others). Assembly instructions are included with the
curb.
2. Install Curb: Locate curb over roof opening
and fasten in place. (Refer to Recommended Roof
Openings). Check that the diagonal dimensions
are within ±1/8 inch of each other and adjust
as necessary. For proper coil drainage and unit
operation, it is important that the installation be level.
Shim as required to level.
3. Install Ductwork: Installation of all ducts should
be done in accordance with SMACNA and AMCA
guidelines. Duct adapter provided to support ducts
prior to setting the unit.
4. Set the Unit: Lift unit to a point directly above the
curb and duct openings. Guide unit while lowering to
align with duct openings. Roof curbs fit inside the unit
base. Make sure the unit is properly seated on the
curb and is level.
Curb Outside Dimensions
Curb Cap Dimensions
Unit Size A B C D E
RT-20 2.00 2.00 1.00 0.88 0.75
RT-45 2.00 4.25 2.00 1.31 0.50
RT-55 2.00 4.25 2.00 1.31 0.50
RT-90 2.00 4.25 2.00 1.31 0.50
All dimensions are in inches.
Rail Mounting
Unit Size A B
RT-20 5.0 41.0
RT-45 7.0 41.9
RT-55 5.5 53.0
RT-90 6.0 59.0
All dimensions are in inches.
Curb Outside Dimensions and Curb Weights (lbs)
Unit Size L W Weight
RT-20 104.88 51.00 310
RT-45 115.75 60.63 400
RT-55 129.88 71.50 510
RT-90 148.13 90.75 720
All dimensions are in inches. Weights are for 12 inch
high curbs. Roof curb details, including duct locations
dimensions are available on RT roof curb assembly
instructions, part #468280
ROOF CURB
SIDE OF UNIT
BASE
1 INCH INSULATION
E
D
C
A
B
Curb Cap Details for Factory Supplied Roof Curbs
Rail Mounting / Layout
• Rails designed to handle the weight of the RT
should be positioned as shown on the diagram
(rails by others).
• Make sure that rail positioning does not interfere
with the supply air discharge opening or the
exhaust air intake opening on the RT unit. Avoid
area dimensioned “B” below.
• Rails should run the width
of the unit and extend
beyond the unit a
minimum of 12 inches
on each side.
• Set unit on rails.
B A
Supply/Exhaust
Outdoor Air
Intake Hood
Opening
Isometric view
of unit on rails
B A
Supply/Exhaust
Outdoor Air
Intake Hood
Opening
Side view of unit on rails

14 Model RT Energy Recovery Unit
The method of compressing and restraining the motor
/ blower assembly varies with each product. If sheet
metal screws or bolts are used, they are installed with
an equal number on both the front and the rear of
each assembly. Screws or bolts used on the rear rail
of the assembly are difficult to see. It is recommended
that the rear screws or bolts be removed prior to the
front ones in order to reduce the chance of injury. If
restraining bands are used instead of screws or bolts,
carefully cut and remove the bands.
Upon receipt, visually inspect motor / blower
assemblies to verify presence of spring isolation
devices. If they are present, carefully remove shipping
restraints to allow free movement of assembly.
NOTE
Many motor / blower assemblies include optional
spring vibration isolation devices. When these
isolation springs are used, the motor / blower
assembly is secured for shipment by compressing
the springs and securing the assembly to
intermediate rails (see photo).
CAUTION
These assemblies are shipped with the springs in
a compressed state and when shipping restraints
are removed, the assembly will bounce upward.
Do not position hands or fingers where they may
be pinched or injured by sudden movement of the
assembly.
Motor / Blower Assembly
in shipping position
Spring Isolation
Device
Vibration Isolators
Any lifting lug that is located as shown should be
removed in order to permit installation of the P trap
drain kit.
NOTE
On some models of the RT, one lifting lug may be
positioned directly in front of the condensate drain
connection. See illustration.
1 Fan
Wheel
Dia.
1 Fan
Wheel
Dia.
R
o
t
a
t
i
o
n
R
o
t
a
t
i
o
n
R
o
t
a
t
i
o
n
R
o
t
a
t
i
o
n
Length of Straight Duct
GOOD
POOR
GOODPOOR
GOOD POOR
Turning
Vanes
Turning
Vanes
SYSTEM EFFECT FACTOR CURVES
FPM X 100
OUTLET VELOCITY
0 5 10 15 20 25 30 35 40 45
1.2
1.0
0.8
0.6
0.4
0.2
0.0
STATIC PRESSURE LOSS
CURVE 1
CURVE 2
CURVE 3
CURVE 4
Recommended Discharge Duct Size and Length
Model Blower
Size Duct Size Straight Duct Length
RT-20 9 14 x 14 36
RT-45 10 20 x 20 36
RT-55 12 20 x 20 36
RT-90 15 28 x 28 60
All dimensions shown in inches.
• Recommended duct sizes are based on velocities across the
cfm range of each model at approximately 800 feet per minute
(FPM) at minimum airflow and up to 1600 fpm at maximum
airflow. Recommended duct sizes are only intended to be a
guide and may not satisfy the requirements of the project.
Refer to plans for appropriate job specific duct size and/or
velocity limitations.
• Straight duct lengths were calculated based on 100% effective
duct length requirements as prescribed in AMCA Publication
201. Calculated values have been rounded up to nearest foot.
Ductwork Connections
Examples of poor and good fan-to-duct connections
are shown below. Airflow out of the fan
should be directed straight or curve
the same direction as
the fan wheel rotates.
Poor duct installation
will result in low airflow
and other system
effects.
1 Fan
Wheel
Dia.
1 Fan
Wheel
Dia.
R
o
t
a
t
i
o
n
R
o
t
a
t
i
o
n
R
o
t
a
t
i
o
n
R
o
t
a
t
i
o
n
Length of Straight Duct
GOOD
POOR
GOODPOOR
GOOD POOR
Turning
Vanes
Turning
Vanes
SYSTEM EFFECT FACTOR CURVES
FPM X 100
OUTLET VELOCITY
0 5 10 15 20 25 30 35 40 45
1.2
1.0
0.8
0.6
0.4
0.2
0.0
STATIC PRESSURE LOSS
CURVE 1
CURVE 2
CURVE 3
CURVE 4
Exhaust Weatherhood
The exhaust weatherhood is shipped
separately as a kit with its own
instructions.
Intermediate
Shipping Rail
(typical)

15
Model RT Energy Recovery Unit
Drain Trap
The RT is equipped with a stainless steel condensate
pan with a stainless steel drain connection. It is
important that the drain connection be fitted with
a P trap to ensure proper drainage of the RT while
maintaining internal static pressures and to prevent
migration of sewer gas back into the unit. A P trap
assembly (kit) is supplied with the unit and is to be
assembled and installed as local conditions require
and according to the assembly instructions provided
with the P trap. If local and area building codes
permit, the condensate may be drained from the P
trap onto the roof, but a drip pad should be provided
beneath the outlet. If local and area codes require
a permanent drain line, it should be fabricated and
installed in accordance with Best Practices and all
codes.
In some climates it will be necessary to provide
freeze protection for the P trap and drain line. The P
trap should be kept
filled with water
or glycol solution
at all times and it
should be protected
from freezing to
protect the P trap
from damage. If
severe weather
conditions occur, it
may be necessary
to fabricate a P trap
and drain line of
metal and install a
heat tape to prevent
freezing.
Drain Trap
Assembly Kit

16 Model RT Energy Recovery Unit
Plumbing
Coil Application Recommendations
Factory installed cooling and heating components
are mounted in the coil section of the unit. The coil
section is downstream of the energy wheel on the
supply airside of the unit.
Note the coil connection locations on the picture.
Airside coil connections are located internal to the
unit as shown.
Water Coils
Water coils are a design option that must be specified
for factory installation. A water coil may be used
for further tempering of the outdoor air. If used, the
optional hot water coil would be located vertically on
the internal cabinet partition that separates the airside
coil from the supply air blower compartment of the RT.
See also Subassemblies/Coils.
1. Piping should be in accordance with accepted
industry standards. Pipework should be supported
independently of the RT unit. Water connections
are male NPT iron pipe. When installing couplings,
do not apply undue stress to the connection
extending through the unit. Use a backup pipe
wrench to avoid breaking the weld between coil
connection and header.
2. Connect the water supply to the bottom
connection on the air leaving side and the water
return to the top connection on the air entering
side. To ensure proper venting, an external air
vent in the piping is recommended. Connecting
the supply and/or return in any other manner
will result in very poor performance. Be sure to
replace factory installed grommets around coil
connections if removed for piping. Failure to
replace grommets will result in water leakage into
the unit and altered performance.
3. The air vent at the uppermost point should be
temporarily opened during system start-up to
release all of the air from the coil. To maintain heat
transfer capacity, periodically vent any air in coil.
Hot
water coil
connections Coil access door
4. Water coils are not normally recommended for
use with entering air temperatures below 40ºF;
however, the energy wheel maintains a pre-coil
temperature higher than 40ºF. No control system
can be depended on to be 100% safe against
freeze-up with water coils. Glycol solutions or
brines are the only safe media for operation of
water coils with low entering air conditions.
Continuous water circulation through the coil at all
times is highly recommended.
5. Pipe sizes for the system must be selected on the
basis of the head (pressure) available from the
circulation pump. The velocity should not exceed
6 feet per second and the friction loss should be
approximately 3 feet of water column per 100 feet
of pipe.
Heat Pump Airside Coils
Outdoor air entering the RT is first tempered by the
energy wheel and then passes through the heat pump
airside coil for further heating or cooling. Refrigerant
in a vapor state will circulate through the airside
coil whenever the heat pump is operating, but the
direction of flow will change, depending on whether
the unit is in cooling or heating mode. When the unit
is operated in the cooling mode, a significant amount
of condensate will be produced and then collected in
the stainless steel condensate drain pan.
The condensate drain pipe should be sized
adequately to ensure the condensate drains properly.
Refer to Drain Trap section.

17
Model RT Energy Recovery Unit
Electrical Information
Warning: DO NOT penetrate the roof of the unit for
any reason since there are hazardous voltage circuits
located between the inner and outer roof panels.
The unit must be electrically grounded in accordance
with the current National Electrical Code, ANSI/NFPA
70. In Canada, use current CSA Standard C22.1,
Canadian Electrical Code, Part 1. In addition, the
installer should be aware of any local ordinances or
electrical company requirements that might apply.
System power wiring must be properly fused and
conform to the local and national electrical codes.
System power wiring is to the unit main disconnect
(door interlocking disconnect switch standard on most
units) or distribution block and must be compatible
with the ratings on the nameplate: supply power
voltage, phase, and amperage (Minimum Circuit Amps
- MCA, Maximum Overcurrent Protection - MOP).
All wiring beyond this point has been done by the
manufacturer and cannot be modified without affecting
the unit’s agency / safety certification.
If field installing an additional disconnect switch, it
is recommended that there is at least four feet of
service room between the switch and system access
panels. When providing or replacing fuses in a fusible
disconnect, use dual element time delay fuses and size
according to the rating plate.
Field Power Connection: The RT is designed for
simple, single-point connection (in the Control Module)
for high voltage supply. In addition to high voltage
power supply, it will be necessary to run low voltage
controller circuitry to the terminal strip in the Control
Center. In some cases, a second high voltage circuit
will be required to power a high capacity electric post
heater. Refer to unit-specific wiring diagram for further
details.
Many RT units will not have any internal circuit fuses.
Some large units may have circuit fusing and those
fuses will be present on the high voltage side of the
Control Center. Optional electric post heaters may be
fused and those fuses are located on the post heater
control panel. In all cases, refer to the unit-specific
wiring diagram.
Once high voltage power is connected to the unit it
still will not operate unless a controller is installed
on terminals R and G of the terminal strip. Do not
install any controller circuit or jumper on the R and G
terminals until ready for the Startup Procedure.
The recommended location for entry of electrical
circuits and high voltage supply wiring is through the
floor of the unit, preferably in the area of the Control
Center. Carefully select a location that does not
interfere with other controls or assemblies such as
the motorized dampers. Seal penetration in cabinet
bottom to prevent leakage.
The electric supply to the unit must meet stringent
requirements for the system to operate properly.
Voltage supply and voltage imbalance between phases
should be within the following tolerances. If the power
is not within these voltage tolerances, contact the
power company prior to operating the system.
Voltage Supply: See voltage use range on the rating
plate. Measure and record each supply leg voltage at
all line disconnect switches. Readings must fall within
the allowable range on the rating plate.
Voltage Imbalance: In a 3-phase system, excessive
voltage imbalance between phases will cause motors
to overheat and eventually fail. Maximum allowable
imbalance is 2%. To determine voltage imbalance,
use recorded voltage measurements in this formula.
Key: V1, V2, V3 = line voltages as measured
VA (average) = (V1 + V2 + V3) / 3
VD = Line voltage (V1, V2 or V3) that
deviates farthest from average (VA)
Formula: % Voltage Imbalance = [100 x (VA-VD)] / VA
CAUTION
If any of the original wire as supplied with the
appliance must be replaced, it must be replaced
with wiring material having a temperature ratings of
at least 105° C.
WARNING
• To prevent injury or death due to electrocution or
contact with moving parts, lock disconnect switch
open.
• For units with a gas furnace, if you turn off power
supply, turn off gas.
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 unit
control center access door. The low voltage control
circuit is 24 VAC and control wiring should not exceed
0.75 ohms.
Refer to Field Control Wiring Length/Gauge table for
wire length maximums for a given wire gauge.
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.
If wire resistance exceeds 0.75 ohms, an industrial-
style, 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 (refer to Typical Control Center
Components). 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.
Field Control Wiring Length/Gauge
Total Wire Length Minimum Wire Gauge
125 ft. 18
200 ft. 16
300 ft. 14
450 ft. 12

18 Model RT Energy Recovery Unit
Typical Control Center Components - individual components and locations will vary
7
1
9
4
3
2
5 6
8
19
Refer to “Heat Pump System”
section for components in
compressor compartment
Access to Control Center Components is
gained through the access panel indicated.
1. Main Disconnect (non-fusible,
lockable)
2. Motor Starter - Exhaust Air Fan
3. Motor Starter - Outdoor Air Fan
4. Motor Contactor - Energy Wheel
5. 24 Vac Control Transformer
6. 24 Vac Terminal strip
7. Fuses for blower motors
8. Grounding lug
9. Distributor block
10. Compressor fuse blocks
11. Compressor contactors
12. Condensing fan contactors
13. Compressor cycle timers
14. Compressor relay
15. Terminal block
Optional Control Center Components
16. DDC controller
17. Dirty filter pressure switches
18. Economizer module
19. Thermostats for:
- Economizer module
- Energy Recovery wheel frost
control
- Compressor lock out
20. Terminal block
21. Frost control pressure switch
22. Energy recovery wheel VFD
Component #6
Exploded Detail
of Terminal Strip
11 12 13 14 15
16
17
18
20
21
22
10

19
Model RT Energy Recovery Unit
Electric Heater Application/Operation
Factory installed electric heaters may be optionally
supplied for energy wheel preheating. The optional
electric preheater is positioned upstream of the air
intake filters and its primary function is to prevent
frost accumulation on the energy wheel. Electric
heaters are available in 208, 230, or 460 VAC (refer
to heater nameplate for voltage). An optional
tempering electric heater may be installed as a
supplementary heat source and is located as shown
in Subassemblies/Optional Electric Heat.
Optional Accessories
Preheaters: Preheaters are standard as two-stage,
step control. Step control heaters are designed with
multiple stages made up of equal increments of
heating capability. For example, a 10 kW heater with
two stages will be composed of two 5 kW stages.
Preheaters are single point wired at the factory.
A temperature sensor (with field adjustable set
point) is mounted in the outdoor airstream after the
preheater to turn the preheater on. See Frost Control
Application/Operation for typical set points. If the
temperature falls below the set point and the wheel
pressure drop sensor is triggered, the first stage of
the preheater will turn on. If the first stage does not
satisfy the set point, the second stage will also turn
on.
See also Subassemblies/Electric Heaters
Post-heaters: Post-heaters are standard as
SCR control; see unit specific wiring diagram. A
temperature sensor (with field adjustable set point)
is mounted in the outdoor airstream after the post-
heater to turn the post-heater on. A SCR heater
provides an infinitely modulating control of the heat to
provide an accurate discharge temperature. A call for
heat is required.
Post-Heater Control Panel: The post-heater is
not single point wired to the RT control center.
Separate power must be supplied to the post-
heater disconnect (located in unit control center).
See Access Door Descriptions and Locations for
access to post-heater control panel. For Model RT,
the exhaust filters must be removed from the unit to
access.
Service Outlet
120 VAC GFCI service outlet ships
loose for field installation. Requires
separate power source so power is
available when unit main disconnect is
turned off for servicing.
Vapor Tight Lights
Vapor tight lights provide light to each of the
compartments in the energy
recovery unit. The lights are wired
to a junction box mounted on the
outside of the unit. The switch to
turn the lights on is located in the
unit control center. The switch
requires a separate power source
to allow for power to the lights
when the unit main disconnect is
off for servicing.

20 Model RT Energy Recovery Unit
Typical Wiring Diagram
Following is an example of a typical wiring diagram located in the unit control center. This wiring diagram
includes a legend highlighting which accessories were provided with the unit. Factory wiring and field wiring
are also indicated. This particular example includes 1) variable frequency drives on the blowers requiring a
modulating input, 2) modulating energy recovery wheel with factory controls for economizer, 3) energy wheel
rotation sensor, 4) outdoor air and exhaust air dirty filter switches, 5) motorized outdoor air and exhaust air
intake dampers, and 6) timed exhaust frost control. Many other factory installed and wired accessories are
available.