Specifications

2
to minimize roof penetrations. The bottom drain can be used in
conjunction with the thru-the-bottom connections. An external
trap must be field supplied.
Standard 2-in. Throwaway Filters
are easily accessed
through a removable filter access panel located directly above
the air intake hood; no tools are required to change the filters.
All Units are Designed with a Single Continuous Top Piece
to eliminate leaking at the seams or gasketing.
Belt-Driven Evaporator-Fan Motors on All Sizes
allow maxi-
mum on-site flexibility without changing motors or drives.
Low-Voltage Wiring Connections
are easily made due to the
terminal board which is conveniently located for quick simple
access.
Single-Point Electrical Power Connections
permit easier
wire estimating and connections.
Field-Installed Accessory Electric Heaters
are available in a
wide range of capacities. Single-point wiring kit makes installa-
tion simple.
QUIET, EFFICIENT OPERATION AND DEPENDABLE
PERFORMANCE
All Units are Equipped with Scroll Compressors
that are
fully hermetic with internal vibration isolators for extremely quiet
and highly efficient operation. Compressors are mounted on an
independent plate for additional sound integrity and structural
support. Efficient condenser fan and motor design permits
operation at low sound levels.
Totally Enclosed Condenser Fan Motors
and permanently
lubricated bearings provide additional dependability.
All Coils Use State-of-the-Art Internally Enhanced Copper
Tubing.
Coils are thoroughly leak and pressure tested at the
factory. Condenser coils have louvered, aluminum lanced fins to
provide maximum heat transfer for optimum efficiency and easy
cleaning.
Refrigerant Circuit Protection
ensures dependability. All units
have standard:
1. Loss-of-charge/low-pressure protection switch which allows
operation at lower ambient conditions while protecting
against low-charge operation.
2. Freeze-protection thermostat, which protects against evap-
orator coil frost build-up.
3. High-pressure switch, which protects against above normal
operating pressure.
4. Filter driers, which trap moisture and debris in the refrigera-
tion system.
5. A fixed orifice metering system precisely controls refrigerant
flow, preventing slugging and floodback, while maintaining
optimum unit performance by metering the circuits
individually.
Two Independent Compressor Circuits
(all 090-150 size
units) provide pinpoint comfort control, improved efficiency, and
back-up capability.
BRYANT CONTROLS ADD RELIABILITY, EFFICIENCY, AND
SIMPLIFICATION
The Standard Control System
is readily adaptable to all con-
ventional and programmable thermostats.
Patented Cycle-LOC™ Protection System
provides protec-
tion against compressor cycling by monitoring compressor cur-
rent. When a lack of compressor current exists, the Cycle-LOC
circuit board locks out the compressors. Cycle-LOC may be
manually reset by simply switching the thermostat to OFF, and
back to the Cooling or AUTO modes. No use of the unit power
disconnect switch is required.
INDOOR-AIR QUALITY (IAQ)
551B units utilize certain key features that assist in improving
the quality of the building air. Sloped condensate pans eliminate
possible biological growth in the rooftop unit. A face-split indoor
coil design (all 090-150 size units) proves effective in additional
moisture removal from the supply air. Two-in. filters are
standard in all rooftop units with an optional filter status sensor
available.
Another Optional Indoor-Air Quality (IAQ) Feature
for the
551B unit is the Perfect Humidity™ dehumidification package.
This is a factory-installed option that provides increased dehu-
midification by cooling the hot liquid refrigerant leaving the con-
denser coil. The Perfect Humidity option consists of a
subcooling coil located on the leaving-air side of the evaporator
coil. The location of this coil in the indoor airstream enhances
the latent capacity of the 551B units by as much as 40%. Many
buildings suffer from humidity damage or poor indoor air quality
due to humid conditions. The improved latent capacity provided
by the Perfect Humidity option reduces the building’s humidity,
eliminating potential property damage and making the space
more comfortable.
The Perfect Humidity option makes the 551B unit the ideal IAQ
rooftop for hot and humid regions. The operation of the Perfect
Humidity package can be controlled by a field-installed, wall-
mounted humidistat, or light commercial thermidistat. The cir-
cuit activates only when needed (using the accessory humidis-
tat) as opposed to some dehumidification systems that operate
continuously. The humidistat can be set for any humidity level
between 20% and 80% relative humidity.
SERVICEABILITY
Servicing a Rooftop Unit has Never Been Easier
with the
new factory-installed Hinged Panel Option. This option includes
hinged access panels for the filter, compressor, evaporator-fan
motor, and control box areas. These panels provide quick and
simple access to the major components by simply unlocking
and swinging open the different panels. Each hinged access
panel is permanently attached to the rooftop unit, eliminating
the problem of access panels being dropped and creating a
hole in the roof (potentially causing a water leak). This type of
damage could void any warranty offered for a new roof.
Standardized Components
for the complete line of products
are found in all safety devices, condenser-fan motors, and con-
trol boards. This allows for greater inventory control, familiarity,
and fewer stocked parts.
Easily Accessible Refrigerant Access Ports
on all dis-
charge, suction, and liquid lines permit easy and accurate
measurements.
Resettable 24-V Circuit Breaker (Sizes 090-150)
allows room
for error without replacing transformers or fuses.
Single-Side Utility Connections
provide easy access to per-
form any necessary service.
Color-Coded Wires
permit easy tracing and diagnostics.
Belt-Driven Motors
are accessible through a single access
door to facilitate servicing and adjusting after installation.
Compressors and Safety Switches are Easily Accessible
for
troubleshooting and system analysis.
TABLE OF CONTENTS
Page
Features/Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
Model Number Nomenclature. . . . . . . . . . . . . . . . . . . . . . . . . . 4
ARI Capacities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Physical Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5,6
Options and Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . 7-10
Base Unit Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . 11,12
Accessory Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . 13,14
Selection Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Performance Data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-46
Electrical Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46-54
Typical Piping and Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56-58
Typical Wiring Schematic . . . . . . . . . . . . . . . . . . . . . . . . . 59-61
Application Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61-65
Guide Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66-68