Supply Fan (Blower) Section; Supply Fan (Direct-Drive) - Bryant 551K 04N Series Service And Maintenance Instructions

17 1/4"
DIVIDER
CLEANABLE
ALUMINUM
FILTER
BAROMETRIC
RELIEF
Fig. 3 — Filter Installation
To remove the filter, open the filter clips. Re-install the filter by
placing the frame in its track, then closing the filter clips.
MANUAL OUTSIDE AIR HOOD SCREEN
This inlet screen is secured by a retainer angle across the top
edge of the hood. (See Fig. 4.)
SCREWS
Fig. 4 — Screens Installed on Outdoor-Air Hood
To remove the screen, loosen the screws in the top retainer and
slip the retainer up until the filter can be removed. Re-install by
placing the frame in its track, rotating the retainer back down,
and tightening all screws.

SUPPLY FAN (BLOWER) SECTION

WARNING
ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in personal inju-
ry or death.
Before performing service or maintenance operations on
unit, LOCKOUT/TAG-OUT the main power switch to unit.
Electrical shock and rotating equipment could cause severe
injury.
OUTSIDE
AIR
HOOD
FILTER
FILTER
CLIP
4

Supply Fan (Direct-Drive)

All 551K units have the Axion™ Fan direct drive vane axial
fan system. The fan is driven by an ECM motor with speed that
is user set through the Unit Control Board (UCB). Speeds are
fully configurable from 40% to 100% of motor's maximum
speed. See Fig. 5 and 6.
MOTOR
PLUG
FAN
ROTOR
ECM
MOTOR
Fig. 5 — Direct-Drive Supply Fan Assembly
BLUE
YELLOW
3 2 1
BLACK
6 5 4
GRN/YEL
9 8 7
WHITE
ORANGE
GRAY
Fig. 6 — ECM Motor Plug Connectors
EVALUATING MOTOR SPEED
The direct drive ECM blower motor uses a constant speed de-
sign. Motor speed is controlled by a 0-10Vdc signal, where
10Vdc is equal to motor's maximum RPM.
SELECTING FAN SPEED
All units come factory set for 7.8Vdc or approximately 78% of
the motor's maximum speed. Fan speed should be set per job
specification CFM (cubic feet per minute) and ESP (external
static pressure) required and per fan speed set up label included
on the unit's high voltage cover. In some cases, the Fan Speed
Set Up label may already include the field setting if unit was
previously installed. Check the box on the lower half of the la-
bel to see if the field voltage setting was filled in and if so, set
fan speed to that voltage. Otherwise see detailed instructions
below.
NOTE: Fan Speed Set Up is for full load airflow. If the unit has
multiple stages of cooling, low cool and ventilation may oper-
ate at lower fan rpms. This offset is factory set and controlled
by the UCB. If fan speed verification is being done with a
strobe, fan speed should be verified in all unit operation modes.
Power L3 (3 phase only)
Power L2
Power L1
Earth Ground
CTL Signal Common
10vdc Source
0–10vdc Signal