Reznor B6BM Unit Installation Manual - Manual (Page 15)

15
DHUM
R R
DHUM
HUMIDISTAT
MOTOR
CONTROL BOARD
Figure 10. DHUM Wiring Configuration
• Terminal 4 = Hi speed
• Terminal 5 = Med speed
• Terminal 6 = Low speed
4. Replace the upper door and secure it to the unit.
5. Restore power to the unit.
High Efficiency Units (Variable & Fixed Speed)
IMPORTANT! This air handler has been designed to
give the installer maximum flexibility to optimize system
performance, efficiency, and comfort. Because there
are so many different ways to set up the air handler it is
important to read and follow these directions carefully.
B6EM & B6VM air handlers use high efficiency circulating
air motors that come in two variations and both are
controlled differently. The fixed speed motor control
board
Figure 15 (page 24) controls the torque and the
variable speed motor control board ( Figure 16 ) controls
the airflow at a constant CFM. Both boards use the same
control board.
Before operation, the air handler must be configured to
match the unit with the system, system options, and climatic
conditions. When configured, the air handler responds
directly to the thermostat inputs, as well as the optional
humidistat (see
page 13 ). During normal operation, the
motor will gradually change speeds during start-up, shut
down, when thermostat inputs change, and when the duct
static pressure changes (vents closed or opened, filter
clogging, etc.). The air handler is configured by setting
the selector switches and removing jumper connectors.
Selecting Basic Heating Airflow
Fixed & variable speed motor control boards (
Figure 15
(page 24) & Figure 16 ) contain a set of dip switches
for setting the blower speed. For B6EM models, pins 1-4
set the speed for heating. For B6VM models, the A/B
switch must be set for the appropriate cabinet size (either
setting can be used for C-size cabinets). The airflow is set
automatically based on the amount of installed heat. For
both B6EM & B6VM models, the cooling speed is selected
via switches 5,6,7,& 8. To determine the appropriate
switch settings for your installation, see Table 6, (page
20) , Table 7, (page 21) , Table 8, (page 21) , or
Table 9, (page 22) .
Selecting Basic Cooling / Heat Pump Airflow
The basic cooling/heat-pump airflow is controlled by setting
switches 5 - 8 on the motor control board (mounted on the
blower). All airflows for other modes of operation (except
electric heat) are determined by this basic setting. FAN
ONLY would deliver 50% of the selected cooling airflow.
Table 8, (page 21) lists the basic airflow values versus
the airflow selector switch settings and ranges of basic
air flow settings recommended for each nominal system
capacity.
• When operating in the heat pump mode, a higher
basic airflow setting will increase the energy efficiency
and capacity but will also decrease the supply air
temperature.
• For maximum capacity and energy efficiency, select an
airflow at or near the top of the range for that nominal
capacity. See Table 8, (page 21) .
• For maximum dehumidification, select an airflow near the
middle or bottom of the range for that nominal capacity.
Additional information on humidity control can be found
in the Humidistat and Delay Setting sections.
• For thermostats with a dehumidifier output, use a field
supplied wire to connect the thermostat’s dehumidifier
output to the terminal marked DHUM. The thermostat
should be set so that the DHUM output should be high
(energized) when dehumidification is needed. See also
Dehumidification Options section.
IMPORTANT! If coil icing is observed, the basic cooling/
heat-pump airflow selected may be too low. Verify the
setting selected is within the range shown in Table 8 and
that the the system is properly charged. Please refer to
the instructions supplied with the outdoor unit. If icing
continues to occur, raise the selected airflow one or two
steps.
NOTE: Variable speed air handlers with SEER ratings
higher than 15 are matched with a 2-stage cooling outdoor
unit. They are programmed to operate at 75% of the
selected airflow while the system is in the lo-cool mode
and 100% of the selected airflow while in hi-cool mode.
Dehumidification Options
(B6EM or B6VM Models Only)
Both motor control boards
Figure 15 (page 24) & Figure
16 (page 24) have a DHUM connection that allows the
system to increase the amount of humidity that is removed
from the circulating air. This is accomplished by reducing
the CFM and allowing the cooling coil to become colder.
There are many ways that this can be electrically wired.
1. If the room thermostat incorporates a humidity sensor
and DHUM output, connect the DHUM on the thermostat
to the DHUM terminal on the motor control board.
2. If using a separate humidistat, connect the DHUM & R
terminals on the humidistat to the DHUM & R terminals
on the motor control board of the air handler. In this
option, the DHUM output of the humidistat must be set
to be normally open and closed when there is a call for
humidification. See
Figure 10 .
3. For cooling only system: If a humidistat is not available,
it is an acceptable option to connect the R & DHUM
terminals on the motor control board together with a
field supplied wire. This option causes the blower to run
at a reduced CFM for 10 minutes after a call for cooling.
NOTE: Heat pump systems must use a thermostat
with humidity sensor or separate humidistat to prevent
blower speed reduction in heat mode.