21
1. Setting the Autostage jumper in the
SHORT
position
signals the control to utilize an 8 minute delay between
LOW
fi re and
HIGH
fi re when a call for heat is supplied
via 24V signal to
W1
. This setting is the same as jumping
R
to
W2
2. Setting the Autostage jumper in the
LONG
position
signals the control to utilize an 12 minute delay between
LOW
fi re and
HIGH
fi re when a call for heat is supplied
via 24V signal to
W1
. This setting is the same as jumping
W1
to
W2
Autostaging for Two-Stage Thermostats
The Autostage setting on the furnace control board (Figure
23, page 33) is disabled when shipped from the factory.
This feature will be not used when paired with a two-stage
thermostat. The autostage jumper setting (
P7
) must be
kept on
NONE
to allow the thermostat to adjust stages.
Please note that on certain thermostats, even without the
autostage jumper in the
LONG
position,
W1
&
W2
may
be energized at exactly the same time when a recovery
from a set-back begins, the user adjusts the set point,
or the system is powered on. If
W1
&
W2
are energized
at exactly the same time for any reason, the control will
operate in the autostage
LONG
(12 minute) mode. If the
autostage jumper is in the
NONE
position and autostaging
is activated unexpectedly for any of the reasons listed, it
will return to normal, staged operation after the completion
of the heating cycle.
Heat Anticipator
Set the heat anticipator according to the instructions
supplied by the thermostat manufacturer.
To determine
the heat anticipator setting:
1. Add the current draw of the system components; or
2. Measure the current fl ow on the thermostat
R
&
W
circuit after the circulating blower motor has started.
Dehumidifi cation Options
Both motor control boards (Figures 21 & 22, page 33)
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. This
will only occur when there is a call for cooling. 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. See
Figure 18.
2. If using a separate humidistat, connect the
DHUM
&
R
terminals on the humidistat to the
DHUM
&
R
terminals
on the motor control board. In this option, the
DHUM
output of the humidistat must be set to be normally
open and closed when there is a call for humidifi cation.
3. If a humidistat is not available, it is an acceptable option
to connect the
R
&
DHUM
terminals on the motor
DHUM
R
R
DHUM
HUMIDISTAT
MOTOR
CONTROL BOARD
Figure 18. DHUM Wiring Confi guration
Blower Speed Confi guration
Two-stage furnaces use high effi ciency circulating air
motors that come in two variations and both are controlled
differently. The fi xed speed motor control board (Figure 21,
page 33) controls the torque and the variable speed motor
control board (Figure 22,) controls the airfl ow at a constant
CFM. Both boards use the same furnace control board.
Fixed Speed Blowers
NOTE:
This section applies only to furnaces with model
numbers suffi xed with two numbers, followed by a letter,
such as 35C1 or 45D1. If your model has suffi x VA1, VB1,
VC1, or VD1, please consult the Variable Speed Blower
Application section.
The fi xed speed motor control board (Figure 21) contains
a set of dip switches for setting the blower speed. Use
pins 1 to 4 to set the blower speed for heating and pins
5 to 8 to set the speed for cooling. To determine the
appropriate switch settings for your installation, refer to
Table 5 (pages 29 - 30).
For thermostats with a dehumidifi er output, use a fi eld
supplied wire to connect the thermostat’s dehumidifi er
output to the terminal marked
DHUM.
The thermostat
should be set so that the
DHUM
output should be high
(positive) when dehumidifi cation is needed. See also
Dehumidifi cation Options section.
CAUTION:
The terminal marked “Y1_IN” on the variable
speed motor control board is not an output to
drive the outdoor unit. DO NOT connect Y1_IN
on the motor control board to the outdoor unit.
Variable Speed Blowers
NOTE:
This section applies only to models ending with
the suffi xes VA1, VB1, VC1, or VD1.
The variable speed motor control board (Figure 22) has a
set of dip switches for setting the base blower speed (CFM).
Use pins 1 to 4 to set the blower speed for heating and
pins 5 to 8 to set the speed for cooling. To determine the
appropriate switch settings for your installation, see Table
6 (page 31) for heating or Table 7 (page 32) for cooling.
control board together with a fi eld supplied wire. This
option causes the blower to run at a reduced CFM for
10 minutes after a call for cooling.
