Tempstar F8MTL, Installation Instructions Manual

Page: 47 / 52

47
441 01 2101 05
Specifications are subject to change without notice.
furnace blower motor BLWM on cool speed.
The electronic air cleaner terminal EAC 1 AMP is
energized with 115 vac when the blower motor BLWM
is operating.
When the thermostat is satisfied, the R − to − G and − Y
circuits are opened. The outdoor unit will stop, and the
furnace blower motor BLWM will continue operating on
the COOL speed for an additional 90 seconds. Jumper
Y/Y2 to DHUM to reduce the cooling off − delay to 5
seconds. (See Figure 24)
b. Two − Speed Cooling
The thermostat closes the R − to − G − and − Y1 circuits for
low − cooling or closes the R − to − G − and − Y1 − and − Y2 circuits
for high − cooling. The R − to − Y1 circuit starts the outdoor unit
on low − cooling speed, and the furnace control
R − to − G − and − Y1 circuit starts the furnace blower motor
BLWM on low − cool speed (same speed as LO HEAT). The
R − to − Y1 − and − Y2 circuits start the outdoor unit on
high − cooling speed, and the furnace control R − to − G − and − Y1
and − Y2 circuits start the furnace blower motor BLWM on
COOL speed. The electronic air cleaner terminal EAC 1 AMP
is energized with 115 vac whenever the blower motor BLWM
is operating. When the thermostat is satisfied, the
R − to − G − and − Y1 or R − to − G − and − Y1 − and − Y2 circuits are
opened. The outdoor unit stops, and the furnace blower
BLWM and electronic air cleaner terminal EAC 1 AMP will
remain energized for an additional 90 seconds. Jumper Y1 to
DHUM to reduce the cooling off − delay to 5 seconds. (See
Figure 33)
4. Dehumidify Mode
(See Figure 26 − Figure 32 for humidity sensing
thermostat connections) The dehumidification output, H
on the humidity sensing thermostat should be
connected to the furnace control thermostat terminal
DHUM. When there is a dehumidify demand, the
DHUM input is activated, (24 vac signal is removed
from the H input terminal). In other words, the DHUM
input logic is reversed. The DHUM input is turned ON
when no dehumidify demand exists.
Activation/Deactivation
Once 24 vac is detected by the furnace control on the
DHUM input, the furnace control operates enables the
dehumidify mode. If the DHUM input is off for more
than 48 hours, the furnace control disables the
dehumidify mode.
The cooling operation described in item 3. above also
applies to operation with a humidity sensing
thermostat. The exceptions are listed below:
a. Low cooling − When the R − to − G − and − Y1 circuit is
closed and there is a demand for dehumidification,the
furnace blower motor BLWM will continue running at
low − cool speed (same speed as LO HEAT).
b. High cooling − When the R − to − G − and − Y/Y2 circuit is
closed and there is a demand for dehumidification,the
furnace blower motor BLWM will drop the blower
speed from COOL to HI HEAT for a maximum of 10
minutes before reverting back to COOL speed. If there
is still a demand for dehumidification after 20 minutes,
the furnace control CPU will drop the blower speed
back to HI HEAT speed. This alternating 10 − minute
cycle will continue as long as there is a call for cooling.
c. Cooling off − delay − When the “call for cooling” is
satisfied and there is a demand for dehumidification,
the cooling blower − off delay is decreased from 90
seconds to 5 seconds.
5. Continuous Blower Mode
When the R − to − G circuit is closed by the thermostat,
the blower motor BLWM will operate on
continuous − blower speed LO HEAT speed. Terminal
EAC 1 AMP is energized as long as the blower motor
BLWM is energized. During a call for heat, the blower
BLWM will stop during igniter warm − up (17 seconds),
ignition (7 seconds), and blower − ON delay (45
seconds in low − heat, and 25 seconds in high − heat),
allowing the furnace heat exchangers to heat up more
quickly, then restarts at the end of the blower − ON delay
period at LO HEAT or HI HEAT speed respectively. The
blower motor BLWM will revert to continuous − blower
speed after the heating cycle is completed. In
high − heat, the furnace control CPU will hold the blower
motor BLWM at HI HEAT speed during the selected
blower − OFF delay period before reverting to
continuous − blower speed.
When the thermostat “calls for low − cooling”, the blower
motor BLWM will operate at low − cool speed (same
speed as LO HEAT).
When the thermostat “calls for high − cooling”, the
blower motor BLWM will operate at COOL speed.
When the thermostat is satisfied, the blower motor
BLWM will operate an additional 90 seconds on COOL
speed before reverting back to continuous − blower
speed.
When the R − to − G circuit is opened, the blower motor
BLWM will continue operating for an additional 5
seconds, if no other function requires blower motor
BLWM operation.
6. Heat Pump
(See Figure 26 − Figure 32 for thermostat
connections)
When installed with a heat pump, the furnace control
automatically changes the timing sequence to avoid
long blower off times during demand defrost cycles.
When the R − to − W/W1 − and − Y1 or
R − to − W/W1 − and − Y1 − and − G circuits are energized the
furnace control CPU will switch to or turn on the blower
motor BLWM at low − cool speed (same speed as LO
HEAT), and begin a low − heat cycle. The blower motor
BLWM will remain on until the end of the prepurge
period, then shut off for 24 seconds then come back on
at LO HEAT speed. When the W/W1 input signal
disappears, the furnace control begins a normal
inducer post − purge period and the blower remains
running at LO HEAT speed. If the R − to −
W/W1 − and − Y1 − and − G signals disappear at the same
time, the blower motor BLWM will remain on for the
selected heat − off delay period. If the
R − to − W/W1 − and − Y1 signals disappear, leaving the G
signal, the blower motor BLWM will remain on for the
selected heat − off delay period then switch to
continuous − blower speed.
When the R − to − W/W1 − and − Y/Y2, R − to − W/W1 − and −
Y/Y2 − and − G, R − to − W/W1 − and − Y1 − and − Y/Y2, or
R − to − W/W1 − and − Y1 − and − Y/Y2 − and − G circuits are
energized the furnace control CPU will switch to or turn
on the blower motor BLWM at COOL speed, and begin
a high − heat cycle. The blower motor BLWM will remain
on until the end of the prepurge period, then shut off for
24 seconds then come back on at HI HEAT speed.
When the W/W1 input signal disappears, the furnace
control begins a normal inducer post − purge period and
the blower switches to COOL speed after a 3 second
delay. If the R − to − W/W1 − and − Y/Y2 − and − G or
R − to − W/W1 − and − Y1 − and − Y/Y2 − and − G signals
disappear at the same time, the blower motor BLWM
will remain on for the selected heat − off delay period If
the R − to − W/W1 − and − Y/Y2 or R − to − W/W1 −
and − Y1 − and − Y/Y2 signals disappear, leaving the G
signal, the blower motor BLWM will remain on for the
selected heat − off delay period then switch to
continuous − blower speed.
Step 4 — Wiring Diagrams
Refer to wiring diagram, Figure 55.
Step 5 — Troubleshooting
Refer to the service label. (See Figure 51 —Service Label)