20
18-BB38D1-1D-EN
S
Stta
arrttiin
ng
g tth
he
e U
Un
niitt iin
n H
He
ea
attiin
ng
g M
Mo
od
de
e
N
No
otte
e:: See the section on Sequence of Operation for a
description of the heat pump heating operating
sequence.
Check that all grills and registers are open and all unit
access panels are closed before start-up.
Set the comfort control above room temperature until
achieving a first stage call for heat and set the fan to
A
AU
UT
TO
O or O
ON
N.
H
He
ea
attiin
ng
g S
Sh
hu
utt D
Do
ow
wn
n
Set the comfort control to O
OF
FF
F or at a setting below
room temperature.
Sequence of Operation
G
Ge
en
ne
erra
all
Operation of the unit heating and cooling cycles is
automatic when the system is in the H
HE
EA
AT
T or C
CO
OO
OL
L
functions (the optional automatic changeover
thermostat, when in the A
AU
UT
TO
O position, automatically
changes to heat or cool with an appropriate room
temperature change). The fan can be set to O
ON
N,
causing continuous evaporator (indoor) fan operation
or set to A
AU
UT
TO
O causing fan operation to coincide with
heating or cooling run cycles. Continuous fan mode
during Cooling operation may not be appropriate in
humid climates. If the indoor air exceeds 60% relative
humidity or simply feels uncomfortably humid, it is
recommended that the fan only be used in the A
AU
UT
TO
O
mode.
C
Co
oo
olliin
ng
g M
Mo
od
de
e
N
No
otte
e:: The T
TS
SH
H and T
TS
SC
C are contacts that are internal
to the indoor comfort control.
With the disconnect switch in the O
ON
N position, current
is supplied to the control transformer. The cooling
cycle is enabled through the low voltage side of the
control transformer to the “R
R” terminal on the indoor
thermostat. With the comfort control set to A
AU
UT
TO
O and
T
TS
SC
C--1
1 contacts closed, power is supplied to the
“O
O ” terminal on the indoor thermostat to the
switchover valve coil ((S
SO
OV
V)). This energizes the switch-
over valve ((S
SO
OV
V)) and places it in the cooling position
(it is in the heating position when de-energized).
When the indoor temperature rises 1-1/2 degrees, T
TS
SC
C--
2
2 contacts close, supplying power to the ""Y
Y"" terminal
on the indoor thermostat, and to the compressor
contactor ((C
CC
C)). This starts the outdoor fan motor and
compressor. The T
TS
SC
C--2
2 contacts also provide power to
the “G
G” terminal which provides power to the indoor
fan motor.
H
He
ea
attiin
ng
g M
Mo
od
de
e
With the comfort control set to O
ON
N, current is supplied
to the transformer. Starting at the “R
R” terminal on the
indoor comfort control, current goes through the
system switch (which is in “A
AU
UT
TO
O” position) to the
T
TS
SH
H--1
1 contacts. When closed, these contacts supply
power to terminal “Y
Y” on the indoor thermostat as well
as to the heating anticipator. The switch-over valve will
not energize because of the high resistance of the
heating anticipator in the thermostat. Power is
provided from “Y
Y” to the compressor contactor ((C
CC
C))
which starts the compressor and outdoor fan motor.
The indoor thermostat contact T
TS
SH
H--1
1 also provides
power to ""G
G"" terminal on the indoor thermostat
energizing the indoor fan motor.
S
Su
up
pp
plle
em
me
en
ntta
arry
y H
He
ea
att
The supplementary electric heat is brought on when
the indoor temperature drops 1-1/2 degrees below the
thermostat setting. T
TS
SH
H--2
2 contacts close providing
power to the “W
W” terminal on the indoor thermostat
and to the supplementary heater control circuit. An
outdoor thermostat may have been added to disallow
the second stage (if provided) of electric heat above a
selected outdoor temperature. If the outdoor
temperature falls below the setting on the outdoor
thermostat, this additional heater stage will come on.
When the outdoor air temperature rises, and the
outdoor T-stat setpoint is reached, the system will
revert back to first stage electric heating.
When the indoor ambient is satisfied, T
TS
SH
H--2
2 contacts
will open and the unit will revert back to the
compressor only heating mode and then off. For
e
em
me
errg
ge
en
nccy
y h
he
ea
att (use of supplementary electric heat
only), an emergency ((E
EM
ME
ER
RG
G)) heat switch is provided
within the comfort control. When placed in the
emergency heat position, it will disable the
compressor, bypass the outdoor thermostats, if
provided, and engage the supplementary electric
heaters and indoor fan.
E
EC
CM
M F
Fa
an
n M
Mo
otto
orr A
Ad
djju
ussttm
me
en
nttss
If the airflow needs to be increased or decreased, see
the Airflow Table in the Service Facts. Information on
changing the speed of the blower motor is in the
Blower Performance Table.
Blower speed changes are made on the ICM Fan
Control mounted in the control box. The ICM Fan
Control controls the variable speed motor.
There is a bank of 8 dip switches located at the upper
left side of the board. The dip switches work in pairs to
match the cooling/heat airflow (CFM/TON), Fan off-
delay options, and electric heat airflow adjustment. The
switches appear as shown in
