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Installer's Guide
Flat Coil Application (Horizontal)
1. Select a location to make a 1-1/2" hole for the bonnet
thermostat to pass thru (see Figure 1).
2. The location of the 1-1/2" hole should be between indoor
unit (furnace) and flat coil and approximately 6" in from
the side of the duct.
3. With the template provided make a 1-1/2" hole in duct,
then install the bonnet thermostat with the screws
provided.
IMPORTANT:
After making the 1-1/2" hole with the template provided, duct,
liner and foil materials MUST be removed so that air flow
restriction does not occur.
INSTALLATION OF CONTROL WIRING
The control wiring is connected to the Plus One Control
Center per the field wiring diagrams and figures. If the gas
furnace has an integrated control, Y from thermostat must be
connected per field wiring diagram Note 4.
SEQUENCE OF HEATING OPERATION
Non-restrictive Mode – (As shipped)
Upon a call for first stage heat, the heat pump (only) operates
in heating. If the outdoor temperature is high enough that
the heat pump can handle the load, first stage will be
satisfied after the required run time and the system shuts off
until the next (first stage) call for heat.
1
S U P P L Y D U C T
H O R I Z O N T A L A P P L I C A T I O N
CLASS 2 LOW VOLTAGE
WIRING TO SYSTEM
CONTROLLER
S U P P L Y
D U C T
© 2003 American Standard Inc. All Rights Reserved
" A " C O I L U P F L O W
A P P L I C A T I O N
" A " C O I L
B O N N E T T H E R M O S T A T
C O I L
" A " C O I L
E N C L O S U R E
F R O N T C O I L B A F F L E
HORIZONTAL
FURNACE
SEE NOTE 1 ABOVE
If the outdoor temperature is below the balance point of the
system, and the heat pump cannot handle the load, when the
temperature in the room drops approximately 1-1/2 degrees
further, second stage heat is called for. Second stage turns
the heat pump off and simultaneously brings the furnace on.
The furnace will now satisfy the second stage only. The first
stage of the thermostat is still calling. After a minimum
delay of 45 seconds, the heat pump will resume operation. If
the indoor temperature continues to rise, the thermostat will
be satisfied. If indoor temperature does not continue to rise
but falls, the second stage will call and bring on the gas
furnace again.
Moving thermostat with emergency heat switch to the
"EMERGENCY HEAT" position converts the system to
"furnace only" operation.
Restrictive Mode – (Requires TAYSTAT250A)
The O.D.T. changeover must be at or above the application
balance point of the system. The heat pump alone cannot
handle the load at outdoor temperatures below the applica-
tion balance point.
At any temperature above the setting of the O.D.T., the heat
pump only will operate when called for by the first stage of
the thermostat. When the outdoor temperature drops below
the setting of the outdoor thermostat, the call for heat goes to
the furnace and the heat pump is cut off. When the outdoor
temperature rises above the setting of the outdoor thermo-
stat, the system returns to heat pump (only) operation.
Moving thermostat with emergency heat switch to the
"EMERGENCY HEAT" position converts the system to
"furnace only" operation.
A " C O I L D O W N F L O W
N O T E 2
2 .
F L A T C O I L
H O R I Z O N T A L A P P L I C A T I O N
N O T E 3
3 .
A P P L I C A T I O N
(from 146682)
18-BH15D7-4
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