Bryant DUAL FUEL THERMOSTAT TSTAT, TSTAT Installation And Start-up Instructions Manual
installation and
start-up instructions
PROGRAMMABLE DUAL FUEL THERMOSTAT
NOTE: Read the entire instruction manual before starting the
installation.
SAFETY CONSIDERATIONS
Read and follow manufacturer instructions carefully. Follow all
local electrical codes during installation. All wiring must conform
to local and national electrical codes. Improper wiring or installation may damage thermostat.
Recognize safety information. This is the safety-alert symbol
When you see this symbol on the equipment and in the instruction
manual, be alert to the potential for personal injury.
Understand the signal words DANGER, WARNING, and CAUTION. These words are used with the safety-alert symbol. DANGER identifies the most serious hazards which will result in severe
personal injury or death. WARNING signifies a hazard which
could result in personal injury or death. CAUTION is used to
identify unsafe practices which would result in minor personal
injury or product and property damage.
TSTAT
Cancels: New II TSTAT-0-6
6-95
®
.
A95221
Bryant’s 7-day programmable dual fuel thermostat is a wall-
INTRODUCTION
mounted, low-voltage thermostat which provides proper control of
a heat pump (HP) and furnace combination without using a
HP/furnace interface kit. Separate heating and cooling setpoints,
plus auto changeover allow setback programming for maximum
energy savings. Up to 4 time/temperature settings per 24 hour
period for 7 independent days may be programmed. Batteries are
not required; during a power interruption, the internal memory
stores programs for an unlimited time and the clock continues to
run for at least 72 hrs.
SYSTEM CONSIDERATIONS
The dual fuel thermostat is designed to be used only in HP/furnace
installations. It replaces a conventional 2-stage HP thermostat and
a HP/furnace interface kit. An outdoor temperature sensor, Part
No. TSTATBBSEN01 MUST be used with this thermostat. It is
not supplied with thermostat.
CAUTION: If HP is not already equipped with a highpressure switch, one must be added for dual fuel applications. It protects HP from overpressure which would
occur if a failure resulted in both HP and furnace
operating at same time. Kit No. KSAHI0201HPS includes required switch and instructions for its proper
installation.
A HP/furnace installation has several special requirements. Foremost is that furnace and HP must not be allowed to operate at same
time, except during HP defrost. A second is to have furnace
complete a heating cycle once it is turned on. A third is the need
to have HP not operate at all when outdoor temperatures are below
a certain value. Finally, HP and furnace must work together
properly to provide an efficient and comfortable defrost. These
requirements are addressed by the dual fuel thermostat itself and
an interface kit is NOT required.
Fig. 1—Bryant Programmable Thermostat
HEIGHT (IN.) WIDTH (IN.) DEPTH (IN.)
7-1/2 4-1/4 1-3/8
APPLICATION
The dual fuel thermostat is designedforthefollowing applications:
1-stage cool, 2-stage heat: 1-speed HP with 1-stage furnace
1-stage cool, 3-stage heat: 1-speed HP with 2-stage furnace
2-stage cool, 3-stage heat: 2-speed HP with 1-stage furnace
2-stage cool, 4-stage heat: 2-speed HP with 2-stage furnace*
*This combination must use furnace algorithm to control furnace
staging.
As outdoor temperature decreases, heat loss increases and HP
capacity decreases. There is a temperature below which HP will
not be able to "keep up" and furnace will be required to maintain
temperature. This is the thermal balance point.
There is also an economic balance point, determined by relative
costs of fuel and electricity, below which the furnace is the most
cost effective and above which the HP is the most cost effective.
Finally there may be a comfort balance point below which leaving
air temperature of HP is not comfortable, even if HP has sufficient
capacity to keep structure warm.
Any of these balance points may be the determining factor in the
selection of an outdoor temperature below which HP will be turned
off and only furnace allowed to operate. This balance point
temperature is entered into thermostat by installer. Outdoor temperatures from 15˚F to 55˚F may be selected. Instructions for
entering this selection is covered in the section: Balance
Point—Value Selection.
When outdoor temperature is below selected balance point temperature, furnace is used exclusively to supply heat.
When outdoor temperature is above both selected balance point
temperature and thermal balance point, HP will be used exclusively, because it will have sufficient capacity to satisfy load.
—1—
If selection of balance point temperature is such that it is below
thermal balance point, all operation between these 2 temperatures
will be part HP and part furnace. A heating cycle will begin with
HP operation. Because HP has insufficient capacity, structure
temperature will slowly fall. After a time, thermostat will issue
next stage call, turning off HP and turning on furnace. Furnace will
operate until thermostat is completely satisfied at which time
furnace will turn off. The next heating cycle will begin with HP
and cycle will repeat.
This operating mode is acceptable as long as selected balance point
temperature is not too far below thermal balance point. This
thermostat has no "droop" between stages, and structure will not
cool significantly below setpoint before furnace comes on. However, there is a 15-minute timer which requires HP to operate for
15 minutes before furnace comes on. If balance point temperature
is set too far below thermal balance point, the temperature loss
during this 15 minute period could be uncomfortable.
For most installations balance point temperature setting should be
in the range of 25˚F to 45˚F. If set too high, HP will not be used
enough and its advantages not realized. If set too low, structure
temperature loss during HP operation will become uncomfortable.
In case of 2-speed heat pumps or 2-stage furnaces, thermostat will
start equipment at low capacity and if this is not sufficient, will
advance to higher capacity. If load demand is between low and
high capacities, it will cycle between these 2 stages, i.e. between
low and high heat pump speeds or between furnace low and high
fire. However, once operation proceeds from HP to furnace, it will
NOT cycle directly back to HP. Furnace will remain on until all
stages of thermostat are satisfied.
DESCRIPTION OF OPERATION
COOLING OPERATION—SINGLE SPEED
HP cooling:
O/W2 energizes reversing valve to select cooling operation.
G energizes furnace blower.
Y/Y2 energizes compressor and selects high blower speed at
furnace.
When cooling demand is satisfied, G and Y/Y2 are de-energized.
O/W2 will remain on to minimize cycling of reversing valve. It
will turn off only when a call for heat occurs.
COOLING OPERATION—TWO SPEED
Low-speed HP cooling:
O/W2 energizes reversing valve to select cooling operation.
G energizes furnace blower.
Y1/W2 energizes compressor at low speed and may determine
furnace blower speed.
High-speed HP cooling:
Y/Y2 is added to low-speed cooling call to operate compressor at
high speed and increase blower speed.
HEATING OPERATION—SINGLE-SPEED HP
HP heating:
O/W2 remains off to select heating operation.
G turns on furnace blower.
Y/Y2 energizes compressor and increases furnace blower speed.
HEATING OPERATION—TWO-SPEED HP
Low-Speed HP heating:
O/W2 remains off to select heating operation.
G turns on furnace blower.
Y1/W2 turns on compressor at low speed and may also adjust
blower speed for low-speed HP operation.
High-Speed HP heating:
Y/Y2 is added to low-speed HP heating call to operate compressor
at high speed and adjust blower for high-speed HP operation.
HEATING OPERATION—SINGLE-STAGE FURNACE
W/W1 causes furnace to operate. Furnace controls its own blower
at heating speed.
HEATING OPERATION—TWO-STAGE FURNACE—
THERMOSTAT CONTROL
Low fire:
W/W1 causes furnace to operate at low fire. Furnace controls its
own blower at low heating speed.
High fire: Y1/W2 is added to low-fire heating call to operate
furnace in high-fire mode. Furnace controls its own blower at high
heating speed.
HEATING OPERATION—TWO-STAGE FURNACE—
ALGORITHM CONTROL
W/W1 causes furnace to operate. Based on amount of time it is
required to be on, it determines when to operate at low fire and
when to operate at high fire. It controls its own blower at proper
speed.
DEFROST OPERATION
A unique feature of this thermostat is that a defrost cycle, once
started, will always be completed. This is true even if thermostat is
satisfied during defrost. The result is that a heating cycle never
begins with an uncompleted defrost and its associated "cold blow".
During operation of HP in heating mode, HP itself determines
when a defrost is necessary. It initiates defrost by energizing its O
and W wires. The signal on the O wire switches HP from heating
to cooling mode and W signal starts furnace. Thermostat monitors
this action by sensing the signal (which it did not create) on the O
line. It responds by turning on its W outputs (both if 2-stage
furnace) to hold furnace on high fire. At completion of defrost,
indicated by removal of signal from HP on O wire, thermostat does
1 of 2 things. If it is satisfied, it turns off all Y, G, and W outputs
which results in all equipment off. If not satisfied, it will turn off
Y and G, leaving W on until it becomes satisfied. In this way it
assures that furnace will be used to satisfy a heat demand existing
after a defrost cycle is completed.
EMERGENCY HEAT
If EHEAT mode is selected at thermostat, all heating will be done
by furnace.
CONTINUOUS FAN
If FAN ON mode in selected, thermostat energizes G terminal,
which causes fan to operate when both heating and cooling are off.
STAGING SEQUENCE—HEATING
Depending on whether HP is single or 2 speed and whether furnace
is single or 2 stage, the staging of thermostat outputs with
increasing demand varies. Table 1 shows the heating staging
sequence for all 4 possible combinations of single- and multi-stage
equipment. Note that thermostat itself has a maximum of 3 heating
stages. Note also that at outdoor temperatures below selected
balance point temperature no HP operation is allowed. As discussed earlier, once furnace is turned on, it remains on to satisfy all
demand.
A "freeze protect" feature is built into the dual fuel thermostat. If
indoor temperature sensor fails, and thermostat is in HEAT or
AUTO mode, heat will be cycled when outdoor temperature is
below 50˚F. The amount of heat supplied will increase as outdoor
temperature decreases, keeping structure from freezing.
INSTALLATION
NOTE: All TSTAT models do not have batteries and are not
"power stealing". They do require 24VAC (R and C terminals) to
be connected for proper operation. Thermostat will not operate
without these 2 connections.
—2—
WIRING
DIAGRAM
Fig. 2
Fig. 3
Fig. 4
Fig. 5
SYSTEM
TYPE
1-speed HP
1-stage furnace
1-speed HP
2-stage furnace
2-speed HP
1-stage furnace
2-speed HP
2-stage furnace
TABLE 1—HEATING STAGES
OUTDOOR TEMP/
BAL. PT. TEMP
Above HP Furnace —
Below Furnace — —
Above HP Furnace Lo Furnace Hi
Below Furnace Lo Furnace Hi —
Above HP Lo HP Hi Furnace
Below Furnace — —
Above HP Lo HP Hi Furnace Lo or Hi
Below Furnace Lo or Hi — —
STAGE 1 STAGE 2 STAGE 3
I. THERMOSTAT LOCATION
Thermostat should be mounted:
• Approximately 5 ft (1.5m) from floor.
• Close to or in a frequently used room, preferably on an inside
partitioning wall.
• On a section of wall without pipes or duct work.
• In a location where the outdoor temperature sensor wires can be
routed to thermostat location. It is acceptable to use 2 separate
wires in thermostat cable to connect outdoor sensor. These
wires may be connected at furnace to another pair continuing to
outdoor heat pump. The outdoor sensor may then be mounted
and connected in vicinity of heat pump, but be sure it is not
located in direct sunlight.
Thermostat should NOT be mounted:
• Close to a window, on an outside wall, or next to a door leading
to the outside.
• Exposed to direct light and heat from a lamp, sun, fireplace, or
other temperature-radiating object which may cause a false
reading.
• Close to or in direct airflow from supply registers and return-air
grilles.
• In areas with poor air circulation, such as behind a door or in
an alcove.
II. SET DIP SWITCHES
There are 4 small switches on the back of the circuit board which
must be set by the installer. The ON position is indicated by small
letters on the switch itself. Ignore numbers 1-4 on the switch. The
switch designation (A through D) is on the circuit board next to the
switch. To change a switch position use the corner of a small
screwdriver to slide it between on and off. Make these selections
BEFORE installing the thermostat--it is much easier.
SWITCH A—NOT USED IN DUAL FUEL THERMOSTATS
This switch must be in OFF position in all dual fuel applications.
DO NOT turn ON.
SWITCH B—SETBACK RECOVERY
Selects between normal and smart recovery from setback. Normal
recovery changes to the new setpoint at the programmed time.
Smart recovery, which is active in heating mode only, starts earlier
and adjusts the setpoint slowly so that room temperature will arrive
at the programmed temperature at the programmed time.
TO SET:
OFF—for smart recovery. This is the factory default.
ON—for normal recovery.
SWITCH C—DISABLE LOW-AMBIENT COOLING
Use to allow or prevent cooling operation below an outdoor
temperature of 55˚F. Prevention of cooling below 55˚F adds to
compressor reliability. If outdoor temperature sensor fails or is
disconnected, cooling is allowed regardless of switch setting.
TO SET:
OFF—cooling is allowed at outdoor temperatures below 55˚F.
ON—cooling is disabled at outdoor temperatures below 55˚F.
SWITCH D—SELECT SINGLE-SPEED OR 2-SPEED HP
Use this switch to tell dual fuel thermostat whether it is controlling
a single- or 2-speed HP. It must be set properly.
TO SET:
OFF—for single-speed HP.
ON—for 2-speed HP.
III. INSTALL THERMOSTAT
WARNING: Before installing thermostat, turn off all
power to unit. There may be more than 1 power disconnect. Electrical shock can cause personal injury or death.
1. Turn OFF all power to unit.
2. If an existing thermostat is being replaced:
a. Remove existing thermostat from wall.
b. Disconnect wires from existing thermostat, 1 at a time.
Be careful not to allow wires to fall back into the wall.
c. As each wire is disconnected, record wire color and
terminal marking.
d. Discard or recycle old thermostat.
NOTE: Mercury is a hazardous waste and MUST be disposed of
properly.
3. Open thermostat rear door (mounting base) to expose
mounting holes. The base can be removed to simplify
mounting. Snap apart carefully at hinge to separate mounting base from remainder of thermostat.
4. Route thermostat wires through large hole in mounting
base. Allow an extra 10 to 12 in. of wire for connection to
terminals. Remove outer sheath over this entire length for
added flexibility.
5. Level mounting base against wall and mark wall through 2
mounting holes.
6. Drill two 3/16-in. mounting holes in wall where marked.
7. Secure mounting base to wall with 2 screws and anchors
provided, making sure all wires extend through mounting
base.
8. Adjust wire length and routing to allow proper closure of
thermostat. Strip each wire end no more than 1/4 in. to
prevent adjacent wires from shorting together. Match and
connect equipment lead wires to the correct terminals of the
thermostat connector. (See Fig. 2 through 5.) Both R and C
must be connected for proper thermostat operation.
CAUTION: Improper wiring or installation may damage
the thermostat. Check to make sure wiring is correct
before proceeding with installation or turning on unit.
—3—
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