Bryant DUAL FUEL THERMOSTAT TSTAT - Manual

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 installa-
tion 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 CAU-
TION. These words are used with the safety-alert symbol. DAN-
GER 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.
INTRODUCTION
Bryant’s 7-day programmable dual fuel thermostat is a wall-
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 high-
pressure switch, one must be added for dual fuel appli-
cations. It protects HP from overpressure which would
occur if a failure resulted in both HP and furnace
operating at same time. Kit No. KSAHI0201HPS in-
cludes required switch and instructions for its proper
installation.
A HP/furnace installation has several special requirements. Fore-
most 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.
APPLICATION
The dual fuel thermostat is designed for the following 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 tem-
peratures 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 tem-
perature, 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 exclu-
sively, because it will have sufficient capacity to satisfy load.
Fig. 1—Bryant Programmable Thermostat
A95221
®
HEIGHT (IN.) WIDTH (IN.) DEPTH (IN.)
7-1/2 4-1/4 1-3/8
installation and
start-up instructions
PROGRAMMABLE DUAL FUEL THERMOSTAT
Cancels: New II TSTAT-0-6
6-95
TSTAT
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