Honeywell T8024D Product Data page 10

T8000C, T8001C AND T8024D PROGRAMMABLE THERMOSTATS
Cooling
CAUTION
Damage To Compressor Possible.
Operating at too low of an outdoor temperature
may cause compressor damage.
Do not operate cooling if outdoor temperature is below
50°F (10°C).
Allow compressor to remain off for five minutes before
restarting. Refer to manufacturer's recommendations.
1. Slide the SYSTEM switch to Cool and the FAN switch
to Auto.
2. Press the key to lower the temperature setting
several degrees below the room temperature; the
cooling equipment should start. The fan starts and
stops with the cooling equipment.
3. Press the key to raise the temperature setting above
the room temperature. Cooling system should shut down.
NOTE: To prevent damage to the compressor the T8000C/
T8001C have a built-in off-timer. See page 11.
Fan
1. Slide the SYSTEM switch to Off and the FAN switch to
On. The fan should run continuously.
2. Slide the FAN switch to Auto. In heating, the fan is
controlled directly by the heating equipment and may
start a few minutes after the heating equipment turns
on (most systems). When using an electric heat
LOGIC/
CONTROL
CIRCUIT
MOSFET
STAGE 1
HEAT OR
COOL
MOSFET
HEAT 2
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2
FACTORY INSTALLED JUMPER.
68-0195–2
THERMOSTAT
POWER
SUPPLY
SYSTEM
SWITCH
HEAT
OFF
COOL
FAN
SWITCH
FUEL
F ON
E
SWITCH
AUTO
Fig. 15. T8000C power stealing internal schematic.
thermostat, the fan starts and stops with the heating
equipment. In cooling, the fan starts and stops with the
cooling equipment.
Make certain all equipment responds properly to the
thermostat.
Power Stealing
Unlike hard wired thermostats which are powered directly
from the system transformer, the T8000C Thermostat steals
power through the heating and cooling system controls and
can be used in applications where existing wiring does not
permit using hard wired thermostats. See Fig. 15 and 16.
Previous Honeywell power stealing thermostats required 80 mA
of load current when the heating and cooling was on. The
T8000C Thermostat requires only 2.5 mA of load current (1/32
of previous models) when the heating or cooling is on. When
the heating or cooling is off, the thermostat operates at 0.1 mA
(1/100 of previous models). Other Honeywell power stealing
thermostats are available, but they have different powering
requirements than the T8000C. This low current draw makes
the T8000C applicable to most 24V heating and cooling
systems.
The thermostats only operate when mounted on the wallplate
with 24V applied. Batteries are not required for operation
because temperature setpoints and configuration settings are
retained permanently in nonvolatile memory.
The T8000C is packaged with a 7870 ohm resistor to insure
compatibility with TACO zone valves. See Fig. 17.
WALLPLATE
10
SYSTEM COMPONENTS
L1
(HOT)
R
2
L2
1
W
HEAT RELAY
B
HEAT CHANGEOVER RELAY
COOL CHANGEOVER RELAY
O
L1
(HOT)
RC
COMPRESSOR
L2
RELAY
1
Y
FAN RELAY
G
M11730