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T6570, T8570 Series  
Digital Fan-Coil Thermostats  
PRODUCT DATA  
FEATURES  
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ꢀꢀ Simple user interface.  
ꢀꢀ Attractive modern styling ideal for offices or hotels.  
ꢀꢀ Digital display of ambient temperature, with user  
activated temperature display.  
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ꢀꢀ Digital display shows mode icons when cooling or  
heating relays operate, or when energy savings mode  
is active.  
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•
ꢀꢀ Push button setpoint adjustment.  
ꢀꢀ Switches allow manual control of system operation  
and fan speed.  
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ꢀꢀ Energy savings mode - external energy savings input  
from time switch, occupancy sensors or hotel cardkey  
overrides comfort setpoint with setback heating or  
cooling setpoint.  
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•
ꢀꢀ Energy savings input configurable, normally open or  
normally closed.  
ꢀꢀ Proportional plus integral (P+I) control algorithm for  
precision temperature regulation.  
ꢀꢀ Mounts directly onto wall or standard junction box or  
vertical junction box with optional adapter plate.  
ꢀꢀ Installer setup mode allows changes of operating  
parameters.  
APPLICATION  
•
•
ꢀꢀ Selectable °C or °F display.  
ꢀꢀ Adjustable deadband (some models) for heat and cool  
control.  
T6570 Series Digital Fan-Coil thermostats provide line voltage  
on/off control for fans, valves, compressors or auxiliary  
electric heaters in fan-coil and small air-conditioner  
applications.  
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ꢀꢀ Selectable energy savings setup cooling and setback  
heating setpoints.  
ꢀꢀ Adjustable maximum heating and minimum cooling  
setpoint limits.  
T8570 Series provides low voltage control of these functions.  
Models are available for control of single stage air-conditioner  
and various fan-coil units  
ꢀꢀ Adjustable minimum relay off-times (heating or  
cooling) for compressor short-cycle protection.  
ꢀꢀ EEPROM permanently retains user settings during  
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2-pipe.  
power loss (no batteries required).  
2-pipe with manual heat/cool changeover.  
4-pipe with manual heat/cool changeover.  
4-pipe with automatic heat/cool changeover.  
ꢀꢀ Capability to display temperature sensor failure for  
easier troubleshooting.  
ꢀꢀ Optional remote sensor (T8575D only).  
All models are suitable for multiple applications. Changes in  
output wiring and external links between wiring terminals can  
configure the thermostat for the appropriate application.  
Contents  
Application......................................................................... 1ꢀꢀ  
Features ............................................................................ 1ꢀꢀ  
Specifications .................................................................... 2ꢀꢀ  
Ordering Information ......................................................... 2ꢀꢀ  
Installation ......................................................................... 3ꢀꢀ  
Operation........................................................................... 4ꢀꢀ  
Operating Modes............................................................... 5ꢀꢀ  
Wiring ................................................................................ 6 ꢀ  
The fan can also be controlled from the thermostat. In some  
cases it is wired to run continuously and can be switched off  
with the On/Off switch. Other models can be installed with fan  
running continuously or cycling with the thermostat.  
Compressors and auxiliary electric heaters can be controlled  
using a relay or contactor controlled by the thermostat.  
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T6570, T8570 SERIES DIGITAL FAN-COIL THERMOSTATS  
SPECIFICATIONS  
Table 1.  
Features  
Number Energy Fan  
Applications  
Switches  
3-Speed  
Fan Heat/ Wiring  
Control  
Auto  
Changeover  
2-Pipe 4-Pipe  
of Savings On/  
Remote On/Off  
Models Voltage Fan Coil Fan Coil Relays Input Auto Deadband Adjust Sensor (SPST) (SP3T) Cool Diagram  
T6574B  
T6575B  
•2  
•1  
•3  
•
1
1
1
2
2
2
2
1
1
2
2
2
2
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•
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Fig. 6  
Fig. 7  
Fig. 8  
Fig. 9  
1
20V,  
2
2
08~  
77V,  
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•
•
•
•
•
•
•
•
•
•
•
•
•
• Fig. 10, 13  
Fig. 11, 13  
Fig. 12, 13  
Fig. 15  
5
0 -  
T6575C 60 Hz  
•
•
T6575D  
•
•
•
T8574B  
•2  
•1  
•
2
4V,  
Fig. 16  
T8575B  
T8575C  
•
•
Fig. 17  
Fig. 18  
Fig. 19  
Fig. 20  
5
0 -  
6
0 Hz  
•
•
•
•
•
T8575D  
•
•4  
1
Heating application  
Cooling application  
2
3
4
2-pipe system with external aquastat.  
optional accessory.  
Setpoint Range: 10°C to 30°C (50°F to 90°F).ꢀꢀ  
Supply Voltages: 24 (NEMA - rated transformer), 120, 230,  
Enclosure: (cover, base, and wallplate) Plastic.  
Control Performance: On/Off control with P+I algorithm  
gives typical control to 0.75°C (1.5°F) at 22°C (72°F) and  
50% duty cycle.  
2
77 Vac (±10%), 50/60 Hz. (depending on model select ed)  
.5 A.ꢀꢀ  
0
Ambient Ratings:ꢀ  
Temperature:ꢀꢀ  
Junction Box Mounting: Direct mounting on single gang  
NEMA 2" x 4" surface mount electrical box, or on 4" x 4"  
box with optional 272878 adapter plate.  
Operating Range: 5°C to 45°C (41°F to 113°F).ꢀꢀ  
Shipping and Storage Range: -20°C to 55°C (-4°F to  
1
31°F).ꢀꢀ  
Humidity Range: 5 to 95% RH, non-condensing at 26°C  
79°F).ꢀꢀ  
Wiring: 11 terminals; screw-in terminals capable of accepting  
up to 2 x 18 AWG, 1 x 14 AWG, or 1.5 mm2 wires. Some  
terminals pre-fitted with color-coded flyleads.  
(
Thermostat Output: 1spdt or 2 spst relay outputs (depending  
on model).  
ORDERING INFORMATION  
When purchasing replacement and modernization products from your TRADELINE® wholesaler or distributor, refer to the  
TRADELINE® Catalog or price sheets for complete ordering number.  
If you have additional questions, need further information, or would like to comment on our products or services, please write or  
phone:  
1
.ꢀꢀ Your local Honeywell Automation and Control Products Sales Office (check white pages of your phone directory).  
2.ꢀꢀ Honeywell Customer Careꢀꢀ  
1
885 Douglas Drive Northꢀꢀ  
Minneapolis, Minnesota 55422-4386ꢀꢀ  
In Canada–Honeywell Limited/Honeywell Limitée, 35 Dynamic Drive, Scarborough, Ontario M1V 4Z9.ꢀꢀ  
International Sales and Service Offices in all principal cities of the world. Manufacturing in Australia, Canada, Finland, France, ꢀ  
Germany, Japan, Mexico, Netherlands, Spain, Taiwan, United Kingdom, U.S.A.ꢀꢀ  
9
5C-10897–6ꢀꢀ  
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T6570, T8570 SERIES DIGITAL FAN-COIL THERMOSTATS  
Energy Savings Input: 24 Vdc dry contact, maximum resis-  
Table 2. Electrical Rating  
24V 120V 208V 230V 277V  
tance of 1000 ohms. Note 'Caution', page 3.  
5
0-60 Hz  
Protection Class: IP30.  
Amps (Resistive)  
3.8  
3.0  
3.8  
3.8  
3.0  
3.8  
3.0  
3.8  
3.0  
Approvals: CSA Certified C/US LR158158 for Canada and  
Full Load Inductive  
.01  
3
the U.S.A. Meets CE requirements.  
Pilot Duty  
100 VA  
Accessories: Adapter plate for mounting on single- or double-  
1
Equivalent to NEMA 1/8 horsepower rating; allowable load  
must be determined by adding nameplate full load and locked  
rotor rating of all loads.  
gang NEMA-standard vertical switch box:  
2
72878 - line voltage models, 24V 2000 series  
272881 - 24 V models, 1000 series  
T8109 - remote temperature sensor for  
T8575D W6380 - fan switching center for T8574/T8575  
products  
Minimum Operational Life (at maximum load): Thermostat  
contacts (at 120 Vac): 100,000 cycles  
Manual Switches: 10,000 operations.  
3
-5/16 (84)  
4
-3/16 (122)  
1-7/16 (37)  
2-3/8 (60)  
1-1/2  
(38)  
3
-11/16  
94)  
(
M12081A  
Fig. 1. Nominal dimensions in inches (mm)  
IMPORTANT  
INSTALLATION  
T6570 Series are line voltage powered devices.  
All wiring must comply with national and local electri-  
cal codes, ordinances and regulations.  
When Installing this Product...  
Provide disconnect means and overload protec-  
tion as required.  
1
.ꢀꢀ Read these instructions carefully. Failure to follow them  
could damage the product or cause a hazardous condi-  
tion.  
T8570 Series thermostats must be powered by an  
Approved 24 Vac, Class 2 transformer (such as a  
W6380 Relay Control Center).  
2
.ꢀꢀ Check the ratings given in the instructions and on the  
product to make sure the product is suitable for your  
application.  
3
.ꢀꢀ Installer must be a trained, experienced service techni-  
cian.  
Location  
4.ꢀꢀ After installation is complete, check out product opera-  
tion as provided in these instructions.  
The T6570, T8570 series thermostats are the temperature  
control element in a fan-coil or air-conditioning system. They  
must be located about 1.5m (5 ft.) above the floor in a position  
with good air circulation to sense room temperature.  
CAUTION  
The optional T8109 sensor can be used to sense temperature  
in return air ductwork, instead of at the thermostat  
Electrical Shock or Equipment Damage Hazard.  
Can shock individuals or short equipment circuitry.  
Disconnect power supply before installation.  
IMPORTANT  
Do not mount device where it can be affected by:  
1
2
3
4
.ꢀꢀ Drafts or dead spots behind doors or in corners.  
.ꢀꢀ Hot or cold air from ducts.  
.ꢀꢀ Radiant heat from the sun or appliances.  
.ꢀꢀ Unheated (uncooled) areas such as an outside wall ꢀ  
behind the thermostat.ꢀꢀ  
5.ꢀꢀ Concealed pipes or chimneys.  
3ꢀꢀ  
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T6570, T8570 SERIES DIGITAL FAN-COIL THERMOSTATS  
3
.ꢀꢀ Use both hands to pull the thermostat straight away from  
Mounting  
the wallplate.  
Any T6570, T8570 series thermostat can be mounted directly  
on the wall on a 65x65mm junction box, or a 2"x4" horizontal  
junction box. An optional adapter plate is available for  
mounting on a 4"x4" or vertical junction box. (See Fig. 2)  
Mounting screws are supplied for alternatives.  
1
ꢀ
2ꢀ  
1
2
3
4
.ꢀꢀ Feed leadwires through wiring access hole of wallplate  
and adaptor plate (if used).  
.ꢀꢀ Attach supply wires using wire nuts (not provided), or  
screw terminals, as appropriate.  
.ꢀꢀ Locate wallplate in the horizontal mounting position. See  
Fig. 2 if using the vertical junction box adapter plate.  
.ꢀꢀ Push leadwires into electrical junction box and attach  
wallplate to box using machine screws provided in the  
appropriate mounting holes.  
3
ꢀ
5
.ꢀꢀ Attach thermostat to wallplate:  
a.ꢀꢀ Locate the two center side holes on the back of the  
thermostat.  
M15396  
b.ꢀꢀ Align the holes with the two wallplate side tabs.  
c.ꢀꢀ Press down firmly to snap thermostat into place.  
Fig. 3. Removing the thermostat  
Thoroughly check wiring to the wallplate before finally  
mounting the thermostat on the wall.  
OPERATION  
Control  
PROPORTIONAL + INTEGRAL (P+I) CONTROL  
4
0007507-001  
Like a mechanical thermostat, the T6570, T8570 Series have  
On/Off control output. However, this output is regulated by a  
P+I algorithm, enabling the thermostat to control closer to  
setpoint than conventional thermostats. This results in  
performance where the space temperature is maintained within  
0.75°C (1.5°F) of the setpoint regardless of fan speed.  
P+I action minimizes the difference between the temperature  
setpoint and the effective control point by adjusting the output  
on-time until the control point matches the setpoint. The on-  
time is based on a fixed cycle rate of 4 cycles/hour for cooling  
(8 cycles/hour for heating), and the proportional band is 1.6°C  
M17505  
Fig. 2. Mounting the vertical junction box adapter plate  
M17505 Optional adapter plate.  
(2.9°F).  
Removing the thermostat  
NOTE:ꢀꢀ Integral action corrects the temperature control errors  
of proportional-only control, but it is slower to react to  
large temperature or setpoint changes.  
These thermostats also feature optional built-in time  
delays for equipment protection which can inhibit  
rapid response to large setpoint changes if active.  
CAUTION  
Improper removal can damage the thermostat.  
Equipment Damage Hazard.  
Carefully follow the thermostat removal directions.  
SINGLE-STAGE COOLING OR HEATING CONTROL (SEE FIG. 4)  
In cooling mode the user setpoint will be positioned at the  
bottom of the Proportional Band, so the setpoint will effectively  
be the temperature where the cooling switches off. In heating  
mode the user setpoint will be positioned at the top of the  
Proportional Band, and this will be the temperature where the  
heating switches off.  
If it is necessary to remove the thermostat from the wallplate  
see Fig. 3):  
(
1
.ꢀꢀ Use a screwdriver to pry thermostat left side away from  
the base.  
.ꢀꢀ Use the screwdriver to pry thermostat's right side away  
from the wallplate.  
2
NOTE:ꢀꢀ This also applies to models with manual heat/cool  
changeover.  
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T6570, T8570 SERIES DIGITAL FAN-COIL THERMOSTATS  
OFF MODE  
When the system switch is set to Off, power is removed from  
the thermostat electronics and output terminals, and the  
display will go blank. The thermostat will reboot when power is  
restored with the On/Off switch.  
SINGLE STAGE COOLING  
C
2
3.0  
2.5  
2.0  
1.5  
1.0  
0.5  
0.0  
2
2
2
2
2
2
PROPORTIONAL  
BAND  
USER  
SETPOINT  
1
NOTE:ꢀꢀ This On/Off switch is a functional switch and should  
not be used as an isolating switch.  
1
USER SETPOINT CHANGED  
TO 21.5 C (71 F) FROM  
23 C (73 F) OR 20 C (68 F).  
STARTUP  
SINGLE STAGE HEATING  
1ꢀꢀ  
USER  
C
On first powering up, or after the On/Off switch has been set to  
On, the thermostat undergoes a startup and self-checking  
sequence: First, all LCD display segments are illuminated to  
check the display. Next a number appears to indicate the  
software version. The final check is a check of the sensor. On  
completion of the startup sequence, after approximately 2  
seconds, the thermostat will resume normal control in either  
Comfort or Economy mode. On initial power on, the  
temperature setpoint defaults are as shown in the following  
table. The current setpoint is stored in EEPROM, and if the  
thermostat is switched off, then on again, it will resume control  
at the last known setpoint.  
23.0  
22.5  
22.0  
21.5  
21.0  
20.5  
20.0  
SETPOINT  
PROPORTIONAL  
BAND  
M17477  
Fig. 4. Single stage control.  
AUTOMATIC CHANGEOVER WITH ZERO ENERGY DEADBAND  
SEE FIG. 5)  
(
This type of control is available on auto-changeover models  
only. The user setpoint centers on the Zero Energy Deadband.  
The cooling switch-off-point is positioned at the bottom end of  
the cooling proportional band. Likewise, the heating switch-off  
point is positioned at the top end of the heating proportional  
band.  
Table 3. Power Up Default Setpoints  
Power Up Default Setpoints  
1
relay or heat cool changeover  
2 relay + cool  
sequence models  
models  
Zero Energy Deadband width is selectable in the Installer  
Setup mode.  
°C Scale °F Scale  
°C Scale °F Scale  
Setpoint  
Default  
22  
–
–
73  
–
–
22  
23  
21  
73  
75  
71  
EXAMPLE: Using a deadband of 2°C (4°F) and a user setpoint  
of 22°C (72°F), the effective heating setpoint is 21°C (70°F)  
and the effective cooling setpoint is 23°C (74°F). A change to  
the user setpoint causes both heating and cooling setpoints to  
change in parallel. This change is restricted to the minimum  
cooling setpoint or maximum heating setpoint limits set within  
the Installer Setup mode.  
CoolingOFF  
point  
HeatingOFF  
point  
COMFORT MODE  
This is the normal operating mode where the thermostat  
controls to the setpoint selected by the user. On initial power  
up, the user setpoint will return to the last known or default  
value. Control action will be determined by either the default  
settings or the installer-set parameters. (See page 6)  
C
COOLING  
2
2
2
2
2
2
2
2
2
2
2
2
5.5  
PROPORTIONAL  
BAND  
5.0  
4.5  
4.0  
3.5  
3.0  
2.5  
2.0  
1.5  
1.0  
0.5  
0.0  
DEADBAND  
USER  
SETPOINT  
ENERGY SAVINGS MODE  
Energy Savings mode is activated by a dry contact closure on  
the special Energy Management System (EMS) input from an  
occupancy detector, window contact, etc. If the signal via input  
terminals 10 and 11 is calling for Energy Savings mode, then  
the thermostat will control to user/installer defined setback  
setpoints for increased energy savings. The display will show a  
1
HEATING  
PROPORTIONAL  
BAND  
1
USER SETPOINT CHANGED FROM  
2 C (72 F) TO 23.5 C (74 F).  
2
M17478  
$
symbol to indicate the Energy Savings mode is active.  
Fig. 5. Sequence control with deadband.  
For example, if the user setpoint is 21°C (70°F) and the Energy  
Savings mode setpoint for cooling (unoccupied cooling  
setpoint) has been set to 28°C (82°F), then the thermostat  
controls to 28°C (82°F) when the input signal activates the  
economy mode. There is no user override as long as the EMS  
signal is present. The default Energy Savings mode setpoints  
are shown in table 4.  
OPERATING MODES  
The thermostat has two main operating modes: Comfort and  
Energy Savings. It also has an OFF mode selected by the On/  
Off switch.  
The Energy Savings mode input can be configured within the  
installer setup mode to be activated by either a short-circuit  
(default) or open-circuit signal.  
5ꢀꢀ  
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T6570, T8570 SERIES DIGITAL FAN-COIL THERMOSTATS  
Installer Setup Mode  
Table 4. Energy Saving Mode Default Settings  
Energy Savings Mode – Setpoints  
The thermostat allows many of its operating parameters to be  
adjusted via an Installer Setup Mode. Each operating  
parameter has a two-letter identifier code, which is shown on  
the display during the Installer Setup Mode programming  
sequence. A description of these is shown in Table 5.  
Heating Setpoint  
Cooling Setpoint  
Description  
Default  
18°C  
Range  
10-18°C  
50-65°F  
Default  
25°C  
Range  
25-30°C  
77-90°F  
°
C Scale  
F Scale  
PROGRAMMING PARAMETERS  
°
65°F  
77°F  
The installer setup mode is accessed by reducing the setpoint  
to 10°C (50°F), waiting 3 seconds or until the room  
temperature is displayed, and then pressing the [UP] and  
Additional Switches  
[DOWN] keys simultaneously for 3 seconds.  
FAN SPEED SWITCH (SP3T LINE VOLTAGE)  
Where supplied, the fan switch allows the selection of three  
different settings: low, medium, or high.  
If the installer setup has previously been entered and the  
Minimum Cooling Setpoint increased above 10°C (50°F), the  
installer setup mode is accessed by reducing the setpoint to  
the new value before pressing the two buttons.  
NOTE: The installer should select Constant Fan mode if the  
fan motor is a type that does not start reliably at low  
speed.  
The first parameter identifier will be displayed at this point and  
the parameter value can be changed by pressing the [UP] key.  
The first press displays the default value and any subsequent  
press alters the value. The values will wrap around.  
SYSTEM HEAT/COOL SWITCH (SPST LOW VOLTAGE)  
Where supplied, this switch signals the microprocessor to  
operate the relays in either heating or cooling mode: In heating  
mode, the cooling relay is disabled. In cooling mode, the  
heating relay is disabled.  
To select the parameter value and move to the next parameter,  
press [DOWN]. After the final parameter is selected, a further  
press of the [DOWN] key will exit from the programming mode.  
User Programming Modes  
PARAMETER VALUES  
Each parameter has a default value that is used when the  
thermostat is first powered up. This value can be changed from  
within the Installer Setup Mode, and once changed, it will be  
stored in the EEPROM so it is not lost in the event of power  
interruption.  
TEMPERATURE (COMFORT) SETPOINT  
The temperature setpoint can be adjusted between 10°C and  
3
0°C in steps of 0.5°C by using the [UP] and [DOWN] keys. If  
°F is set within the installer setup mode (see later), the range  
will be 50°F to 90°F, adjustable in 1°F steps.  
If the user wishes to restore the parameters to the default  
values, this can be done by changing the temperature scale tS  
from °C to °F (or °F to °C) and back again.  
DISPLAY  
The measured room temperature is normally displayed (unless  
rt = 0 in the installer setup mode), and the first press of the  
[UP] or [DOWN] keys will switch to display the user setpoint. If  
PROGRAMMING EXAMPLE  
no key is pressed for 5 seconds, the display will return to  
To enter the installer setup mode:  
showing the room temperature.  
1.ꢀꢀ Press to change the temperature setpoint to 10°Cꢀꢀ  
When the cooling relay is closed, this will be indicated by a  
(50°F).ꢀꢀ  
(snowflake) symbol, whereas closure of the heating relay will  
2.ꢀꢀ Wait 3 seconds, or until the room temperature is dis-  
be indicated by a (flame) symbol.  
played.  
.ꢀꢀ Press and hold together until [tS] is displayed.  
3
If there is a wiring problem or the room temperature is less  
than 5°C (40°F) or over 38°C (100°F) the display will return a  
SF (Sensor Failure) warning. If this warning is not due to a  
wiring problem it will disappear once the remote sensor or  
thermostat comes within the 4.5 to 37.8°C (40 to 100°F) range.  
If the SF warning is due to a faulty remote sensor connection  
the thermostat will not transfer measurement to the internal  
sensor. To resolve the faulty connection the thermostat must  
be powered down, the remote sensor connection must be  
removed or fixed and then the thermostat must be re-powered.  
4.ꢀꢀ Press once to show the default Temperature Scale ꢀ  
value. Continue to show all possible values of this ꢀ  
parameter in sequence.ꢀꢀ  
5.ꢀꢀ When the desired value is displayed, it is selected by  
pressing once. This will also move to the next parameter,  
whose identifier will now be displayed.  
6.ꢀꢀ Continue to use to move from one parameter to the next,  
and to alter the parameter value.  
7.ꢀꢀ When the last parameter [rt] has been selected, a final  
press of will return the display to its normal operating  
mode.  
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T6570, T8570 SERIES DIGITAL FAN-COIL THERMOSTATS  
Table 5. Thermostat Parameter Options  
C Scale  
Values  
°
°F Scale  
Values  
Parameter  
ID  
Description  
Allows selection of either °C or °F scale Yes  
Setting deadband (Zero Energy Band)  
Default  
Default  
Temperature Scale tS  
–
No  
4
–
Dead Band  
db  
2
2, 3, 4  
3, 4, 5  
Heat or Cool  
Operating Mode  
OP Setting operating mode on single relay, 0  
non-changeover models, to either Heat  
or Cool  
0: cool  
1: heat  
0
0: cool  
1: heat  
Unoccupied Cooling uC  
Setpoint  
Program unoccupied cooling setpoint  
for energy savings.  
25  
25 to 30  
10 to 18  
77  
65  
0
77 to 90  
50 to 65  
Unoccupied Heating uH  
Setpoint  
Program unoccupied heating setpoint 18  
for energy savings  
Minimum Cooling  
Off Time  
CO Setting cooling off-time for short cycle  
0
0, 3, 4, 5  
0, 3, 4, 5  
10 to 30  
10 to 30  
0, 3, 4, 5  
0, 3, 4, 5  
50 to 90  
50 to 90  
prevention.  
Minimum Heating  
Off Time  
HO Setting heating off-time for short cycle  
0
0
prevention.  
Minimum Cooling  
Setpoint (Low Limit)  
CL  
HL  
ES  
Sets the minimum allowable cooling  
setpoint.  
10  
30  
1
50  
90  
1
Maximum Heating  
Setpoint (High Limit)  
Sets the maximum allowable heating  
setpoint.  
Energy Savings  
Activate energy savings mode by a  
choice of either contact closure or  
contact opening.  
1: normally open  
0: normally closed  
1: normally open  
0: normally closed  
Configuration  
Display of Room  
Temperature  
rt  
Allows installer to restrict temperature  
display to set point only. With this  
parameter, the unit will only display the  
set point temperature. Useful where  
setpoint limits (HL and CL) will affect  
control performance and Room  
Temperature display will disagree with  
user setpoint.  
1
1: room temp.  
0: setpoint only  
1
1: room temp.  
0: setpoint only  
WIRINGꢀꢀ  
Table 6. Leadwire Color Code (if fitted)  
Terminal  
Color  
Black (BK)  
White (WH)  
Orange (OR)  
Yellow (YL)  
Gray (GY)  
Violet (VI)  
Red (RD)  
Blue (BU)  
Brown (BN)  
–
Use  
1
2
3
4
5
6
7
8
9
L1 (Hot)  
L2 (N)  
Heat  
Cool  
Damper  
Fan Common  
Fan Low  
Fan Medium  
Fan High  
Fig. 6. Wiring 2-pipe cool-only thermostat with fan On/Auto  
switch.  
10  
Energy Mgt.  
System  
11  
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95C-10897–6  
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T6570, T8570 SERIES DIGITAL FAN-COIL THERMOSTATS  
Fig. 10. Wiring 4-pipe, heat/cool with manual heat/cool  
changeover switch, continuous fan.  
Fig. 7. Wiring 2-pipe heat-only thermostat with fan On/Auto  
switch.  
Fig. 11. Wiring 4-pipe, auto heat/cool changeover.  
Fig. 8. Wiring 2-pipe seasonal heat/cool changeover with  
external aquastat, fan On/Auto switch.  
Fig. 12. Wiring 4-pipe, auto heat/cool changeover, with fan  
On/Auto switch.  
Fig. 9. Wiring 2-pipe heat/cool with manual heat/cool  
changeover switch, continuous fan or cycled fan.  
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T6570, T8570 SERIES DIGITAL FAN-COIL THERMOSTATS  
Fig. 13. Wiring 4-pipe, heat/cool with manual heat/cool  
changeover switch, cycled fan, using external relay.  
Fig. 16. Wiring 2-pipe 24V heat thermostat with fan On/ꢀ  
Auto switch.ꢀꢀ  
Fan-Relay Control Center  
T8570 thermostats are typically used with load relays to switch  
line voltage loads. Honeywell offers a convenient fan-relay  
center, the W6380, that provides 24 Vac power, three  
interlocked fan relays, and wiring center terminations for valve,  
relay and contactor loads. The W6380 schematic can be found  
in Fig. 14.  
Fig. 17. Wiring 2-pipe heat/cool with manual heat/cool  
changeover switch, continuous or cycled fan.  
Fig. 14. W6380 wiring diagram.  
Fig. 18. Wiring 4-pipe 24V heat/cool with manual heat/cool  
changeover switch, continuous fan.  
Fig. 15. Wiring 2-pipe, 24V cool-only thermostat with fan  
On/Auto switch.  
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T6570, T8570 SERIES DIGITAL FAN-COIL THERMOSTATS  
T8575D will find the new sensor source and use this for  
control. To extend the sensor cable, up to a maximum of 70  
feet (20m), use only shielded cable. For example, Beldfoil® 18  
AWG cable is a suitable cable. The sensor connections are  
polarity sensitive, so be sure to connect the shielded wire to  
the sensor blue wire, as shown in Fig. 21 below.  
Fig. 19. Wiring 4-pipe 24V auto heat/cool changeover with  
continuous fan.  
Fig. 21. Wiring optional remote sensor for the T8575D  
model.  
CAUTION  
Equipment Damage Hazard.  
Operation at low temperatures can cause fan coil  
damage.  
This thermostat is not a safety device. Do not use it  
where the space temperature is outside of the device  
operating range.  
A display of SF indicates a space temperature outside  
of the thermostat operating range (5°C to 45°C).  
With SF displayed, the thermostat ceases to  
operate.  
Fig. 20. Wiring 4-pipe 24V auto heat/cool changeover  
thermostat with fan On/Auto switch.  
Wiring Remote Sensor  
CAUTION  
The T8109 is a optional remote sensor that can be used as an  
alternative to the internal sensor of the T8575D. The T8109  
remote sensor plugs into the J2 header in the back of the  
thermostat. On power-up the T8575D will look for a T8109 and  
if there is one connected it will use this control. If it does not  
find a T8109 connected it will use the internal sensor. To  
change the sensor source, turn off the thermostat power and  
disconnect the current sensor source. Then connect the new  
sensor source and re-power the thermostat. On powerup the  
Equipment Damage Hazard.  
Improper operation can cause compressor  
damage.  
Do not operate cooling if outdoor temperature is below  
5
0ºF (10°C). Refer to manufacturer recommendations.  
To avoid compressor damage, allow the compressor to  
remain off for five minutes before restarting.  
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T6570, T8570 SERIES DIGITAL FAN-COIL THERMOSTATS  
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T6570, T8570 SERIES DIGITAL FAN-COIL THERMOSTATS  
Automation and Control Solutions  
Honeywell International Inc.  
985 Douglas Drive North  
Honeywell Limited-Honeywell Limitée  
1
35 Dynamic Drive  
Golden Valley, MN 55422  
customer.honeywell.com  
Scarborough, Ontario M1V 4Z9  
®
©
U.S. Registered Trademark  
2005 Honeywell International Inc.  
9
5C-10897–6 M.A. Rev. 09-05  

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