Honeywell T6800 Series Large LCD Digital Thermostat
110/220 VAC, 2-pipe fan coil control
Data sheet
Application
The T6800 digital thermostats are designed for the application of 3-speed fan and valves in 2-pipe fan coil systems. This includes:
- 2-pipe cool only, heat only, or manual changeover between heat and cool.
- Ventilation mode.
- Manual or automatic 3-speed fan control.
- Water valve control.
Fan speed can be selected to automatic or manual 3-speed control mode. In ventilation mode, the fan only supports manual speed control.
Features
- Modern appearance design, suitable for office, hotel, and residential buildings.
- Horizontal and vertical models available for varied applications.
- Slim design, direct installation on an 86-size box.
- Large LCD with English and icon display.
- Easy to install and set up.
- Selectable room temperature or setpoint display.
- Manual or automatic fan speed selection by button press.
- Remote temperature sensor compatibility.
- Energy saving mode activation by button press or dry contact (key card) ⚡.
- Cycle per Hour (CPH) function.
- Adjustment of display room temperature.
- Temperature unit selectable between °C or °F.
- User settings are retained when power is off.
- Freezing protection function available.
- Option to lock or unlock keys or part of keys in Installer Set-Up.
- Heat and cool setpoint limitation for energy saving.
Model Summary
| Model | Horizontal/ Vertical | 2-pipe/ 4-pipe | Operating voltage (V) | Energy saving | Ventilation | Manual /Automatic fan | Remote sensor |
|---|---|---|---|---|---|---|---|
| T6800H2WN | Horizontal | 2 | 220 | Y | Y | Y | Y |
| T6800V2WN | Vertical | 2 | 220 | Y | Y | Y | Y |
| T6800H1WN | Horizontal | 2 | 110 | Y | Y | Y | Y |
| T6800V1WN | Vertical | 2 | 110 | Y | Y | Y | Y |
Note: Horizontal models are taken as samples for display, operation, and installation pictures shown in below parts.
Mechanical Design
Thermostat Appearance
Image of the Honeywell T6800 thermostat showing its front panel. Key controls include FAN BUTTON, POWER BUTTON, and MODE BUTTON. The display area is labeled DIGITAL DISPLAY, with UP BUTTON and DOWN BUTTON for adjustments.
LCD Display
The LCD display provides various indicators: "INDICATES THE KEYPAD IS ENTIRELY OR PARTLY LOCKED", "CURRENT FAN SETTING", "CURRENT MODE SETTING", "INDICATES THERMOSTAT IS OFF", "INDICATES ROOM TEMPERATURE", "INDICATES INSTALLER TEST", "INDICATES INSTALLER SETUP", "INDICATES THERMOSTAT IS 'CALLING' FOR HEAT OR COOL", "INDICATES THERMOSTAT IS IN FREEZING PROTECTION MODE", and "INDICATES WHETHER THERMOSTAT IS IN OCCUPIED OR NOT".
Function
Valve Control
The thermostat acquires room temperature via its integrated or external sensor and maintains the setpoint by delivering on/off valve control commands. The image shows a thermostat display with "Room 24.5°C", "Cool on", and "Occupied" status. Instructions indicate: "PRESS THE MODE BUTTON TO SELECT HEAT, COOL OR VENT".
Fan Operation
Fan speed can be selected as manual or automatic 3-speed operation. In Manual mode, the fan is switched via control outputs Gh, Gm, Gl. In automatic mode, fan speed depends on the difference between room temperature and setpoint. When room temperature reaches setpoint, the valve and fan will close. The image shows a thermostat display with "Room 24.5°C", "Cool on", and "Occupied" status. Instructions indicate: "PRESS THE FAN BUTTON TO SELECT LOW, MED, HIGH OR AUTO".
Temperature Display
The displayed temperature can be set to show either the acquired room temperature or the setpoint. This setting is made during the Installer Set-Up process.
Cycle per Hour (CPH)
To achieve more accurate temperature control, the CPH function may enable the thermostat to open the valve multiple times per hour, even when the temperature is close to the setpoint (difference less than 1/2 P-band). The default value is 4 for heating and 3 for cooling, adjustable in the Installer Set-Up process.
Remote Temperature Sensor
The T6800 provides control based on either the acquired room temperature or the return air temperature. The model for the remote temperature sensor is NTC20K.
Keypad Lock
Keypad lock can be set in ISU. The default status allows all keys to be available. Options include locking out the mode button, fan and mode buttons, or all buttons.
Fan Speed Ramping Control Algorithm
This diagram illustrates the fan speed control based on the difference between Room Temperature (RT) and Setpoint (SP). For COOL mode: >4°F difference results in high fan speed or off; 2°F-4°F difference results in medium fan speed or off; <2°F difference results in low fan speed or off. For HEAT mode: <-4°F difference results in high fan speed or off; -2°F to -4°F difference results in medium fan speed or off; < -2°F difference results in low fan speed or off.
Operating Modes
The following operating modes are available:
Comfort Mode
In comfort mode, the setpoint can be changed using the up and down buttons. Applications include cool only, heat only, and manual heat/cool changeover. The image shows a thermostat display with temperature setting controls.
Ventilation Mode
Pressing the mode button enters ventilation mode. In this mode, there is no valve output, and the fan operates according to the selected fan speed.
Energy Saving Mode
This mode can be activated by a potential-free dry contact (e.g., hotel key card) or by pressing the mode button for 3 seconds. An energy saving icon ⚡ appears on the screen. The dry contact can be configured as normal open or normal close in ISU. If activated by dry contact, all buttons are locked except the multi-key for ISU. If activated by button press, any subsequent button press stops energy saving mode. For heating, the setpoint changes to a remote setback heating setpoint (10°C-21°C, default 18°C). For cooling, it changes to a remote setback cooling setpoint (22°C-32°C, default 26°C).
On/Off Mode
Pressing the power button switches the thermostat between on and off modes. The image shows a thermostat display indicating "OFF" mode.
Freezing Protection Mode
Freezing protection can be disabled (default) or enabled. In freezing protection mode, if the thermostat is in OFF mode and the acquired temperature drops below 6°C, it will activate heat mode until the temperature rises to 8°C or the thermostat is turned on. The image shows a thermostat display indicating "OFF" and "Freeze Protect".
Technical Specifications
| Specification | Details | |
|---|---|---|
| Power supply | 110 (+/-10%) VAC, 220(+10%, -15%)VAC | |
| Frequency | 50/60Hz | |
| Control algorithm | PI, On/off output | |
| Accuracy | +/-1°C at 21°C | |
| Rating capacity | For 220V power supply: 4(2)A for fan load, 2(1)A for zone valve For 110V power supply: 4(2)A for fan load, 2(1)A for zone valve | |
| Cycle times | 100,000 | |
| Setpoint range | 10~32°C | |
| Display range | 0~37°C | |
| Installation | Installed on 86×86mm junction box or US2×4 inch. | |
| Protection Class | IP20 | |
| Environmental Conditions | Operation temperature -18~49°C Shipping temperature -35~65°C Relative humidity 5~90% |
Terminal Designations
| Item | Terminal | Description |
|---|---|---|
| 1 | L | AC Power |
| 2 | Ch/Cc | Heating close/Cooling close |
| 3 | W/Y | Heating open/Cooling open |
| 4 | N | AC Ground |
| 5 | Gh | High speed fan relay |
| 6 | Gm | Medium speed fan relay |
| 7 | Gl | Low speed fan relay |
| 8 | Sc | Ground for remote sensor and remote setback |
| 9 | RSB | Remote set back |
| 10 | Rs | Remote sensor |
Wiring Diagrams
Application 1: 2 pipes heat only wiring diagram
Typical wiring for ON/OFF control in 2 pipe heating only (VC4013): This diagram shows connections for a 2-pipe heating-only system using ON/OFF control. It connects L (AC Power) and N (AC Ground). Terminal 2 (Ch/Cc) connects to the Heat valve. Terminal 5 (Gh) is for the High speed fan relay. Terminal 9 (RSB) is for Remote Setback. Terminal 10 (Rs) is for the Remote Sensor.
Typical wiring for 3-wire control in 2 pipe heating only (VC6013): This diagram shows connections for a 2-pipe heating-only system using 3-wire control. It connects L (AC Power) and N (AC Ground). Terminal 2 (Ch/Cc) connects to the Heat valve. Terminal 5 (Gh) is for the High speed fan relay. Terminal 9 (RSB) is for Remote Setback. Terminal 10 (Rs) is for the Remote Sensor.
Application 2: 2 pipes Cool only wiring diagram
Typical wiring for ON/OFF control in 2 pipe cooling only (VC4013): This diagram shows connections for a 2-pipe cooling-only system using ON/OFF control. It connects L (AC Power) and N (AC Ground). Terminal 2 (Ch/Cc) connects to the Cool valve. Terminal 5 (Gh) is for the High speed fan relay. Terminal 9 (RSB) is for Remote Setback. Terminal 10 (Rs) is for the Remote Sensor.
Typical wiring for 3-wire control in 2 pipe cooling only (VC6013): This diagram shows connections for a 2-pipe cooling-only system using 3-wire control. It connects L (AC Power) and N (AC Ground). Terminal 2 (Ch/Cc) connects to the Cool valve. Terminal 5 (Gh) is for the High speed fan relay. Terminal 9 (RSB) is for Remote Setback. Terminal 10 (Rs) is for the Remote Sensor.
Application 3: 2 pipes 1 stage Heat or 1 stage Cool MCO wiring diagram
Typical wiring for ON/OFF control in 2 pipes 1H1C (VC4013): This diagram shows connections for a 2-pipe 1-stage Heat or 1-stage Cool system using ON/OFF control. It connects L (AC Power) and N (AC Ground). Terminal 2 (Ch/Cc) connects to the Valve. Terminal 5 (Gh) is for the High speed fan relay. Terminal 9 (RSB) is for Remote Setback. Terminal 10 (Rs) is for the Remote Sensor.
Typical wiring for 3-wire control in 2 pipes 1H1C (VC6013): This diagram shows connections for a 2-pipe 1-stage Heat or 1-stage Cool system using 3-wire control. It connects L (AC Power) and N (AC Ground). Terminal 2 (Ch/Cc) connects to the Valve. Terminal 5 (Gh) is for the High speed fan relay. Terminal 9 (RSB) is for Remote Setback. Terminal 10 (Rs) is for the Remote Sensor.
Installation & Commissioning
- Pull wires through the wire hole. Loosen screw terminals, insert wires into the terminal block, then retighten screws. Visual shows wires entering a junction box and a terminal block.
- Push the Power box into the junction box. Visual shows the thermostat's power module being inserted into the junction box.
Back Cover Installation
Install the thermostat about 5 feet (1.5m) above the floor in an area with good air circulation at average temperature. Visual shows the back cover being attached to the thermostat. Step 3: Align 4 tabs on the back cover with corresponding slots on the back of the thermostat, and then push it until the thermostat snaps in place.
Installation Location Guidelines: Do not install in locations where the thermostat can be affected by: Drafts or dead spots behind doors and in corners; Hot or cold air from ducts; Sunlight or radiant heat from appliances; Concealed pipes or chimneys; Unheated/uncooled areas such as an outside wall behind the thermostat. Visuals show recommended and 'NO' installation locations.
Troubleshooting Tips
| If... | Then... |
|---|---|
| Heating system does not turn on. | Set the mode to Heat by pressing the Mode button. Check that the heat temperature setting is set above the room temperature and "Heat On" shows solidly in the display. Wait five minutes for the heating system to respond. |
| Cooling system does not turn on. | Set the mode to Cool by pressing the Mode button. Check that the cool temperature setting is set below the room temperature and "Cool On" shows solidly in the display. Wait five minutes for the cooling system to respond. |
| The fan doesn't work. | Check whether the Fan mode is set to Auto. Check whether the heating or cooling system works. |
| The Mode button doesn't work. | Check whether the keypad is locked or not. Check whether the system is working in Energy saving mode. Check whether the thermostat is off. |
| The Fan button doesn't work. | Check whether the keypad is locked or not. Check whether the system is working in Energy saving mode. Check whether the thermostat is off. |
| The Up or Down button doesn't work. | Check whether the keypad is locked or not. Check whether the system is working in Energy saving mode. Check whether the thermostat is off. |
Dimensions
Horizontal model: Width: 119.6mm, Height: 95mm, Depth: 41.9mm.
Vertical model: Width: 95mm, Height: 119.6mm, Depth: 41.9mm.
