Venstar T1900 Programmable Thermostat Thermostat
Preparation
- Proper installation of the thermostat will be accomplished by following these step-by-step instructions. If you are unsure about any of these steps, call a qualified technician for assistance.
- Assemble tools
- Make sure your Heater/Air Conditioner is working properly before beginning the installation of the thermostat.
- Carefully unpack the thermostat. Save the screws, bracket, and instructions.
- Turn off the power to the Heating/Air Conditioning system at the main fuse panel. Most residential systems have a separate breaker for disconnecting power to the furnace.
Remove & Replace the Old Thermostat
- Remove the cover of the old thermostat.
If it does not come off easily check for screws. - Loosen the screws holding the thermostat base or subbase to the wall, and lift away.
- Disconnect the wires from the old thermostat. Tape the ends of the wires as you disconnect them, and mark them with the letter of the terminal for easy reconnection to the new thermostat.
- Keep the old thermostat for reference purposes, until your new thermostat is functioning properly.
Configuring the MISC Outputs
Configuring the Jumpers
For additional flexibility, your thermostat has three configurable outputs. These outputs are designed to have different functions depending on how the jumpers are set (below). Each output, labeled MISC1, MISC2, and MISC3 may be set for one of the five choices available. In the diagram below, the MISC3 jumper has been set for HUM (humidification) operation, the MISC2 jumper has been set for DEHUM (dehumidification) operation, and the MISC1 jumper has been set for PROG (programmable) operation.
Explanation of Jumper Settings
W3 JUMPER SETTING
If the jumper for MISC1, MISC2, or MISC3 is set to W3, the corresponding MISC screw terminal on the backplate will control a third stage of heat.
W3 MULTI-STAGE OPERATION EXPLAINED
The 3rd Stage of Heat is turned on when
- The 1st and 2nd stages have been on for the time required (steps 27 and 28, page 14.6). It is adjustable from 0-60 minutes and the default is two minutes.
- The temperature from the setpoint is equal to or greater than the setpoint plus the 1st stage deadband (step #24, 14.5), plus the 2nd stage deadband (step #25, 14.5) plus the 3rd stage deadband (step #26, 14.5). This 3rd stage deadband is adjustable from 0-10 degrees and the default is two degrees.
PROG JUMPER SETTING
If the jumper for MISC1, MISC2, or MISC3 is set to PROG, the terminal on the backplate will control a pilot relay or other accessory. the corresponding MISC screw
PROGRAMMABLE OUTPUT – SECTION 15 of the Owner’s Manual
This jumper setting allows the MISC outputs to control a pilot relay by time, temperature, or a signal from the Internet/Phone. The following are three possible scenarios:
- By Time: A device that requires a start and stop time. An example of this would be an exterior lighting system that needed to be energized every day between the hours of 8pm and 1am.
- By Temperature: An exhaust fan that needs to energize whenever the temperature from RS2 rises above 90 degrees F.
- By Remote: Remotely arming a security system through the web or phone.
HUM JUMPER SETTING
If the jumper for MISC1, MISC2, or MISC3 is set to HUM, the corresponding MISC screw terminal on the backplate will control a humidification system.
HUMIDIFICATION OPERATION – SECTION 9 of the Owner’s Manual If your HVAC unit is equipped with a humidification system the thermostat will provide power to the MISC1, MISC2, or MISC3 terminal of the thermostat whenthe humidity in the home falls below the humidity setpoint you have chosen. The value for this setpoint ranges from 0% to 60%. If no humidity is desired or if a humidification system has not been installed, set the value to OFF.
DEHUM JUMPER SETTING
If the jumper for MISC1, MISC2, or MISC3 is set to DEHUM,the corresponding MISC screw terminal on the backplate will be connected to the dehumidification terminal of a furnace board.
NOTE: Not all furnaces have a dehumidification terminal.
DEHUMIDIFICATION OPERATION – SECTION 10 of the Owner’s Manual If your HVAC unit is equipped with a dehumidification system the thermostat will operate in one of two ways.
- Normally Closed (NC): The thermostat will de-energize the MISC1, MISC2, or MISC3 terminal of the thermostat (this MISC terminal is connected to theDEHUM terminal on your furnace) to allow the fan to run in low speed when the humidity in the home is above the dehumidify setpoint you have chosen and there is a call for 1st stage cooling.
- Normally Open (NO): The thermostat will energize the MISC1, MISC2, or MISC3 terminal of the thermostat (this MISC terminal is connected to the DEHUM terminal on your furnace) to allow the fan to run in low speed when the humidity in the home is above the dehumidify setpoint you have chosen and there is a call for 1st stage cooling.
Y2 JUMPER SETTING
If the jumper for MISC1 is set to Y2 the MISC1 screw terminal on the backplate will control a second stage of cooling.
Y2 OPERATION – SECTION 14 of the Owner’s Manual
Control up to two Cool stages.
The 2nd Stage of heat or cool is turned on when:
- The 1st Stage has been on for the time required (step #27, page 14.6). It is adjustable from 0-60 minutes and the default is two minutes.
- The temperature spread from the setpoint is equal to or greater than: the setpoint plus the deadband (step #24, page 14.5), plus the 2nd deadband (step #25, page 14.5). This 2nd deadband is adjustable from 0-10 degrees and the default is two degrees.
Wire Connections
If the terminal designations on your old thermostat do not match those on the new thermostat, refer to the chart below, or the wiring diagrams that follow.
Sample Wiring Diagrams
6 Wire, 1 Stage Cooling, 1 Stage Heat
Residential & Commercial 1 Stage Cooling, with 1st stage Gas Heat
Commercial Heat Pump 1 Stage Cooling with 2 Stage Heat
6 Wire, 1 Stage Cooling, 1 Stage Heat
Residential & Commercial 1 Stage Cooling, with 1st stage Electric Heat 
6 Wire, 1 Stage Cooling, 2 Stage Heat
Residential Heat Pump with O Reversing Valve 1 Stage Cooling, with 2 stage Heat 
6 Wire, 1 Stage Cooling, 2 Stage Heat
Residential Heat Pump with b Reversing Valve 1 Stage Cooling, with 2 stage Heat 
Adding a 2nd Stage of Cooling (MISC1), Sprinkler System (MISC2),and 3rd Stage of Heating or Dual Fuel Applications (MISC3)
Adding a Humidification System (MISC1) and Dehumidification System (MISC2)
CK1 and CK2 terminals wired to a Time Clock
For instructions on wiring the optional Remote and Outdoor Sensors, please see page 16.2 of the Owner’s Manual 
DRY CONTACT SWITCH – The terminals are ‘normally open’ (or may be programmed for normally closed operation, see page 17.2 of the Owner’s Manual). Closing or completing the circuit will cause the thermostat to do one of the following:
- If Vacation is selected in step #41 of the Advanced Setup (see page 17.3 of the Owner’s Manual), when the dry contact is energized the thermostat will be forced into Vacation mode (see Section 20 of the Owner’s Manual).
- If Service Pan is selected, when the dry contact is energized the thermostat will lockout Y1 (compressor) and write Service Pan on the display.
Test Operation
- Turn the power on to the Heating/Air Conditioning system.
- Press the MODE button repeatedly until the HEAT icon appears on the display. Press UP or DOWN buttons until the set temperature is 10 degrees above room temperature. The furnace should turn on.
- Press the MODE button repeatedly until the COOL icon appears on the display. or DOWN buttons until the set temperature is 10 degrees below room temperature. The air conditioner should turn on. NOTE: Most equipment has a time delay of 5 minutes between cool cycles. This feature is defeatable on the thermostat. Consult the Owner’s Manual under Setup, cycles per hour (page 14.3).
- Press the UP button until the setpoint is equal to the room temperature. Press the FAN button to Fan On. The fan should turn on and run continuously.
Calibrating the Thermostat Sensors
Under normal circumstances it will not be necessary to adjust the calibration of the temperature and humidity sensors. If calibration is required, please contact a trained HVAC technician to correctly perform the following procedure.
After calibration is complete, press the MODE button once to return to normal operation.
Troubleshooting
- SYMPTOM: The air conditioning does not attempt to turn on.
CAUSE: The compressor timer lockout may prevent the air conditioner from turning on for a period of time.
REMEDY: Consult the Owner’s Manual in the Setup section to defeat the cycles per hour and compressor time guard. - SYMPTOM: The display is blank.
CAUSE: Lack of proper power.
REMEDY: Make sure power is turned on to the furnace and that you have 24vac between R & W. If C is used, 24vac between R & C. - SYMPTOM: The air conditioning does not attempt to turn on.
CAUSE: The cooling setpoint is set too high.
REMEDY: Consult the Owner’s Manual in the Setup section to lower the cooling setpoint limit. - SYMPTOM: The heating does not attempt to turn on.
CAUSE: The heating setpoint is set too low.
REMEDY: Consult the Owner’s Manual in the Setup section to raise the heating setpoint limit. - SYMPTOM: When controlling a residential heat pump, and asking for cooling, the heat comes on.
CAUSE: The thermostat reversing valve jumper is set for “b”.
REMEDY: Set the reversing valve jumper for “O”. See pages 5.4 and 5.5. - SYMPTOM: When calling for cooling, both the heat and cool come on.
CAUSE: The thermostat equipment jumper is configured for “HP” and the HVAC unit is Gas/Electric.
REMEDY: Set the equipment jumper for “Gas”. See pages 5.2 and 5.3.
References:
Download Manual
Venstar T1900 Programmable Thermostat Thermostat Installation Instructions
OTHER MANUAL
Venstar T1900 Programmable Thermostat Owner Manual
Venstar T1900 Programmable Thermostat Installation Instruction