The thermostat is powered directly by the HVAC unit and should be receiving 24V AC across the R and C terminals of its baseplate.
Check the circuit breaker for the unit and make sure it has not been tripped. If the air filter has been replaced recently, make certain that the furnace panels are all secure. If you cannot find anything obvious, we would suggest reaching out to a local licensed heating / air conditioning company for assistance.
Symptom: This is usually caused by a high temperature safety limit opening on the furnace. When the safety opens, the furnace shuts off the burners and disconnects the 24VAC to the thermostat causing the thermostat clock to stop. In order to cool down the heat exchanger, the furnace blower will remain energized for approximately 15 minutes before restoring power to the thermostat and, if there is still a call for heating, allowing the furnace to re-energize. In this situation homeowner may never notice a problem, except that the clock will be off by the number minutes power was disconnected.
Correction: Determine what is causing the high temperatures to occur - dirty filter, etc.
WARNING: Correction #2 will reset all Time Period and Advanced Programming to the default settings. Any information entered prior to this reset may be permanently lost.
Symptom #1: Most of our heat pump compatible thermostats will allow Emergency Heat to be activated by pressing the FAN and the UP buttons. This will display ‘EH’ in the cool setpoint and lock out all modes except the OFF and HEAT modes.
Correction: Pressing the MODE and UP buttons should return the thermostat to normal operation.
Symptom #2: If the thermostat is displaying some unexpected values like “-9 dy” or “EH”, the thermostat has experienced a voltage spike or been subjected to odd recovery after a power outage. The memory of the thermostat needs to be reset to factory defaults in order to clear any errant settings.
Correction #2: Perform the factory default procedure.
Press/hold the MODE and FAN buttons together until all of the icons appear on the screen. Release both buttons. Then press/hold FAN until ‘Fd’ momentarily appears. Release FAN button, then press/release MODE a few times until the thermostat returns to normal operation. Note that if you also see a picture of a keypad lock on the screen, first press the combination of MODE, UP and DOWN arrow buttons in order to toggle the keylock function.
Symptom: Many of our thermostats have the ability to, in addition to other security features*, lock out the thermostat buttons entirely.
Correction: To lock or unlock the thermostat buttons, press and hold the MODE button. While you are holding the MODE button, press the UP and DOWN arrow buttons as well.
*NOTE: Many of our commercial thermostats have advanced security features that also disable certain button functions. If some, but not all, of your buttons are locked out, then you will need to disable the security setting. Consult the Owner’s Manual of the thermostat in order to disable the security setting of your thermostat.
Symptom: The temperature reading of thermostat may be incorrect due to the incorrect connection of the sensor, electrical interference on the remote sensor wiring, a wall location that receives very little airflow, and/or proximity to devices that emit heat.
Correction #1: Check to see if the degree symbol is flashing. If it is not flashing, the remote sensor reading is not being displayed.
Correction #2: Check your wiring. The Remote Sensor should be connected to the thermostat using solid conductor CAT 5, CAT 5e, or CAT 6 type network communication cable. This is an unshielded cable with four twisted pairs of 24 gauge solid wire; DO NOT use stranded cable. The cable length should not exceed 250 feet. If less than 75 feet of cable is required to connect the thermostat to the Remote Sensor, a three conductor thermostat cable (18-24 gauge) may be used; this cable is NOT suitable for any length greater than 75 feet.
IMPORTANT: Do not use shielded wire. Do not run sensor wiring in the same conduit as the 24VAC thermostat wiring. Electrical interference may cause the sensor to give incorrect temperature readings.
WARNING: Under normal circumstances it will not be necessary to adjust the calibration of the remote sensor. If calibration is required, please contact a trained HVAC technician to correctly perform the following procedure.
Correction #3: It is important to determine the exact reason why the remote sensor reading is incorrect before attempting this calibration procedure. Please note that not all thermostats support the remote sensor calibration feature. Place your temperature probe next to the remote sensor in order to determine the correct temperature. Once you have determined the correct temperature reading, follow the calibration steps below:
Press the MODE and FAN buttons at the same time until all of the icons appear. Then press the UP and DOWN buttons at the same time twice. When the current room temperature appears, press the MODE button once more to display the remote sensor calibration screen. Use the UP or DOWN button to adjust the temperature. If the thermostat does not have a remote sensor calibration screen, then calibrate the remote sensor in the normal temperature sensor screen. Press the MODE button one, two, or three times to exit calibration.
NOTE: Do not use an ohmmeter to test the sensor - these are digital sensors, not thermistors, and they can be damaged by an ohmmeter.
Symptom: When the thermostat is placed on a wall that has no insulation, air will often blow on the thermostat sensor from behind the wall. This air will remain the same temperature even though the space temperature is being heated or cooled.
Correction: Insulate the hole behind the thermostat with insulation, spray foam, or even duct tape - whatever will stop the airflow from behind the wall.
Symptom #1: This usually occurs when a gas/electric thermostat is attempting to control a heat pump system.
Correction #1: If your thermostat is heat pump compatible, follow the instructions below to program the thermostat for heat pump operation. This will entail changing the jumper settings on the thermostat circuit board or selecting heat pump operation in the advanced setup programming.
Jumper Setting – Pull your thermostat away from the sub-base. The jumpers will be located in the upper right hand corner of the circuit board. Locate the middle jumper that can be set for GAS or HP operation. Place the jumper on the two pins closest to HP.
Advanced Setup – Press the MODE and PROGRAM or MODE and FAN buttons to enter advanced setup. Then press the MODE button repeatedly until HP appears in the middle of the screen. Press the UP button so that ON is displayed. Press PROGRAM or MODE and FAN to exit advanced setup.
Symptom #2: This may also occur when the reversing valve setting of a heat pump compatible thermostat has been programmed incorrectly.
Correction #2: Follow the instructions below to program the thermostat for the correct reversing valve setting. This will entail changing the jumper settings on the thermostat circuit board or selecting the operation in the advanced setup programming.
Jumper Setting – Pull your thermostat away from the sub-base. The jumpers will be located in the upper right hand corner of the circuit board. Locate the bottom jumper that can be set for O or B operation. Place the jumper on the two pins closest to the correct reversing valve setting.
Advanced Setup – Press the MODE and PROGRAM or MODE and FAN buttons to enter advanced setup. Then press the MODE button repeatedly until HP appears in the middle of the screen. Now press the MODE button once. ‘O’ or ‘b’ will appear on the display. Press the UP or DOWN button to display the correct reversing valve setting. Press PROGRAM or MODE and FAN to exit advanced setup.
NOTE: If your system is a commercial heat pump, then the thermostat may not need to be programmed for heat pump operation. Commercial heat pumps usually require gas/electric thermostats for proper operation. If the terminal connections in the equipment do not have an ‘O’ or ‘b’ terminal, but do have a ‘W1’ or ‘W’ terminal, then a gas/electric thermostat will most likely be required.
Symptom: This usually occurs when a heat pump thermostat is attempting to control a gas/electric system.
Correction: If your thermostat is gas/electric compatible, follow the instructions below to program the thermostat for gas/electric operation. This will entail changing the jumper settings on the thermostat circuit board or selecting gas/electric operation in the advanced setup programming.
Jumper Setting – Pull your thermostat away from the sub-base. The jumpers will be located in the upper right hand corner of the circuit board. Locate the bottom jumper that can be set for GAS or HP operation. Place the jumper on the two pins closest to the GAS.
Advanced Setup – Press the MODE and PROGRAM or MODE and FAN buttons to enter advanced setup. Then press the MODE button repeatedly until HP appears in the middle of the screen. Press the DOWN button so that OFF is displayed. Press PROGRAM or MODE and FAN buttons to exit advanced setup.
Symptom: Some types of heating systems require the thermostat to operate the indoor fan (like electric heat and, of course, heat pump systems).
Correction: Program the Electric Heat (EH) setting of your thermostat. This will entail changing the jumper settings on the thermostat circuit board or selecting electric heat (EH) operation in the advanced setup programming.
Jumper Setting – Pull your thermostat away from the sub-base. The jumpers will be located in the upper right hand corner of the circuit board. Locate the top jumper that can be set for EH or GAS operation. Place the jumper on the two pins closest to EH.
Advanced Setup – Press the MODE and PROGRAM or MODE and FAN buttons to enter advanced setup. Then press the MODE button repeatedly until EH appears in the middle of the screen. Press the UP button so that ON is displayed. Press PROGRAM or MODE and FAN to exit advanced setup.
This is a common problem when replacing a mechanical thermostat or a thermostat powered by batteries. These older thermostats require 4 wires, but newer more sophisticated thermostats require a 5th wire known as the Common wire to power the digital display. There are three ways to add the common wire to a four wire installation:
Note: Before starting, we recommend that you take a picture of the original wiring to the old thermostat as reference to help remember what terminal each thermostat wire was connected to.
Option #1: The easiest and least expensive option is to sacrifice independent control of your indoor fan.
Caution: if your heating and cooling system is powered during the thermostat installation process and you accidentally touch the R (red) power wire to the C (blue or brown) common wire, then you will permanently damage either the equipment fuse or the transformer in the equipment.
Option #2: The second way to add a wire is to install the ACC0410 Add-A-Wire accessory. Add-A-Wire allows two thermostat signals to be controlled from one thermostat wire. As above move the green wire from the G terminal to the C terminal on the thermostat and at your heating and cooling equipment. Now use the Yellow wire to carry the Add-A-Wire signal.
Add-A-Wire Diode and Add-A-Wire Box:
Add-A-Wire Model #ACC0410 In applications where additional wiring cannot be run, the Add-A-Wire accessory can be used to add a wire to the thermostat.
Option #3: The final way to add a wire is to contact a licesned HVAC contractor. This contractor will be able to run the necessary number of thermostat wires from your heating and cooling system to your thermostat. Please visit the Distributors section of our website to find the nearest HVAC wholesale distributor to your location. You may contact any of these distributors for an HVAC contractor referral in your area.
To control thermostats using an external timeclock, simply connect the two wires from the relay output on the timeclock to CK1 and R on the thermostat. You should set the ‘dry contact use’ step for the function that you want to achieve. Depending on your model, the dry contact can force the thermostat to enter energy savings setpoints (like Vacation or Holiday) or to switch to comfort setpoints (Occupied).
Note: The thermostat requires a dry contact signal to control this function. That means that NO VOLTAGE can be presented by the external timeclock. If your device doesn’t provide a dry contact output or you are trying to slave multiple thermostats to the single device, you must use isolation relays for each thermostat. Contact support via the widget on this webpage to contact us for more information.
The light sensor is built in to the thermostat. The light sensor is adjustable to accommodate different light levels. The sensor adjustment screw is located in the inner cover of the thermostat near the down arrow button. A small screwdriver is included with the thermostat. Turning the screw clockwise increases the sensitivity, counterclockwise decreases the sensitivity. The light sensor responds to overhead light only, so it is not affected by side windows. The minimum light level that will put the thermostat into occupied mode is approx. 24 fcd at the highest sensitivity setting, and approx. 96 fcd at the lowest sensitivity setting. The easiest way to test light level is to use a flash meter from a camera store, such as the Minolta Flash Meter V. Make sure to test the light level right up against the wall where the thermostat will be mounted.
Whenever the thermostat senses light, it is forced into Occupied 1. The thermostat must be in Program On mode to use the light sensor, in all other modes the sensor is ignored. When the lights are off, the thermostat reverts to its regular program, which allows programming of morning warm-up, different setpoints, etc.
It may be desirable to start the heating (or cooling) in the morning before the building is occupied in order to have the building comfortable by the time the occupants arrive. This is easy to do with the light activated thermostats, just use the regular program and set any of the Occupied periods for the desired time and setpoint. When the occupants arrive and turn on the lights, the stat will be forced into Occupied 1. For example, if the desired normal occupied temperature is 72 degrees and the building is occupied at 8 am, set Occupied 1 to start at 7am and end at 8am with a setpoint of 72 degrees. This will provide one hour of morning warm-up. If the lights are not on at 8 am, the thermostat will go to Unoccupied. If the lights are on, the stat will go to Occupied 1 at 72 degrees and stay there as long as the lights remain on.
It may be desirable to have two (or more) different setback temperatures, based on the time of day. For example, consider a building that is normally occupied from 8 am to 5 pm. The building owner wishes to save energy by using a light activated stat to set the temperature back when the offices are unoccupied (lights are off). The owner sets the cooling Occupied setpoint to 72 and the cooling Unoccupied setpoint to 85. Now, whenever the lights are off, the thermostat will go to Unoccupied at 85 degrees. But, if an office worker goes to lunch just for an hour (and the lights are off during that time), he/she may not want to return to a room that's 85 degrees! In this case, simply set Occupied 2 to run from 8 am to 5 pm at 75 degrees. Whenever the lights are on, the stat will go to Occupied 1 at 72 degrees, because Occupied 1 overrides Occupied 2. When the lights are off, if it is between 8 and 5 the stat will revert to Occupied 2 at 75 degrees, giving a 3 degree setback which will save energy without allowing to room to heat up too much.
Venstar thermostats are sold only to authorized distributors in North America. Our distributors sell our products to their dealers and contractors. Most of these dealers/contractors sell & professionally install Venstar products. A few of these dealers sell Venstar products online through their own website or through an online retailer such as Amazon. Venstar itself does not sell thermostats direct to the consumer or online.
As the manufacturer of Venstar branded thermostats we offer training and support primarily to our distributors and their dealer/contractors.
Your place of purchase should be your first avenue of support. That being said, Venstar technicians will make every effort to answer your thermostat support questions by email. From this page you may access basic troubleshooting and helpful tips.