Honeywell ST9400C ( Everything You Need To Know About Honeywell ST9400C )

Honeywell ST9400C

The Honeywell ST9400C is not your average programmable thermostat. This thermostat is equipped with 4 different sensors ( 1 Outdoor, 2 Window/Floor, and 1 Motion Sensor) that work together to make sure your house is at the temperature you want.

The Honeywell ST9400C device makes it’s decisions based on what its internal software feels will be best for your home presets while also making sure energy consumption and costs stay low. The device does all of this ‘learning’ on its own and you can monitor and control everything from your PC or any android, iOS-enabled device, and Amazon’s Alexa.

Even though the sensors work well the thermostat is still very easy to install for anyone that has done anything with home heating/cooling systems. Installing this Honeywell Thermostat is as easy as replacing your old thermostat with a faceplate. Once you do that just connect the Honeywell to your home wifi network and you are ready to start controlling from anywhere in the world.

The Honeywell does have some advanced features for people who need them, such as “Hold” mode so heat/cooling will stay on when you are on vacation in a different time zone, and “Secure Lock” so you will always know if someone has been in your home. The Honeywell Smart Home Thermostat is priced so low and is available for purchase from

How Programming Honeywell ST9400C Works.

Getting a hang of how programming works with your Honeywell ST9400C is probably one of the first things you want to do.

You can pretty much look at programming as storing presets; things like “Heating” or “Cooling” are what your presets are called. Once you save them for the first time, they’ll be available on any device (mobile phone, tablet etc.) that you’ve downloaded the Honeywell App onto.

You can also program your Honeywell Thermostat to turn on and off at specific times. Although this is not needed with the ST9400C model, it’s good to know if you want the AC or heat to come on before everyone wakes up.

Programming is as easy as 1-2-3 with a Honeywell Programmable Thermostat.

You’ll first want to go into the settings of your Honeywell App and set an access code for yourself (and anyone else who wants to use the device) to keep things secure.

Once you’re in there you can control all sorts of other settings like time zone, whether or not your AC unit fan should run after the air has been turned off, if you want to have a vacation function or not and what kind of heating or cooling system you have.

This is where things get interesting with the Honeywell ST9400C…

After your settings are saved for the first time you can access them easily by scrolling down past all the different options until it says “My Thermostat”. This is where your presets will show up.

You can then select a preset and edit it if you want, or press that little green arrow to copy it into another slot. Pretty simple!

So let’s say you have a morning preset for the heating system to come on before you wake up from work, and then an evening preset for the AC to go on when you get home.

You can copy your morning preset into the even presets section, which will create a version of that preset but with slightly different settings (such as the time it turns on or off).

This would mean all you need to do is press “Away” in the morning if you change your mind about what you want the house to be doing on your way to work, and then press “Home” on your way back for it to be on full blast.

It’s so simple but it makes life so much easier! This is especially true if you have a large family who all have different schedules on different days.

No more trying to remember who turned what system on or off and when!

Controlling Your Smart Thermostat Through the App.

Using the app is easy enough, but there are a lot of things you can control with it so we’ll go into that in a bit more detail.

You can see what your home’s temperature is currently set at, as well as the mode your heating/cooling is in (programmed or not).

You can also see when the next time your system will be activated from when you pressed “Away” or when you pressed “Home”. If you want to edit a preset you have stored just tap on it.

This will open up a settings menu where you can make any necessary changes to the preset before saving it (or discarding it if you don’t want to keep it).

You also have access to all of your presets in the “My Thermostat” section of this app, which is probably what you’ll use more regularly.

From there you can decide whether you want to copy, activate or edit your presets.

The app also has weather forecasts in there so you’ll always know when the sun’s going to start shining even if it isn’t currently!

If you want to get rid of the sensor on display where this information is; simply go into settings and turn off “Show HVAC Mode” if you would rather it wasn’t there.

The app also has a “Remote Temperature Control” setting built in which allows you to remotely set your heating or cooling system up or down by a certain number of degrees depending on the time and whether you’re home or not.

This is great for people who have friends, family members or house sitters who need to be able to monitor the temperature in your home regardless of whether they are there or not.

The final option on the settings menu is called “Power Extender” which is built in for people who live in extreme climates with specific needs. Essentially if you live somewhere where your system keeps turning on and off at certain times to prevent it from freezing you can use the power extender to turn this feature off or on.

Honeywell ST9400C Navigation

The physical buttons on the device are fairly straight forward, but there are quite a few of them so let’s go through each one briefly.

From left to right: The lock button allows you to lock the device so that it will not be activated or adjusted by anyone. The exterior temperature sensor is what you point at outside of your home so it can read the current weather conditions.

Think of it like a calculator, but this one tells you how cold/hot it actually is outside! This should always face upward so that the device gets an accurate reading.

The up and down buttons adjust the temperature in your home by 1 degree at a time. Pressing “Energy Saving” will activate the power saving mode, which turns off heating or cooling when you’ve reached certain temp targets (the lower target is set to 64 while the higher target is set to 86). This basically means it will only heat/cool your home to those temperatures and no further.

From left to right: The mode button lets you cycle through the heating, cooling and off modes as well as turning programmable mode on or off. If you want to go back a screen/setting just press “Cancel” rather than holding down for 3 seconds which will bring up the menu.

The star button brings up the main configuration settings where you can edit everything from the name of your home to what wifi network it is connected to and which mode you want programmable mode set at. From here you can turn on “Wi-Fi Connect” so you never have to search for your device in order to adjust any settings.

This is also where you can go to delete presets if you want them gone or edit existing ones.

The # button brings up your main preset list so that you can adjust the temperature of your home in whatever way suits you most! Unless you have increased the limit on the “Max Number Of Presets” then it will only show 5 of your presets, but you can press “Add More Presets” so that they are all listed.

For example if you have 2 of them set for heating and cooling during the day at different temperatures then it will show both of these presets here so you can easily access both of them without scrolling through everything.

As well as changing how many presets you want to view it also lets you change how many of each type; heating, cooling and the fan only setting.

The last button is for selecting whether your device is currently in “Home” or “Away” mode which can be useful if you’re using the power saving setting mentioned earlier.

For example if your preset is set to set to 70 degrees when you’re away from home then it will raise the temperature by a certain number of degrees per hour until it reaches that target.

Overall, I think that buying a smart thermostat is definitely worth considering as they have so many benefits, especially if you live in a place with extreme weather conditions where your system keeps turning on and off to prevent it from freezing.

How To Reset A Honeywell ST9400C Programmer?

When your Honeywell ST9400C programmer is not meeting your heating and cooling needs, resetting the Honeywell ST9400C presets is the fastest and the easiest way to fix it. Resetting your Honeywell ST9400C programmer can save you time and money (Instead of calling a repairman, you can do the reset by yourself). Here are simple steps on how to reset a Honeywell ST9400C Thermostat:

  • Turn off power for at least 10 seconds to your Honeywell ST9400C Thermostat.
  • Remove the batteries (If present).
  • Reconnect the batteries and turn on power to the Honeywell ST9400C programmer.
  • Tap and hold on “Energy Saving” for at least 5 seconds or until the display shows “PLEASE WAIT”. Then release.
  • The heating and cooling presets will be reset to default values (Accepted values: 0,1,2,3,4,5).

If you need any further assistance resetting your Honeywell ST9400C programmer, please feel free to contact us by filling out the “Ask a Question” form on the bottom of this page. We look forward to helping you with all your heating and cooling needs.

How do you set the timer on a Honeywell heater?

Setting a heater timer on Honeywell heaters is easy and done in a matter of minutes. There are two different types of timers on Honeywell heaters: the programmable timer and the 3-speed fan timer .

To set the programmable timer, press “Mode” until you reach either “Program 1”, “Program 2”, or “Program 3”. The selected mode will show up in the display.

After reaching the desired mode, press “Set” until you reach the time that you would like to set for that program. You can then use “Up” and “Down” to change the hour and minute.

To set a 3-speed fan timer, simply press “Fan” until you reach your desired fan speed. Then press “Set” to activate the timer for that fan speed.

Once your timer is set, just push in your power button and your heater will automatically begin working at whatever time you chose! Setting a heater timer on Honeywell heaters can save you money by not having them running when the house is empty or when they are not needed.

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