Temperature differential, is the difference between the turn-on and turn-off temperatures on a thermostat, whether heating or cooling, and generally ranges between one and three degrees.
Many modern digital and mechanical thermostats provide for adjusting this value, to account for differing home construction types and locations, types of furnaces, and personal comfort preferences.
However, the Honeywell RTH9580WF WiFi thermostat does not provide temperature differential adjustments. It attempts to keep the room temperature within one degree of the set value, using its Smart Response technology if enabled. We’ve found this sufficient in our apartment central air / hydronic heating system.
However, if you find that your dwelling becomes too chilly before the heat comes on, or too hot before the heat shuts off, here are some suggestions to reduce the size of these temperature swings.
Verify Correct System Type Settings
Make sure that the settings that tell the thermostat what kind of furnace / HVAC system you have are set correctly. Included below are pictures of moving through the System Setup menus on the RTH9580WF. Press the Menu button, then use the arrow keys to scroll to the “System Setup” button, as shown next.
Press the System Setup button. The “Language” selection screen then appears as shown next.
Press the green Next button. The “Thermostat Installed In” screen appears, as shown next.
Again, press the green Next button. The “Your Thermostat Location” screen then appears, as shown next.
Again, press the green Next button. The “Your Thermostat Controls” screen then appears, as shown next.
Once more, press the Next button. The “Your System Type” screen then appears, as shown next. Check the setting here (found at Menu–>System Setup, and then press the Next button until you arrive at the System Type). The choices there are Forced Air, Heat Pump, and Hot Water & Steam.
Determine the correct climate control system you have, and then tap the appropriate button. That button will then become highlighted. Warning: It’s imperative that you set this parameter correctly for proper operation of your heating / cooling system.
Then press the Next button. What you see subsequently, depends on which system type you selected in the previous step. In our case, we chose Forced Air. So, the RTH9580WF prompted us to enter the type of forced air heat we have, as shown next, as the “Your Forced Air Heating System Type” screen is displayed.
Then, verify that the Forced Air Heating System Type parameter is set correctly (pick either Gas / Oil, or Electric). Ours is Gas / Oil. Tap the corresponding button on this screen. Note that your choice then becomes highlighted.
Then, when pressing Next from here, the RTH9580WF prompts for the System Efficiency value by displaying the “Efficiency of Your Heating System” screen, as shown next.
The choices are either Standard Efficiency (less than 90 percent efficient), and High Efficiency (greater than 90 percent efficient). We set ours to Standard Efficiency. We opted for Standard Efficiency, as our forced air system draws in hot water from the building’s hot water system, in which the water is heated elsewhere in the complex.
Then, we pressed the Done button, followed by the Home button, to return the thermostat display to the Home screen. The Home screen is shown in the first picture of this article.
Next, we allowed our system operate for several hours and noted any uncomfortable temperature swings. Chances are that you’ll feel none, as the RTH9580WF regulates the furnaces quite tightly; especially when the Smart Response technology is activated. However, if the room becomes too cold before the furnace kicks on, or too hot before it kicks off, try adjusting the set temperature up or down respectively by a degree or two. This may help. If not, then read on.
Try Changing System Efficiency Setting
If ultimately, you decide that the temperature swing allowed by the RTH9580WF is too great, THEN try changing the System Efficiency setting as described above. Navigate to this setting as illustrated in the previous pictures. This parameter varies the number of times per hour the thermostat will cycle the furnace on and off to maintain set point temperature. So you may get less temperature spread if you increase the number of cycles per hour, by toggling between Standard Efficiency and High Efficiency. Experiment to figure out which of these provides the least differential.
Check for Proper Thermostat Positioning
Also, larger temperature differentials may occur in the room, if the thermostat is positioned too close to a window or exterior wall. If it’s located in a stubbornly cooler area (such as near an exterior wall or drafty door), this particular space will require longer heating from the furnace to reach the temperature set on the thermostat. However, areas more interior to the house typically require less heating to achieve set point temperature. So while the thermostat might call for enough heat to maintain the exterior wall area at the set point temperature, the more interior areas of your house may become way too hot before the thermostat shuts down the furnace. So, proper thermostat positioning within the home is essential for controlling low-high temperature swings by the climate control system.
If you cannot reposition the thermostat, then we suggest that you buy a thermostat that provides a temperature differential adjustment. Many of the older, non programmable thermostats provide this. However, it’s not found on many of the most popular digital models. Again however, this Honeywell smart thermostat will regulate the temperature quite precisely in the areas around it.
Add Zoned Climate Control
If you like tinkering with climate control systems and have a little money to throw into the project, you could add more thermostats throughout your house along with appropriate duct or water valves (depending on your system type), to better regulate the temperature in problem areas of the house.
Or, Just Put Up With The Temperature Swings
You may ultimately decide that you can tolerate the temperature swings. Keep in mind that all furnaces exhibit SOME temperature differential. If so, you’ll definitely save yourself some dollars. However, in the vast majority of homes, the tips provided above do indeed mitigate temperature swing, bringing it into to tolerable limits.
- RTH9580WF Wireless Thermostat Product Page
- Where to buy the Honeywell RTH9580WF WiFi Smart Thermostat
- Fixing WiFi Problems on Honeywell RTH9580WF Smart Thermostat
- Honeywell Smart WiFi Thermostat Manual RTH9580WF
- Honeywell WiFi Wireless Programmable Thermostat RTH9580WF Review
- How to Register Honeywell Wi-Fi Thermostat Online for Remote Control, RTH9580WF
- How to Unregister Honeywell WiFi Thermostat RTH9580WF
- 2016-12-14: Added more links to the Suggested Reading section.
- 2016-02-13: Originally published.