HoneywellRTH8500D 7-Day Touchscreen Programmable Thermostat, "C" Wire Required, White, 1Package (Thermostat) (RTH8500D1013/E1)

The Honeywell RTH8500D is a feature packed thermostat for nearly all installations. It features a wide array of programming parameters and fully touch enabled interface. This T-stat can be used with a wide variety of systems ranging from heat only or cool only, combined gas heating and central air conditioning, boiler and electric systems (provided they are wired for 24V controls), and multistage and hybrids systems. This stat will provide up to two cooling stages and two heating stages. So what does all of this mean? Basically it should cover better than 95% of all thermostat replacements.Features. The 8500 series features a fully touch enabled interface with a backlight. The back light will turn on when touched then stay on for about 30 seconds after the user has stopped touching it. This is obviously to conserve battery power. This stat required 3 AAA batteries for operation or the connection the your systems "C" wire (assuming your system has one.) It will operate with or without a "C" connection however without, it will run on the batteries which should be changed about every 6 months in my experience. It also features a backup internal battery to protect the system clock and settings. The touch interface is intuitive and well thought out. System, fan, and temperature settings are all on the home screen and feature "one-touch" (or one button) activation. This is obviously a programmable stat which features 7-day independent scheduling. Simply put every day of the week can be I individually programmed for up to four "changes" per day. They can also be grouped together for quicker programming. I like the schedule programming interface, it's one of the best I've seen. You can also de-activate one or more of the changes if it's not needed that day. The changes are called "wake", "leave", "return", "sleep" in the menu, but of course they can be anything you want. With each scheduled change or event in the system you get two settings a cool and a heat setting. These settings can be anything you want except in the case of "automatic changeover" mode. Once set your display shows the current room temp and the target or "set" temp on the main screen. It shows the time as well. When the next scheduled change arrives the new target temp will appear and the system will switch on or return to standby depending on the what the room temp and target temps are. There are up and down arrow keys on the target temp which activate "hold". Pressing up or down will set a new temporary setting for that period. The system also gives you an option for duration. It will ask you when you want this temp hold to end. You can use the clock to select up to 24 hours. There is also a permanent hold feature which will hold the temp until the user cancels it. Finally there is a vacation hold feature I've not used, but apparently it will hold the temp for a preset number of days. After all holds expire or are canceled the system returns to normal operation following the schedule. I mentioned above the auto changeover feature. This allows the system to select heat and cool on its own and will display both target temps on the main screen at the same time. I really like that! There is one small drawback. There must be a minimum 3 degrees of separation between the heat and cool settings. For instance if you have your heat set to 68 degrees, the closest the cool setting can be is 71 degrees. Not such a big deal but 2 would've been optimal. This doesn't prevent you from increasing the heat temp or decreasing the cool temp, it just "pushes" the other up or down to maintain that 3 degree separation.Setup is a simple enough affair with the included quickstart guide. You will need to know whether you're furnace is gas or electric, if you have A/C or a heat pump. But past that most features are simple yes / no style answers.Basic Connections.R / RH - Heating RelayRC - Cooling Relay (included is a jumper for RH to connect the two together, remove it if your installation has separate RH and RC wiresW - Heating WireG - Fan ControlC - Common for 24V power to power thermostatY - Cooling WireO / B - Changeover Wire for Heat Pump to A/C Changeover ValueW2 - 2nd Stage Heat Mode (may also be used for Auxilary connection to gas or electric furnace for backup heat to a heat pump.)Y2 - Used if you have a two stage A/C compressorThere's more but these are the most common.As much as I like this thermostat, there are a few features that could stand some improvement. First is as mentioned above, I'd like to see a two degree separation of temperatures for the automatic change over system. Second is the ability to use external (outdoor temperature) sensors for use with heat pumps and aux heat. This would allow the thermostat to automatically select backup heat when the outside temp drops below the efficiency threshold of the heat pump. There is a Honeywell 8000 series thermostat under the model name Vision Pro with the ability to use external sensors, however it would be nice for this model to include that as well. Lastly I would like to see more than 4 scheduled events per day. Four is plenty for families. However homes where persons work split shifts require more than 4 events. Many comparable t-stats are starting to show the ability for 7 day and even 365 day programmability with a dozen or more events per day. It's time that Honeywell caught up. I wouldn't be saying this if this was a $50 stat, however past $100, you start to expect top tier functionality and quality. All of that said, this is a really good thermostat. As others have said there is a click with this stat but I don't find it bothersome in the slightest, and I sleep 6 feet from it. The screen is clear and the touch interface is accurate. I have to say I really enjoy this unit and it has kept me comfortable over the last 10 months.

I replaced my 22-yr old Honeywell ChronoTherm with this more modern unit. My old thermostat worked as it was supposed to, but it allowed the temperature to swing about 2 degrees before activating. In the summer, I would be feeling overly warm and as I was about to adjust the thermostat it would click on. That was getting tiresome although I endured it for years.This new thermostat does not disappoint. It turns on the air just as I am starting to feel a bit warm and I like that. I don't know how it works in winter yet, but I have no reason to believe there would be any problem there, either.Some folks argue that having it turn on and off more frequently is a problem. I disagree. Those guys need to live here where it's over 98 degrees most of the summer and see if they mind the a/c coming on too often. Besides, I keep the temperature on 78 day and 79 night with the help of this unit and I can see that it is more energy efficient than the prior unit.Here we have "smart" power meters and I can check my usage every day. This thermostat has made a difference. Although the peak cooling season is right now (August) my heaviest usage days were all back in July before installing the new thermostat when it was actually cooler outdoors. Now I'm using about 5 kwh less per day on a 2-story 2200 sq ft home with single a/c and heat.Also, I never feel the need any longer to go and crank the temp down because I am feeling too warm. Do that in the heat of the day does cause a great loss of efficiency. So basically I am MUCH more comfortable which is very nice indeed.I really don't need the 7-day program ability or the vacation hold. However I did want the automatic changeover between cool/heat so my decision was clear. Also, I could not convince myself that any brand other than Honeywell would be a good choice since I know from experience they have a great reputation for making fine thermostats.Installation could hardly have been any easier. Setting it up was simply a matter of following the very clear Installation Guide. Almost all the options were factory set as I needed them except I turned on the automatic changeover. That makes no difference now, but later in the fall when we are still having 90 degree days and 60 degree nights it will be nice not to awaken in a chill.The lighted touch screen is nice, since my hallway is usually quite dark. Not a big deal, since other than to do a little fine tuning on the program I haven't needed to touch it. Yes, the light does turn off a bit quickly but I've learned to tap in a blank area of the display and turn it on again while I ponder my next move.This unit does not offer the option to be illuminated continuously. That at first annoyed me but to be reasonable about it, it only means that the light will not be deteriorating over its life and getting dimmer every year. It should last for many years (my guess) by turning on only when really needed rather than being an expensive night light.To wrap up, it's a great thermostat. I wish it would pay my utility bills but at least it is helping to ease the monthly pain by a dollar or two and the savings will add up. I like it.