What does c-wire required mean?

This unit works fine on my circa 1998 central air furnace/AC using G,W,Y,R wires only, so the C wire is definitely not required. My guess is if you have a C-wire, it powers the thermostat while on the wall, and the 3 AAA power it if you pull it off the wall to program it (not necessary as you can program it on the wall). If you don't have a C-wire, then the 3 AAA power it all the time. Net effect: you'll change AAA batteries more often without a C-wire. Again, just a guess, but C-wire definitely not required for this unit to work. This unit also has a lithium battery, likely for its real time clock. You activate it when you pull off the little tab during installation.

does this unit work without a c wire?

Hi Randy! The RTH8500D does not require a C wire. There will be 2 scenarios that the C wire will be required. 1. If the thermostat that will be installed is a Wi-Fi thermostat. 2. If the thermostat that will be installed is a RedLink thermostat and a accessory will be pared to it. -John

Can you dim or turn off the backlight?

Are you asking if the backlight can be turned off when you're actively using the keypad? In my installation, the backlight only comes on when there's activity on the keypad and shuts off shortly after changes are complete. Without the backlight, I can't see the text on the display well enough to change any settings. I'm not aware of a setting that turns of the backlight entirely.

Will the honeywell thp9045a1023 wiresaver work with this thermostat?

Sorry not familiar with the wire saver. Do not know if it will work or not.

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Honeywell RTH8500D 7-Day Touchscreen Programmable Thermostat, "C" Wire Required, White, 1Package (Thermostat) (RTH8500D1013/E1)

Honeywell RTH8500D 7-Day Touchscreen Programmable Thermostat, "C" Wire Required, White, 1Package (Thermostat) (RTH8500D1013/E1)

Product ID: 1628911

Details

Brand
Honeywell
Color
White
Controller Type
Hand Control
Model Name
RTH8500D
Special Feature
Programmable

⚡Smart Response tech for energy savings

🕒7-day programmable with 4 periods/day

🌡️±1°F precise temperature control

Description

🌟 Upgrade your comfort game with smart precision and effortless control!

POWER OUTAGE PROOF - Programs and settings are safely stored in memory, so you never lose your personalized comfort plan.
PRECISION THAT PAYS OFF - Maintain consistent comfort with ±1°F accuracy—no more guessing or wasted energy.
UNIVERSAL COMPATIBILITY - Works seamlessly with conventional and heat pump systems up to 2H/2C—one thermostat to rule them all.
TAILORED COMFORT EVERY DAY - Customize your schedule with 7-day, 4-period programming for ultimate control.
SMART LEARNING SMARTER SAVINGS - Adaptive Smart Response technology anticipates your heating/cooling needs to optimize efficiency.

The Honeywell RTH8500D is a sleek, touchscreen programmable thermostat designed for professional-grade comfort and energy efficiency. Compatible with most conventional and heat pump systems, it offers 7-day scheduling with 4 customizable periods per day, ±1°F temperature accuracy, and Smart Response technology that learns your system’s timing to optimize performance. Its memory retention safeguards your settings during power outages, making it a reliable, energy-saving upgrade for any modern home.

Specifications

ASIN	B0026ES9UQ
Additional Features	Programmable
Backlight	Yes
Best Sellers Rank	#421,880 in Tools & Home Improvement ( See Top 100 in Tools & Home Improvement ) #487 in Home Programmable Thermostats
Brand Name	Honeywell
Color	White
Control Method	Touch
Control Type	Touchpad Control
Controller Type	Hand Control
Customer Reviews	4.4 4.4 out of 5 stars (1,742)
Display Type	Digital
Global Trade Identification Number	00783961592196
Included Components	sdfsd
Item Type Name	Honeywell RTH8500D 7-Day Touchscreen Programmable Thermostat, "C" Wire Required
Item Weight	1 Grams
Manufacturer	Honeywell
Manufacturer Part Number	RTH8500D
Manufacturer Warranty Description	1 year.
Material Type	Plastic
Model Name	RTH8500D
Model Number	RTH8500D1013/E1
Number of Batteries	1 CR2 batteries required.
Power Source	Battery Powered
Product Style	Touchscreen,Smart
Screen Size	1 Centimeters
Shape	Curved
Smart Home Compatibility	Not Smart Home Compatible
Specific Uses For Product	Heat Pump
Specification Met	Energy Saving Thermostat
Temperature Control Type	Heating and Cooling
UPC	783961592196 085267256865
Unit Count	1.0 Count
Voltage	32 Volts
Wattage	1 Microwatts

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