Help Needed: Connecting and Replacing Old Honeywell T694B with Nest Thermostat (Pictures Attached)

[JoeGio]

Hi everyone,

I'm in the process of upgrading my old condo Honeywell T694B thermostat to a new Nest thermostat, and I could really use some help with the wiring. I've attached some pictures of the existing Honeywell setup.

From what I can see, the Honeywell has the following 4 wires coming from the wall plate:

• BLACK goes to LO
• BLUE goes to MED
• RED goes to HI
• YELLOW goes inside T694B

I have no idea how these correspond to the terminals on the Nest. I've done a bit of research, but I'm getting mixed information, and I want to make sure I get it right to avoid any issues.

If anyone has experience with this specific Honeywell model or general advice on connecting to a Nest thermostat, your guidance would be greatly appreciated!

Thanks in advance for your help!

https://www.dropbox.com/scl/fo/zwc8z34yfyqweuyd4xazw/AI2q6HWWdlGohwoXU5i87G8?rlkey=uq5tvc1fne7o746wg... 

[CoolingWizard]

@JoeGio , the problem you have is that your system thermostat operates with 120VAC or 240VAC. That type of system is not compatible with low voltage conventional thermostats. The Nest series of thermostats are on compatible with low voltage 24VAC systems. 

If you want to use a smart/programable thermostat like the Nest Learning Thermostat, you will need a HVAC service company to come and convert your system from 120/240 to a low voltage 24V control system. 

AC Cooling Wizard