Thermostat compatibility with 2 wires (C and R)

[rDraut]

• On my current Honeywell, just these two, blue to C, and red to R. Compatible?
• Thanks, Richard

[CoolingWizard]

The configuration you have provides for power to the thermostat.  Since there are no other wires, this thermostat does nothing. The HVAC conventional control system uses Y for cooling, W for heating, G for Fan, R for Power 24VAC and C for Power 24VAC. Think of the R as the Line and the C as the Neutral.

The AC Cooling Wizard

[rDraut]

Thanks for the quick reply!  It's puzzling, as the thermostat does work normally, separately for A/C, heat, and fan control. Thoughts?

Richard

[CoolingWizard]

I have no earthly idea with only those two wires the system would work at all. What is the make and model number of your thermostat?

[rDraut]

 Honewell TH8321R1001

[rDraut]

Apparently, it works with a Honeywell equipment interface module or with truezone wireless adapter.

[CoolingWizard · Accepted solution]

Yes indeed, it uses a Honeywell RedLINK to communicate wirelessly with the HVAC Equipment.  The Nest Thermostat cannot do this.  Your thermostat cable in the wall would need to have more conductors and the HVAC equipment would need to be rewired.  

The AC Cooling Wizard

[rDraut]

Thanks!

[Markjosephp]

Hello there,

I wanted to ensure that everything was covered here.

Thanks for all the information, @CoolingWizard. Big help!

@rDraut, I hope you've found the answer you're looking for. If you're still in need of assistance, feel free to let us know.

Regards,

mark

[Markjosephp]

Hi rDraut,

I'm checking back in — how's it going? Still need our help?

Regards,

Mark

[rDraut]

Thanks for checking. As it turned out, I bought an old RedLINK gateway for my existing, non-WiFi Honeywell. Alexa is now controlling that part of my life also 🙂 !

[Markjosephp]

Hello rDraut,

Thanks for keeping us in the loop. I'm glad to know that you have a new RedLink hub, so you can control your HVAC system with your thermostat. It looks like we can consider this one complete, so I will lock the thread within 24 hours unless I can help out with anything else.

Regards,
Mark