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Replacing a Honeywell T6069A with a Google Nest Thermostat

The Honeywell T6069A, while reliable in its time, may feel outdated compared to the sleek design and intuitive interface of the Google Nest Thermostat. With its minimalist aesthetic and vibrant display, the Nest Thermostat seamlessly blends into any modern home decor. Its user-friendly interface makes it easy to adjust settings and program schedules, ensuring effortless control over your home's temperature.

In the ever-evolving landscape of smart home technology, one area that has seen significant advancement is thermostat technology. If you're considering upgrading your home's heating and cooling control system, replacing your old Honeywell T6069A thermostat with a Google Nest Thermostat could be a game-changer. Let's explore why making this switch is a step towards enhanced comfort, convenience, and energy efficiency in your home.

Disclaimer: I am not an electrician nor an HVAC expert. I am just sharing my experience and NOT providing any instruction or advice on how to replace a thermostat or perform electrical work in your home.

Technology is constantly evolving, and by upgrading to a Google Nest Thermostat, you're future-proofing your home for years to come. With regular software updates and ongoing support from Google, your thermostat will continue to receive new features and improvements, ensuring that your home remains at the forefront of smart home innovation.

One of the most compelling reasons to upgrade to a Google Nest Thermostat is its smart capabilities. Unlike the Honeywell T6069A, which operates on a traditional thermostat system, the Nest Thermostat is equipped with built-in Wi-Fi connectivity and intelligent sensors. This allows you to control your home's temperature remotely via the Nest app, whether you're lounging on the couch or miles away from home. Additionally, the Nest Thermostat learns your preferences over time and adjusts its settings accordingly, providing personalized comfort without the need for manual intervention.

With rising energy costs and growing environmental concerns, energy efficiency is a top priority for many homeowners. The Google Nest Thermostat is designed to help you save energy and reduce your carbon footprint without sacrificing comfort. Its Energy-Saving features, such as Eco Mode and HVAC system insights, provide valuable data and recommendations to help you optimize your home's energy usage. By making intelligent adjustments based on occupancy and weather conditions, the Nest Thermostat can help lower your utility bills while minimizing environmental impact.

If you've already invested in a smart home ecosystem, integrating a Google Nest Thermostat is a seamless process. With compatibility with popular platforms like Google Assistant, Amazon Alexa, and Apple HomeKit, you can control your thermostat using voice commands or automate temperature adjustments based on other smart devices in your home. Whether you're adjusting the thermostat with a simple voice command or setting up automated routines, the Nest Thermostat enhances the interconnectedness of your smart home.

1. Understanding the Circuit

The main issue of replacing the Honeywell T6069A with a modern smart thermostat is its operating voltage. The condo that I am living in is an older building constructed in the 1990s. The suite has a ceiling hideaway fan-coil unit that operates at line voltage. The T6069A is perfect for controlling this unit but not for a modern 24VAC thermostat. After opening up the ceiling tile, I found that it is a SnyderGeneral TSH041EL fan-coil unit with an operating voltage of 115VAC and a motor current of 1.1A.

After a bit of research, I found a generic wiring diagram for SnyderGeneral fan-coil unit. I am not 100% sure if the wiring diagram is for the TSH041EL but it looks close enough for my purpose because when I opened up the T6069A, I found a similar wiring configuration.

5 wires plus a line match with the 5 wires required at the fan-coil unit. Looking at the T6069 manual, it looks like the thermostat I have is connected per the 6-wire configuration with a matching colour. The only difference is I have an ON/OFF switch instead of a HEAT/OFF/COOL switch. I also confirmed that yellow or orange wire will connect to L1 (black) depending on the temperature setting on the dial.

2. Re-wiring the Circuit from 115VAC to 24VAC

Looking at the wiring configuration above, I can conclude that the 5 wires are 5 mechanical connections controlling the various aspects of the fan-coil unit. I am not an electrician nor an HVAC expert so do not take this as instruction or advice. Find an electrician or an HVAC technician before working on your HVAC system. Therefore, if I can bring line power to the various fan-coil connections and resemble the T6069A thermostat, then the fan-coil unit should work. So here's the plan:


Here we go, I got a 24VAC 40VA transformer and a brunch of 24VAC coil relay with 240VAC 5A contact rating. I might be better off with 10A relays but given that I'll most likely just be using the medium fan speed so 5A is sufficient. I also got a 6" x 6" electrical box to fit everything into so I won't kill myself.

The tricky part is finding a space to hide this additional control box not too far away from the thermostat so I don't have to run multi-meters of new wire. I found a corner in my kitchen that has a common wall with my living room to hide it.

I installed the relays and transformer (attached to the outside of the box due to lack of space) to the 6" x 6" box before placing it into the wall. Once it was in place, I switched OFF the circuit breaker that controls the HVAC system and confirmed the wire was not live with a multimeter before proceeding further. After confirming that it's safe to work on the high-voltage side, I bring the 115VAC wires into the control box and run the 24VAC control wire to when the thermostat will be. I have a brunch of CAT5 cable lying around so I just used that instead of properly colour coding them.

3. End Result


I have some drywall patching to do but now I have a smart thermostat that can monitor temperature and humidity instead of the outdated non-programmable ON/OFF thermostat I had before. I looked up smart line voltage fan-coil thermostats but purchasing them cost about the same as building this circuit myself plus the Google Nest.

Lastly, I found some of the newer smart thermostats with more wire connections can be programmed to control multi-speed fan-coil units at 24VAC so I don't need a mechanical switch to select the fan speed but I can't justify the exact $200 for it because I've never touched the fan speed switch on my old thermostat. However, I'll still need to convert the voltage down to 24VAC, there's no easy way around that. There are HVAC control boards that will do the conversion but the cheapest one I found is around $500 unless I buy one from an unknown original from a distant land.

Replacing your old Honeywell T6069A thermostat with a Google Nest Thermostat is more than just a simple upgrade – it's a transformation of your home's comfort and efficiency. With its modern design, smart features, energy-saving benefits, and seamless integration with your smart home ecosystem, the Nest Thermostat offers a comprehensive solution to your heating and cooling needs. Make the switch today and experience the convenience and peace of mind that comes with a smarter, more connected home.


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