I by no means consider myself a DIY enthusiast. I am certainly no Harvey Homeowner. But a few years back, I figured I was more than capable of installing a new thermostat. I was wrong. Modern thermostats are far more advanced than their older counterparts.
I have replaced many thermostats in my day. Thirty years ago, thermostat replacement was a snap. It involved two screws and three wires. Anybody with a modicum of DIY skills could replace a thermostat in under 15 minutes. Things are not so easy anymore.
Below are some of the lessons I learned by trying to install a modern thermostat and failing miserably. According to Comfort Solutions, an HVAC and plumbing contractor out of Utah, I am not alone. The problems I ran into are fairly common with modern thermostats and HVAC systems.
Lesson 1: There Are Lot More Wires Involved
My mechanical thermostat of 30 years ago had only three wires. My modern thermostat of 2021 had eight wires. I had never seen such complex wiring on a thermostat before. But that was not the most worrisome thing. A more important matter is that my HVAC system only had six wires. Now what?
I knew enough to label the wires coming out of a wall based on the labels I found on the existing thermostat. I even took a picture of the wiring before I disassembled everything. Yet I still hooked things up incorrectly. That led to a repair bill of several hundred dollars, money I was hoping not to spend by installing the thermostat myself.
Lesson 2: Some Modern Thermostats Require a C-Wire
Prior to this particular thermostat project, I had never heard of a thermostat being hooked up to a C-wire (a.k.a. common wire). But lo and behold, Wi-Fi enabled smart thermostats require this connection. The C-wire completes the circuit between thermostat and HVAC transformer, always delivering a steady power supply.
There are multiple solutions if a homeowner’s current setup does not include this wire. I knew none of them, let alone the fact that I needed a C-wire. Now I know. Still, I do not intend to ever attempt a new thermostat installation again.
Lesson 3: All Thermostats Are Not Compatible
It was only after I called in an HVAC contractor that I learned not all thermostats are compatible with all HVAC systems. Even if I had correctly connected all the wiring on my new thermostat, it would not have worked with my system correctly.
Fortunately, my older thermostat was working just fine. My only reason for installing a new one was to have access to more advanced programming. But learning that it wasn’t compatible meant going back to the original thermostat. I spent an entire afternoon and several hundred dollars to learn this painful lesson.
As a side note, we moved to a new home and eventually had the HVAC system replaced. The new system came with a thermostat because, of course, the existing thermostat was not compatible.
Lesson 4: It’s No Longer an Easy Job
The last and most important lesson I learned is that replacing a thermostat is no longer an easy job. Just like our cars are essentially computers on wheels, our HVAC systems are highly complex systems that rely heavily on sensitive electronics. They are now officially out of my league.
If I ever need a new thermostat in the future, I will not even try to do it myself. I will leave the job to professionals. At least that way, they will bear the financial loss if the job gets mucked up.
