How to Pick a Thermostat

We talked about installing a Thermostat and a little bit of the install process. Today, we’re going to look a little deeper into the factors and reasoning behind picking the perfect thermostat for your needs.


The Key Factors

  1. What type of HVAC System do you have? Heating, cooling, multizone?
  2. What can your existing system support?
  3. What do you want out of your new thermostat? Efficiency, ease of use, programmability, automation?

If you can answer these questions, you can begin to narrow down what type of thermostats will fit your needs. There is a wide range of options out there, from simple, old fashioned set it and forget it units straight up to smart thermostats that detect and learn the building’s occupancy over time. Let’s dig a little deeper.


The Existing Hardware

Your first concern is going to be making the best out of the hardware you’re already using. If you own a multizone system, it would be a tremendous step backwards to install a single, old fashioned thermostat for the whole building. If you own a simple hot water furnace with some radiators in a single zone system, a multi-room thermostat is probably going to be overpriced for the limited returns it can deliver.

If there’s a full heating and cooling system, that too needs to be factored in. There are thermostats out there which are heating only. There’s probably even thermostats out there which are cooling only (though I’ve never seen one). When you start shopping, look at your system and see what hardware there is to work with.


The Existing Capability

At this point, you know what you have, whether that’s an existing multizone system, a basic furnace, or something in between. You need to know what is compatible with that hardware. This may be where you consult your HVAC Professional or do some brief probing around your thermostat to see what connections are available. It’s important to count and document the number of wires and their labels present in order to find a replacement that will work with all your existing hardware.

Many products on the market are sold on the basic compatibility: “Works with most systems, 6 wires or less.” That is that the thermostat can handle a lot of functions, multi stage heating and cooling, but that it has its limits. Other thermostats will state a need for a dedicated C wire, which provides 24 volt power. For still others, it’s important to monitor online reviews. Certain C-Wire thermostats are advertised as working without, but that’s not always the case. The with-or-without C-Wire try to sip up enough power from the heating system without causing it to turn on altogether. This doesn’t always work.

For more advanced multi-zone installations, there’s also the challenges of making sure the hardware can work together. There’s zone controllers involved, there may be BACnet hardware involved, and there’s sure to be some system-specific compatibility to be accounted for.


What Do You Want?

At this point, you should know what your building has, what can be easily installed, and you need to narrow down the field a bit. Every product category has a mixture of features across the available thermostats. NEST has their smart thermostat that integrates with their smoke detectors and every app in the world. Honeywell and Ecobee both support Google Home. On programmable thermostats there is the level of programmability, running the same schedule every day or running a different schedule for the weekends. Some programmable thermostats will be easier to use than others. Even for the simplest thermostat, you can consider the mechanism of sensing the temperature and how you set it as major features to consider.

These wants will make an enormous pack of competing systems and platforms narrow down to just a handful that are compatible with your facility, have the features you want, and will get the job done every time.


Breaking the Compatibility Barrier

The lack of a certain wire or component in your system isn’t the end of the “I want a smart thermostat” campaign for dedicated people. If you’ve done your research and concluded the best thermostat for your needs is not compatible, it’s worth looking into just how hard it is to make it compatible. In many installations, the bare minimum wiring is run to make everything tick.

Perhaps the original furnace only needed four wires to be operated. It’s been replaced with a more advanced model that has features controllable with seven or eight wires, but there’s only four going to the thermostat. Some compatibility issues can be resolved with an hour or two visit from your HVAC Professional and a quick install of a new wire between the HVAC system and the thermostat.

For those of you out there with older systems lacking a C-Wire, hell-bent on getting a smart thermostat, there’s good news! Smart thermostats don’t care where that 24 Volt Common Wire comes from. There are adapter kits which can add a 24 Volt Common Wire to most systems and ultimately make a clean, simple Smart-thermostat install possible almost anywhere, with some extra work.


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