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Reviews and General Information on Programmable Thermostats
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Thermostat / HVAC Compatibility

For anyone reading this page who thinks they’re about to get some really technical information on HVAC systems and their compatibility with various thermostats, I’m sorry to disappoint you. I don’t work in this industry, and I certainly don’t have the sort of knowledge a technician does.

However, since I have done my research regarding thermostats, I thought it would be prudent to at least pass on some of the information I’ve come across that’s really helped me. You see I thought it would be easy to find a model of thermostat to suit my needs and the needs of my HVAC system, however it transpires that the very first thing you must do is check what type of heating or cooling you have in your home.

Of course, most thermostats will work with different systems, but you just might end up with a thermostat that won’t work with your system at all, or if it does you might cause damage to your equipment and that will only lead to an expensive repair job.
So, there are various steps you need to take before you even start to think about the sorts of features you would like with a thermostat.

What Type of Heating and Cooling System Do You Have?

Your HVAC systemThis is what makes finding the right thermostat a bit of a headache, especially if you don’t have any technical experience. The main reason is there are a wide range of different systems on the market and this will determine what type of thermostat you can have.

For instance, you may have a gas furnace, electric baseboard, oil fired with a boiler or a heat pump based system (to name but a few). This may all sound very complicated but once you know what type of system you have there are only three different thermostats to choose from.

  • Low voltage systems are the most common systems today and only require a 24v power supply. Most thermostats will work with this system.
  • Direct line or high voltage systems use a 110v to 240v power source. These are generally baseboards and other electric heating systems and they require special attention when looking for a thermostat (meaning not all thermostats will work with these). What you should also remember is that in some older homes, direct line voltage is also used to power the thermostat.
  • 24 millivolt systems are usually gas or oil powered furnaces that don’t use electricity, wall or floor type.

Again you might be thinking there is “no light at the end of the tunnel” but if you know a few of the basic terms you’re likely to come across, it won’t be that difficult to determine which type of thermostat you need.


You will more than likely come across the terms “one stage” and two stage” often, but just to help you a little further I’ve added the information below.

  • Stage one heat and cool means you have units that work either at full capacity or not at all, it’s like an on/off switch.
  • Stage two (or multi-stage) means your system is capable of heating and cooling on both low and high speeds.

There are ways you can check what both the type of system you have and how many stages it is, but this usually involves taking a look inside your current thermostat. This will give you the information you need but since this will also involve you having to deal with a power source to your system, if you’re not sure the best thing to do is ask a technician to help.

A side note also worth mentioning here is that

How to Check Heating and Cooling Stages

wiringIf you are confident enough to check the system you have, it’s pretty easy to confirm what number of stages you have.
You will have to look inside your current thermostat, and this is where you will more than likely be met with a series of numbers and letters. For systems that have more than one stage for cooling look out for wires that are attached to an “y1” and “y2” terminals. The same applies to a two stage furnace. If you have this, there will be wires attached to the “w1” and “w2” terminals.

You may also want to check the information I have added on my , the videos all include wiring info so I’m sure this will help make you more confident.

What This All Means

If you currently have a low voltage system, you can use most (if not all) of the systems I have reviewed on my site. Some models of programmable thermostats on the market will only work with one and two stage heating and one stage cooling, but the manufacturer usually states this in their description.

If you have anything more complicated such as a multi-stage system or a system that’s zoned you should look for the more advanced models of thermostat on the market. Your options will be less, but there’s something to be found for nearly any system.

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