The subjects of home automation and HVAC control have gone hand-in-hand for some time, but it is often discussed in the recounting of war stories retelling the battles waged in search of solutions. It has taken a long time for a fairly good selection of automated products to develop for the HVAC area. The number of companies manufacturing products for the consumer/residential market is still limited, but at least there are a few solutions from which to choose. When discussing a solution, I am speaking of a tested, integrated solution, and in the area of HVAC control for a residential application, that solution is a thermostat. There are a number of technical people out there who are knowledgeable enough to build their own HVAC control using relays and temperature sensors, but for a complete solution that is tested and safe, you must use a thermostat. If you have truly automated thermostats in your home, you have the power to control the setpoint, preferably with variable changes instead of fixed changes, you can control the fan (On/Off/Auto) and the mode (Heat/Cool/Auto/Off, and Aux Heat for a heat pump system).
All of these thermostat parameters give you an enormous amount of control over your environment. To give you some examples, let’s run through some scenarios where you might change your own thermostat if you didn’t have to get up off the couch. Everybody knows that 67 degrees in your home feels much different in the winter than it does in August, and much of that depends on humidity levels and your own personal preferences. With an automated thermostat, you can not only have different setpoints depending upon the season, but you can increase or decrease the setpoint depending upon your current comfort level. Additionally, you can take into consideration other factors, such as relative humidity and outside weather conditions, if those measurements are available to your system. The great thing about having the thermostat automated is that, if you happen to increase the heat setpoint for your personal comfort and forget to set it back, an automated thermostat is forgiving and will restore everything to normal operation before the surprise heating bill comes in the mail. Another benefit I have taken advantage of is turning on the fan so that it runs continuously. In the winter, that causes the humidifier to run, increasing the moisture level in the home. Occasionally, I use the fan to help circulate air around the house if my wife happens to be cooking with some potent-smelling spices.
So what about energy savings? Is there a place for energy savings to coincide with personal preferences? The answer is yes, but the amount depends on – you guessed it – your own personal preferences! If you are at home all the time and always tune the thermostat to how your body is reacting to its environment, then you are probably not going to get a lot of energy savings out of an automated thermostat. Let’s not forget though that for most people, the struggle to pay for home automation through energy savings was given up long ago, and now many people realize that home automation is a personal mixture of convenience along with SOME energy savings. The mixture of convenience and savings is controlled by the detail that you put into the automation routines that control the system, and that leads into the second half of the subject of this article.
One of the best sources of information for your HVAC control schedule is your security system. If you have a security system that has multiple arming modes such as day, night, away, and vacation, as many of today’s systems are equipped, then you have several different modes for your HVAC as well. Here are some examples of what those different modes could mean:
AWAY – In a conventional heating/cooling system, you set the temperature back. The bigger the difference in the setpoint with the outside temperature, the greater the savings. In a heat pump system where restoring the normal setpoint can consume a lot of additional energy and take a long time, you might want to set a timer and wait a while before setting the temperature back so, if the absence is for a short period, you can set the temperature back a smaller amount, or even skip the setback until you have been absent for at least an hour.
NIGHT – While you may have one security system, you could have two or more thermostats, and arming in night mode could cause you to set the temperature back on the main floor thermostat, but keep the setpoint at a comfortable sleeping temperature on the second floor where all of the bedrooms are located.
The meaning of other arming modes could be just as significant in your home as the two examples provided above. If you agree in principle with everything that has been written thus far, this next statement will not be hard to swallow either: It is not as important how much you change the thermostat (as that is mostly a logical choice depending on your HVAC equipment and your house), as it is the amount of information or data that goes into deciding when you change it. In the case of my home, I have a fairly sizable set of information points with which to work. Here is a summary of my system:
Two fully automated thermostats with separate heat and cool setpoints – this is particularly useful because when I need to establish new setpoints when the security system is disarmed, I can set both heat and cool setpoints without having to decide on a single calendar-dependent setpoint. They also provide the current settings for the rest of the thermostat along with, obviously, the current temperature.
A security system with several arming modes and an interface to my main home automation system from that system give me all of the benefits of the security system mentioned above.
Several individual input zones on the security system so I have granular information, such as when windows or doors are open. When doors and windows are connected together in the same zone, it is not known which is open. A door with an outer storm door or a door to a garage can be open without affecting the inside environment as much as an open window.
Some additional temperature sensors for particular areas of the house, and a humidity sensor as well since humidity ranks right up there with the temperature in our perception of what is comfortable.
A home weather station that gives me the outside temperature and/or wind chill. When the outside temperature drops below 35 degrees, it is time to put my heat pump thermostat into Auxiliary Heat mode, because at 35 degrees or less, the propane auxiliary backup I have is more efficient than the electric heat pump.
A method in my home automation system to create and manipulate flags. Flags take care of many other remaining data points such as house modes (entertaining, watching a movie, eating dinner, etc.), whether or not there are guests in the house (since the guest room is on the main floor where the temperature is usually set back at night), or perhaps even if I want to be a little more energy conservative by wearing some warm socks and covering myself with a blanket while watching TV.
And finally, a home automation system in HomeSeer, that brings it all together in one place, powerful enough to run my custom events and do all that I want.
Triggers are changes in a device or sensor that causes a set of rules (conditions) to be evaluated and, perhaps, cause actions to take place. In my HomeSeer system, changes in the security system provide triggers, changes in the temperature or humidity sensors provide triggers, and changes in flags invoke triggers. The end result is an HVAC control system with near real-time reaction to life in an automated home.
It can be a lot of work integrating all of that information in with your family’s personal lifestyle habits, preferences, and budget, but when it is done, you have a home automation “keeper”. We all want the home automation “keepers”, as these are the things that our spouses ask for and miss the most if they are gone. They are the shining examples that we keep reminding our spouses of when the new home automation routine you just wrote isn’t quite right and all of the lights in the house turn on at 3 o’clock in the morning. My wife’s HVAC “keeper” is having the temperature up an extra four degrees just before she wakes up early on winter weekday mornings. My “keeper” is my entire HomeSeer system.
With the increased reliability of HVAC home automation solutions, you can enjoy the benefits of control, convenience and energy savings in your home. By integrating the security system to the HVAC system, you can greatly simplify the effort of pulling it all together. Now, there is no reason to have cold feet about implementing your own system. In fact, there is no reason to have cold feet at all!