| Home Toys Article - Oct98 - [HTI Home Page] |
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Honey.... will you go
downstairs and turn on the Air Conditioning??? |
Jeff started Smart Electronics in 1994. He graduated from the University of Detroit Mercy in 1991 with a Bachelor's degree in Electrical Engineering. Then, in 1994, Jeff completed his Master's degree at U of D. He's done home automation research and development for his Master's Thesis, his company, and other projects for about 6 years. VogelJC@aol.com www.smartgateway.com |
One of the great features of a home automation system is having the ability to control your HVAC (Heating Ventilation and Air Conditioning) system. You can save a lot of money if your HA system can turn off your HVAC system when it's not required! Using the Smart Housekeeper with RCS or Enerzone Thermostats, you can achieve the following:
- Control different zones by time of day, date, or event
- Change temperature by X-10 commands, door/window open sensors, or IR commands
- Control baffles based on temperature, time of day, or door/window open status
- Easily support up to 20 thermostats and 8 independent baffle controls
- Log temperatures, setpoints, and any other activity on your PC
This month's project will utilize two RCS Thermostats, and 4
baffles. We'll control the baffles based on motion sensors from our Home Automation system
as well as date and time of day. We'll organize the project in the following manner:
- Installation of the RCS thermostat
- Installing the Baffles
- Connecting the Baffles to the Smart House Keeper hardware
- Setting up your thermostat in your Household layout
- Programming the Baffles to respond to a set of requirements
- Programming the Smart House Keeper to respond to energy saving and convenient macros.
Installation of the RCS Thermostat:
The RCS thermostat consists of a control head, a base controller, a power supply, and a power line interface. The control head should be installed in place of your existing thermostat. The controller should be installed near your furnace and be accessible to a 120 volt outlet.
Installation if the RCS thermostat is quite simple. If the home is equipped with a 4 wire thermostat, the easiest thing to do is to cut the 4 conductor wire near the furnace where the base controller is installed. Hook up the fan, AC, and Heat control from the furnace to the controller. The control head requires power, ground, signal, and a clock from the control head. Click here for a hookup diagram for our application. Click here to view the scanned hookup from Home Automation Systems, Inc.
Combining two thermostats to control one furnace:
It seems simple, but when two thermostats are fighting to control one furnace, there are some general precautions that should be taken. Typically, the home automation system will keep the thermostats speaking 'cool' in the summer, and 'hot' in the winter. However, there is a chance that the thermostats could get out of sync. If one thermostat is requesting heat while the other requests cool, you may be running your A/C compressor and your furnace burner simultaneously. We will connect the two thermostats with isolation relays so if this situation does occur, the relay will inhibit both heat and cool from being simultaneously requested. Click here for the circuit and it's explanation.
We will use four baffles to control air flow to the Family Room, the office, living room, and the second floor. The baffles will be connected directly to the Smart Housekeeper controller. A separate 24 volt AC powersupply similar to that used for your doorbell will power the baffles.
Zone Control:
Many people have different opinions regarding zone control. 100% zone control requires
one thermostat in each zone. However, most people with a four bedroom home or less can
still take advantage of partial zone control without having to supply a thermostat for
every room. We'll expand on that philosophy, and use two thermostats to control four
zones. The zones are defined as follows:
Zone 1: First floor. This zone controls all heating and cooling to the kitchen, family room, living room, dining room, and first floor bath. (1st Floor Baffle)
Zone 2: Upstairs Master Bedroom: This zone will control the forced air to the Master Bedroom suite including the master bath. (Up Master Bedroom)
Zone 3: Upstairs second and third bedrooms: (Up Bedroom 2 & 3)
Zone 4: Upstairs hallway and bath (Up Hall & bath)
Our general HVAC automation philosophy will be as follows:
- Keep the upstairs comfortable during the nights
- Keep the downstairs comfortable during the day
- Tie in comfort control to X-10 mini controllers for convenience
- Automatically adjust all settings to run the most cost effective when nobody is home.
The baffles will be
installed in the basement from where the main duct breaks off into the individual feeds.
We will be using normally open baffles (available from Home Automation Systems, Inc) for
our system:
Connecting the Baffles to the Housekeeper Hardware (The GateWay)
Connection of the baffles to the hardware is simple. The GateWay provides four double pole, double throw relays controlled by the Smart Housekeeper software. If you wish to add more than 4 zones, you can connect external relays to the GateWay's remaining four outputs to realize the same control.
When designing a home automation system, it is always best to keep failure modes in mind. That's why I recommend that systems like HVAC be enhanced by the home automation system, not replaced by it. In the case of our HVAC system, we will design it so that if the PC is turned off, fails, locks up, or explodes, the HVAC will still function as a normal HVAC system, that is, when the home automation enthusiast's spouse wants to turn the air conditioning on, it will work!
Given our failure mode goals, We'll use normally open baffles that close when they are energized. When the output to the GateWay is ON, the baffle will be CLOSED. Connecting the power supply common to the baffle, the remaining baffle wire to a Normally Open set of contacts on the GateWay relay, and the remaining power supply to the common on the GateWay relay, we now have computer control of our baffles. Click here to view the connection diagram.
Setting up the Thermostats in your layouts.
Now for the fun part. Controlling our HVAC system with the computer. We have two
thermostats; one for upstairs, and one for the main floor. I recommend creating two
layouts -- one for each floor. Once you are in design mode, click on the 'Add RCS
Thermostat' icon on the Smart Housekeeper tool bar as shown:
Now, place two thermostats, one for each floor as shown:
The configuration box shown is where the name of the thermostat is
set as well as its controlling house code. The RCS thermostats need one dedicated
housecode per thermostat. Once you switch from 'Design' mode to 'Run' mode by clicking on
the 
(design) button, the thermostats
will display the room temperatures on the computer.
Now that we've got the thermostats added, we need to let the Smart Housekeeper know about our baffles and how to control them!
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