Thomas W. Lewis produced two excellent projects to remotely control his HVAC system and monitor his home power usage.
He wanted to turn off his HVAC system completely before leaving for an extended period of time, like going on vacation, and then turn it back on just before he gets to his house. Thomas found the controls wires on the thermostat and uses a relay to turn on or off the thermostat. He made it remote controllable with the ioBridge IO-204 module and control widgets placed on a mobile phone.
HVAC and Thermostat Control with the ioBridge IO-204
In additional to remotely being able to shut down his HVAC system, Thomas also monitors his temperature and whole house power using the analog inputs of the IO-204. He used AC clamps around the house power mains to get a power utilization relative to the current through the wires.
Power Monitoring for the Whole House
More details and photos are available on Thomas’ Smart Grid section of his blog.
I have been thinking about how to do something like this for a while. My concern is that the iobridge relies on an internet connection for the logic, and if the internet connection goes down then I will be unable to control the HVAC. This could be a problem if I told it to flip in the heat and then I loose internet, or I flip on the AC and then loose internet. Then the AC or heat would be running all day long until I get home to fix it.
I think I’ll start off with something simple. Controlling the blower. I would like to be able to override the thermostat to flip the blower on to circulate air to the upstairs whenever the temperature in my upstairs bedroom becomes too hot or too cold, rather then running the AC or Heat anymore, I could simply re-circulate the air a bit.
A kill switch for the power to the thermostat seems like a good idea.
So last night I connected my iobridge to the HVAC computer at home. I just connected the red(hot) wire and the green(fan) wire to the relay module. I can now control the fan from the iobridge. The thermostat still has control to turn the fan on when heating or cooling the house.
The reason I did this is because my upstairs bedroom is always too hot since heat rises.
The thermostat downstairs thinks the temperature is much lower then it is upstairs.
I also know that the blower motor in my furnace uses 300 watts of power when running and I pay ~ $0.09 per 1kWh so if I run it 24×7 it would end up being 216kW per month costing me about $19.44 per month to operate.
Now I can control the fan via remote processes. Last night I setup a cronjob to schedule when the fan runs. It’s scheduled to run at times that I will be in the bedroom.
My next task will be to add a temperature sensor to the bedroom so I can only run the fan when I am in the bedroom, and if it is too hot.
Offline logic is coming in the next firmware release. We will announce more soon…Your fan control sounds very interesting.
You can now have logic online or offline.
http://www.iobridge.net/wiki/onboard-actions
New Firmware C4.1