HVAC for 21st century

Design a HVAC system for a house/apartment that responds to each rooms temperature.

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A normal HVAC system for a house usually has a single temperature sensor located at the thermostat. Depending on what the temperature a user sets the HVAC system will turn on and adjust the temperature of the house/apartment until the temperature read at the thermostat is at the level the user selected. In my experience this means that other rooms of house will be at a different level, higher or lower than what I want, and where the thermostat is will be at the correct temperature. I propose a system that will have sensors in each room and vents that will know when to open or close so that the temperature of the entire house/apartment will be at the user selected level. The system will be designed so that as a room reaches its correct level of temperature the vent will close. The benefit of this system is that the HVAC will not have to run as much to meet the requirements of the user.

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akajefm wrote 03/20/2015 at 15:10 point

This has been staple in commercial buildings and more advanced home automation for decades. I wound up in charge of a medium sized system for too long, not because I know HVAC, but it was computer operated which to a manager means "the network guys run it". Here are some basics you can build from.

Everything was organized in zones. A zone had a thermostat. A zone could be one room or an entire wing. The thermostats could be user set for a desired temp to control the zone, or we could lock them out and dictate what the desired temp is. Which is what we usually did since real people don't understand air conditioning and would set the wheels either for 50F or 85F. 

Each zone was typically served by a VAV which was a big variable flow valve in the ductwork. The RTU's (roof top units) fed into the VAV's. At building peripheries there were FTU (fan terminal units) which tied in with the ductwork but had their own fans to give a boost and a heater to help the system out in the winter.

The VAV's were slick, they could tell how much CFM of air was going through them and report the valve position (what % it is open). You could send it to a specific position, like whenever someone complains you can open it 100% and blow papers off their desk. An older method is a pneumatic piston that moves a damper in the duct. If you are in some old building and hear hissss, then a thump in the ceiling, that is what's happening. One home automation solution I saw was an inflatable bladder which hangs in the duct, it inflates to cut off a room or zone.

Some systems are so big they can deal with heating and cooling in the same building at the same time. The zones are organized to deliver a "heat call" or a "cool call" to the BCS (building control system), an RTU would go into heat or cool mode, and the VAV's route it around. 

Sounds really neat but it was huge PITA. Everyone has a different idea of what a comfortable temperature is. Sometimes a multi-tenant zone would be controlled by what one person with a thermostat in their office liked. There were wierd situations where the building would pressurize and doors could not be shut. Measuring air pressure was a big deal and there were sensors throughout the building for it.

Not that you'd need all this stuff for home, but might give you some starting ideas. I'd check out home automation first and catch up with what's been done there.

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Christopher Atwood wrote 03/20/2015 at 14:03 point

No offense, but this is not novel. It is already done all the time in commercial office buildings and a small number of houses. Each room has its own thermostat, central HVAC units provide the air to a large number of rooms, and a VAV unit controls the flow to that specific room. 

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