Heating Up and Cooling Down, Pt. II: Monitoring the HVAC System
 
Figure A As we mentioned in the first segment of this episode of Home IQ, the heating-and-cooling system (HVAC) is divided into two zones. One is upstairs in the Oberg home and the other is downstairs. The system will allow for the temperatures upstairs and downstairs to be controlled separately.

To accomplish this, the subcontractors installed a special section of duct called a plenum (figure A), which divides the air flow from the furnace to the two different zones in the Oberg home.

Figure B

Figure C

Figure D
The plenum has two dampers with motors on each side (figure B) that open or close the dampers, which in turn control the air flow to the different zones. The blades in the motors reduce or increase the air flow.

The different areas of the house call for heating or cooling through the use of thermostats (figure C). Each zone has it own and they can be set at "different" temperatures. This is similar to most houses, but this system has a brain (computer) that constantly monitors the house and takes control of the system so the homeowners won't have to.

The information from the thermostats feeds into the computer mother board/hard drive (figure D), and the computer tells which dampers to open. If all the thermostats are calling for heat or cooling at the same time, they'll all open. If only one is calling it will open that particular damper.

Tip: Our homeowners (Brad and Lynn Oberg) worked with the builder early on to choose a furnace and air conditioner that will operate efficiently with this complex duct system.

Figure E

Figure F
What to Consider When Choosing a HVAC System

According to Kevin Waldo, a product manager for Carrier Corp., a homeowner needs to consider three things when shopping for a HVAC system:
Comfort

Energy Efficiency

Indoor Air Quality

Waldo says the Oberg's picked the most efficient system available on the market today (for more information, click on the "Energy Recovery Ventilators and Air Conditioning" listing, under Resources, below) from both a gas and electrical perspective. This particular system (figure E) works on low speed (where the fan is running on "slow" speed at all times) and the gas valve is running on "low" heat -- to where low heat is being delivered constantly instead of receiving a sudden burst of heat or all at once. By having the longer running times, the system is able to better maintain the set thermostat temperature.

The comfort level is measured by two variables -- temperature and humidity. For example, if the temperature is where you want it to be yet the humidity is high, it will still feel hot. Special thermidostats (figure F), which monitor humidity, are incorporated into the thermostats. Along with the temperature readings, humidity levels are also sent to the system's computer, which then adjusts the heating and cooling for maximum comfort.

It's also possible to have too little humidity in the air. In fact, in the winter it's common for homes to have air that's too dry. What this can lead to is dried-out woodwork, static electricity, nasal passages become dry, itchy skin, etc. And adding a humidifier can prevent these problems

Note: Brad chose not to put in a humidifier because he feels that the moisture from cooking and showers will supply enough humidity in the house.

Find out how to get rid of the old stale air in the house in the next segment when we discuss the ventilation.