We have an addition that was built onto our house. It is like a long hallway with three rooms and a big bathroom. The furnace system was upgraded to handle the extra square footage, and a zone heating system was put in because the addition was isolated through a big doorway from the rest of the house. It worked fine for years. Then I had to call professionals familiar with zone heating systems at a company that provides Sacramento HVAC services close to our home.
A zone heating and cooling system has more than one thermostat in the house. We can adjust the temperature to different settings at each zone. The south side of the house is the original part, and it always feels warmer as it catches the most sun. So, the furnace does not need to heat it as much in the winter, but it does have to provide extra AC to cool it in the summer. If the south side of the house was heated and cooled to keep it nice, the addition would end up getting too cold in the winter and in the summer. The zone system uses dampers to adjust airflow from the furnace and central air conditioning system to each part of the house. We can also control the heat and AC to the master bedroom by itself.
It is a really neat system when it is working right. It had no problems for years. Then the temperature control for the addition of the house was lost due to a problem with the dampers. Of course the system had to be out of warranty when it happened. Plus, the company that put it in was no longer in business. We called another company that provides Sacramento HVAC services to come out and fix it.