I need help with information about my current heating system, I will try to be as brief as possible.

We built a 5200 sq ft duplex home (2600 each side), with 4 levels. The heating contractor told us he could put in 4 zones, one for each floor. We moved in late fall of 2006 and discovered the house is actually 3 zones.

The contractor said he had to put the bottom two floors on the same zone, each floor has its own thermostat. The top two floors are zoned separately. The contractor said he had to do this because the furnace needs to push enough hot air so it will not burn up. In addition he did not install dampers on some of the other heat vents, for the same reason. I do not have what I consider a 4 zone system, which is in the contract.

I had another contractor look at the system and he said there is a hot air return on this furnace (10" duct work) , and if it is installed correctly it should handle the overflow of the hot air supply, and dump it right back into the furnace. In the opinion of the heating tech I asked to look at my system, he said the system should handle 4 zones, and I should tell the original contractor to set it up that way.

I have been looking for more information about this with out any luck. I am hoping someone can provide more opinions about this.

I am not there to see the system, but I feel something is wrong with your contractor. I am also surprised they allow to sepperate dwelling to run on 1 furnace. Most codes do not allow you to share air between 2 residents. Unless it is family (health reasons). Only on a boiler could that be done.

I did not explain the setup correctly. It is two completely separate dwellings, with individual furnaces, water heaters, etc. The heating system for each unit has the same identical problem, is what I meant to explain.

The second opinion I have is that this furnace can operate as 4 zones, and it will not burn up. Two of the floors have only 3 supply vents on each. He said a hot air return correctly installed on the furnace, will take the excess hot air that is produced and put it right back into the furnace. I am not sure if I am making this understandable. At the time he was telling me this it seemed completely understandable. I have been trying to find out more information on this, and everyone I talk to thinks I am talking about cold air return. So now I am not really sure what to think.

My basic question start with, is there such a thing as having a hot air return that will allow the furnace to operate when there is not enough hot air supply vents to keep the furnace from burning up?

I really appreciate any help with this, and if I am confusing please let me know.

I have additional problems with this setup. The contractor did not even put dampers in all of the heat runs. So in reality it is not zoned at all. I have been giving this guy 6 months to correct the problem, and now I am at the point where I need to start taking serios action. I am trying to get as much information as possible. I have started by demanding he put dampers in every heat run, and they are accessible for future repair. Then I am hoping it will push more air down to the 1st floor. I now know that the way he setup the heat runs, the hot air is just not going to the duct he setup for the 1st floor. The hot air is simply going the easiest way up the largest duct work, and not down the leg that is small with several 90 degree turns.

I look forward to any reply!

The 10 inch duct you talk about is called a bypass damper. If you have a 5 ton system that moves 2000 cfm and only one zone calls for heat that moves 600 cfm the bypass damper opens up to move the extra cfm from the unit. If it did not open you would have loud air noise at the supply grills and the furnace would trip on high limit. As far as ducts with out dampers this is common it dumps the extra air in a common parts of the house - stairwell,foyer,hallway. The info sounds right but the system may need to be balanced.

Allot of contractors do things the same, some do it different. I have allot of forced air zoning experience.I design a system that does not need a bypass damper or dump into common area. We used to do that, but the customer does not get what they were expecting. How's it done differently? Slight under size of equipment, like a 60,000 BTU furnace in a 2900 sq ft new constucted house in place of a 80,000 most would install and or use of 2 stage furnace and 2 stage a/c... 1 zone open= 1 stage and more than 1 zone open = 2nd stage. Works like a charm compared to the noisy bypass system or the over conditioned hallway.
Have Fun!