Single zone to two zone (contractors, zoning, costs)

[Azb999]

Hi all, anyone have experience converting a single zone central AC to two zones using Honeywell or Aprilaire zoning systems with dampers?

It's a small cape with approx 1500 sq ft. Do we need new ducts or can we install the dampers in the existing ducts? Any ideas on costs (parts and install)?

Woukd also appreciate any good HVAC contractors. Thank you.

[Kbinspections]

In my opinion, zoning central a/c does not work well. You will not be happy with the results. It really shows it faults when you really need it , August!

[Azb999]

Any particular reason why it doesn't work well? Just trying to understand our options. Thank you.

[Kbinspections]

Problems occur when the system is trying to satisfy zone 1 on a hot day. It takes too long to satisfy (cool) zone 1, zone 2 gets overly hot. Finally zone 1 is satisfied, zone 2 is boiling hot, so now it takes to long to satisfy zone 2. Zone 1 now is too hot. Basically you end up with a cycle of too hot then blasting cold. Which is worse than just being warm.

Works OK in the spring and fall but they system falls apart in the summer.

It was used in the early 1990's by builders but quickly abandoned. I rarely see they systems, when I do, they are abandoned.

If it worked well, it would be widely used by HVAC companies.

[JB from NC]

Converting an existing single zone system into multie zones is a nightmare. Almost everything, including the units, would need to be changed to make it work properly.

A multizone system with a single speed AHU uses dampers to control the airflow to each zone and then dumps the excess air somewhere in the building. Each zone needs it's own supply ductwork and return, and the "dump" has to added in somewhere.

Newer systems will use variable speed fans and compressors to be more efficient, but everything has to sized and balanced almost perfectly in order to work right. Comfort-wise, you'd probably be happier installing two smaller units rather than going with a multizone system.