The Arzel "AloneZone" was designed to do just what you are looking for.
Originally Posted by vegas_guy
It will allow that "Zone" to be included in the heat/cool cycle of the main t-stat or it can be shut down (dampers closed). That zone will not be allowed to bring the system on by itself.
Shutting down that small zone will have very little if any effect on the systems operation.
A second system...what are you guys thinking?
"When you perceive zoning not as a bandage but as an enhancement, you truly understand the dynamics and limitations of forced air heating and cooling"