That's interesting. I wondered how they did that, and luckily I found the document which explains how it works: http://dms.hvacpartners.com/docs/1009/public/0d/zone-02dg.pdflleo said:Also does not need or work with bypass dampers to compensate for too small zones
Here's the pertinent excerpt:
"The Infinity’s sophisticated algorithms were constructed to maintain comfort to the occupants by continuously monitoring each zone’s
temperature to satisfy the comfort conditions. If a zone cannot handle the minimum equipment cfm the Infinity Control will find a zone that
is slightly out from the setpoint and open the damper to allow the system to run. If none of the zones are away from the setpoint the Infinity
Control looks for unoccupied zones or setback zones to allow the system to run to satisfy the original zone caller.
Zones that do not handle minimum equipment airflow will cause other zones to be heated or cooled above or below their setpoint
temperatures. If this is an acceptable alternative then the undersized zones will not present any major issues. In most circumstances this is not
an acceptable situation and the only way to relieve this to make sure each zone handles the minimum airflow of the installed equipment.
Remember the Infinity System tries to satisfy all zones simultaneously so it is common for zones to open incrementally to satisfy the comfort
So, interestingly, it sounds like one option is running adequate ducting to each zone such that each zone could take the entire minimum CFM's (40% of maximum) all by itself if needed. If that's not the case, and the zone or zones calling for cooling can't fully dissipate the minimum CFM's, then the zone controller follows the prescribed algorithm above to open other dampers also. I'm impressed that it even takes into account zone occupancy when picking which other dampers to open to meet minimum dissipation requirements.
Theoretically I suppose it would be nice if the controller could open some dampers partially rather than "modulate" them open/close. However, that would presumably require more sophisticated control--possibly more than exists in mainstream residential zoning controls. Or, perhaps it would be splitting hairs and doesn't actually matter. Are you conscious of the system modulating the dampers, or is it not something that's noticeable?