Zoning question

[Serhito]

If I have 4 zones hooked up to a variable speed AC. 1 big room and 3 smaller ones. If 1 small zone calls for air, is there a way for the Omnipro II to tell the AC to run at slower speed, so that the pressure in the system will be less ?

How is the overpressure managed ? I know of the bypass valve, but I am more interested in knowing if it is possible to control the AC to run at slower speed.

Thanks

 

[Desert_AIP]

The Omni doesn't control the HVAC unit.

The thermostats talk to a zone controller via the standard T-stat wiring harness.
The zone controller runs the calls for heat and cooling to the HVAC and opens and closes the dampers to the zones.

The thermostats talk to the Omni via the RS-485 bus.
The Omni only automates the calls for cooling/heating based on time, occupancy, temperature and other triggers.

The Omni tells the thermostat to make a demand call, the thermostat talks to the zone controller, which in turn operates the HVAC system.

The HVAC system needs to be designed as a zoned system. The design and the controller used will take into account the combination of demands on the system and will size the ducts and blower speeds accordingly.

 

[ano]

I am planning on having a zoned system installed as well. It would seem that each Omnistat would be sending out a stage 1 or stage 2 AC request depending on how far off the temp is compared to the set temp. (Omnistats DON'T support variable speed AC units, only two stage)

With this information from each Omnistat, it would then be the zone controller that determines what to send to the AC unit, and what dampers to close/open. I would think that stage 1 would be requested unless an Omnistat was requesting stage 2.

My guess would be, and this is only a guess, that for a small room, only use a single stage Omnistat and only connect it to stage 1 of the zone controller. That way this room could never request stage 2 cooling. I'm assuming that zone controller handle 2 stages but I would think they would have to.

 

[Desert_AIP]

You could use a constant speed blower motor and an auxiliary duct blower in the larger zone.