Frequently Asked Questions

What is a Residential Zoning System?
A zoning system is made up of a controller that receives information from Zone Thermostats in multiple locations.  The controller then gives commands to HVAC equipment and specific Motorized Zone Dampers in order to control temperature in each of the thermostat locations.
 
Why do I need a Zoning System?
  • Based on the comfort temperature of the occupant... individual people are comfortable at different temperatures for different reasons.
  • Orientation to exterior loads... on a cool morning the east sun will shine on rooms that can cause cooling to be required, yet in rooms on the west side, no cooling or even heating might be required to maintain the same temperature in both spaces.
  • Upstairs vs. downstairs... heat rises.  Any heat that is gained throughout the building will try to accumulate in the upstairs area.  This fact means that cool air remains in lower areas.  The stairwell in some town homes with as many as four small floors will thermodynamically operate similar to a chimney.  As the outside temperature becomes more extreme, this temperature differential will increase.  A zoning system operated by a thermostat on each floor will maintain the correct temperature on each floor.
  • Usage of a room... some rooms have a specific use that requires more conditioning than others.  An example is an exercise room.  When this room is in use, the occupant may require cooler temperatures than normal because exercise makes the room seem hotter than normal.
  • Appliances in a room... modern kitchens may have large heat producing cook-tops, ovens, bread warmers, dish washers, etc.  These appliances can overheat the kitchen, while the occupant may be doing work such as stirring, mixing and cleaning.  A zoning system with a thermostat in the kitchen will keep the kitchen comfortable, yet not overcool other areas
  • Exhaust equipment... again, modern kitchens are a good example.  Some exhaust systems over a large gas range can exhaust the conditioned air in a matter of minutes.  Without a makeup air system, the exhausted air gets replaced with outside air that may not be fully conditioned.  A zoning system will allow these specific areas to be reconditioned to the comfort temperature required by the thermostat in that area.
 
What is a Zone Thermostat?
Multiple thermostats are placed in specific areas that need control based on temperature variations throughout the building.  Each SmartZone system can have 2, 3 or even 4 thermostats that control different areas in the building.
 
What is a Zone Damper?
Supply Air Motorized Dampers are air stopping devices placed in the duct system that open to allow air into a specific area or close when that area does not require conditioned air or ventilation.
Bypass Damper is also an air stopping device that is placed in a duct that is usually directly between the supply side and the return air side of an HVAC duct system.  The bypass damper is designed to allow any excess air pressure to escape from the supply side of the system to the return air side.  This pressure, if not controlled, can cause air noise from the supply air outlets.
 
Can I use a zoning system without a bypass damper?
Any zoning system larger than two equally sized zones should have a bypass damper.  The bypass air should be applied into the return air plenum.  This allows a normal duct system to be applied and the use of the excess air to precondition the return air.  Any time air is bypassed into the return air plenum, the system must include a supply air sensor.  There are certain specific 2-Zone applications where a bypass might not be necessary.
 
What is a Supply Air Sensor?
The supply air sensor (SAS)- is a probe placed in the supply plenum that monitors the supply air temperature.  The temperature of bypassed air used as air that is reentering the equipment can cause extreme supply air temperatures.  The SAS, in conjunction with other electronics on the controller does not allow temperature to become too extreme so that the equipment can run safely and reliably.
 
Does a zoning system control humidity?
A zoning system will control humidity as a byproduct of controlling the sensible temperature in each zone.  In a single zone system that may even be equipped with a humidity-sensing thermostat, the system still only has one point of control.  With a zoning system the building has several points of control.  Any time even one zone is calling as a result of a sensible call, humidity is also being removed in that area because in the cooling mode dehumidified air is being applied or in the heating mode, the air temperature is being raised without adding moisture to the air, thus decreasing relative humidity in the zone.
 
Can a zoning system save money on utility bills?
  • Certain buildings use less power when a zoning system is installed.  If all or most of the thermostats are set in an unoccupied temperature, only the thermostats that call will require conditioning.  This allows air to be applied only where necessary to maintain temperature in the specific calling zone.  Excess air is bypassed through the bypass damper back to the return air plenum.  This air is mixed with the return air as it enters the apparatus.  The bypassed air effects the entering air so that air supplied from the apparatus is cooler or warmer than it normally would be if return air only were being conditioned.  The supply air is able to condition the calling zones with cooler or warmer air than normal, thus changing the zone’s temperature relatively quickly.  The zone is then satisfied and the system is turned off, saving energy.
  • In other instances there will be no appreciable difference in energy savings because if all zones are set at a comfort temperature the system may be opening and closing zones based on the thermostats’ demands.  This may amount to about the same run time, however, comfort is much more achievable as there are thermostats in each space monitoring that space temperature.
 
What is a dump zone?
Some zoning manufacturers advocate a dump zone... WE DO NOT.  A dump zone is an area in the building where the bypassed air may be applied instead of applying bypassed air back into the return air plenum.  This can be a large quantity of very cool or warm air that is completely uncontrolled.  Since the bypassed air is a function of supply air dampers that are closed, thus causing excess air to be available, there are no conditioned areas where this excess air should be dumped in order to get rid of the excess pressure in the system.  This is largely a waste of energy and in most cases will effect zones that are satisfied so that they become unsatisfied and call for either heating or cooling.  Uncontrolled dump zones will also cause equipment to run longer because the wasted energy should be used to precondition the entering air so that the zoning system is as efficient as it can be.
 
 
For further questions please contact us info@xcicontrols.com or 1-800-XCI-HVAC