Homeowners would like to increase their comfort level while conserving energy. An excellent method to do this is through zoning. Most two-story homes have an 8 to 10 degree temperature difference between upstairs and downstairs (because heat rises). Additionally, larger ranch homes generally have a big temperature difference between one end of the house and the other (due to the distance of the duct runs). By using motorized dampers and multiple thermostats that connect to a zone control panel, control of temperature in individual areas can be achieved.

Details

The zone control system allows a single HVAC unit to have separate temperature zones in the house (the number of zones allowed is determined by the zone control equipment manufacturer and the HVAC contractor). Each zone is controlled by its own space thermostat and motorized zone damper. If any of the zone thermostats call for heating or cooling, the zones not calling will have their dampers powered closed, and the zone(s) calling will have its (their) damper(s) remain open. The heating or cooling equipment will also be brought on at the same time. When all zone thermostats are satisfied, the heating or cooling equipment turns off and all zone dampers return to the open position to allow for continuous air circulation.

If one of the zone thermostats is calling for heating and another zone thermostat is calling for cooling, the one calling for cooling will take priority and the system will operate in the cooling mode. When the thermostat that is calling for cooling is satisfied, the system will change over and take care of the heating requirement. This is referred to as "Auto Changeover - Cooling Priority." Other systems offer "Auto Changeover - Heating Priority" and "First Call Priority".

Most zone control systems work with standard, heat / cool thermostats. The thermostats can be either manual or auto changeover. For additional energy savings, the homeowner should use programmable thermostats. Programmable thermostats will allow each zone to set back (this means maintaining a cooler temperature for heating) or set up (this means maintaining a warmer temperature for cooling). As an example, the bedrooms will only be conditioned at night, while the living space (kitchen, family room, etc.) is turned off. During the day, the living space is conditioned while the bedrooms are turned off. This method of "setting back" and "setting up" with zone control can save the homeowner as much as 30% on their fuel bills.

Installation

The best time to install a zone control system is while the house is being built. It will make it much easier to install the ductwork and dampers properly and run the additional wiring that is required. A licensed HVAC contractor should do the installation, as they can insure proper duct sizing and airflow.

There are two methods that can be used to insure proper airflow with zone control systems.

1. If only two zones are required, size each zone to handle about 75% of the total system CFM. This method does not require a bypass damper. If one zone requires substantially more CFM than the other, it is recommended that the larger zone damper be set to bleed about 20% of its air (or more, if necessary).
   
2. If more than two zones are required, up-size duct system 10% if possible, and install a bypass damper. It should be set to bypass just enough air to maintain a quite, draft- free system. Manual balance dampers should be installed on all branch runs to facilitate the balancing of the air system.

Benefits / Costs

The average zoning system will cost the homeowner about $1500. This is about a third the cost of adding a complete second HVAC system (i.e.: a furnace & air conditioner for upstairs and a furnace & air conditioner for downstairs). The benefits of zoning are (1) better temperature control and (2) reduced fuel costs.

Code / Regulatory

The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), the Sheet Metal and Air Conditioning National Association (SMACNA), and Air Conditioning Contractors of America (ACCA) oversee the HVAC industry. Local and state government agencies also regulate the installation of heating and air conditioning equipment.

Availability

Comfort System™ zone control from Jackson Systems, LLC is in stock and ships the same day (this includes panels, dampers, accessories, and thermostats). Jackson Systems can be reached toll-free at 1-888-652-9663 or visit their website at www.hvaczoning.com.

Contacts

Do you have a specific question about this technology and/or its 'real life' applications? Try the contacts listed below:

JACKSON SYSTEMS, LLC 100 E. Thompson Road Indianapolis, IN 46227-1621 888-652-9663 http://www.hvaczoning.com

ASHRAE American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. 1791 Tullie Circle, N.E. Atlanta, GA 30329 404-636-8400 http://www.ashrae.org/

SMACNA Sheet Metal and Air Conditioning Contractors' National Association 4201 Lafayette Center Drive Chantilly, VA 20151-1209 703-803-2980 http://www.smacna.org

ACCA Air Conditioning Contractors of America, Inc. 2800 Shirlington Road, Suite 300 Arlington, VA 22206 703-575-4477 http://www.acca.org