Reposted from http://www.aacpnet.org/Newsletter-2017-03#zone
Homeowner demands for comfort have changed. They want ultimate comfort, greater system efficiency, and less noise. Simply installing a new HVAC system no longer meets these demands.
Zoning Solves Comfort Issues
More of today’s new homes have “open concepts,” more windows, higher ceilings and multiple levels. Solutions on how we will heat and cool those types of spaces must now be considered in the HVAC plan.
The most comfortable new homes today have a “zoning system” installed with their heating and cooling equipment. Zoning is the method by which temperature is managed differently for certain areas of a home with multiple thermostats, rather than controlling the whole house from one thermostat.
Zoning not only increases the level of comfort, but it also helps homeowners save on the cost of heating and cooling their home—up to 30% annually. This is achieved because only the amount of heating and cooling needed in a particular zone is supplied and system usage is minimized. For a homeowner that also could mean a longer lasting system.
What a Zoning System Looks Like
A zoning system has six main components: a zone panel that manages the entire operation and gets installed with the HVAC system; a transformer to power the zone panel; zone dampers (one for each zone); one thermostat for each zone; a discharge air sensor and a bypass damper to release air pressure.
The zone panel gets installed at the system and is where all of the wires come together. Zone panels are preset to “plug and play,” but do allow for auxiliary needs or add-on’s like air cleaners or humidifiers.
Zone dampers reside in the ductwork – one for each zone – and channel conditioned air to the right places at the right times. As calls for heating and cooling come in, a zone damper opens and closes to provide the air into the zone. Most operate so quietly, a homeowner doesn’t even know they are moving about inside the ductwork.
Calls for heating and cooling are controlled by a thermostat; one placed in each zone. Using an example of a two-story home, a homeowner may only use the upstairs in the evening, and the basement even less frequently. While the main living space (zone 1) may have the thermostat set to 72˚, the upstairs thermostat (zone 2) could be set to 65˚ and the basement (zone 3) to 68. Zoning saves money on utility bills and wear and tear on the system because calls for heating and cooling are minimized in zones that need it less.
The discharge air sensor is also mounted in the supply duct before any zone dampers. It probes the air, sensing the temperature, and cuts off the heating or cooling when the delivered air temperature goes above or below normal operating limits.
Finally, bypass dampers eliminate the buildup of excess pressure. Bypass dampers automatically bypass air when increases in duct static pressure occur due to closing of zone dampers.
5 “Rules of Thumb” About Zoning That Should Always be Followed
- Ductwork must be configured properly to accommodate a zoning system. It must never be undersized. In most cases, it will not be necessary to modify duct sizing when installing a zoning system.
- It is always better to slightly undersize the HVAC equipment than to oversize it. Two-stage equipment is always a better choice.
- Dampers should be installed at least 2 feet away from the plenum, when possible.
- It is a good practice to size the smallest zone to handle approximately 25% of the system CFM. And, upsizing registers in the smallest zone to the next larger size should be considered.
- Always use a separate 24-volt transformer to power the zone panel. (Do not use the equipment transformer.)
Whole-house zoning systems are effective, easy to install and many come with lengthy warranties for years of guaranteed comfort and energy savings. Contractors can gain a technological advantage with homeowners when offering zoning as a comfort solution but should look for a supplier who can also provide knowledgeable support and troubleshooting when purchasing zoning system for their customers.