Zoned heating and cooling systems are an option builders can provide for homeowners who want more control over comfort.

A builder returns to his office after a stressful day. His voicemail does little to ease his stress. One message is from a new homeowner who says she's planning to renovate her basement but is concerned the space will be too cold. Another is from a recent homebuyer who has a second-floor bedroom he wants to convert into an office but says the area is too warm during the day. And a third message is from a homeowner looking for HVAC modifications to her new house that will reduce her energy bill.

Nothing relieves stress like knowing a catch-all solution to a series of problems. All of these customer concerns can be answered with one solution: zoning comfort control systems (ZCCS). Many homeowners aren't familiar with the concept and don't know that it's an option for their particular style and size of home. Consider that when zoning is offered as a solution, homeowners will buy it 50 percent of the time, according to Equifax Marketing Services.

The concept of zoning with multiple HVAC systems has been around for more than 40 years, while forced-air ZCCS using motorized dampers in the home's ductwork was introduced to the market more than 20 years ago. Acceptance of ZCCS has grown in the past 10 years. However, many builders often view zoning as a niche offering--one with a high degree of risk of homeowner callbacks and dissatisfaction.

Today, new technology-based features--such as flat panels and 1-2-3 wiring configurations--have made zone control systems more economical for homeowners. Builders can sell ZCCS with confidence, knowing that newer systems are less likely to cause confusion for customers.

A forced-air ZCCS has a zone control panel and zone dampers inserted into the ductwork that enable two or more thermostats to be placed throughout the home. Compared to systems that employ multiple heating and air conditioning units to establish temperature zones, a ZCCS allows for more control and comfort. It is also less expensive to install and to maintain.

Candidates for Zoning

Comfort and savings are the key selling points for ZCCS. With zoning, homeowners have more control over temperatures throughout their homes and access to conveniently located thermostats. The systems generally pay for themselves through energy savings. When used with programmable thermostats, zoned control systems can reduce energy costs 25 percent to 30 percent when compared to central, non-setback systems.

What makes a home a strong candidate for zoning? Zoning is particularly useful to homeowners who want to make a basement or upper floor, those who do a lot of entertaining or spend a lot of time in the kitchen, and those who have a home office. The design of the home plays a role as well. Zoning is highly recommended for a home that has:

• Multiple levels
• Sprawling design (wings or "ranch" style)
• Rooms with large expanses of windows
• Large open areas (vaulted ceilings, foyer, atrium, solarium)
• Rooms in a finished basement or attic
• Rooms with exposed concrete floor
• Indoor swimming pools or hot tubs

Sizing the Dampers

Sizing the zone damper is as simple as sizing the ductwork. For example, a 6-inch round duct requires a 6-inch round damper, and so on. In addition to zone dampers, a bypass damper is often needed, especially if a zone is created that is significantly smaller than the rest of the home. This is because constant airflow volume must be maintained through the HVAC unit, regardless of the number of zones. The damper bypasses excess airflow from the supply duct into the return duct or into a dump zone.

On systems up to five tons in capacity, a static pressure regulating damper (SPRD) should be used. A modulating automatic round damper (MARD) should be used in conjunction with a static pressure switch (SPC) for static-pressure regulation on larger systems.

Supply duct systems should be sized to handle a 100 percent load from all areas of the home. Bypass size can be determined using the following formula:

CFM of the system – CFM of the smallest zone = CFM of the bypass

Once duct accessibility and damper size are determined, installation of the system can take place in as few as six steps: 1. Mount the control panel near the furnace 2. Cut slots into the ducts and slide in the appropriate sized and type of damper 3. Run two wires from the damper to the control panel 4. Wire the furnace and the air conditioning units to the control panel 5. Wire each thermostat back to the control panel 6. Wire each damper or group of dampers to the appropriate zone on the control panel

It's always necessary to try to mount dampers in a location where they can be accessed if service is needed later. And it's important to remember that manual balancing dampers are still necessary in each duct to manually balance a system.

When installing the air handler or plenum assembly, always ensure there is enough room to install the bypass damper. If using a static pressure regulating damper, make sure there is enough room for the counterweight arm to move without restriction. If using a static-pressure control and modulating damper, make sure there is enough room to adjust the SPC after installation.

In most installations the zone panel will be located near the indoor unit, garage or basement. Typically zone panels are installed on the return air duct.

However, in some applications, the homeowner or building occupant may require access to the panel to change from occupied to unoccupied mode or to change into the emergency heat mode in heat pump applications. To meet these needs, locate the panel in a utility closet or other convenient area where these switches can be accessed easily.

Easing Installation

When evaluating ZCCS to offer their customers, builders must consider the following features to help ensure easy installation and customer satisfaction:

1-2-3 wire configuration
Three-wire configurations make install simple; many of the systems will automatically self-configure once installed.

Thermostats that operate independently
Homeowners might run heating and air conditioning simultaneously in different zones. Standard "master-slave" thermostat systems won't allow this convenience.

Power-close/spring-open dampers
Dampers that rest in the open position allow the barometric bypass damper to do its job--and reduce energy use

Visible open/shut indicator bars
Damper indicator bars allow damper status to be monitored without removing it from the duct.

Flat terminals
Compared to stacked terminals, flats are easier to wire.

LED panel lights
LED lights on the panel enable the installer to troubleshoot the system without removing the cover.

Wireless control
In homes where it is difficult to run a wire from a thermostat to the duct, wireless systems provide a solution. Thermostats automatically communicate with the zone control panel.

Levi Bouwman is sales director for Honeywell's Home Builder National Accounts.