Forced Air Zoning Solutions for your Home to target different heat loads.
Zoning in air conditioning mode
Upstairs vs. Downstairs
In the Maryland hot and humid summer, the upstairs level of your home is going to natuarally have warmer air. This is especially the case when one air conditioning system serves a two story house. In some homes the thermostat will be in the downstairs hallway. In some homes, people will try to outsmart the heat and place the thermostat upstairs somewhere. This can lead to the downstairs getting too cold. Either way, one “zone” or space in your house will suffer.
Solar Heat
A major contributor of heat into your home is the sun. The sun is not stationary. Throughout the day the sun will heat different rooms of your house as it moves. So throughout the day, your rooms will vary in warmth. In the first half of the day, the east side of your home may get too warm. Just as in the afternoon, the west side of your home may get too warm. Especially if your kitchen is on the west side of the house. During dinner making time, the kitchen area can get unpleasant especially if walled with several large windows.
Human Activity
As the sun moves over your home and varies the heat gain in different rooms, human activity varies as well. Later in the day as you are cooking in the kitchen, the kitchen gains heat and has a greater heat load than other rooms. The kitchen will likely warm up before your centrally located thermostat turns on the cooling equipment. Likewise, if you use a room as a gym, that room will get warmer than other rooms. The room may become hot and moist before the thermostat turns on the air conditioning.
Components of Air Damper Zoning System
Zone Panel
The zone panel is at the heart of the zoning system. The panel allows you to use multiple thermostats to separately control the temperatures in different rooms or zones in the house. This can all be accomplished even though you only have one heating and air conditioning system.
The panel operates the heating and air conditioning equipment based on the signal received from the thermostats. This includes running the indoor unit fan as well as turning on the outdoor unit for heat and cooling.
But how does this all work when you have two different thermostats, one calling for heat and one calling for cooling? Depending on the panel type, the panel will honor the thermostat that sent it signal to the panel first (first in time, first in right). Once the first thermostat is satisfied, the panel moves on to honor the second thermostats call.
Some panels even enforce a curfew. This is perfect for when someone sets a thermostat low or high and leaves without changing it back to normal. This would lock out the second and third thermostats from ever being honored. So the panel sets a curfew of when the first thermostat should satisfy. So after 1 hour for example, the panel will start honoring additional thermostats.
Air Duct Dampers with Actuators
Actuated dampers play a pivitol role in a zoning system. They receive a signal from the zone panel. They open or close depending on the signal or lack of signal. For every zone you wish to control, a zone damper is installed in the ductwork supplying that zone.
When a call is made by one thermostat, for example, a call for “fan on”, the dampers will all close except for the zone in which the thermostat is calling for fan. Likewise, if a thermostat makes a call for cooling in zone 1, all dampers will close except the damper in the ductwork serving zone 1. The zone panel will turn on the air conditioner and the zone damper will fully open to allow the maximum amount of air to the zone.
This dampers are not always installed in the ductwork when the heating and air conditioning system is first installed. When this is the case, these dampers can be installed at a later time. This is a retrofit that is intended to solve the homeowner’s problems with rooms having varying heat gains and heat losses. The goal is to have a home that is more comfortable with similar temperatures in each room.
Thermostats for Zones of your House
The thermostats used for the zoning system are not complicated or complex. In fact, most normal thermostats can be used. At a minimum, the thermostat must match the type of equipment being used. We install many thermostats for these applications.
There is the capability to use more sophisticated thermostats. Humidity control is achievable. Wireless thermostats are also an option when access is limited or does not exist to install control wires to the zone where the thermostat is to be installed.
Bypass or ESP control
A zoning system requires a mechanism to handle excess air that becomes blocked by closed dampers.
Usually when only one zone calls, the other dampers in the system shut. The total system air is still being produced by the indoor unit and it needs a place to go. If not, it will increase the external static pressure on the ductwork and create loud air noise at the supply registers that remain open.
The modes of operation would also be affected due to a lack of proper air flow across the cooling coil and heating elements.
To remedy this restriction of air flow, a bypass is installed in the system. This allows the air to continue to move through the system.
As an alternative, some applications may be able to use an ESP (external statis pressure) control in the zone panel. In this option, a bypass is not required. Instead, the zone panel can be programmed to only close non calling zone dampers a certain percentage of fully closed. This allows some air by each of the non calling dampers, making it safe for the system while having hardly any impact on those zones.
Is Forced Air Duct Zoning a good solution for your Home?
Zoning might be a good fit for your home. It can be used to more accurately treat different areas of your home while only using 1 heating and air conditioning system.
Here are some relevant factors to consider:
Level of exposure to sunlight?
The type of construction of your home. Is it centralized or spread out?
Do you have 2 stories?
Do you have rooms in your home that have different cooling and heating requirements (gym, room over a garage, large windows)?
Where is your thermostat located in relation to other rooms in the house?
Have you had a heat load / loss calculation performed for your house and for each room?
Do you have heat loads calculated for different times of the day?
