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Duct System selection
Duct System selection in HVAC systems involves a number of variables:
In many installations, ducts from adjacent rooms are routed to the end duct and outside at the same height.
In other installations, the ducts are routed to different heights based on the height of the ceilings in each room.
For HVAC systems with a large distribution, there are a number of ways to design ductwork so as to eliminate unintended layers.
In many applications, ductwork is installed in a loop, with each room connected to the adjacent room by means of one open entry or exit duct.
The open duct runs around the room and connects to the drain, leaving the loops open for maintenance or cleaning.
This type of system can be very efficient in energy management because only one space is heated or cooled at a time.
Another example of a loop system is when the exhaust duct for the central heating system runs around a room (even though the room is connected to the central heating system through an open entry duct), typically for the purpose of blocking draft.
If the building's heating and cooling ductwork is for heating and cooling only, a small duct is used in the loop.
Such a duct runs the length of the loop so that air entering the loop is "frozen out".
Ducts in this system are often the small cylindrical ducts typically used in older systems.
Duct System selection in HVAC Applications
Ducts are available in various types and sizes. Ducts are available in various types and sizes.
Ducts are available in various types and sizes. A PVC or ductless system has an access door. There are two types of PVC systems: internal (adjacent walls) and external (all walls and roof).
In a fixed segmental system, the air and air conditioning flow through a wall that is insulated. This method involves in-floor air ducts and in-wall electrical components.
In an open system, the air and air conditioning flow through a system that is self-contained and separated by wall or roof.
With a hybrid system, the air is pumped through walls of alternating formers and laminates or existing ceiling fans and vents. It is equipped with a single-stage duct that moves air between a low-pressure zone and a high-pressure zone.
Duct System selection in HVAC Units
After you have decided on the HVAC unit, you should also decide on the ductwork which will be used to collect and carry the hot or cold air. In most cases, you will find that you will need to combine ductwork to service the system as well. This is due to the fact that you may have additional ductwork installed for particular units, or the ducts will be set up for a condensing system, and not a free-standing heating and cooling unit.
Using a combination of ductwork, and new-home heating systems, you can provide adequate service to your new home. Check out ductless condensing HVAC systems, which have been designed to provide complete temperature control in both the home and outdoors. As such, the air is stored in a condensing unit, which can be mounted in an attic space. This allows for the hot and cold air to be stored in the same space. Heat is also transferred through the unit for overall heating in the home, and cooling for the exterior.
The most important parts of a duct system are the weather stripping and the duct work. When you have less than ideal outside conditions, you should choose outside weather stripping over duct work. Since duct work is difficult to get into, you should also choose a door to screen the opening with.
A great way to find out how well your ductwork is installed is to have a professional service your duct system, if possible. Make sure to keep your door closed as much as possible in order to prevent air from leaking out of the system. You also want to keep your ductwork clean; it’s easier to clean ductwork than a raw wall.
Tips on selecting duct systems in HVAC.
1. Know your system.
Before you choose a new duct system, make sure you understand what duct work is for.
Listed below are general descriptions of these systems, along with other important factors to consider.
General duct systems
An air-ducting system has a variety of covers and controls to help ventilate or circulate air.
A non-intrusive humidification system uses a sensor to monitor indoor and outdoor air conditions and uses warm air blowing through vents to humidify the air. This system also reduces moisture levels in the air.
A recirculating/heating system relies on an air handler to blow air through ducts to heat or cool a home. It is the most common type of duct system for larger houses and apartments.
A home-duct heating system heats or cools a building from the inside, usually using ducts, rather than through windows or doors.
2. Consider where duct work will go.
Most new homes have one or two air-ducting systems in the HVAC system. If this is the case, try to locate air-ducting systems near windows, doors, and entrances in the first floor of your home.
If there are more than two air-ducting systems, consider positioning them in the kitchen or living room.
Window- and door-mounted air-ducting systems are more complicated to install and require a licensed HVAC contractor to install them.
Duct selection in HVAC systems is the selection of either dry or wet heating and cooling ducts.
Each type of duct is selected based on certain needs.
When choosing the type of duct, the home's specific environmental conditions, space constraints, and budget must be considered.
In order to select a proper duct, the installer must understand the different duct characteristics, such as:
The following table shows the characteristics of each type of duct to make selection easier.
The insulating materials used in the enclosure are the choice of the home owners.
The type of insulation is in the highest amount and most common in a typical garage.
Insulation is important because it decreases the heat loss of the building.
The materials that can be used for insulation are:
There are three types of insulation materials that can be used in the enclosure: mineral wool, fiberglass batts, and cellulose insulation.
The types of insulation vary slightly but generally, each of these insulators are made from a fiberglass core coated with a loose mix of mineral wool and cellulose.
During installation, the insulation must be installed in the exact position and location specified by the HVAC system manufacturer.
The types of ducts are designed to allow the release of warm and cold air and to direct the heat of the incoming air to the required location.
However, a duct can also restrict air flow if not properly installed.
The diameter of the duct openings is determined by the type of installation that is being used for the HVAC system.
Ducts generally range from 4" to 15", but some high-performance ducts can be wider.
Ducts with larger openings must include weather stripping that is used to seal the duct to the building to prevent air leakage.
In a typical installation, the home owner may only have to patch the holes, not replace the duct.
The amount of duct work required is dependent on the size of the building.
A typical installation will require 7 to 16 ducts.
In a typical residential installation, the installer will not need to work on individual ducts that go from the furnace to an occupied room, but may have to seal ducts.
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