Frequently Asked Questions About HVAC Dampers

What is a motorized damper?

A damper is anything within a home’s HVAC system that helps to stop or regulate air flow. Dampers can be weighted or spring loaded to regulate when they open or close, or they can be controlled remotely through a powered motor. A motorized damper is common in newer homes with HVAC systems that control the air flow to different areas or zones in a house. 

A zone can be designated to individual rooms of a house so each room’s air temperature can be regulated by the central unit, or zones can be as simple and wide reaching as upstairs and downstairs zones. Motorized dampers in your air duct system are placed at the joints where the air is supplied to a particular zone. The system will then open or close a duct through the use of a motorized damper to cut off or redirect airflow from one zone to another. 

The reason we have zones is to help ensure that your home’s HVAC system is running at peak efficiency and is fulfilling the desired purpose (heating or cooling) by supplying hot or cold air to only occupied zones of the house rather than trying to heat or cool the whole house at once. This helps save money by reducing wear and tear on the HVAC system and on making sure you don’t have to run the heater or A/C unnecessarily which soaks up power very quickly. 

A well functioning damper network in your HVAC system is a great way to be able to enjoy your home in the summer and winter with the peace of mind that you are getting the most out of your HVAC system and are saving money on your power bill. With modern AI controlled smart thermostats like Google’s Nest and the Honeywell T9 becoming more of the norm you will want to have an HVAC system that can be intelligently controlled and regulated, which means that dampers are becoming more important than ever to have in your home. Do a regular systems check each summer to ensure that all of your dampers are functioning properly. 

FAMCO sells several high quality HVAC damper products, including motorized dampers. Our dampers are quality constructed in 28 gauge Galvanized steel. The FAMCO ADO Motorized HVAC Damper come in a range of diameters: 4 inch, 5 inch, 6 inch, 7 inch, 8 inch, 10 inch, 12 inch, and 14 inch. The FAMCO ADO Motorized HVAC Damper is manufactured by Famco in the United States and comes with a 1-year warranty against product defects and workmanship. If you have any questions about this product, please refer to the FAQs page or feel free to contact us by phone or email.

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Motorized Damper Installation And Replacement

Getting started

In a home, motorized dampers for zone control are typically located in the attic or crawlspace of a house. Carry all your tools and supplies to the area and make sure that you have your safety glasses and breathing mask in place before entering the crawlspace or attic in order to avoid inhaling insulation particles or other potentially harmful particulate matter.

Recommended Tools:

  • Safety glasses
  • Gloves
  • Disposable dust mask
  • Flashlight and/or lantern
  • Utility knife
  • Duct tape
  • Cordless drill

Motorized HVAC Damper

Measure and inspect current damper:

Make sure that you have measured your air duct diameter and determined which type of damper you are replacing as it does make a huge difference. Motorized dampers are either “normally open” or “normally closed” types, so you’ll have to figure out which one is installed in your house before purchasing and attempting to replace the current one. We recommend this damper for “normally open” and this model for “normally closed.” It’s also a good idea to cut power to the HVAC system entirely during the duration of the replacement because it may come on during the replacement and hinder your progress.

The process:

Locate the damper motor section to be replaced

You want to make sure that you have located the exact damper and the area around it so you can set up a safe working area while the replacement is going on.

Check the wires

Motorized dampers are usually hardwired into a control board in the area. Since you’ll have to safely disconnect the wires before you replace the motor, you may want to cut power to the area with your breaker box to reduce the risk of electric shock. Follow the wires from the damper unit to the control box or zone board.

Disconnect the wires

The damper motor’s wires should be easily removed from the control box by following the instructions of the manufacturer. Some may be held in by a tensioned clip or screw. Follow the directions associated with that model of control unit.

Expose the area around the damper unit

Most of the time the duct that is connected to the damper unit will be surrounded by insulation. You’ll have to use your utility knife to carefully slice open the insulation material around the seals where the damper housing is connected to the rest of the duct. Peel away the insulation to expose where the damper unit is connected so you can get at the screws (usually self tapping metal screws) or bolts holding it in place. You may also have to cut through duct tape around the seams of the damper’s duct.

Note: sometimes a damper will have been installed around a piece of flexible plastic duct rather than a metallic duct. Follow similar instructions, but you may have to re-seal the flexible duct around the new damper body with cable ties. 

Remove old damper

Take the old damper off and carefully set it down outside of your working area. Inspect the duct around where it was connected and make sure there is no debris or other contaminants that have gotten into the air system. This is rare, but a good idea as a precaution. Sometimes as you’re removing the old unit some insulation or small parts might fall into the duct.

Install new damper

Place the new damper over the exposed hole area and replace any screws or bolts that you had to remove from the last one. Seal seams with duct tape or aluminum printed foil tape. Replace the insulation covering and tape up the seams that were cut.

Replace the wires

Once the damper is in place, install the wires used to power the motor in the main control board as per manufacturer instructions.

Test for functionality

Restore power to the house and adjust the thermostat in order to kick on the zone that the new damper is part of. If the air is flowing correctly and the damper is sending air to the right place, then you have successfully installed your new damper!

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How does a motorized fire damper work?

Motorized fire dampers work by automatically shutting off the air supply to an affected part of the HVAC network which prevents the spread of smoke and fire through the duct system. These dampers are typically activated in one or more ways. Make sure that you have your motorized fire dampers inspected regularly to ensure that your facility’s fire suppression system is working properly. 

By temperature: If the area in the duct system or in the surrounding environment exceeds a certain temperature, then the dampers will automatically close off air supply via a tensioned spring mechanism which naturally shuts when power is cut. 

By power failure: In the event of a power failure due to a fire or other causes, dampers will automatically spring shut, closing off air supply in order to stop the spread of a fire or smoke to the rest of the building. 

By smoke alarm or contamination alarm: Some facilities have their smoke detectors wired into the HVAC system to trigger a damper closing in case of an alarm. Medical or chemical facilities will have a similar detection system for non-smoke air contaminants which also need to be isolated. These facilities will often also have a separate HVAC system for areas of potential microbial or chemical airborne contamination as well. 

Manually by computer remote control: Many HVAC systems have a zone control board that can be manually accessed or accessed remotely via software on a computer or smart device.

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What is the purpose of a backdraft damper?

Backdraft dampers help to stop cold air from leaking back into your home. These are typically installed near the outside of your duct work where it is close to the open air. Backdraft dampers can also keep your home smelling clean and fresh as they can help prevent mold and bacteria from contaminating your duct system. They push the exhaust air out of your home while preventing outside air from flowing back into the home. We recommend using the FAMCO Butterfly Damper used as a back draft damper for heat exchangers, exhaust systems, solar heating systems and other intake or exhaust applications where a powered damper is not needed.

You will find backdraft dampers most commonly in three areas of the house: the laundry room, the kitchen, and the bathroom. That is because these areas have exhaust fans that pump air out of the house. You may notice that on a windy day you will hear a banging or clanging near your kitchen or bathroom exhaust fan area. This could be due to gusts forcefully slamming the dampers open or closed. If this is the case, then you may have a faulty damper. You will want to visually inspect these areas and determine if you need to replace a malfunctioning unit. If it is making clanging noises during a wind gust, then it could be letting outside air back in to the house, which should be prevented at all costs in order to keep heating and cooling costs down.

How do I know if my damper is open or closed?

If you can’t visually inspect a damper, or don’t want to remove it from its housing inside your home’s ducts, then you can turn on all zones of A/C in your house and check the air flow in that damper’s zone. If air is flowing properly, then it is open. If not, then the damper is closed. Some motorized dampers will have a colored indicator switch to show whether they are open or closed. Usually it will be green for open and red for closed.

If you’re looking to see if your damper type is “normally open” or “normally closed” then there is an easy way to tell. If you have the damper close by, then cut the power to it and observe the damper blades. If they spring shut, then you have a “normally closed” type of damper. If they spring open, then you have a “normally open” type.

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How much are HVAC dampers?

FAMCO sells high quality HVAC dampers for a variety of uses. The prices vary by damper type, so we will outline a few here to paint a better picture:

Motorized damper: Our motorized dampers start at $115.01 for a 4 inch 24 volt damper with no end switch. Sizes range from 4 inches to 16 inches. 

Butterfly backdraft damper: These galvanized steel beauties start at $22.39 for an 8 inch diameter damper. They are available in sizes from 4 inches up to 20 inches in diameter. 

Aluminum wall vent reversible backdraft damper: Available in sizes as small as 4 inches in diameter to 12 inches. The prices range from $38.79 to $71.32 respectively. This hooded wall vent comes with a positive seal, removable back draft damper, hooded wall vent with a short tube and a 1/8 inch insect screen.

Inline butterfly backdraft damper with spring: This damper starts at $20.07 for the 4 inch model and ranges up to $42.81 for the 10 inch model. 
Pressure Relief/Barometric Damper: Depending on the size, these cost between $79.28 for the 6 inch diameter version to $181.90 for the 18 inch version. This damper is commonly used to relieve built up pressure in zoned duct system that could potentially cause damage to HVAC equipment.