By-Pass Sizing Calculator

Often with zoning systems a By-Pass is needed to relieve excess air when only a small zone or number of small zones cannot deliver the required air flow thru the HVAC System. A by-pass is often ducted back into the return air or into non-critical, common conditioned temperature areas such as entry ways, hallways, basements, etc.

Select your Maximum Total System Cubic Feet per Minute (CFM), then enter the CFM of your Smallest Zone to calculate the type of By-Pass Damper you require.

Note: If the By-Pass CFM amount is 30% or less of the Total System CFM, No By-Pass is required.



The By-Pass Damper you are looking for is SPRD08.

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The By-Pass Damper you are looking for is SPRD09.

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The By-Pass Damper you are looking for is SPRD10.

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The By-Pass Damper you are looking for is SPRD12.

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The By-Pass Damper you are looking for is SPRD14.

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The By-Pass Damper you are looking for is SPRD16.

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The By-Pass Damper you are looking for is RDM18 w/SPC.

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The By-Pass Damper you are looking for is RDM20 w/SPC.

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The By-Pass Damper you are looking for is ZDSM2020 w/SPC.

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The By-Pass Damper you are looking for is ZDSM2420 w/SPC.

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The By-Pass Damper you are looking for is ZDSM3024 w/SPC.

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Existing Zone SystemsMost Homeowners do not know they can actually zone their existing HVAC System!

Take the Test

1. Can you precisely control the temperature in every room of your home?

2. Are all areas of your home, top to bottom, comfortable all the time?

3. Do you have rooms in your home that no one occupies, yet you still cool & heat them?

4. Do you have a light switch in every room of your home?

5. Would you like to save up to 30% on your energy bill by adding zoning?

If you answered:

1. No
2. No
3. Yes
4. Yes
5. Yes

Install Zoning to your HVAC System Today!


1. Zoning allows you to precisely control the temperature in every room or (zone) of your home. How? By placing a thermostat in every room and an automatic damper in the duct controlling airflow to that room.

2. Your entire home cannot be comfortable all the time. The reason, typically most homes only have 1 thermostat located in a central hallway of the house. If that thermostat is located upstairs, how are you controlling your comfort downstairs?

3. Unoccupied rooms. Why waste heating & cooling on rooms no one is using? For example; it’s 10pm and you are ready for bed. No one is in the downstairs living areas so why cool or heat them? Shut them off by adding zoning and save on your energy costs.

4. You wouldn’t control all the lights in your entire home with just one switch, why control the heating and cooling in your entire home with just one thermostat? Especially when heating & cooling counts for over 50% of your utility bill!

5. Who wouldn’t want to save up to 30% on their monthly utility bill? With zoning, you can!

1. Zone Control Panel: The Zone Control Panel is the central control that will communicate between thermostats, dampers and your HVAC equipment. It is mounted by your equipment and is the brains of the entire zoning application.

2. Thermostats: Thermostats read the air temperature in each room (or zone) of your house. If the temperature is too cold or too hot for your liking, the thermostat will send a signal to the control panel to either bring on cool or warm air to that room or zone.

3. Zone Dampers: Dampers are placed in your ducts to control the airflow to certain rooms (or zones) of your home. The dampers are wired to a specific zone on the control panel, which is controlled by a specific thermostat in your home. Dampers automatically open and close depending on which thermostats are calling.

Zoning Made Simple

It’s the middle of the summer:

You are ready for bed, it’s 10pm. You make one last inspection downstairs, lock up and shut off the thermostats that control the air downstairs. (Just like you would shut off all the lights) You head up to your bedroom and set the temperature at 70 degrees F. The control panel reads that thermostat call, it activates your AC and shuts all the dampers in your duct system except the damper (or dampers) that control airflow to your bedroom.

Now, only your bedroom is receiving cool air.

1. You are staying comfortable in your bedroom because you now have a thermostat in there.

2. You are not wasting AC on the downstairs because the dampers that control areas of the downstairs are closed. Those thermostats are not on.

3. You are automatically saving energy by shutting the downstairs off. Up to 30% in fact.


Watch these short videos to learn more about zoning and how it can benefit you!

How Zoning Works

Zoning installed on an existing system