ZoningSupply.com - Zone Control

HVAC Zone Controls & Zoning Dampers


Need more than 40VA to power LOTs of dampers on one SmartZone?

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Some systems with many small ducts leading to each zone can require lots of dampers.  The example below is a 2 zone system that requires 6 dampers per zone (12 total).  If you look at the zoning guide, you will find that you should budget for at least 55VA for this system... but you only have 40 VA transformers.  75 and 100 VA transformers can get VERY expensive!  Instead you can use two 40VA transformers, but not how you think.  It can be dangerous and unreliable to connect transformers in parallel to create ~80VA.  We recommend the method below that employs the use of a simple relay to separate half of the dampers to be powered from a second transformer and the other half being powered by the SmartZone and it's transformer.

See the SmartZone Install Guide to calculate required VA.

It is always necessary to verify that the PRIMARY side power is sufficient to power the transformer connected.  A dedicated PRIMARY circuit is best but not always possible.  If sharing the 110V or 220V circuit, make sure the total power required for all devices connected (including zoning transformers) doesn't exceed the capacity of the circuit (usually 15 or 20 AMPS).

Where to get a relay?
Any 24V relay with a DPST or DPDT configuration will work.  The one pictured in the above diagram is available at ZoningSupply.com (see below).   If you are chosing your own relay, the "Contact" current rating will determine how many dampers can be connected.  (For example: A 10 Amp relay can handle up to 10 power open, power closed dampers)

24V Relay - DPDT
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Power Open/Close Motor
59.99 79.99
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Replacing old 2-wire spring damper with a high quality ecojay damper

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UPDATE: March 2017 - NEW Dampers available now.  TAKE-OFF ROUND, INSERT ROUND & RECTANGLE Dampers all available now ... scroll down to see all damper models. OR click here.

Some older zone control panels have only two connectors for damper wiring (common & power-close).  These were designed when predominately 2-wire (spring open) dampers were used for zoning.  In recent years, 3-wire (power-open, power-close) dampers have become more common because of their low power consumption and higher reliability.  You might think you have to upgrade your zoning panel to accommodate for these preferable 3-wire dampers... not with Ecojay dampers and belimo actuators.  The wiring diagram below shows how to connect the Ecojay Power Damper to an older zone panel that is only designed to work with 2-wire dampers.

If you are planing to replace the zone controller with SmartZone, this diagram is NOT necessary.

If you have any questions, call or email us.

What type of damper is best Spring or Power?

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smartzone damper sizes.png
smartzone 8 inch spring damper.png

Damper Type Selection

There are two basic types of dampers available in mass today.  Although, there are other damper types such a “balloon” type and pneumatic controlled dampers (used more commonly on DDC systems not included), for this context we will discuss these two main types of dampers:

  • Spring Open or Close (Spring Damper)
  • Power Open & Power Close (Power Damper)

Power Dampers

Power Open /Power Close dampers use three wires to either power open or power close.   They zone panel is responsible for supplying a 24VAC signal to either the PO (Power Open) or PC (Power Closed) terminal of these dampers.  This type of damper was traditionally reserved for “higher-end” or commercial applications because of the cost.  In recent years, however, motor prices have decreased and power dampers have become much more affordable (often no more expensive than the spring equivalent especially when labor and reliability are factored in.)  Primary advantages of Power Dampers include lower power consumption, quiet operation and more reliable parts.  Given the choice, Power Dampers, are almost always preferable.  The only exception to this is when code requires Spring Dampers.

PRO-Grade Power Zone Damper (Round)
from 99.00
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Spring Dampers

The way Spring Dampers work is they have a motor that, when energized by the zoning panel, it closes the damper.  When the damper is ready to open, the motor stops powering the damper closed and a spring opens the damper blade back up.  Spring Dampers have been used in an “economy” application for many years.  The two primary advantages of a Spring Damper are: 1. If the system loses power they “fail” open… but if the system loses power, the equipment isn’t going to be running either and therefore will not matter in MOST cases.  2. They only require two wires for operation.  One of the negative arguments against Spring Dampers has historically been reliability.  This mostly a result of one of its benefits… the cost.  The inherent lifecycle of any spring actuated mechanism (even if it is in the millions) is less reliable than a system that doesn’t include this potential failure point.   In addition to this, the motor that is used has to be a very specific model that allows for running backwards without damage yet still has to be powerful enough to overcome the spring trying to pull the blade in the opposite direction.  This leads to probably the BIGGEST downfall of using a Spring Damper - the power consumption.  Most Spring Dampers on the market use 3 to 4 times the power of the equivalent Power Damper (10-12 VA vs. 2-3VA).  This could be the difference in using a standard sized transformer and having to go to a very large (and expensive) over-sized transformer.   In summary: spring dampers are NOT recommended unless absolutely necessary for some reason.

Spring Zone Damper
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