So, maybe you have decided to upgrade to a Wifi thermostat, or even just a standard "programmable" thermostat... only, you come to discover that your old thermostat has one less wire connected to it than the new thermostat needs.   This is usually the "24VAC Common" wire sometimes just called "C" or "24C".   This means that your old thermostat was either mechanical, power stealing, or battery operated... which isn't a problem if you don't want a modern thermostat.  MOST modern thermostats (especially WiFi) need a "C" wire from the 24V transformer to power the thermostat... this means getting a "C" wire to the thermostat.

This isn't a new problem, it started showing up in the 1980s with the first programmable thermostats... over the years, I have suggested and used several different methods to overcome this issue both with zoning and with typical single thermostat applications.  Until recently, I couldn't really recommend anything other than running a new wire... and running a new wire isn't always possible.

METHODS to add "C" Wire

Run another wire to the thermostat The most straightforward and full-proof method is obvious: run another wire.  If possible, this is ALWAYS your best solution.

Power thermostat from separate transformer Don't use this method... it is risky and not all thermostats support the ability to separate the "R" from the equipment transformer.

Use the "G" wire for "C" This method DOES work but it limits the functionality of your thermostat control.  (ie. you will not be able to independently control fan from the thermostat)  The reason this works, is that the equipment automatically turns the fan on during a heating or cooling call, so the "G" wire controlling the fan from the thermostat is only necessary to turn the fan on by itself.  You will NOT be able to turn fan on from the thermostat by itself with this method. NOTE: This works with MOST equipment, but you should check or test before employing this method. (#3)

ADD-A-WIRE Device It is the BEST method and really the only method I would use if a wire cannot be run.  This is a relatively new concept to me... it has been around for a few years at least but we just started recommending it within the last 2 years.    Several companies have started offering an "ADD-A-WIRE" device that allows the addition of a "COMMON" wire.  These devices range from $15 - $40 and are very simple to wire (you have to be able to get to your equipment furnace/blower). 

How an ADD-A-WIRE Device works:

It will come in 2 pieces, one is a small box with several connections labled "R", "C", "Y", "G", "W".  You will follow the included wiring instructions to connect this box at your indoor HVAC equipment.  The other piece that comes with the ADD-A-WIRE is a wiring connector with 3 leads, this connects at the back of your thermostat as shown in the wiring instructions. Once these two pieces are wired properly you will have the "C" you need for any thermostat... it's almost like magic (electrical engineering magic).

NOTE: Make sure all wiring is done with the power to the HVAC equipment OFF at the breaker.

A few different models to choose from (prices on amazon at time of writing)  There are many others available but they all do the same thing (NOTE: we are not compensated by any of these companies or any others for our opinions):

LUX Products LPB-WH - $18  (Our favorite because it's the easiest to wire)

Venstar ACC0410 - $27

Honeywell THP9045A1023 - $15

For more information about specific use with zoning and zone control systems such as SmartZone... contact us

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).

We are proud to announce the continuation of our damper product line here at ZoningSupply.com with the "Insert-able" damper.

Some applications call for dampers that can be "slipped" into round duct that is spiral or other hard pipe style duct.  This is not intended for use with flex-duct but can be used with any other type of hard duct.  Simply cut a slit in the duct, insert the damper and screw it down.

These and many other common problems can occur during the winter months when the heater is running more than normal.  This can especially happen in areas that have cooling systems to handle warm and hot summer months.  The duct is often designed to be optimized in the summer months and when heat season rolls around, the airflow balance is all wrong.  The solution is Zone Control.  Even in the best designed duct systems, dampers are often used to balance the airflow on site.  This is tedious and inexact... but with SmartZone controls and power dampers, your home can be comfortable everywhere year round.

"I have personally been in too many to count homes with two stories that NEED zoning... there is nothing wrong with the equipment capacity or the ductwork, they just need the ability to direct airflow in the areas that need it in different seasons of the year or even times of day"  -- SmartZone Contractor

2016 has been an incredible year for ZoningSupply.com and we hope that 2017 is even better.  We are a small business that has been building to this point for over 10 years, 2016 was our best year ever and we are on an upward trend.

Thank you to all our loyal customers... 2017 has more things to come including rectangular dampers and more that we cannot announce yet.  We will continue in our pursuit to be the best HVAC zoning supplier in the USA.

Are Zoned Heating/Cooling Systems a Good or Bad Idea?

Excerpt from homeenergypros discussion about HVAC Zone controls.

QUESTION by Jon LaMonte

 For starters, I live in Atlanta, Ga and I am not an HVAC pro so this is a serious question that I would like answered for one of my clients.  I understand the premise of a zoned system and on the surface, it sounds like a good idea. Then I considered the fact that I have always told my customers that it is a bad idea to close off vents in rooms they are not in because of duct leakage.  Also, the second law of thermodynamics simply states the hot goes to cold, so now the unheated areas are doing their best to rob warm air from the heated areas.  Finally, if your zoning a single system, aren't you creating on oversizing issue because the unit (that was probably oversized in the first place) is now servicing a smaller area than what it was designed for?

  Reply1 by Chris Heenan

Zoning has benefits beyond temp control. Most often the home does not require the full 2 stage heat or cooling as the system only needs to satisfy a portion of the home. So, then if 1/2 the heated air goes through a properly sized and balance bypass, the return air (from home) will mix with warm supply (from bypass) before going thru the system again. You may not need to go beyond 1stage heat (or cool) except in extremes. This is most beneficial in raising supply temps from heat pumps when in winter mode. Most supply vents feel 'cool' to homeowner. Not so when zoned and not call on all zones.

Flip it to cool, and the bypass send dehumidified cooler air across the coil. Decreasing high side pressures and amp draw of compressor. Then the air gets more heat extracted and further dehumidified. Pulling out additional condensate and running less. Remember systems have to be careful not to oversize as dehumidification is crucial to comfort. Dry and cool temps out supply vent. Not too shabby.

 Reply2 by dale conner

Zone sytems are rarely installed properly but can be efficient if properly designed. The goal is to be able to set back the temperature a few degrees in a zone that isnt being utilized while keeping another zone comfortable that is being utilized.  A single unit with a zone system will have a by-pass duct sytem to dump the air thats been cut off from one zone back into the duct system to be used in the zone that is being used.

 *Reply3 by James Jackson on

Have you ever been driving down the interstate hwy and come up on an exit ramp that has traffic backed up? As the traffic backs up and eventually fills the exit with cars you end up with a slight back up on the entire highway. this is the closest scenario i have been able to come up to help people understand why closing doors and vents is a bad idea. if you have a run off of a main trunk and you close the outlet or register you will cause the air to back up into the trunk causing turbulence in the trunk line resulting in a decrease in air flow in other areas on the system. this can also cause multiple other problems like pulsing and excessive noise from the increase in pressure.

another thing to remember when you shut doors in a home with no return air you cause a difference in pressure in the home. The room you have closed is now significantly positively pressurized and the house is now under a negative pressure. This why some homes have the doors undercut by 3-4 inches trying to allow the air to get back to the return.

Ok as far as the zone system goes... There is so much more thought involved in properly setting up a quality zone system that i see very few done correctly. If you want to do one correctly you first need to make sure you are using a multi-stage HVAC unit so the unit can run on low speed if it is only conditioning one zone. A bypass or crossover duct with a barometric damper is needed if you are conditioning a small zone and the air handler is still supplying too much air, but if you are going the zone route don’t use contractor grade units and piece it together with a simple zone controller. Get a high efficiency v speed unit that is designed for this application.

But what happens when you change the temps in a zone in the house 4-5 degrees?? Energy moves from hot to cold so you end up indirectly heating or cooling the entire space regardless. This brings us to another scenario. The return air in the zone that is off. My experience with working on correcting issues with homes using zone systems has been the returns are never dampered so if the zone is completely shut off you have just installed a permanent blower door. if the zone is off one you are returning hotter or colder air to the system and two you are causing that zone to have a negative pressure.

Just some things to think about !!

 Learn more at www.zoningsupply.com

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My editorial conclusion: Zoning CAN be effective if and ONLY if it's designed and installed properly.  This means ducts, dampers, equipment size (tons).  It also means the right zone panel setup with energy saving features like SmartZone.  Finally, to make zoning work best and comfort control and energy savings, the home owner must properly control the thermostats.  Zoning isn't a "set-it-and-forget-it" system, it must be managed to be effective.  More articles about zoning

HVAC.com recently had a great blog about why NOT to use so-called Smart-Vents.  Read the whole article here: https://www.hvac.com/blog/smart-vents-vs-zoning-zoning-methods-best

It boils down to a couple of key factors:

You don't gain anything "smart" from these systems. - If you want a "smart" system, simply use a standard zoning system and add a smart thermostat like ecobee or nest

Closing the register to create zoning doesn't work as well as a damper - HVAC systems are not designed to handle the air pressure increase when registers are closed without a bypass or some other pressure relief.  This can cause damage to the equipment or at a minimum not create the desired effect.

The maintenance and cost is much higher - Battery operated vents means replacing batteries, not to mention the initial cost of many register vents that would have to be installed.  Instead of 1 damper per zone you might have 4 or 5 or even more of these so-called smart vents.