How hard is it to add a zone to an A/C system (Lennox iHarmony)

2 years ago

My house is 2 stories (3100sqft) and originally had a 2-zone system. That system was 23 years old and basically reached end of life. I recently replaced the entire system with much more modern equipment:

Lennox EL18XCV variable stage A/C
Lennox EL296V two-stage (variable speed) furnace

They will also be installing a iHarmony zoning board soon (it was backordered). Originally, when we set up the work plans, they said they would try to have the upper level of the house split into 2 zones (for 3 zones total, which I know the zoning system can handle). But now they are making that sound like they don't necessarily want to do it.

There are two thermostats in wall already corresponding to the current two zones (one on each level). These are old basic thermostats. I know that the plan moving forward is for the main Lennox iComfort smart controller interface to replace the downstairs thermostat, and something simpler will replace the upstairs thermostat.

What other work would be needed to make a new zone upstairs? I imagine a thermostat device of some sort needs to exist in every zone (otherwise the system cannot receive feedback about the temps being reached). Does this require new wiring in the walls? Or is there some simple plug and play theromstat they can install that wirelessly communicates with the zone system?

Our upstairs consists of 4 bedrooms and 2 bathrooms. I know that from the main plenum, 2 ducts cover that floor, each one hitting 2 beds and 1 bath. So it would seem the perfect candidate for 2 zones upstairs, especially considering how unevenly this level heats as the sun shifts throughout the day. Thoughts on whether it is a good idea to push for the extra zone up here? I can't think of any downsides.

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PRO
Austin Air Companie
2 years ago
last modified: 2 years ago
Thoughts on whether it is a good idea to push for the extra zone up here? I can't think of any downsides.

The more thermostats you have, the better the control of the system. Given the variable aspects of the condenser if implemented properly can work very well.

The bad news... Lennox variable speed AC as well as the furnace is designed around Lennox's "communication" protocols in order to operate this system as designed.

If the Iharmony zoning has an option to use "regular run of the mill" thermostats -- of which I seriously doubt --- because communicating relies on thermostat input and is different from a regular "off the shelf" thermostat. Maybe the installer wasn't quite sure of this... a salesman often sells things erroneously. I think you should press them to do the job as quoted. However, you may find this won't be possible.

Communication type systems are proprietary signals from all things attached to the system in question. Proprietary means: This system will "always" need a thermostat from Lennox to operate this system... in some cases these systems can be converted back to legacy controls (meaning a regular off the shelf thermostat) --- but in most cases this turns your variable speed AC into a less than variable AC. In some cases a lowly two speed AC condenser.

I put in a couple of communication based systems in the past (around 6 years ago) so I am ahead of the curve in how most of these work / what you can / what you shouldn't mix with them to get them to perform as designed. At that time there was nothing better... so people who wanted something better chose them. (That was then, this is now to help you understand how things change over time.)

Due to the "communication protocol" of the system chosen you then also have to choose a proprietary zone system to relay that communication around the system -- furnace and outdoor condenser. So you will always be bound to this communication problem. All the big manufacturers Lennox, Trane, Am. Stnd., Carrier, Daikin/ Amana do things this way. It's one way to do it --- they all chose to do it similar ways but proprietary to their brand. Daikin / Amana appear to be changing with comfort bridge technology the communication stuff is in the furnace, this maybe relayed in some fashion to the condenser usually via a two wire communication from furnace to AC condenser.

The Bosch Inverter, a marvel in it's own right does things differently. It doesn't rely on proprietary anything to run. I like to consider them a disruptive technology to beat up the big behemoths that seem more interested in keeping control over you and how their systems function.

So because the Bosch Inverter operates this way gives freedom to use other zoning options that are better, not to mention less costly.

It may be too late for you to consider Bosch so this reference is mostly for those who might stumble across this thread later on... weeks, months and some cases years into the future... looking for comparisions in the AC inverter realm.

I service the Katy, Texas area.

So I did a quick check. It is as I say.... click to enlarge if necessary.
PRO
Charles Ross Homes
2 years ago
Well, we've endured the oft-imposed Bosch inverter heat pump commercial. Bosch offers only two different size heat pump systems to meet the needs of replacement HVAC contractors who don't have a clue how to size a system.

Now, let's cut through the b.s. and get back to our regularly scheduled program to answer the OP's question....

I had a Lennox HVAC system with the Harmony Zoning system for the 1st floor HVAC system in my former home. It worked well and was performing well when we sold the home 17 years after the Lennox system was installed.

A zoned system requires a zone controller, zone-control dampers, and thermostats for each zone in addition to the basic HVAC equipment (air handler plus furnace and air conditioner or heat pump.) It's not unreasonable, in my opinion, for Lennox to require their proprietary thermostat be used to control each zone. When weighed against the overall investment in a new, zoned system, the cost of proprietary thermostats is not all that significant and compatibility with generic thermostats might involve compromising functionality.

With respect to zoning, your description of the existing ductwork sounds compatible with a zoning strategy provided the rooms served by each duct have a similar heat loss/gain. Zone control dampers would need to be installed-- controlled by the Harmony system, based on inputs from the thermostats.

If your replacement HVAC contractor quoted a zoned system, then that's what you should get. If it's not possible (and a lot of HVAC replacement contractors are clueless) then there should be some sort of price concession for a non-zoned system.
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In non-communicating mode, you'll forgo wi-fi communication wi-fi has no bearing on a communicating system. wi-fi is merely an application that allows the user to control the system remotely --change temp settings, shut the system off etc. Your system can be non-communicating still work with a wi-fi enabled thermostat. Personally I don't recommend any wi-fi type controls for a number of reasons I won't get into here. If you need to control a HVAC system remotely there are better options to do so than via wi-fi. Communicating systems are "hard wired" to communicate between the various pieces of equipment & the thermostat in most cases. (1 manufacturer has taken the thermostat out of play so users can chose any thermostat they want and still maintain the benefits of a communicating system that communicates info from the outdoor unit to the furnace and back.) If there is a depreciated value of those "hard wired" communicating connections -- interference, improper materials, improperly fastened and so on... there is no "communication". This communication is like that of a network, like when you connect to the internet. The problem is? The list is long if you ask me. I've installed communication systems as well as trouble shoot systems I didn't install as well as those I did. For the most part they work well, but... this is a repeatable business. It never ends. My job is mostly to mitigate problems as much as possible. Given that you're having these issues early on doesn't point anywhere good. The EL18XCV outdoor control has advanced control algorithms using the EL18XCV suction pressure sensor to provide true variable capacity operation. If this is true then how does it work with the Lennox EL296V two-stage furnace? Wouldn't the furnace blower speed have to ramp up and down as the the EL18XCV capacity changes? The furnace is variable speed, however this reference is the blower motor - not in reference to modulating furnace. This is why when the furnace has the ability to ramp heat out put up and down we call this "modulating" not variable. So the furnace in question is a two stage variable speed condensing furnace with 96% efficiency. Condensing furnace is 90% efficient and above. Two stage refers to heating stages that the gas valve operates in. Some may call this low fire and high fire mode. The variable speed blower is not a fixed speed blower unless: there is a feature to set it as such. Typically manufactures will ship furnaces in a common most used setting. But certain applications an installer can choose from as many as 4 different algorithms in which the variable speed blower will run. Typically in communicating systems the blower speed is lowered when the system is running in dehumidification mode. This doesn't mean there is no dehumidification at a higher blower speed though. Because there is more than one way to do it to force longer run times. If you slow the compressor speed? This drops capacity and will force the machine to run longer. Bosch keeps things quite secretive how they do it without communicating from indoor unit or thermostat either one. It works quite well and much less than a proprietary type communicating system.
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Austin Air Companie
2 years ago
Now, let's cut through the b.s. and get back to our regularly scheduled program to answer the OP's question....

That's rich Charles. ~The builder grade king? I love manufacturers who challenge the norm. It will make HVAC change for the better. Come 2023 and beyond everything changes again.

While Bosch won't be for everyone it will be for more people than those who choose proprietary induced coma for selection of critical add-ons like HVAC zoning.

Design of the system includes choosing parts, equipment etc. When you are hampered by those decisions or forced to choose this over another product, it doesn't result in anything good. That little tidbit is based on 27 years of actually doing HVAC work for a living. I think all my points are valid... that being said it's your decision after you digest all the facts --- that in this realm (inverter AC paired with zoning) are long complicated and tedious.

I service the Katy, Texas area.
PRO
Charles Ross Homes
2 years ago
Ray,

The OP asked about zoning and your response was the all too frequent commercial for Bosch. Bosch isn't a one-size-fits-all (well, they have two) solution for every HVAC need. Their system is aimed at the replacement contractor and it looks like they've hit their mark, at least in Katy, TX.

You apparently missed this important detail n the OP's original post:

"I recently replaced the entire system with much more modern equipment:
- Lennox EL18XCV variable stage A/C
- Lennox EL296V two-stage (variable speed) furnace"
Use of the past tense indicates a fait acompli. They've got the Lennox equipment installed. Just need the zoning part.
PRO
Austin Air Companie
2 years ago
last modified: 2 years ago
Charles the goal was to inform them of what they have and the challenges they will have to get it to work... now and into the future.

But I know reading and understanding are not your strong suits.

Just need the zoning part: yes, and because of the nature of the system they have they are limited to iHarmony zoning. Proprietary system -- requires proprietary parts, proprietary thermostats (all of them connected to this system)

No other way around that... except to rip it all out and start over. This is why people pay me -- my opinion is worth something. Maybe not to you Charles. But my posts aren't really directed toward you... other than to cut through your bs as you put it...
mike_home
2 years ago
Hi Dave,

In order to split the upper floor into two zones, you will need to wire another thermostat back to the control board. I am not an expert on Lennox thermostats, but I don't think a wireless solution exists. You will also need dampers to control the air flow.

You want to avoid making a single zone too small compared to the air flow the furnace will produce in the low stage. A small zone could become noisy. Most installers are not good a zoning. Ask a lot of questions about how the zones will work.
PRO
Charles Ross Homes
2 years ago
By way of clarification, the Lennox EL296V is a two-stage furnace coupled with a variable speed air handler. The burner has two heat ouputs and the air handler fan has variable speed capability. The turndown capability of the combination is excellent. You shouldn't have a problem dividing the 2nd floor of your home into two zones with respect to controlability or noise.

How hard is it to add a zone to an A/C system (Lennox iHarmony)

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Austin Air Companie

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