In order for a 2 stage communicating system to actually be a 2 stage communicating system is that the system is controlled with a proprietary thermostat. (in it's current form 2019)

If you take different thermostat and try to control your 2 stage communicating system with it --- that stat will need to be at least a 2 stage 'legacy' thermostat.

The 'legacy' means that your 2 stage communicating Is now reduced to merely an analog way of controlling this system (it's no longer communicating - which really defeats the purpose of having a communicating system to begin with if you do this).

If you're wanting remote control features it would be better to purchase red link accessory that was designed to work with the communicating thermostat that (typically comes with a communicating system)

If you don't have the comfort net thermostat from Goodman, your system is not communicating.

In addition to all that info: It is not recommended that you attempt to change your thermostat on your own with this type of HVAC system installed. Any changes made should be made only by professional servicer otherwise damage to system components are extremely likely.

I service the Katy, Texas area.

sktn77a - It currently doesn't have a Y2 wire. What happened was they originally installed it with a Y2 and no common wire (at the time we had a nest thermostat). Well a week after install a technician came out to look at things and he said they didn't need it hooked up to Y2 so he switched it to a common on the thermostat and computer board. I'm just not sold on how the goodman computer that doesn't know anything other than the outside temp is supposed to do a good job of knowing how to control itself. The other day for example the AC ran for about 1.5hrs to precool our house. It kicked on at 79 degrees and was supposed to try and cool as much as it can until 3pm when we go on peak pricing. After about 20 mins it kicked into 2nd stage and started to bring the temperature down. Well about 30 mins after going into 2nd stage it must've went into the 1st stage cause all of the sudden the air didn't feel as cool coming out and it held the temperature at 77 instead of trying to get it down to 74. I don't think the ecobee has a dehumidification terminal and not sure about the furnace either.

What is the Goodman furnace model number? You want to verify it is at least a 2-stage furnace.

If your thermostat currently doesn't have W2 (high stage heat) and Y2 (high stage cooling) wires, then the staging is being done by the furnace using the algorithm built into the furnace control board. That is not the best way to install 2-stage equipment. I assume this was done because either you don't have enough wires, or the installer didn't want to be bothered to wire the thermostat so it can control the staging.

To answer your question you can install a Y2 wire to allow the Ecobee thermostat to control the cooling stages. I think you are also going to need to run a W2 wire to control the heating stages. . Some DIP switches on the control board may need to be changed. If you don't know how to do this then you will need to call back your installer makes the changes.

If you don't have enough wires to wire the Ecobee thermostat in the legacy mode, then consider installing Goodman ComfortNet thermostat. It communicates with the furnace with only 4 wires.

The furnace is a GMVC80805CNCA and yes we are using all 5 of the wires coming out of the wall. Y1, G, W1, C, RH

Here is the GMVC8 installation manual. You can search for the W2 and Y2 wire connections. There is a section wiring a single stage thermostat on page 5. Your thermostat supports two stages, but you don't have enough wires. You are not getting the benefits of the Ecobee control features.

I think your installer is experimenting how to control the AC condenser with 5 wires. You probably will have similar issues in the winter when the thermostat is in heating mode.

Thanks mike_home that's exactly what I needed. I'll run 2 more wires one for W2 and the other for Y2 and then make sure the DIP S1 3(Thermostat) is in the ON position.

Are you going to have the installer do the wiring and reconfigure the control board? I think you should since this is the proper installation if you are not going to use the Goodman communicating thermostat.

I've had nothing but troubles with the company that installed it and they would find some reason to tell me not to do it

Any reason you don't want the Goodman thermostat?

They installed a Nest and then I found a good deal on a Ecobee so I swapped it out and am using that right now. They never even mentioned or offered the Goodman thermostat.

mistycargo,

Your system is not communicating without the Goodman comfort net thermostat. This is what is recommended to get this system to work as designed.

Because you don't have the thermostat wires needed to control this system properly using 'legacy' control methods, using the Goodman comfort net thermostat is your best option.

Trying to control this system with a nest is a bad idea, especially with not enough wires. Nest thermostats are energy stealing. They will steal power from the furnace. When that happens the power that is needed by the furnace is not available which can (at various times) cause erratic behavior. This is why the tech took one of the speed wires and repurposed it as a common wire.

That doesn't mean it will work like that. This is a stupid is, is stupid does moment. The salesman that sold you this system told you what like to hear. The nest is very popular and hip. That doesn't mean it's a smart device. You want sexy and sleek or do you want something that actually works?

It's impossible to run a 2 speed machine in legacy mode in both speeds without the necessary wires needed to operate both speeds. In legacy mode an electric signal is required for each speed, otherwise that speed will not function.

In order to enter stage 2 in legacy mode --- a power signal must be on both 1st stage as well as 2nd stage.

How this is achieved with not enough wires? both first and second stage are jumped together.

I service the Katy, Texas area.

From the Goodman brochure:

ComfortBridge off-the-wall communicating technology constantly monitors the performance of a high-efficiency heating and cooling system. As ComfortBridge technology gathers data, it uses it to make automatic adjustments, as needed; to use the minimum amount of energy required to create consistent and comfortable indoor heating and cooling.

Rather than installing the communications technology circuit board in the thermostat (which is connected to an inside wall in a home), the ComfortBridgecircuit board

is securely installed in the indoor unit of the energy-efficient heating and cooling system. ComfortBridge technology works with any single-stage thermostat to help create customized indoor comfort specifically for you and your family.

I'm not a Goodman expert but I believe your furnace is a Comfort Net furnace. That's not the same as the newer Comfort Bridge furnaces.

Both the AC and furnace are comfort bridge according to the brochure for each and it also appears the comfort net thermostat has been discontinued after looking at a couple online retailers.

Ok, I did some lengthy searching and looking on this comfort bridge stuff. From what I have found thus far it is a complete 180 from the 'communicating system' that is controlled via the comfort net stat. If you have the comfort bridge furnace, I don't think the comfort net stat will work with it from what I can see thus far.

The document I found is so new, the ink has barely had a chance to dry. If you understand manufacturer cycles and how long it takes to get products from development to actually in someone's home... well Goodman was never known for that.

So this is likely a 'Daikin' parent company type change / stunt whatever you want to call it.

To say this properly.... you can have a communicating system using normal simple R, Y, G, W, and possibly C for thermostat control (IF AND ONLY IF) you have the comfort bridge furnace. So in this way, the thermostat wires are normal legacy type wires or 24v analog signal.

What they've done is made changes to the system board and moved the communicating function to that board and off the previously mentioned thermostat.

Now here's where things get dicey and complicated:

In addition to needing the comfort bridge furnace it has to be wired 'correctly'.

What does that mean exactly? you have to know what you are doing.

Because this comfort bridge furnace has the ability to control a 'non-communicating' legacy AC as well as the communicating version.

All of this depends on 'how the system is wired'. If you don't know what you are doing the potential to get wires crossed is high. Mixing DC signal wires with AC voltage wires --- well you're going to tear something up if you do that.

The GSXC16 is a communicating 2 speed condenser. However, it also has the ability to be wired with legacy 2 stage controls. In other words if the communicating furnace or comfort bridge furnace is not present it can be wired with legacy controls.

BUT if this condenser is wired with legacy controls you will need stage 1, stage 2 and probably 24v hot and common wires. If this condenser is wired as communicating it only needs 2 communication wires from the comfort bridge furnace or the previously mentioned communicating furnace of yesteryear.

So if you've managed to understand all that thus far... if the system is 'WIRED' as communicating AND this is indeed attached to a comfort bridge furnace you will not get this to work by running new 2 stage wires for heating or 2 stage wires for cooling.

The comfort bridge (if it's present in your furnace) handles the switching from 1st stage to 2nd stage via the communication aspect. (The signal is digital in this sense)

THE KEYPOINT IN ALL OF THIS IS: IT DEPENDS ON HOW THE SYSTEM IS WIRED.

I believe this change is primarily to allow someone to change the thermostat without causing damage to the systems control board. To many DIY's and OR low skilled installers that don't understand that mixing voltages don't mix.

It's either that or it's a cost cutting move... but I suppose it could also be a combination of the two.

I service the Katy, Texas area.

OK, on further research, it looks like both your furnace and AC are Comfort Bridge, as you say. I believe you can still use the Legacy wiring for control of both AC and furnace from a 2 stage thermostat (don't know anything about the new Comfort Bridge thermostat). Will this be better than the communicating setup? No idea!

:(

sktn77a,

comfort bridge isn't a thermostat... it is a technology that is included in 'certain' Goodman / Amana / Daikin furnaces that allows the consumer to use any thermostat they want (single stage only) to operate a communicating multiple stage system.

The comfort bridge technology controls the operation of the multi stage equipment and decides (without the help of the single stage thermostat) which stage (or speed) the equipment will ultimately run in.

The comfort bridge technology is only communicating when it is properly wired to do so. 'It has to be properly wired.'

Because of this wiring complexity, you will need to find a licensed HVAC company to ensure this system is wired properly. It is not a DIY system outside of replacing a thermostat.

I service the Katy, Texas area.

"comfort bridge isn't a thermostat"

Probably why I haven't come across one! Sounds like if you can use any single stage legacy thermostat, then this is the way for a homeowner to go.

That's what they had in mind. The Comfort net thermostat was very expensive and the system was proprietary. People now like to pick their thermostats and the hvac manufacturers (Goodman with Comfort bridge) are giving them that option.

Seeing that this has been commented recently, I'll toss in my 2 cents. First, I am not an AC professional, but I am very technical. I design cloud software for a living and have done a lot of DIY home automation. I'll break out the soldering iron or breadboard without a second thought.

I picked an Amana ComfortBridge system primarily because of the warranty and price. It was competitive with the single stage systems I was also looking at. Of course with it being 100 degrees outside and my larger AC unit being down, I didn't do enough homework. But given the price and warranty, I'd probably end up exactly where I did.

Honestly, it's working great, my house is comfortable and the temperature has been consistent. I am using Ecobee thermostats, so I'll probably replace my 5 conductor wire with a 6 conductor wire to get the dehumidification control. But it kills me that they didn't put thermostat contacts on the board for second stage cooling and second stage heat. The logic around fan speed and everything else could certainly stay in the furnace. But the ability for the thermostat to signal if we are near or far from the current setpoint seems so trivial and like it would make it even better.