2 Stage Communicating AC System

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Old 08-02-19, 03:11 PM
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2 Stage Communicating AC System

Hello everyone, we just purchased a new GSXC16 2 stage communicating Goodman AC/Furnace system for our house in Arizona. Is it possible to let our ecobee thermostat control when the AC switches between first and second stage by adding a Y2 or will the goodman computer still override the thermostat?
 

Last edited by mistycargo; 08-02-19 at 05:57 PM.
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Old 08-02-19, 05:01 PM
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Hello.. Hmmm I always try to steer people away from communicating equiptment. What goodman is doing is putting the cummicating part which is normally the t stat out at the outside unit.

what you have is just a two stage unit. True communicating to me are for the inverter units that truely vary the speed of compressor in regards to load. ( repairs on this units are very costly, as well as common for breakdowns)

IMO I would put a regular 2 stage unit outside and use just a honeywell t6 pro t stat. The algorithm they use is good and you will be comfortable..

Im in the deep south of SC and run a 2 stage temp star with a honeywell t 6. I run 77f t stat temp and about 42% humidity. Im often cold in the home.

My system comes on around 11 am and stays on all day in 1st stage only. Goes off when it cools down at night. This is a properly sized system. Only 2 ton. I have great humidity removal. I believe it kicked on 2nd stage when we had a heat wave with 109f heat index last week or so.

to answer your question:

You can use any t stat with your system, but you always want the equipment to control the system IMO.

On normal 2 stage the t stat controls the staging

on the comfort bridge the system controls the staging., You will have less control IMO with the goodman
 
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Old 08-02-19, 05:12 PM
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Also no unit will work correct unless they size the duct work properly.

Often an HVAC unit is oversized and ductwork is undersized.

If the ductwork is not sized correctly, your wasting your $$$

What was there before? What size returns and supply?
 
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Old 08-02-19, 05:16 PM
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Just looked it up.. Thats a 1050 CFM system on hi, 760cfm low.

At a minimum I would say 16" return and 14" supply is needed. I have to get my ductulator,, but I think 18" return 14" supply would be ideal.

Otherwise you will have high static pressures and shortened life of the equipment.

Static pressure should not be more then .7 on those units..
 
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Old 08-02-19, 05:35 PM
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I'm just not yet sold on letting the goodman computer control everything when its up in the attic and has no clue as to what the weather is outside, what the desired temperature is and what the actual temperature is in the house where as the thermostat knows all of that. Today for example the AC ran for about 1.5hrs to precool our house. After about 20 mins it decided to kick 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 it started getting warmer in the house by maybe a degree until it then kicked into 2nd stage again for the last 20 mins before it had to turn off. So essentially after running for 1.5hrs it barely did much to cool our house before going on peak pricing.

Our home had a previous 5 ton single stage.
 
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Old 08-02-19, 06:45 PM
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Yes thermostat control is best. You can use any t stat with that system. even a single stage one. But let me read more on that system and see if I can help you more. ( you should really be going through the installer)

Our home had a previous 5 ton single stage.
Did they change the duct work? Or what size is it?
What CFM was your old unit?
What size is the current unit?
How many square feet is the home?

It may be the install and not the t stat at all.. Just trying to get proper info from you.

Most likely they will come out and increase your blower speed to try to rectify a possible bad install this in turn will raise static pressures, and cause more issues.

Did they give you a final static pressure reading upon commissioning?

Tell them you want a commissioning report, and ask for your manual J report. If no manual J then they are hacks.
 
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Old 08-02-19, 06:50 PM
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what air handler do you have? Gas heat?

I would think this one.

https://www.goodmanmfg.com/products/...96-afue-gmvc96
 
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Old 08-02-19, 07:05 PM
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Also page 35 starts with all the dip switch settings. also with what unit will control the air flow, outdoor or indoor unit. This is all in the hands of the installer.

The old cliche is KISS. This is why I dislike communicating equipment. It gets very complicated. Read a few pages and you will see.

I dont have time to read and self teach myself this system to help you. would be near impossible. But you can see there are so many delays and such. 50% fan, 85% fan, 7 1/2 minutes, timed stuff, etc etc.

This is why IMO 2 stage non communicating is best.

They should be able to disconnect that communicating board and rewire the outside to inside unit and t stat so you have the control at the t stat.

the fun starts on page 35

https://www.questargas.com/ForEmploy...stallation.pdf
 
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Old 08-02-19, 07:14 PM
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one more thing..

I would attempt to leave communicating and have the installer give you the t tstat that goes with these units.

On communicating equipment you always should use the company's t stat. It will give you the features you want to control that system.

If that fails with this t stat then as I said have them remove the communicating board and rewire

once they rewire then use the ecobee.

https://www.goodmanmfg.com/products/.../ctk04-control
 
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Old 08-02-19, 07:18 PM
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from ecobee .

Regarding Proprietary Systems:

If you currently have a communicating thermostat and equipment with proprietary features (such as variable fan speed), ecobee thermostats will not be compatible right out of the box. If you're unsure whether or not your current thermostat is communicating, there are a couple of things to look for:

Your current thermostat has non-standard terminals (ex. ABCD or 123)
There is an Equipment Interface Module (EIM) board present at the equipment-level bridging your thermostat and furnace
The ecobee requires standard terminals (R, G, Y, W, C) at the furnace control board, so if you do have these terminals present, it's possible that the ecobee can be made compatible with some re-wiring of your equipment.

Things to note:

ecobee thermostats do not support proprietary features supported by communicating thermostats (such as variable fan speed), so these features will be lost
Depending on the make and model of your equipment, you may need to contact your equipment manufacturer to verify the correct settings
 
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Old 08-02-19, 07:19 PM
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communicating t stst

They are $500 bucks and probably why the installer did not give it to you. He dont want to lose $$$$$

https://www.goodmanmfg.com/pdfviewer....pdf?view=true
 
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Old 08-02-19, 07:25 PM
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too complicated for my liking.

Im going to bed. But here is the manual for that t stat

https://www.alpinehomeair.com/relate...TSTAT03-4D.pdf
 
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Old 08-02-19, 08:08 PM
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Haha thanks for the info. I'll read into that manual and see if any of it can answer my question. Once again thanks for all the input.
 
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