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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 5648
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I have questions about my Goodman air con unit and my stiebel

Customer Question

I have questions about my Goodman air con unit and my stiebel eltron accelera 300 water heater
Submitted: 6 months ago.
Category: HVAC
Expert:  Phil replied 6 months ago.
Hello, thats two questions you have there, but I will try answer them both for you anyway. Tell me what questions you have, we can go from there.
Customer: replied 6 months ago.
Don't worry about the water tank now. We can deal with it another time.I have a Goodman DSXC160361a two stage condenser hooked up to a Goodman variable speed furnace - GMVC960804..I would like to know how many control wires need to be run from the furnace to the outside condenser so that I can get the two stage function active, and which terminals they hook up to on both units.
The system was installed late last year but the local hvac engineer used the original two wire set up from my old single speed condenser, so it runs on high all the time.
Thanks Phil!
Expert:  Phil replied 6 months ago.
HelloThis is the manual for the condenser unit is the manual for the furnace I am posting them here for ongoing reference We can go from there in the morning if I miss you tonight, I am off to bed shortly.
Customer: replied 6 months ago.
Thanks phil. I will look this weekend. My cell phone barely works where we live and it definately won't work in the basement.
Expert:  Phil replied 6 months ago.
That will work, I am here all weekend, 7 am to 9 pm west coast USA time
Customer: replied 5 months ago.
Hi PhilNot sure about one of the diagrams you sent me to check on. On my unit, there is only one terminal strip in the furnace and the wires from the thermostat connect to it and the two wires that go to the outside unit also connect to it. I have taken some photos to show you.Regarding the two wires that run to the outside unit. One is red and is connected to 'O' and the other is white and connects to 'C'.The thermostat I use is a nest 3. The yellow wire is spare.There is no rush to answer this problem today as it isn't particularly warm here yet.Thanks PhilKen
Expert:  Phil replied 5 months ago.
Hello, that thermostat is not intended to work with a variable speed furnace of that type...beyond that, the wire connections at the thermostat and at the thermostat terminal strip in the furnace are not compatible. Tell me a lot about the history of this installation and if it ever worked at all, or if this is just a new thermostat and before you changed it, the system worked. Generally speaking you should use the Goodman thermostat designed for the furnace electronics.... what we have here is something like taking a world class apple computer mother board and trying to make it work in an IBM pc clone. Let me know about all that, we can go from there.
Customer: replied 5 months ago.
Hi PhilThats really weird.The local professional installer used all the original wiring and just hooked it up to the new system. It all worked perfectly, but only at single speeds and gas valve stages. Whenever the thermostat called for heat, it would come on high and the same if it called for air conditioning.We had a simple thermostat that only had the original 4 wires hooked up to it. It was a hunter programmable thermostat - model 44905.(Please see photo '1' of the hunter thermostat with the original 4 wires).I contacted you last year to ask about how many wires I would need to get increased functionality and you answered. I wired them the same as the original except that I now had an extra wire for two stage heat. It works.The only thing I am not 100% sure of is that one of the two wires that go from the terminal strip came out when I put the new wires in. I put it into the 'O' on the terminal strip. It is possible that this came from another terminal I suppose. I don't want to try the air conditioning until I know for sure.With regard to the nest 3 thermostat. The instructions say that it can handle multiple stages of heating and cooling. And according to the goodman instructions, I could use legacy settings for that and get the functionality I want. All I wasn't sure of how many wires go from the furnace to the outside unit and where they went.Please see also, photo '2' - This is the original 4 wires as the installer attached them to the new furnace. I am holding the two wires in the photograph which go out to the outside unit.Photo 3 is the four wire setup with the nest thermostat before I ran the new wires to it. It worked for heat and cooling but as I said before, only at single speeds.Thanks for your help PhilKen
Expert:  Phil replied 5 months ago.
Hello again, for me, helping you get the NEST wired to properly operate the furnace for *variable speed*, not just heating and cooling single stage, is going to greatly exceed my time budget on this and probably end up wearing your nerves a bit thin.... I will opt out for a while so you can see if any of our few dozen HVAC experts here think they can help you cost effectively. Its a taller order than you have imagined I believe.
Customer: replied 5 months ago.
Hi PhilThanks for your reply. You misunderstood my question. All I want is for the outside unit to slow down when the demand for cooling is lower. I don't care about the internal blower variable speed particularly.Thanks anywayKen

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