Wiring Problem for Honeywell RTH9580WF1005 Smart Thermostat


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Old 09-26-14, 05:47 PM
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Exclamation Wiring Problem for Honeywell RTH9580WF1005 Smart Thermostat

I am looking to upgrade my current thermostat to this newer Honeywell Smart Thermostat. My problem is that I currently do not have a C wire at the thermostat unit. In addition, once i open the control panel at the furnace unit, i see that there is no Y wire connected to the Y terminal (But there is a Y wire at the terminal in the wall unit). Is it possible to still upgrade to the new thermostat or do i have to rewire the entire system? Its very weird how the wiring does not match from the poles at the wall unit to the furnace. i will include pictures for further explanation. any help will be appreciated.

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Last edited by PJmax; 09-26-14 at 06:03 PM. Reason: reoriented/enhanced second picture
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Old 09-26-14, 05:56 PM
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It appears that whomever wired the two wires going outside to the a/c condenser did not use the Y terminal at the control board. They wire nutted the black wire from the Y terminal at 'stat to the red wire going out to condenser. The white wire on the C terminal at the control board goes outside with the red wire to provide control voltage to the contactor at the a/c condenser. To get a C wire at the thermostat the best method is to run a new thermostat cable. If that is too difficult to run you can use an external transformer to power the C wire.
 
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Old 09-26-14, 05:59 PM
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More information. The thermostat is for heating (gas) and cooling. Model is a Goodman. works fine but i want to upgrade the thermostat and need some answers before i do it.

thanks again,

Edgar
 
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Old 09-26-14, 06:03 PM
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Thanks for the help, Honeywell says that i can get away with substituting the C wire with the G wire. I would just lost fan control for recirculation. but they also state that i need to make a jumper connection between the Y and G terminals at the control panel. Will that still work without having a Y terminal hooked in to begin with?
 
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Old 09-26-14, 06:05 PM
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The Y terminal is just a splice point. So whether it's on the board or under a wirenut... it will work.

When you go to put your second wire under the C terminal you'll know why they used a wirenut.
 
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Old 09-26-14, 06:11 PM
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Thanks for the help, so if i were to make a jumper between the Y and G terminals like honeywell is saying to do, would that still work?
 
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Old 09-26-14, 06:16 PM
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Yup... that would work fine as the furnace will turn the blower on when it's warm and the call for A/C will turn on the fan and condensor at the same time.


PS... welcome to the forums. Also... your same question was removed from the other thread.
 
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Old 09-26-14, 06:24 PM
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Thanks for the help, i appreciate it.
 
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Old 09-26-14, 06:33 PM
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I also had another question. If i take the G wire and put it on C terminal like honeywell is saying to do, is it alright to have that C terminal at the control board double wired?
 
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Old 09-26-14, 06:49 PM
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Yes it is okay to have the thermostat C and the condenser C on the Furnace C terminal.

What is the model number of your Goodman furnace?

I would connect the two Y wires to the furnace Y terminal. This increases blower speed in cool mode with some furnaces. A model number might allow us to view the furnace manual.
 
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Old 09-29-14, 01:20 PM
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Hello again, I installed the thermostat today according to the instructions and including the switching of wire G and C wires as well as the jumper between Y and G. Upon testing, Heating cycle works good everything running. upon A.C. testing, the unit outside the house starts up but no blower unit inside the house. Please advise.
 
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Old 09-29-14, 01:36 PM
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The jumper between Y and G only works when the stat Y is connected to the furnace Y terminal.
 
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Old 09-29-14, 02:04 PM
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HOUSTON WE HAVE A PROBLEM hahaha sorry couldn't resist....SO to recap, attach Y coming from t-stat to Y terminal at furnace control board correct? next question, what do i do with the other red wire that the Y that is coming from the t-stat is wire nutted to? i was having fun up until 30 minutes ago when i started playing with this thing.
 
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Old 09-29-14, 02:18 PM
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also i believe the model number to my unit is

GCS90703BXA
Goodman, Natural gas forced air.
 
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Old 09-29-14, 02:30 PM
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Stat Y and condenser Y connect to furnace Y.
 
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Old 09-29-14, 02:32 PM
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You should have two wires on the Y terminal at the furnace. One comes from the thermostat and the red wire that goes outside to the a/c condenser should also be on this Y terminal.

Edit: Houston204 and I provided the same info but he beat me to the punch. LOL
 
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Old 09-29-14, 02:36 PM
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Got it.....I am going to have 3 wires into that Y terminal at the furnace. I'm not in violation of some HVAC code or anything am I?
 
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Old 09-29-14, 03:32 PM
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Nope, you are in good shape.
 
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Old 09-29-14, 05:13 PM
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Thank you fellas, we are up and running normally.

Thanks for all your help and patience with me.

Ed
 
 

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