Help with wiring - Goodman furnace to Honeywell stat


  #1  
Old 12-29-13, 10:09 AM
T
Member
Thread Starter
Join Date: Dec 2013
Posts: 6
Received 0 Votes on 0 Posts
Help with wiring - Goodman furnace to Honeywell stat

So I'm having some trouble getting a new wifi thermostat powered. I have a Goodman furnace and a/c. The furnace only has connections for R, W, G, no C. It is this control board:

Name:  Goodman B18099-13S close.jpg
Views: 15699
Size:  42.2 KB

My old thermostat was an old Honeywell unit that didn't need power. It was using R, W, G, Y only, but there is an unused blue wire. The new unit I am trying to install is a Honeywell RTH9580, and requires the C wire.

Here is what the furnace looks like currently:

Name:  photo.jpg
Views: 16898
Size:  50.4 KB

In the picture, the bundle with the blue, yellow, and green wires go out to the a/c. The red goes to the block on the unit, and then the blue wire connected is grounded to the furnace by a screw. The white wire connects directly to the yellow wire that goes to the stat, and runs to the power box outside through the white wire.

The other bundle with the blue wire straight up goes to the stat. That blue wire is not connected to anything currently. The Yellow goes right up to the stat, the R, G, and W go to the matching terminals on the power control and up to the stat.

So, I've read many threads on here with the similar furnace, and all say to ground the blue wire somewhere to a screw on the furnace. I've tried that, but there was no power to my stat (the screen just stays blank). I've tried grounding it to both the screw near the transformer, and the screw where the thicker blue wire grounds. I also read of someone with pretty much the exact same set up, to splice into what my red wire going out to the a/c and blue wire grounded onto the furnace. That also lead to no power to my stat. All wires connected to the new stat match what was connected to the old stat.

I'm at a loss for what to do. I'm beginning to think my stat is dead on arrival, or I'm missing something. Any help would be very much appreciated.
 
  #2  
Old 12-29-13, 11:17 AM
Jay11J's Avatar
Member
Join Date: Sep 2001
Location: Rochester, Minnesota
Posts: 18,427
Received 0 Votes on 0 Posts
For kicks, undo the wire from G on both spot, and then wire that on C and ground it out on the furnace..

If that works, then the blue wire you tired to use for C may have a break some where along the line.
 
  #3  
Old 12-29-13, 12:01 PM
T
Member
Thread Starter
Join Date: Dec 2013
Posts: 6
Received 0 Votes on 0 Posts
OK, so doing that powered the stat. Switched it back with the exact same set up, but with G to G and blue grounded to same spot I grounded G and blue connected to C and stat and back to no power. So it seems to be something with that blue wire.

What would the next step be here?
 
  #4  
Old 12-29-13, 12:04 PM
Jay11J's Avatar
Member
Join Date: Sep 2001
Location: Rochester, Minnesota
Posts: 18,427
Received 0 Votes on 0 Posts
is there an other wire in the bundle that isn't used?
 
  #5  
Old 12-29-13, 12:11 PM
T
Member
Thread Starter
Join Date: Dec 2013
Posts: 6
Received 0 Votes on 0 Posts
Nope, just red, green, blue, white, yellow. All were previously being used by the old thermostat. Red to Rc jumped to Rh, green to G, white to W, and yellow to Y on the stat. At the furnace, green went to G, white went to W, red went to R, and yellow was spliced and runs to the a/c.
 
  #6  
Old 12-29-13, 12:29 PM
T
Member
Thread Starter
Join Date: Dec 2013
Posts: 6
Received 0 Votes on 0 Posts
So looking at Honeywell's videos you can use the G in place of the C. However, that involves jumping the Y to G at the furnace. Since I don't have a Y at the power control, what would be the way to jump Y to G?
 
  #7  
Old 12-29-13, 01:52 PM
Jay11J's Avatar
Member
Join Date: Sep 2001
Location: Rochester, Minnesota
Posts: 18,427
Received 0 Votes on 0 Posts
Do you ever use the fan "ON" switch on your stat? If you don't, then you can join the splice from the Y, and then join Y at G at the furnace.
 
  #8  
Old 12-29-13, 02:03 PM
T
Member
Thread Starter
Join Date: Dec 2013
Posts: 6
Received 0 Votes on 0 Posts
No, I don't. It is always set to auto.

So, would it work to take the thick green wire that is in the wire nut with the thin green wire, and splice that into the wire nut with the yellow wire? That thick green goes to the G on the power control. Then ground the thin green that goes to the stat?

Just wanna be completely sure, I'd prefer not to fry my system.
 
  #9  
Old 12-29-13, 02:07 PM
Jay11J's Avatar
Member
Join Date: Sep 2001
Location: Rochester, Minnesota
Posts: 18,427
Received 0 Votes on 0 Posts
Yes, tie the thicker green wire with the Y and wire going outside to the A/C unit.

Then changed the thin green wire to C at the t-stat and furnace.

When you get this stat up and going, set the t-stat to 3 for heat cycle/equipement type.
 
  #10  
Old 12-29-13, 03:20 PM
T
Member
Thread Starter
Join Date: Dec 2013
Posts: 6
Received 0 Votes on 0 Posts
Worked perfectly. Thank you very much for your help, you are a lifesaver.
 
  #11  
Old 12-29-13, 05:04 PM
Jay11J's Avatar
Member
Join Date: Sep 2001
Location: Rochester, Minnesota
Posts: 18,427
Received 0 Votes on 0 Posts
Thanks for the update, and enjoy your evening!
 
  #12  
Old 02-20-14, 05:20 AM
S
Member
Join Date: Nov 2013
Posts: 9
Received 0 Votes on 0 Posts
Jay11J, can you elaborate a little more on this? I have this same board and furnace too, and am trying to plan ahead to get a wifi t-stat. My question is, how does the t-stat get power from grounding the wire to the furnace chasis? My electrical knowledge is limited, but it only makes sense to me that the power would flow from the board to the t-stat, not from the chasis to the t-stat. I'm confused ... Thanks in advance ...
 
  #13  
Old 02-20-14, 07:12 AM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 62,170
Received 1,528 Votes on 1,411 Posts
Normally a thermostat didn't need the common side of the transformer unless it had a clock/timer in it. A thermostat only switches 24vac(hot) so it doesn't need the common line to operate.

If you have extra wires from your thermostat to your furnace.... then you can recoonect one of them as the C wire. In most, not all, Goodman units..... one side of the 24vac transformer is connected to chassis or ground. It's that connection your wifi thermostat requires.
 
  #14  
Old 02-20-14, 07:28 AM
S
Member
Join Date: Nov 2013
Posts: 9
Received 0 Votes on 0 Posts
Thanks PJ ... Mine is a GMNT060-3b. So just look for a wire that goes from the green card to the chasis? What if i dont find one? I do have extra wires coming from the thermostat to the furnace and they are easily available, but i'd just need to figure out where to screw them to the chasis if there is nothing there already, correct?
 
  #15  
Old 02-20-14, 10:32 AM
S
Member
Join Date: Nov 2013
Posts: 9
Received 0 Votes on 0 Posts
And after further reading, is the c just a ground? maybe that's what I'm not understanding. I just know that there are times in the spring/early summer and fall that we dont need our furnace/a/c at all, so it stays turned off, and I want to make sure that the wifi t-stat never runs out of power ...
 
  #16  
Old 02-20-14, 07:54 PM
Jay11J's Avatar
Member
Join Date: Sep 2001
Location: Rochester, Minnesota
Posts: 18,427
Received 0 Votes on 0 Posts
Yes, C is ground. A ground screw works.
 
  #17  
Old 02-21-14, 06:36 AM
S
Member
Join Date: Nov 2013
Posts: 9
Received 0 Votes on 0 Posts
And just because I'm stupid and need to have things repeated, hooking up the t-stat to a red and common wire will complete the circuit and allow the wifi t-stat to receive power 24-7, even if the furnace is not being used due to a comfortable climate? I've just read some horror stories where owners turned off their furnace because it wasnt needed and the wifi t-stat bled out and stopped working because it wasnt constantly triggering the furnace and pulling power from it during a run cycle... Thanks again in advance ...
 
  #18  
Old 02-21-14, 10:41 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 62,170
Received 1,528 Votes on 1,411 Posts
Well...... I don't know if I'd call it a horror story. Once you turned the furnace back on the thermostat would recharge.


Yes.... connecting your thermostat with an R and C connection will keep it active year round.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: