Nest Compatibility / Wiring Questions

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  #1  
Old 05-31-18, 09:32 AM
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Nest Compatibility / Wiring Questions

Hi All, I've been reading all posts that are similar to my units and questions but I've still got a few questions.

I believe I have the upstairs wiring down for a 3d gen nest.

The downstairs is where I could use a little help.

Downstairs is powered by gas Trane XV80 for heat and XL16i (need to double check #) for AC.

Thermostat is TCONT802AS32DAA

Based on the current wiring & features, would the nest make sense for this setup?
 
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  #2  
Old 05-31-18, 09:47 AM
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Yes, as long as you donít get the stripped down Nest E. You can install a Nest thermostat on your 2 heat / 2 cool system.
 
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Old 05-31-18, 10:10 AM
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Thanks, Houston! Would this be correct for downstairs wiring?

7-Wire TRANE Wiring: -------------> NEST
Red = 24v hot ----------------------> Rh
Black = Heating 2nd stage --------> cap off *
White = Heating 1st stage --------> W2/AUX
Yellow = Cooling -------------------> Y1
Green = Fan ------------------------> G
Orange = SOV ---------------------> O/B (program for O)
Blue = 24V Neutral ----------------> C

With that, I do think I've confused myself with all the photos. The upstairs 8 wire thermostat was where I was scratching my head. It's an xl16i too but with heat pump. Unfortunately, I don't have a photo of the board at the handler. Same thermostat .Here's wiring...

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Last edited by PJmax; 05-31-18 at 06:09 PM. Reason: cropped/enhanced picture
  #4  
Old 05-31-18, 01:18 PM
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Brown on Y2
Black to * terminal and configure for emergency heat.

Is this also a dual fuel application? ( Propane furnace paired with a heat pump)
 
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Old 05-31-18, 06:02 PM
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We were told the upstairs was all electric when we bought the house last fall. The air handler in the attic does not have an easy access door. Iíll have to bring tools up there to take a look at the board. I did take a photo of the unit.

 
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Old 05-31-18, 06:13 PM
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Second floor all electric heat pump system.

Red - Rh
Green - G
Yellow - Y1
Brown Y2
Orange - O/B
Blue - C
White - W2/AUX
Black - * (programmed for E heat)
 
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Old 06-01-18, 05:08 AM
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Thanks for the replies!

Here's the upstairs air handler. Is it worth taking the cover off to see where the wires are placed before I install the nest?

Going to read the pro guide before I install.
 
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Old 06-04-18, 05:11 PM
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Placed the order for two nests last night. Can anyone confirm my downstairs wiring detail on post #3?
 
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Old 06-04-18, 07:51 PM
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Red = 24v hot ----------------------> Rh
Black = Heating 2nd stage --------> * (program for E heat)
White = Heating 1st stage --------> W2/AUX
Yellow = Cooling -------------------> Y1
Brown = Cooling- 2nd stage ------> Y2
Green = Fan ------------------------> G
Orange = SOV ---------------------> O/B (program for O)
Blue = 24V common ----------------> C

When you set up the nest..... you must tell it dual fuel in programming.
 
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Old 06-05-18, 11:33 AM
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Thanks for the reply, Pete. I don't have an orange at the downstairs tstat but there is one at the handler. Would I just ignore orange in your list or does that change things? Thanks!
 
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Old 06-05-18, 10:28 PM
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Now I'm confused. I knew discussing two systems in one thread would be confusing.
I thought the board in the first picture was the downstairs unit.

Hmmmm..... is that correct.... an orange jumper from R to O ?
That's not a usual connection.
 
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Old 06-05-18, 10:52 PM
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PJ that is normal when a Trane or American Standard furnace or air handler is matched with a two step scroll compressor.

What usually throws people off is that stat Y1 doesn't connect to furnace YLo. Stat Y1 connects to furnace Y2.

Stat Y2 connects to furnace BK.

The BK jumper to R (dip switch) and jumper between O and R must also be addressed at the furnace.

This is to address the fact that Y1 is 50% of Y2 airflow with Trane. They have a two compressor condenser that is indeed 50% capacity with Y1. I hat is when the Y1 terminal is used.

I prefer the Trane furnace that had a Marquis. It allows you to configure for two step scroll without losing the BK for dehumdification feature.
 
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Old 06-05-18, 11:06 PM
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Thanks for the info partner.
 
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Old 06-05-18, 11:18 PM
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https://www.doityourself.com/forum/t...-needed-2.html


You are very welcome.

Post 7 has a diagram .
 
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Old 06-06-18, 05:40 PM
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Thanks for the follow up. looks like Iíve some reading to do. Nests came in today.
 
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Old 06-10-18, 11:24 AM
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Got the upstairs nest in and working properly. Thanks guys!

Im still a little unsure about the downstairs. Maybe Iím over thinking it.

Houston-my stat wiring matches post #7 in the thread you linked. Would I just hook it up the same way with the nest? When you say the jumper needs to be addressed, do you mean removed or changed when I install the nest?
 
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Old 06-10-18, 12:09 PM
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The changes at the furnace should already have been made.
You should be able to connect the new stat like the old stat was connected.
 
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Old 06-10-18, 12:31 PM
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Thatís what I was thinking. Is there any more info I can provide to be sure or were the photos okay? Would a close up of or switches help? Anything special to address in the pro set up?
 
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Old 06-10-18, 10:39 PM
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It looks looks the dip switch settings are ...

S3 = Off. Off, Off, On
S4 = On, Off, Off, On

What about S5 ?
Is S5 switch 2 Off? It needs to be off.

I see that thee R to O jumper has been installed as required.

What is the model number of the downstairs furnace?
What is the model number of the downstairs outdoor unit?

We want 350CFM per ton (if you are in a humid climate) but we need the tonnage of the outdoor unit and of the furnace.


 
  #20  
Old 06-11-18, 02:27 PM
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Hi Houston,

Here's what I have for the downstairs...

Looks like S 5 #2 is on?

Downstairs Outdoor: 4TTX6048E1000AA
Downstairs Furnace: TUD2C080A9V4VBA

Im in Maryland.
 
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Last edited by cb242; 06-11-18 at 02:49 PM. Reason: Location
  #21  
Old 06-13-18, 04:55 AM
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I see that blower ramping is not on.
Counting from left to right 5 and 6 should be On for ramping. (AKA S3 -1 & 2)

1-Off
2-Off
3-Off
4-On
5-On
6-On
7-Off
8-On

S5-2 needs to be Off
 
  #22  
Old 06-13-18, 05:00 AM
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The dip switch information is on the blower door. I took that picture with an old camera and it is difficult to read.

It would be great if you could post a better picture of the dip switch chart on your blower door.
 
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Old 06-13-18, 02:11 PM
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Hey Houston,
Here are a couple pics of the blower door diagram. I split it in two for easier reading. Let me know if it's not clear.

I'm going back down to the basement to look over the switches again. I haven't changed anything since we moved in last fall.
 
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Old 06-13-18, 02:25 PM
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Here's a close up of the chart. It must have dropped off in my original reply.
 
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Old 06-13-18, 05:18 PM
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From your pictures I can tell you that S3...
1-off
2-off


S5-2 = off
 
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Old 06-14-18, 08:11 AM
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Thanks, Houston! I'm not sure I comletely understand the settings for S5-2. Does it need to be switched off because of the installed jumper?

I wrote out my notes on the nest wiring but I left them at home. I think the only changes to the nest wiring were blue C and red to Rh? Does that sound right? I'll confirm later today.
 
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Old 06-14-18, 05:50 PM
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S5-2 needs to be off because we have a 2 step scroll compressor connected to it.

When you turn the switch off it will open an internal jumper between BK and R.

The thermostat Y2 will then control the BK terminal.
 
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Old 06-15-18, 01:28 PM
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I think I've got it now. I guess it's been operating less efficiently than it could be. Thanks!

Here are my nest notes:

Yellow - Y1
Brown - Y2
Green - G
White - W1
Black W2
Blue - C
Red - RH

Should I set up anything special in the nest other than dual fuel?
 
  #29  
Old 06-15-18, 02:47 PM
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I'm sorry but you don't have a dual fuel setup.
A 4TTX condenser is not a heat pump.
Trane puts a W early in the model number with heat pumps. Like 4TW...

You have a 2 heat / 2 cool conventional system with a 2 step scroll compressor.

The use of the O terminal may have caused some confusion early in this thread but you don't have a dual fuel system .

A dual fuel system is usually a heat pump paired with a gas furnace.
 
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Old 06-15-18, 06:33 PM
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Thanks for the clarification, Houston. I probably should have started two separate threads for the different systems .
 
  #31  
Old 06-16-18, 09:41 AM
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Quick question...would there be any reason to enter the pro set up when I install the nest? It seems like the downstairs is a standard set up knowing what i know now.
 
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Old 06-16-18, 01:39 PM
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While the Pro entrance would not be of much use , I like the test option.
I think it is around two clicks to the right of that.

I energize stage one cooling and count the flashes at the furnace LED.
I also measure the temperature in stream and leaving the evaporator coil.

I then energize stage two cooling at the thermostat and again count the flashes at the furnace and measure the temperature entering and leaving the evaporator coil.

Each flash at the furnace is 100 CFM, and we want 18 to 21 degrees delta T in both low speed and high speed.
 
  #33  
Old 06-19-18, 02:23 PM
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Thanks for the reply, Houston. I'll have to try that in a bit.

I installed the nest last evening and it seemed to be working properly last night. I did the basic tests and let it do its thing all day. This afternoon, the stat reads nest can not continue without a wiring change. The app says there's an issue with the Y1 wire? Possibly too much current? I'm still reading at the moment...any ideas?
 
  #34  
Old 06-19-18, 03:13 PM
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Looks like E103 is the error.

Here's the old, the new and the diagram i used for reference.

I reconnected the old stat and everything appears to be working as it was.
 
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Last edited by cb242; 06-19-18 at 03:56 PM.
  #35  
Old 06-20-18, 05:01 AM
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My first thought is that the contactor in the outdoor unit needs to be replaced.
Does it smell like burnt popcorn?

If you have a solenoid valve on the 3/8" liquid line it could also be the culprit but they are not very common because of hard shut off expansion valves found in evaporator coils.

A long line set paired with some thin 20 gauge control wire to the outdoor unit might also cause over current. An isolating relay could be used to address that.
 
  #36  
Old 06-20-18, 07:04 AM
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I'll check the outdoor unit this afternoon. When I originally took photos, it looked like a mouse made a home at some point near where the wires were connected.

I'll take some photos of the line connections for confirmation. One strange thing i noted on the outside unit was the downstairs unit had an inline gauge of some sort and the upstairs unit did not.

The control wire bundle does travel from one end to the other end of the house. Maybe too far?

Thanks for the follow up!
 
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Old 06-20-18, 10:50 AM
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A guage might be strange but a sight glass is not uncommon.
 
  #38  
Old 06-20-18, 03:01 PM
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Looks like it's a sight glass. Wires don't seem to be too small gauge.

I couldn't smell any popcorn or burnt smell. ANyhting look out of the ordinary except for the paper nest?
 
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Old 06-20-18, 06:16 PM
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The ICM delay on break is a likely suspect.

Is it just 2 terminals or is it more?
 
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Old 06-21-18, 06:57 AM
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I was thinking about asking on the ICM delay. I'm pretty aure it only has two terminals. I'll pull the cover and check again this afternoon. Is this not compatable with the nest?
 
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