2nd Gen Nest not activating 2nd Stage Cooling

[RE4]

I have an American Standard Heritage 18, Model-2A6H8060A1000AB, dual compressor heat pump with natural gas supplemental heat, mfd’ in 03/2005.  I have installed a new 2nd Generation Nest Learning thermostat.  It seems to work fine, except the Nest is not activating 2nd stage cooling when I believe it should.  I had one  professional HVAC guy check my wiring, and another who said the thermostat might be broken.  The last guy uninstalled the Nest and reinstalled the original American Standard thermostat, and the 2nd stage cooling was activated.  I don’t know if the Nest was wired incorrectly, or if the 2nd stage cooling circuit on the Nest is broken.

I’ll try to post some photos of the wiring flow from the outside unit to, a terminal strip in a box on the outside of the indoor unit to, a terminal strip inside the indoor unit to, the wiring of the original and the Nest thermostats.

Any help would be greatly appreciated!

Rick

Spoiler

Spoiler

[RE4]

 

 

 

 

 

 

 I hope these photos help.

[CoolingWizard]

@RE4 ,

is the first picture the outdoor unit?

AC Cooling Wizard

[RE4]

Additionally, I have these other questions to complete my understanding of how these things are wired:

1.  Since my heat pump has two compressors, and natural gas supplemental heat, in HVAC parlance does that mean it has two stage cooling, and three stage heat?

2.  Does the wiring code of ?3, i.e. X3, Y3, W3, on a terminal strip indicate that is the wire that goes to the thermostat.  Like does Y1 and Y2, roll to Y3 and then Y3 goes to the thermostat as Y, or Y1?

3.  Is W1-1st stage heat, W2-2nd stage heat, and X2-gas heat?

4.  Does X2 and W2 roll to W3 and go to the thermostat as W2/AUX?

5.  The old American Standard thermostat had two terminals labeled OT.  There was a separate 3 conductor wire group that had green-red-white insulated wires in it, the red and white wires went to these two OT terminals.  Were they perhaps for sensing outside air temperature?Do/should they play any role in the proper wiring of the Nest?

6.  The Nest has two terminals I did not use.  They are labeled ALT STAGE 2, and RH.  Do/should they play any role in the proper wiring of the Nest?

Thanks to anyone who can help me with this knowledge!

Rick

[CoolingWizard]

@RE4 ,

1.  Since my heat pump has two compressors, and natural gas supplemental heat, in HVAC parlance does that mean it has two stage cooling, and three stage heat?

Your heat pump is a 5-ton R22 based heat pump with two 2.4 ton compressors. Your outdoor unit requires a special wire harness adapter for using a conventional thermostat.  Each compressor has dual stages.  The control board in the outdoor unit is want accepts the second stage cooling call.

2.  Does the wiring code off ?3, i.e. X3, Y3, W3, on a terminal strip indicate that is the wire that goes to the thermostat.  Like does Y1 and Y2, roll to Y3 and then Y3 goes to the thermostat as Y, or Y1?

You do not have 3 stages, but there are systems with 3-stages. You have a Duel-Fuel system. The Electric is the heat pump and the second is your gas furnace.  I notice your dual stage gas furnace has W1 and W2 (stage 1 and stage 2) are connected to each other with a wire jumper. The control box on the outside looks like an electric heat stager but you say you have gas heat. 

3.  Is W1-1st stage heat, W2-2nd stage heat, and X2-gas heat?

In the heat furnace world with gas heat, W1 is stage 1 heat, and W2 is stage two heat.  The X2 is heat pump emergency heat.  The Nest presumes that on a duel fuel heat pump system, the primary heat is electric heat pump.  The secondary heat is presumed to be electric heat strips in the air handler. These heat strips are the auxiliary heat (W2) and the emergency heat (X2) With a dual fuel system, the W1 is stage 1 alternative heat and * is stage 2 secondary heat. 

4.  Does X2 and W2 roll to W3 and go to the thermostat as W2/AUX?

X2 and W2 are only used in single fuel heat pump applications. These are Auxiliary Heat (W2) and Emergency Heat (X2) both are same electric heat strips in the air handler. W2 is 100% controlled by the heat pump defrost board and the thermostat. The thermostat would activate auxiliary heat when it determines the heat pump is not keeping up.  Ie., the ambient temperature indoors continues to drop. It that situation the thermostat will activate W2.  The purpose of Emergency Heat is so a homeowner can activate the more expensive heat strips in the case the heat pump is out of service.  This way you have heat in the home while wit for the repairman to arrive. 

5.  The old American Standard thermostat had two terminals labeled OT.  There was a separate 3 conductor wire group that had green-red-white insulated wires in it, the red and white wires went to these two OT terminals.  Were they perhaps for sensing outside air temperature?Do/should they play any role in the proper wiring of the Nest?

The Outdoor Temperature sensor is not needed by the Nest Thermostat.  Nest uses the WiFi and get the weather from the internet. 

6.  The Nest has two terminals I did not use.  They are labeled ALT STAGE 2, and RH.  Do/should they play any role in the proper wiring of the Nest?

The RH is for power in from a separate heating system. Your heating system is combined with your heat pump air handler.  Even though you have a gas furnace, it uses the same forced air system. The power for then control system comes from this air handler.  

There are three separate cables thermostat cables entering the controller on the outside of the cabinet.  One goes to the thermostat, one goes to the furnace control board. Where the third go or come from? This controller appears to be some kind of sequencer for stage 1 and stage 2 heating and cooling. 

AC Cooling Wizard

[RE4]

@CoolingWizard , thank you so much for your detailed explanation to my questions.  

Did you see anything in the wiring of the Nest that was incorrect, to the point that the 2nd stage cooling would not be activated?

Rick

[CoolingWizard]

@RE4 ,

can you describe for me what action you took on the nest thermostat in an effort to try to activate stage 2 cooling?

AC Cooling Wizard

[RE4]

@CoolingWizard Yes, sir.  The residence is in NW Alabama.  The Nest in question was installed in early December 2022 and appeared to work fine during the heating season.  My wife, admittedly, likes it cool (cold, to me) in the house, 69F or 70F.  Once the cooling season had really kicked in, the conditioned air in the space being controlled by the Nest would rarely reach the set point.  According to the metrics the Nest was calling for cooling 23 hours, and a couple of days even 24 hours a day.

That caused me to call an HVAC professional to investigate.  He determined the contactor for the  2nd compressor was not being activated.  I suggested he look at the wiring for the Nest in question, (he is not a fan of Nest thermostats, I am a fan as I have four of them across two properties, this subject Nest being one of them).  I showed him the photo of the wiring for the old American Standard thermostat, he asked if I still had it, I did, he wanted to reinstall it.  He did, and the 2nd compressor fired off.

That’s where I am now, … with the old American Standard thermostat reinstalled, and with me wanting the Nest reinstalled … if it can be wired to fire off the 2nd compressor when needed!

Additionally, to follow up on your much appreciated first post:

I will post below a photo of how the wiring flow from the outside unit to the thermostat is run through the different terminal boards.  Perhaps you might see why I asked if some of the terminated wires in that terminal box “roll up” to another, (i.e. Y1 and Y2 “roll up” to Y3 (via that relay) on that terminal strip which goes to the thermostat terminal as Y1 … probably as the output from the relay in that terminal box).

I was not able to determine the impact of the different relays in the system.  There is one relay on the control board on the compressor unit outside, and the relay you mentioned in your post in the terminal box attached to the outside of the indoor unit, (your suspected sequencer for heating and cooling you mentioned, which is exactly what I think that relay does.)

In your response to my Question #1, you stated my outdoor unit requires a special wire harness for using a conventional thermostat.  Would I already have that special wire harness from the use of the original American Standard thermostat, model #32207643-002, Revision A?

In your response to my Question #1, you also state “The control board in the outdoor unit “is want accepts” the second stage cooling call.  Did you intend to say the outdoor unit “won’t accept“ the second stage cooling call?  If that is the case, is my trying to use a Nest for this application an exercise in futility?

In your response to my Question #2, you state that I, “say I have gas heat.”  I certainly feel that this unit does have gas heat as a yellow gas line goes to the unit.  I have attached a photo of the inside of the heating/air handler unit for your review.  I don’t believe there are any electric heating strips for this unit… but, I could be mistaken about that.

In my Question #5, you state the Nest goes to WiFi to get outside air temperature.  That’s good to know.  For my own edification, are the terminals on the American Standard thermostat labeled “OT” indeed for “Outside Temperature”?  I understand they are not to be used with a Nest.

In my Question #6, I inquired if the terminals on the Nest labeled “ALT STAGE 2” might play a role in the proper wiring of my Nest, thinking that might send the signal to fire off the 2nd compressor.  What do you think about that?

At the end of your responses, you asked about the 3 separate thermostat type cables that enter the controller box on the outside of the cabinet.  There is one each coming from the outdoor compressor unit, the air handler/furnace unit, and the thermostat.  The below photo will hopefully show where each of those wires, in each of those cables, terminate.  Please pay no attention to my guesses as to the purpose of those wires, as I was merely trying to figure out what their purpose is.  The terminal labels, i.e. B-G3-W3-X2-Y1 … are all good though.

Again, @CoolingWizard , I cannot thank you enough for your time and expertise in helping to get my Nest wired correctly!

Rick

[RE4]

 

 

Again, I hope these photos help.

Rick

[CoolingWizard]

@RE4 ,

Yes indeed you must have the special wire harness installed. If not those American Standard equipment could only communicate using the digital AccuLink interface.  The special wire harness has to be installed in the Air Handler and the outdoor unit.  This special wire harness provides the R, W1, W2, Y1, Y2, G and C connections.  You furnace has a label on the inside right side, can you get me the model number listed on that label?

 Now the question about roll-up of Y1+Y2=Y3 attached to thermostat Y1. Is that the thermostat is all output with the only exception the R wire is input. So the flow is from thermostat Y1->Y3 which splits to Y2+Y1 on terminal strip via the relay. 
The relay you describe on the outdoor unit, are called contactors and there should 2 of them. These are high voltage and #1, called CLO, turns on the #1 compressor and the condenser fan motor. The second one when energized by Y2, turns on the #2 called CHI compressor. 
There are never electric heat strips inside a gas furnace.  There is not place to install them and why would you want to.  The ALT Stage 2 is your gas valve stage 2, when activated your gas valve opens the second internal port increasing the BTU output.  Typically it increases by 20k BTUs more heat. 

As to question #5, the outdoor unit has the outdoor temperature sensor that is a 10k-Ohm thermistor. Both wires of OT are connected to the two wires of the thermistor.  They will not be needed. The American Standard thermostat used the temperature data the adjust the defrost cycle time.  It allows the thermostat to know when it should activate the auxiliary heat.  Since you have dual fuel system, there is no need to have that since the American Standard Gas Furnace you have is not appear to be heat pump knowledgeable. This is why I feel that external relay box is being utilized.  And, to confirm this, I need the furnace model number. 

When you look at the green circuit board inside the furnace, you see the terminals Y, YLO , W1, W2, O, G, R, B/C, and BK. YLO is stage 1 cooling and Y is stage 2 cooling. W1 is stage 1 gas heat, W2 is stage 2 gas heat. The O is a landing point for the heat pump reversing valve. This tells me your furnace is heat pump smart. Why does have the two stages? This allows the Integrated Furnace Control board (IFC) to adjust the blower speed.   

In the thought of education, let us learn about the heating cycle.  When the thermostat energizes W1, on the IFC, the imitates the induction fan motor. This motor pulls air into the heat exchanger expelling out the big white pipe you see going outside.  After 60-seconds, the IFC checks for a vacuum on VS1, that is the round disc looking things left of the induction fan. If the vacuum is present, it energizes the igniter and activates GAS Valve Stage 1. After 3 seconds, the IFC looks for Flame Ratification Sensor to the positive. If so, the IFC waits for the exhaust temperature to reach 250°F, and then it turns on the Blower Fan at Medium Speed.  The IFC sets a timer for stage 2 lockout.  When the timer expires, the IFC will accept a call on W2.  When W2 is energized, the induction fan motor switches to high speed and the IFC looks for VS2 to be closed.  if it is, Gas valve stage 2 is energized and the blower fan speed is increased to high. When the thermostat set-point temperature is met, the thermostat de-energizes W2 and W1 and the IFC turns if the gas valve, and blower reduces to Medium speed and runs for few minutes more to get more heat from the heat exchanger into the living space. 

Now the cooling cycle. When the thermostat energizes Y1, the IFC turns on the Blower Fan on Medium High and sends YLO power to the outdoor unit energizing contactor #1 and thus compressor #1.  There is a stage 2 lockout timer that waits 90-seconds before allowing Y can be acted upon. If the thermostat energizes Y2, it is connected to Y at the IFC, the IFC increases the blower speed to High, and the second contactor is energized thus starting compressor #2.  

That relay box on the outside of the ducts, has a label on the cover, can you get me screen shot of that label?

I hope that this information helps you to understand your HVAC system. 

AC Cooling Wizard

[RE4]

@CoolingWizard , thank you for lending your expertise to help me understand my HVAC system!

Sorry, I am not clear as to whether I “now have”, or whether I “will need to obtain” the special wiring harness you mentioned.

Below you will find the photo of the label inside the upper half of the Furnace / Air Handler cabinet.  As well a photo of the labels on the cover of the relay / terminal box attached to the duct panel.

It’s interesting, and makes sense that the signals travel from the thermostat back to the relay / terminal board and the furnace / air handler board.  I should have realized that….  So, instead of the different terminals “rolling up” as I surmised, they actually “roll out” to the rest of the system.  Thanks for helping me understand that.

The HVAC professional that came out and reinstalled the American Standard thermostat, showed me the two contactors you mentioned.  He showed me that the #2 compressor contactor engaged indicator was not extending from its case, like the #1 compressor contactor was.

I certainly misspoke when said there were two Nest terminals I did not use… the ALT STAGE 2, and the RH.  I think you caught that, I did not use the “*” (asterisk), and the RH terminals.  In the image of the wired Nest, I noticed the ALT STAGE 2 indicator on the Nest screen was greyed out and not green.  Is that indicative of a problem in my wiring … besides the problem that caused the #2 compressor to not be activated?

In your paragraph in which you detail the furnace circuit board terminals, you state that W1 and W2 are both gas heat stages.  That leaves X2 to be Heat Pump heat … is that correct?

Which of the wires on the Nest install were correct, and which ones do I need to change in order to activate the #2 compressor?

You have been so generous to share you knowledge with us, I cannot thank you enough!

Rick

[RE4]

 

I hope these are the photos you requested.

Rick

[CoolingWizard]

@RE4 ,

Ok, I have reviewed the documentation of the Heat Pump kit. (the relay box) and the manual of the furnace.  Bottom line, the heat pump kit is not needed for your system.  The fact that the Nest Learning Thermostat  is far more intelligent and the fact that your Furnace has a heat pump IFC, the heat pump kit is not needed. Perhaps it was part of an older furnace or something.  You do not need the special wire harness because it’s already installed in your outdoor unit. Below is the wiring schematic of your furnace air handler and a 2-stage heating and a 2-stage cooling application.  

You feel up to rewiring everything to make it all work properly?

Technically you can wire up a gas furnace so as to act like auxiliary and emergency heating for a heat pump.  This is highly not recommended however.  So for the Nest Learning Thermostat, in a duel fuel setup, the 2-stage gas furnace would be wired to W1 and W2.  You would have to make some cost calculations to determine at what temperature do we turn off the Heat Pump and switch the heating to Gas Furnace.  The variables to consider is the  cost of the gas and the kilowatts of heat produced compared the kilowatts of electricity used by the heat pump. For a heat pump, there comes a point I call the point of  diminishing return.  The colder it gets the less efficient the heat pump becomes.  At about 22°F, your particular heat pump will start to become less efficient and at 10°F it simply spends more time in defrost mode than in heating mode.  Some homeowners prefer the gas heat because it feels better but it drys the air and a humidifier is beneficial to have.  The heat pump heat feels moist or even cooler than gas.

AC Cooling Wizard

[zoeuvre]

Hi folks,

@RE4, thanks for reaching out, and I'm sorry to hear about the situation. I want to check if you managed to see the response above. Please let us know if you still have questions or concerns, as we'll be willing to assist you more. 
 

I appreciate your help, @CoolingWizard. 

Best,

Zoe 

[RE4]

 @CoolingWizard 

So sorry I have been absent for a few days, I’m now able to devote some more time to this thermostat, … with your able assistance!  

Since the system seemed to work properly before the Nest install, I am hesitant to remove the Heat Pump Kit from the system since it has an airflow switch and a relay with 16 terminals that must do all kinds of magic, depending on the functions in use.

Due to your very helpful posts, I have made a couple of wiring changes and a couple of configuration changes.

We now have both Heat Pump stages working correctly for both cool and heat.  We also have the Natural Gas alternate heat working for Stage 2 on the * (asterisk) terminal.

I have not been able to get the Natural Gas - Stage 1 heat to fire off.  I cannot even get the fan for that selection to run.  When I test the Alternate Stage 2 heat, I get all three burner tubes firing off and the heat output at the nearest duct vent is over 100 degrees F.  I am supposing that’s because the Furnace’s W1 & W2 terminals are jumpered?

I think I have figured out where the problem lies, but I don’t want to make any changes without running it by you first.

Here’s the current situation for the Alt Heat wiring:

Thermostat W1 WHITE wire to the Heat Pump Kit terminal W3.

Thermostat W2/AUX is empty.

Thermostat * (asterisk) BLACK wire to the Heat Pump Kit terminal X3.

Heat Pump Kit terminal W1 WHITE wire to Furnace Board W1, which is jumpered to W2.

Heat Pump Kit terminal X2 WHITE wire to outdoor compressor unit BLACK wire. (The schematic shows it goes to two optional ODTs, and is labeled as X2.)

I believe the jumper needs to be removed from the Furnace Board W1 & W2 terminals leaving that WHITE wire connected to the W1 terminal.  And, the unused BLACK wire at the Furnace Board needs to be connected to the Furnace Board W2 terminal, with the other end to be connected to the Heat Pump Kit terminal X2?  

1.  The thing I am unsure about is what the BLACK wire at the compressor unit does with respect to the Nest’s * (asterisk) terminal?

2.  And, can I have the Furnace’s W2 terminal connected to the Heat Pump Kit’s X2 terminal … “along with” the WHITE wire that connects to the compressor unit’s BLACK wire?

Am I barking up the wrong tree here?

Rick

[CoolingWizard]

@RE4 ,

Lets talk about how your gas furnace works in terms of sequences. 
Call for first stage W1 and second stage W2 heating. 
W1 thermostat contact close, signaling the control module to run its self-check routine. After the control module has verified that the 1st stage pressure switch contacts are open and the limit switches contacts are closed, the induction draft blower will be energized on low speed.

As the induced draft blower comes up to speed, the 1st stage pressure switch contacts will close and the igniter warm up cycle will begin. The igniter will heat for approximately 20 seconds, then the gas valve is energized in 1st stage to permit gas flow to the burners. The flame sensor confirms that the ignition has been achieved within four seconds of the ignition trial period. 

As the flame sensor confirms, the ignition has been achieved, the delay to fan on begins timing and after approximately 45 seconds the indoor blower motor will be energized at the low speed and will continue to run during the heating cycle.

Call for 2nd stage:

W2 thermostat contact closes signaling a call for 2nd stage heat. After 30 second delay, the induced draft blower will be energized on high speed and the second stage pressure switch contacts will close. The gas valve is energized in 2nd stage and the indoor blower motor switches to high speed.

If you want to see Stage 1 in action, disconnect the jumper between W2 and W1. Then turn on the heat. The problem is if you want to have the Nest thermostat control W2, you need to change some wiring in the Heat Pump Kit. 

AC Cooling Wizard

AC Cooling Wizard

[RE4]

@CoolingWizard 

Thank you for that explanation!  That certainly helps my understanding of what’s going on when Aux Heat is called for.

Can you tell me:

What the black wire at the outdoor compressor unit does, and how it relates to the the * (asterisk) terminal on the Nest?

And, can I connect the Furnace W2 wire to that black wire at the compressor and to the Nest’s * (asterisk) terminal?

Rick

[CoolingWizard]

@RE4 ,

I need to show you the Heat Pump Kit and it’s typical wiring. 

Your Stage 1 and Stage 2 Heat is the heat pump. Your stage 3 Heat is the W that goes to your oil burner. When the thermostat energizes the W wire, this is what causes the K1 Relay to to engage. When that happens power is sent to the W wire to the oil burner to start the heating cycle. At the same time this disconnects stage 1 of the heat pump. Notice the brown wire of Y2. This second stage cooling is wired direct between the thermostat and the heat pump. 

AC Cooling Wizard

[CoolingWizard · Accepted solution]

@RE4 ,

The Heat Pump Kit that you have is designed to integrate a gas furnaces with a heat pump. It is a hybrid solution that is no longer needed with the advancement made in programable and intelligent thermostats which essentially preforms the same function.  As I previously stated, with the Nest Thermostat, you no longer need to use the Heat Pump Kit.  The thermostat cable going to the outdoor heat pump unit, needs to disconnected from the heat pump kit, the cable routed to the furnace. The cable between the furnace and the heat pump kit, needs to be disconnected and removed. With the cable going to the heat pump routed to the Furnace cabinet.  You will attach the wires as follows:

Yellow, attach to YLo this is Stage 1 Cooling, stage 1 Heat Pump Heat

Brown, attach to Y This is stage 2 Cooling, Stage 2 Heat Pump Heat

Orange, attach to O, Heat Pump Reversing Valve. 

Green, Not connected

White, not connected 

Black, not connected

Red not connected

Blue, attach to C

Take the cable from the thermostat disconnect it from the Heat Pump Kit and route it to the furnace.

Attach the wires as follows,

Red, attach to the R

Blue, Attach to the C

Yellow, Attach to Y-LO

Brown, Attach to Y

Orange attach to O

Green, attach to G

White attached to W1

Black, attach to W2, remove the white jumper between W1 and W2.

 Now for the Nest Thermostat, you will set this up as a Duel Fuel, Heat Pump, Forced Air

The wires are attached as follows

Red, to Rc

Green, to G

Blue, to C

Yellow to Y1

Brown to Y2,

Orange, to OB

White, to W1

Black, to W2

Ready to assist you with the reconfiguration,

AC Cooling Wizard

[RE4]

@CoolingWizard

Thank you SO much! I will get on that first thing tomorrow morning. I will report back... 

Rick 

[CoolingWizard]

@RE4 ,

When you get the re-wiring done, check back with a picture of the IFC, and the Nest Backplate before you turn the power back on.  Also, I will need to walk you through reprogramming your equipment the Nest Thermostat without doing a full factory reset.  

AC Cooling Wizard

[RE4]

@CoolingWizard 

Thank you, will do.  I started the project this morning and then got re-routed to another project.  Please find below what I’m understanding from your rewiring post.

I want to verify with you that the R wire, and the X2 wire at the Heat Pump are not connected.

The R wire at the Heat Pump was connected to the Furnace and the Thermostat.

The X2 wire at the Heat Pump was connected to the X2 terminal at the Heat Pump Kit.

Also, will the IFC at the Furnace, control the speed of the Air Handler Fan?

 In yesterday’s post you mentioned an Oil Burner, I don’t have one of those, I assume I can replace any mention of an Oil Burner, with Gas Burner?

Additionally, after the rewire, will W2 act as my new Emergency Heat?

I cannot thank you enough, for all your effort!!!

Rick

[CoolingWizard]

There is no need for R at the outdoor heat pump.  Now, having said this, allow me to explain. There are the CLO and the CHI contactors in the heat pump.  The common is wired to one side of the coil, and the other side has Y on CLO, and Brown on CHI and that’s the 24VAC from R.
 The X2 is auxiliary heat from the heat pump and you do not have auxiliary heat. You have a duel fuel system. Just tape off the X2 wire.  When it comes to gas furnace, the IFC does indeed control the fan. When the thermostat calls for cooling, the thermostat controls the blower fan. 
You do  or need emergency heat because you have a duel fuel system. The Nest thermostat will give you an option setting, a temperature setting, that your system will switch from Heat Pump heating and turn on the gas furnace.  In the ever your heat pump fails, you will need to go into your nest thermostat and change the duel fuel setting to say never use the heat pump.  At that point the Nest thermostat will only use the gas furnace for heating.  

Having said all of this, you need to decide if you would prefer to configure the system as a single fuel system and then have the gas furnace as auxiliary heat and emergency heat.  If that is what you prefer, we need to wire the thermostat and IFC different.  We can start with duel fuel and switch to single fuel later if you desired.  

AC Cooling Wizard

[RE4]

@CoolingWizard 

I agree that it would be best to keep the dual stage gas, and to change the programming of the Nest should I ever need to lock out the Heat Pump.

In the first picture you will see, at the bottom, the Red & White wires from the Heat Pump capped off.  The orange wire nuts have three wires in each of them.  Those three strands connect the Heat Pump, the IFC, and the Nest,  The blue wire nuts have two wires in each of them.  Those two wires connect the IFC, and the Nest.

There are now no wires connected to the Heat Pump Kit.

The jumper has been removed from the IFC W1/W2 terminals.

I believe I’m ready for power-up and programming!

Rick

[RE4]

 

 

Standing by for the reprogramming.

Rick

[RE4]

@CoolingWizard 

I did power the system up, after double checking my wiring.  There is something not correct as the Nest is calling for second stage cooling and the CHI is not pulling down to engage the Stage 2 compressor.

[RE4]

Additionally, in case the problem is with the 2nd Stage compressor, I pulled the Y1 wire from the Nest, it recognized that and asked for 1st stage cooling, but to no avail, the compressor did not engage,  In both circumstances the Air Handler Fan did run.

[CoolingWizard]

@RE4 ,

I am sorry I have not replied sooner. Let’s check the wires. Swap Y2 and Y1 wires at the Nest thermostat. Check the cooling. This will prove the Y2 brown is working. 

The decision about when to switch from Heat Pump to Gas Heating is a financial one. Your furnace at stage 2 produces 120,000 BTU of heat. That takes a fair amount of natural gas. To make these calculations you need to turn on the gas furnace all the way to stage 2, then go to the gas meter and measure how many cubic feet of gas is used in 1 minute. You then need to convert that to kilowatts of energy.  There is a point where the energy consumed by the heat pump exceeds the gas furnace. For the heat pump the colder it gets the less effective at heating it becomes.  At the point the lines cross, is when you switch. This is typically near 25 degrees down to 20 degrees.  

AC Cooling Wizard

[RE4]

@CoolingWizard 

Well, here’s the latest in my ongoing saga:

Since I’m in NW Alabama and the A/C had been off since yesterday morning, it had gotten pretty warm in the house, so I triple-checked your instructions, and powered up the system.  That failed as neither of the compressors, nor the compressor fan engaged.  Then I started doing some research online (sometimes dangerous, I know!).  Most of the wiring diagrams I looked at for similar systems (I couldn’t find the Installer’s Manual for mine) showed the Red wire being connected to the compressor unit outside.  Last night I was hesitant to make that change without your approval.  

This morning I did some more research and looked at the wiring schematic that is folded up in the outside compressor unit.  It shows the Red wire being connected and, I think, through a K6 relay, becoming an “OR” wire that is being used for power to the reversing valve, and through a K7 relay to a wire nut labeled “F”, which I’m thinking is not used.

Anyway, since the house had gotten up to 80 degrees F, we slept in the basement last night where there is a second A/C unit, and this morning I decided to connect the R wire to the compressor unit.  I ran the tests for 1st Stage Cooling and 2nd Stage Cooling and they both engaged their respective compressors.  It appears the A/C is working.

So, this is where I am now:

Your recommended wiring, except the Red wire is connected to the compressor unit.  I still have the White wire that was wire nutted to the X2 wire at the compressor disconnected.

Below you will find the wiring schematic for the compressor unit, if that provides you with any information you perhaps did not have.

Thank you again for all your help.

Rick

[RE4]

@CoolingWizard 

I just saw your message.  Apparently you were replying while I was also typing.

Given that the 1st and 2nd Stage Cooling is now working with the Red wire connected to the compressor unit, do you want me to disconnect the Red wire from the compressor and swap the Y1 and Y2 wires?

Rick

[RE4]

@CoolingWizard 

What is the appropriate setting for the Fan activation for W1 and W2 in the Nest?

BTW, please do not worry about when, or even if, you reply.  Everyone deserves some time off, especially someone like you, who is willing to help someone like me!

Rick

[CoolingWizard]

@RE4 ,

The IFC controls the fan for Heating.  So no need to make any changes.  I forgot the your Heat Pump has a control board and it needs power from the R wire.  Your heat pump system controller has a relay controller that sets K1 and K2, and K3. The strange part, the way it is operating, only a single compressor can start at a time. There must be 2 different size compressors in your system.  The way the system control appears to work, only 1 compressor can be running at any time.  There is a controlling relay that energizes Yellow/Black wire for CLO, and a Yellow/Orange wire for CHI.  The arrangement is such that only one of them can be energized at a time.  I am curious to see the two model numbers on the label of the compressors.  The wiring schematic also shows you system is using 3-phase power.

AC Cooling Wizard

[RE4]

I am unable to see any data labels on the compressor while the compressor/s are catching up.  I did snap another picture of the compressor unit’s data label though, as well as a picture of the circuit breaker for you.  I’ll try to catch the compressor being off tomorrow to see if I can see the data labels for you.  

While I was looking at the compressor unit in question, I looked at the compressor unit for the basement.  I can see a data label on the orangeish/pinkish colored insulating blanket around the compressor.  That insulating blanket has popped open, as it appears the Velcro strips have turned loose of each other.  Should I take the grill off and try to reaffix the two strips together again, or is that not a big deal? 

I have not tested the Heat Pump Heat, or the Gas Heat yet.  I’ll try to get to that tomorrow and will let you know.  As I understand what you said about the IFC, if the Nest is setup to “Not Activate” the Fan, that is OK, correct?

Rick

[RE4]

@CoolingWizard 

I forgot to mention you in my previous post, so, I expect you haven’t seen it.

In addition to my questions about removing the grills for the data label and the insulation blanket, as well as my question about the Nest Fan settings, I have another question about testing the Alternate Gas Heat.

I did get to test the Stage 1 & 2 Heat Pump heat, they appear to work fine.  

When testing the Gas Heat, it appears all burner tubes fire up for both Stage 1 & 2.  Is that to be expected?  Is it just less gas  in Stage 1 than in Stage 2?  I “think” the output temperature for stage 1 was about 87F and for Stage 2 about 108F.  Does that sound about right?

Rick

[CoolingWizard]

@RE4 ,

That Square D breaker looks like your equipment service disconnect.   Electrical code requires that there be a power service disconnect within eye sight of the equipment.  As to the thermal blanket that maintains the compressors temperature so it is not affected ambient air.  It also serves as a noise damper.  If you want to check the compressor, you would have to remove the orange blanket momentarily. However, the reason they nest needs to use the red wire going to the outdoor unit is because there’s a special control board out there that needs the power. That’s why the red wire has to be sent out there. And as I looked at the schematic, what I noticed is there can only be one compressor running at a time. What this means to me is in rather than having two same size compressors, what you probably have is a 3 ton compressor for stage, one, and a 5 ton compressor for stage two. If you look at the wiring schematic the way, the wires or run through the relay because the controllers only one compressor could be running out of time.

as for your furnace, it’s not a matter of only lighting up one or two burners, and then lighting up the other two, the way to stage gas furnace works is, there is a gas valve which has to feed. So when you go to Steve’s to the second, or the high side of the gas valve is turned on which increases the amount of gas flowing to the burners. Additionally, the induction fan motor will jump too high speed as well. Additionally, the blower motor will go from medium high two full high on stage two heating.

AC Cooling Wizard

[RE4]

@CoolingWizard 

So, that is not a circuit breaker, only a disconnect switch.  I have learned another thing from you!

I now understand better the way the gas heat works, thanks again.

I think this closes out my need for assistance in getting my Nest installed and programmed.  Is there anyway I can show you my appreciation for your help, education and advice?  You have been the best!

I have not yet looked for a data plate on the compressors.  Should I remove the grill and the insulating blankets to get that information for you?

Rick

[CoolingWizard]

@RE4 ,

If everything is operating correctly, 2-stages of AC and 2-Stages of Furnace, then there is no need to go any further. Because the out door temperature is to warm no need to test the heat pump heating. If the outdoor temperature is 70 or above, do not test heat pump heat.

AC Cooling Wizard