The problem is your installer! Get him back and tell HIM to try a different thermostat. Your Goodman system is a very nice system but you should probably have gone with OEM thermostat.

There could be two problems. First you have to verify the Nest model you have can control two stages of cooling and it has been properly set up.

The second thing to investigate is the air handler control board. The control board is usually set up at the factory to run the staging and not use the thermostat. The first and second staging is done by a simple timer. You want the thermostat to make the staging decision because it knows the indoor temperature conditions. If you allow the air handler to make the staging decisions then you have wasted money on the Nest thermostat.

Thanks, yes this is a 2nd generation NEST. It can run 2 stages. I appreciate that if go spend another $500 for an OEM Communicating Thermostat it might work, but why should I have to do that.

How about this? If I check the voltage at the wires in the air handler, to make sure that I'm sending 24 volts on Y1 when asking for low stage cooling. I suspect that I'm sending 24v to both Y1 and Y2, giving me stage 2 cool. Or is that too simple? Maybe it's just that the thermostat is asking for cool, and the air handler is making a decsion to give stage 2.

I read up on the OEM model, it only uses 4 wires to communicate everything. Is there any way I can prove any of this out before having to put down $500 on that thing. There are other good Honewell thermostats, that should be able to run 2 stages, but as I said I can check voltage at the air handler to see what my nest is doing first. Any thoughts on that?

You can check the voltages and the wiring as you suggest. Normally if you are in the low stage Y1 should be energized, and if in the high stage, then Y1 and Y2 should be energized.

Either you or the installer need to check the DIP switches on the air handler control board have been set properly. You may need the air handler installation manual to find the correct settings. I suspect this is the problem and the air handler is ignoring what the thermostat is telling it to do for low and high stage operation.

I would suggest not spending another $500 just to get the staging working properly. I would hope the second generation Nest can do this properly. There may be other features the communication thermostat offers but I don't know what they are. Perhaps a Goodman expert can explain it. Then you can decide whether is is worth the extra money.

thanks, you say that in Stage 2 only Y2 should be energized. - From my original statement - When Testing my NEST, when testing Stage 1 Cool, it says "Connecting Ground to Y1" Then when testing Stage 2 Cool, it says "Connecting Ground to Y1 and Y2. " Why does it say connecting both Y1 and Y2?

I've been through all of the DIP Switches. I set the Fan Speed, a Trim Speed, Continuous Fan Speed, Aux Heat value for 10kw, and I set a Profile, for it to come on at 50%, then ramp to 82% for 7 minutes then up to 100%. I've read it all, I see nothing for setting stages. But I will go back and read some more, because I think that could be the problem.

The DSZC18 and AVPTC are compatible with both the 4 wire communicating thermostat and the regular multiwire thermostat. You don't have to spend $500 to get a good compatible thermostat from Goodman. Your installer should ideally be working on this to make you happy.............

Having said that, the Nest should work with your system.

Again, where's the guy who installed this?

You are correct that Y1 and Y2 are energized during high stage cooling. I edited my previous post.

So if I disconnect my Y2 at the thermostat, turn on cool, go down to the air handler and check voltage, I should only see voltage on Y1. Except that the Compressor could be energizing Y2. I've already done this test, and the system is running in High Stage. Meaning Y2 is energized. Brings me back to the system controlling itself and only allowing the thermostat to turn it on and off.

SKTN77 - Sorry, not getting much help from the installer.

One more thing real quick. how about if I take the thermostat out of the loop and connect Y1 to Ground. Should get stage 1. Then connect Y1 & Y2 to ground, should get stage 2. Even though the Nest thinks it's connecting things properly, maybe it's not.

I would not short any connection to ground. You could blow the fuse or damage the circuit board.

I don't think the problem is with the Nest thermostat. Do you have a voltmeter? What you could do is disconnect Y1 and Y2 at the thermostat terminals and leave R and C connected. Lower the thermostat one degree. You should read 24v between Y1 and C, and zero between Y2 and C. Then lower the temperature several degrees. You should read 24v between C and Y1 and Y2 respectively. If you see that, then you know the Nest is working properly and the problem is with the control board set up.

The thermostat probably has an open connection on Y2 when it is calling for the low stage. So if the control board is energizing Y2 it can raise it to 24v.

I read the AVPTC installation manual. I don't see a way to switch between the non-communicating and communicating thermostat. I am thinking that when you use a non-communicating thermostat the control board is always working with its timer based algorithm. So it decides when to switch to the high stage except in the case when the thermostat energizes Y2. I don't see any way to change the timing between low and high stages. I suppose if you want better staging control you need to get the Comfortnet CTK0* thermostat.

That's great info. thanks. I'll run that test tonight.

Your final statements, about the control board setting the staging, if the nest is working probably it should be able to overide that control....correct? BTW, I know the NEST uses an algorithm based on the Time to Temperature to control stages. That's probably fine with me. I have not mentioned in this thread my huge power consumption, this new system will hopefully help with that. I'm looking forward to running this thing in Low Stage to see what it can do.

Thanks all.

Hef

There is more to this system than just "speed 1" or "speed 2". Certainly you can control it "normally" via any 2 stage thermostat if wired properly and set up properly.

However, a communicating system knows more than an "non-informed" nest or a "non-informed" run of the mill 2 stage thermostat.

If you live in a part of the country where there is high humidity, the communicating OEM thermostat is the way to go with this system. Nothing will perform even remotely as well as the OEM stat, because it knows what is going on with the whole system rather than just the indoor temperature.

You spent all this money on a great HVAC system and now to operate it you try to cut corners?

PS: the OEM stat comes with a 10 year warranty. The nest only 2 years.

"Certainly you can control it "normally" via any 2 stage thermostat if wired properly and set up properly."

I could be wrong, but it seems a legacy thermostat has limited control on the staging. I believe the Nest has the cool to dehumidify feature so it may be able to do a good job in humidity control if it could keep the air handler and condenser in the low stage for long periods of time. The Nest can't display any of the diagnostics which is nice feature for trouble shooting.

I do agree that if you buy a communicating furnace or air handler, then you should spend the money on the matching communicating thermostat. Especially in this case where staging features are limited if you don't use the OEM thermostat.

The Goodman installer should have explained all of this to you.

Interesting, it seems difficult to find good info on the CTK04 thermostat. So it can control your system more than just the Low and High Stage, taking advantage of the Variable Speed air handler more than a regular thermostat. Is that correct?

The air handler documentation has good info on installing the Communicating Thermostat, only the 4 wires, replacing a plug-in module, and other things. Would you say it is a difficult install? I saw some people having trouble with some "Learning Function"

thanks

I found this installation manual for the CTK04 thermostat. Take a look and see what you think. It should not be difficult to install.

That's great info, thanks. Looks easy. Has anyone used the Goodman TrueSteam humidifiers? Not cheap, but might be nice.

If you havent already, you may want to check the wiring from the air handler to the compressor/condenser. Y1 and Y2 may be reversed or jumpered together.

Have you tried calling NEST technical support (855‑469‑6378)?

I'm having the same problem, did you ever resolve this??

I am also having a similar problem...cant get the system to go into stage 2...even though the nest is calling for it

Solution to this problem. When you update your system from single stage to 2 stage, you must have C wire from outside unit. My old single stage system came with 3 wires from outside unit to indoor (blower) and Indoor unit to thermostat had 5 wires.

I solve this problem with new wiring the whole house. I install 4 wires from outside unit to indoor (blower) (red(Rh), blue(C), yellow(Y1), purple (Y2) (mine had a purple)); Indoor unit to thermostat install 7 wires, which following below.

red (Rh)

blue (C)

yellow Y1 Cooling stage-1

Gray Y2 (Purple Y2) Cooling stage-2

Green (Fan)

white (W1) Heating stage-1

brown (w2) Heating stage-2

If you don't want to rewire, I recommend to get CTK04 thermostat, which will be fine with your old wiring.

I have a similar problem with a brand new goodman packaged heat pump GPH1642H41 that will not seem to heat in 1st stage heat, only 2nd stage. I am using a Honeywell vision pro 8000 and everything is wires up correctly to my knowledge. It's is set up for for a two stage compressor, but only seems to run the indoor fan when 1st stage is being called for?

The GPH16 Packaged heat pump is only a single stage unit. You can see this on page 3 of the product specification. The Vision Pro 8000 thermostat needs to be set up as a single stage heat pump in order for the heating and cooling to operate correctly.

I suggest you start a new posting if you have additional questions.