Nest Thermostat blowing cold air

[marcusmoreno23]

Hi there,

As most of the posts out there when my thermostat is set to blow hot air but it blows cold air. I've attached photos of my old and new wiring. I've also written out the connections on the old thermostat as the labels are hard to read behind the wiring.

I've tried switching the heat pump from B to O. 

I have no experince in HVAC but I believe I have 1 Stage Heat Pump with Aux heat and Emergency Heat. I've used the diagrams here (http://support-assets.nest.com/images/pro-faq/Nest-Pro-Installer-Guide.pdf) with no luck.

Old connections:

Rh -> Rc

Rc -> Red wire

Y1 -> Yellow

G -> Green

W1/E -> Black

W2 -> White

O -> N/a

B -> Orange

C -> Blue

[dhx227]

I assume you followed this diagram:

It does sound like the changeover valve is not getting signalled correctly.

Also, did you confirm the * is set to E?

If it is cold enough where you are, the heat pump may not be warm enough without emergency heat.  You could try connecting the black wire to the W1 terminal and see if that changes anything.

[marcusmoreno23]

You are correct! I did follow that diagram. If I try to move the black cable to W1 then it thinks that its gas and not electric.

[Patrick_Caezza]

Do not move the back wire to the W1 terminal. It is in the correct location now

[marcusmoreno23]

The * is set to E. I tested the emergency heat and that works fine. Heat pump heating or auxiliary heating does not work. If I try to move the black cable to W1 then it thinks that it's gas and not electric.

[dhx227]

Well, I don't got much for you then.   Maybe you should confirm that the white wire is actually making good contact in the W2/Aux terminal.   Sometimes it seems like the wire is all the way in, but in fact, it's not.  Also, if you happen to have a voltmeter, then you could test whether the Nest is signaling Aux heat by testing the voltage of the white wire (and blue) at the heat pump.  It would be 24vac if the thermostat is calling for aux heat.

[MelbaDT]

Hey folks, 

Thanks for taking care of this, dhx227,RomanandsonAC, and Patrick_Caezza. 

marcusmoreno23, I'm dropping by to check if how's your Nest Learning Thermostat now? Were you able to try Patrick's suggestion above?

Best, 

Melba

[MelbaDT]

Hey marcusmoreno23,

Checking back in here if you still need help with your Nest thermostat. 

Best, 

Melba

[MelbaDT]

Hi, 

I haven't heard from you in a while so I'll be locking this thread if there is no update within the day. Should you have any new issues, updates or just a discussion topic, feel free to start a new thread in the community.
 

Best, 

Melba

[RomanandsonAC]

You must have a Rheem or Ruud System. Reason it blows opposite of what you're calling for is due to this manufacture energizes the HP changeover valve in Heating. 90% of all HP systems use O to energize in cooling not heating. That being said when you provision the Nest you have to change it to energize in heating, or switch from O to B. The nest is wired correctly, however you need to provision to energize in heating or B like your old tstat 

[marcusmoreno23]

I am not home right now to send a pic but I made sure to set it to B like it was on the old thermostat. I think it has to deal something with the change valve like the previous commenter said. It’s not changing from cold to hot. I could be wrong as I know nothing about hvac systems. 

[Patrick_Caezza]

Have you tried this?

If your system starts to blow cool air when your Nest thermostat is in Heat mode (or if it blows warm air when its in Cool mode), change the settings for orientation of your heat pump.

Nest Learning Thermostat

1.  On your thermostat, go to Settings.
2. Select Equipment.
3. Select Continue > Continue.
4. Select Heat Pump.
5. The Nest Thermostat defaults to an O setting for heat
   pumps. 
   • If the O option is highlighted, select B.
   • If the B option is highlighted, select O.
6. Test your heating and cooling again to make sure the issue is resolved.

[marcusmoreno23]

Hey Patrick,

I changed it back to O and no heat. I moved it back to B and still no heat.

[RomanandsonAC]

Is your system a Rheem or Ruud? 

[RomanandsonAC]

If it is than you either have one of tow issues. One your thermostat wire(orange wire) is broken or open. Or two your change over valve is stuck and doesn't engage into heating. How old is your system?

[RomanandsonAC]

Here is a option to validate the issue. If you go to condenser and with the system set to heat, touch the orange and yellow wire together. If your changeover engages, your orange wire is open and reason you are unable to bring on the heat. If you touch the orange and yellow wire and nothing happens, your changeover valve is faulty, or disconnected. I have seen where the changeover valve connection has vibrated off the solenoid. Its a plug that plugs right on to the solenoid. I'm looking for a picture to send you

[RomanandsonAC]

Here is a pic of a generic solenoid, the black cylinder is the solenoid. See the two pins on it, that's where the plug goes to energize the valve. 

[Patrick_Caezza]

Let's figure out if it's a thermostat problem or a system problem.

Take the Yellow, Green, and Red wires and connect them together (be sure to turn the system power off and back on).

Does it blow cool or heated air?

Add the orange wire to the bundle and it should blow the opposite of what it did without it.

With a heat pump system, the yellow wire turns it on or off, and the orange wire changes between it heating or cooling.

Post if this works as expected